Feralis Ch 3 Flashcards
Tissues
Groups of cells that have similar structure and function together as a unit
Types of tissues
Epithelial (skin or internal organ covering), connective (bone, cartilage, blood), nervous, and muscle
Negative feedback
Bringing conditions back to their normal or homeostatic function
Positive feedback
An action that intensifies a condition so that it is driven further beyond its normal limits (ex. Labor contraction, lactation, or sexual orgasm)
Respiration
Movement of gases in and out; can also mean cellular respiration in which ATP is produced in the mitochondria
Thermoregulation
Control of exchange of heat with the environment
Ectotherms / poikilotherms / cold-blooded
Obtain body heat from the environment
i) Include invertebrates, amphibians, reptiles, and fish
Endotherms / homeotherms / warm- blooded
Generate their own body heat and have a much higher basal metabolic rate (BMR) than ectotherms
Evaporation
A regulatory mechanism. Body heat is removed as liquid evaporates (endergonic process)
Metabolism
A regulatory mechanism. Muscle contraction and other metabolic activities generate heat
Surface area
A regulatory mechanism. Vasodilation or vasoconstriction of extremity vessels results in heat retention or removal
i) Blood flow to ears reduces body temperature, or concurrent exchange keeps central parts of the body warm
External respiration
Entry of air into the lungs and the subsequent gas exchange between alveoli and blood
Internal respiration
Gas exchange between blood cells and intracellular respiration processes.
Invertebrate Respiration - Cnidaria
Protozoa and Hydra.
Direct with environment - have large surface areas and every cell is either exposed to environment or close to it —> simple diffusion of gases directly with outside environment (flatworms; small animals only)
Invertebrate Respiration - Annelids
i. The mucus secreted by earthworms provides a moist surface for gaseous exchange via diffusion
ii. The circulatory system brings oxygen to cells, and waste products back to the skin for excretion
Invertebrate Respiration - Arthropods (80% of all living species; insects, spiders, crustaceans) - Grasshoppers
i. Grasshopper - series of chitin-lined respiratory tubules called trachea that open to the surface via openings called spiracles, through which oxygen enters and carbon dioxide exits
i) No oxygen carrier like hemoglobin is needed due to the direct distribution and removal of respiratory gases between the air and body cells
ii) The moistened tracheal endings ease the rate of diffusion
Invertebrate Respiration - Arthropods (80% of all living species; insects, spiders, crustaceans) - Spiders
ii. Spider - have book lungs
that are stacks of flattened membranes enclosed in internal chambers
Invertebrate Respiration - Fish
When water enters the mouth, it passes over the gills, which are evaginated structures that create a large surface area and take in oxygen and deposit carbon dioxide. Gills can be external/unprotected or internal/ protected, and water exits via the operculum (gill cover)
Countercurrent exchange - exchange between opposing movements of water and underlying blood that maximizes diffusion of oxygen into the blood and carbon dioxide into water
Aerobic respiration - Plants
i. Glucose —> 2 ATP + 2 pyruvic acid
ii. Gases diffuse into the air space by entering and leaving through stomata of leaves or lenticels in woody stems
iii. Anaerobic respiration takes place in simple plants when oxygen is lacking
Right vs left lung
Right lung has 3 lobes. Left lung has 2 lobes that are smaller to accommodate the heart
Pleurae
Membranous cover of the lungs. Two layers: visceral and parietal pleura. Space between the two layers is the intrapleural space
Visceral pleura
Lines the surface of the lungs
Parietal pleura
Lines the inside of the chest cavity
Intrapleural space and inhale/exhale logic
Has negative (lower) pressure relative to the atmosphere. If stabbed, air rushes in and causes the lung to collapse
i. The pressure of this intrapleural space decreases as we inhale: as the diaphragm contracts, the lung cavity opens up, and this increase in volume equates to a decrease in pressure
As we inhale, the volume of lungs expands as the diaphragm drops. Thus, we create a negative pressure relative to the atmosphere, causing air to rush in. The sequence events during an exhale occurs as follows: Diaphragm rises —> volume in lungs decreases —> the pressure inside of the lungs increases relative to the atmosphere —> air rushes out
CO2 and HCO3(-)
CO2 is transported as HCO3(-) (bicarbonate ion) in blood plasma. The conversion is catalyzed by the enzyme carbonic anhydrase via the following reaction:
CO2 + H2O H2CO3 H+ + HCO3(-)
This process occurs in red blood cells (RBCs). Some of the CO2 can also mix directly with the plasma as a gas or can bind with hemoglobin inside of the RBCs, forming carbaminohemoglobin.
Carbaminohemoglobin
CO2 binding with hemoglobin inside the RBCs
Alveoli
Where gas exchange between the circulatory system and lungs occurs. The alveoli are coated with surfactant, a liquid covering that reduces the surface tension, preventing H2O from collapsing the alveoli.
Two types of epithelial cells in human alveoli
Type 1 (structural support) and type 2 (produce surfactant)
Nose
Filters, moistens, and warms incoming air. The mucus secreted by goblet cells traps large dust particles here
Pharynx
Throat, passageway for food and air; dust and mucus are swept back here by cilia for disposal via spitting or swallowing
Larynx
Voice box; if non-gas enters the cough reflex activates
i. Note that the larynx is actually after the epiglottis in terms of sequence
Trachea
Epiglottis covers the trachea
during swallowing; contains C-shaped ringed cartilage covered by ciliated mucus cells
Bronchi / Bronchioles
2 bronchi, which enter the lungs and branch into narrower bronchioles
Alveoli
Each bronchiole branches ends in these small sacs, which are surrounded by blood-carrying capillaries
Diffusion between alveolar chambers and blood
Gas exchange occurs across the moist, sac membranes of alveoli via simple diffusion. O2 diffuses through the alveolar wall, through the pulmonary wall, into the blood, and into RBC. CO2 follows the same sequence, except in reverse. The greater the distance O2 needs to travel, the lower the efficacy of gas exchange
Bulk flow of O2
O2 is transported through the body within hemoglobin containing RBC
Diffusion between blood and cells
O2 diffuses out of RBCs, across capillary walls, into interstitial fluids and
across cell membranes. CO2 does this in reverse
Bulk flow of CO2
CO2 is mainly transported as HCO3(-) ions in plasma, which are produced by carbonic
anhydrase in RBC.
CO2 can also directly mix with plasma as CO2 gas, or bind hemoglobin inside red blood cells.
Bulk flow of air into and out of lungs - Inhalation
Diaphragm and intercostal muscles (between the ribs) contract and flatten. The lungs increase in volume and decrease in pressure, leading to a bulk flow of air into lungs
Bulk flow of air into and out of lungs - Exhalation
Passive process; decrease in lung volume / increase in pressure leads to air rushing out, and the diaphragm relaxing and expanding
Bohr Effect
Refers to the shift in the oxygen dissociation curve caused by changes in the concentration of CO2 or pH.
Hemoglobin O2 binding affinity decreases under conditions of low pH (which results from high CO2 and H+). A decreased binding affinity leads to oxygen being released by hemoglobin. A decrease in CO2 or increase in pH will result in hemoglobin binding more O2.
Bohr effect curve - High CO2
When we have a high concentration of CO2, it diffuses into the blood and into the RBC where carbonic anhydrase converts it into H2CO3. This H2CO3 then becomes HCO3(-) and H+
Hemoglobin now comes into play as it interacts with the H+ to form a more reduced form of hemoglobin that has lower affinity for O2, and greater affinity for CO2, causing O2 to be released.
Bohr effect curve - Low pH
High CO2 and low pH are related. Because low pH means a greater presence of H+ ions, the hemoglobin structure is altered to the reduced form that will release its oxygen.
Bohr effect curve - High temperature
At higher blood temperatures, hemoglobin becomes less likely to bind to oxygen and releases oxygen to tissues
Bohr effect curve - High 2,3-DPG
2,3-DPG (also known as 2,3-BPG) is produced from an intermediate compound in glycolysis and decreases the affinity of hemoglobin for oxygen. At low O2 levels, an enzyme catalyzes the synthesis of 2,3-DPG, hence, high [2,3-DPG] = low affinity of hemoglobin for O2
i. This is helpful for unloading oxygen during anemia or at high altitudes, which in both cases, we are struggling for O2
ii. At high O2 levels, oxyhemoglobin inhibits the enzyme that synthesizes
2,3-DPG, leading to low concentrations of the compound.
CADET, face right
The factors (CO2, Acid, 2,3- DPG, Exercise, and Temperature) that shift the oxygen dissociation curve to the right. A right shift involves physiological states where tissues need more oxygen
Haldane Effect
Describes how the deoxygenation of blood increases its ability to carry CO2. When there is an increase in CO2 pressure, there is an increased CO2 blood concentration. However, when hemoglobin is saturated with oxygen, its capability to hold CO2 is reduced.
Hemoglobin without oxygen acts as a blood buffer by accepting H+ —> this reduced hemoglobin has a higher capacity to form carbaminohemoglobin, rather than the oxygen carrying kind
Haldane Effect relates how [O2] is affecting hemoglobin’s affinity for CO2 and H+, which work in synchrony to facilitate the liberation of O2 and uptake of CO2 and H+.
Bohr and Haldane Effects - 3 interacting equilibrium systems
CO2 + H2O H2CO3 H+ + HCO3(-)
H+ + HbO2 H+Hb + O2
CO2 + HbO2 HbCOO(-) + H+ + O2
Medulla oblongata
Signals the diaphragm to contract, completing the following:
- When partial pressure of CO2 increases, the medulla stimulates an increase in the rate of ventilation
- The diaphragm is signalled to contract. The diaphragm is also the only organ which only and all mammals have, and without which no mammals can live.
- When the lungs inflate, the thoracic pressure decreases as the thoracic cavity size increases
This pattern repeats over and over again, giving us a steady breathing rate.
Methods/forms of CO2 transport in blood
Majority of CO2 in blood is transported in the form of bicarbonate (HCO3(-)). To a lesser extent, CO2 can be transported bound to
hemoglobin/plasma proteins. To an even lesser extent, CO2 is simply dissolved in the plasma. CO2 is significantly more soluble in blood than O2.
Central chemoreceptors
Contained in medulla. Indirectly monitor [H+] in the cerebrospinal fluid
Peripheral chemoreceptors
Contained in heart. Located in carotid arteries and aorta and function to monitor the atrial concentrations of CO2, O2, and pH via H+
Ciliated pseudostratified columnar epithelial cells
Found in trachea and upper respiratory system; may contain goblet cells for mucus production
Emphysema
A pathology marked by destruction of the alveoli
Effects of smoking
Damage to cilia of respiratory cells and allow toxins to remain in the lungs
i. Mucus produced by goblet cells increases, and lungs have a decreased means of moving mucous out, leading to a persistent yet unproductive cough
ii. Can lead to bronchitis emphysema, and lung cancer
Oxyhemoglobin
98% of blood oxygen binds rapidly and reversibly with protein hemoglobin inside of RBC’s, forming oxyhemoglobin
Hemoglobin
Structure has 4 polypeptide subunits, with each subunit hosting a heme cofactor (an organic molecule with an iron atom in the center)
i. Each iron atom can bind with one O2 molecule
ii. Exhibits cooperativity - when one O2 binds, the rest of the O2 molecules can bind easier, hence explaining the
sigmoidal curve graph of hemoglobin binding. The same is true for the opposite: when one O2 is released, the rest are released easier
As O2 pressure increases, O2 saturation of hemoglobin increases
This is ideal: in the lungs we are O2 rich and want to hang onto it, but in the tissues, we are O2 poor (lower O2 pressure) so the hemoglobin will release O2 to tissues
O2 saturation of hemoglobin also depends on CO2 pressure, pH, and temperature of blood
i. The oxygen dissociation curve shows the percentage of hemoglobin bound to O2 at various partial pressures of
O2
ii. Curve is shifted right (O2 released easier) when there is an increase in CO2, decrease in pH, increase in 2,3- DPG, or increase in temperature. CADET, face right!
iii. Bohr Effect - hemoglobin binding affinity decreases under conditions of low pH (high CO2/high H+) which
leads to O2 loads released by hemoglobin since both O2 and H+ compete for hemoglobin binding sites
Chloride shift
Chloride shift occurs to balance bicarbonate entering and leaving the cell. Carbonic anhydrase is in RBCs, so at the tissues to balance bicarbonate diffusing out of the cells, Cl- enters.
Respiratory acidosis
Results from inadequate ventilation; we don’t clear enough CO2 and it builds up, so more H+ is formed, lowering the pH
Respiratory alkalosis
Results from breathing too rapidly (hyperventilation);
we are losing CO2 too quickly, so H+ and HCO3(-) start combining to form more CO2, and the pH begins rising
Myoglobin vs Fetal Hemoglobin Curves
Myoglobin of muscle has a hyperbolic curve since the structure doesn’t participate in allosteric cooperative binding due to the single subunit shape. Myoglobin also saturates quickly and releases in situations of very low oxygen “emergency situations”
Fetal hemoglobin curve is shifted left of the adult hemoglobin curve because the structure has a higher binding affinity in order to grab O2 from maternal blood.
Carboxyhemoglobin
Carbon monoxide (CO) has a 200x greater affinity for hemoglobin than oxygen does [forms carboxyhemoglobin] and requires administration of pure O2 to displace it once bound
Avian respiration
Due to the unique anatomy of birds, respiration is both continuous and unidirectional. Air sacs allow birds to exchange gas during both inhalation and exhalation — oxygen rich incoming air is first stored in air sacs before entering lungs for exhalation, so it is not mixed with the deoxygenated outgoing air.
Mammalian respiration
Tidal breathing. Breathe in and out through the same tubing, inhibiting gas exchange during exhalation. Deoxygenated air is mixed with some fresh air during inhalation, some it is re- breathed. Much less efficient than birds.
Tidal volume (VT)
Volume of air that is normal inhaled or exhaled in one quiet breath
Inspiratory reserve volume (IRV)
Maximum volume of air that can be inhaled after a normal tidal volume inhalation
Expiratory reserve volume (ERV)
Maximum volume of air that can be exhaled after a normal tidal volume exhalation
Residual volume (RV)
Amount of air remaining in the lungs after maximum exhalation; air that cannot be exhaled
Vital capacity (VC)
Maximum volume of air that can be exhaled after a maximum inspiration; expressed as IRV + VT + ERV
Inspiratory capacity (IC)
Volume of air that can be inhaled after a normal exhalation; expressed as VT + IRV
Functional residual capacity (FRC)
Volume of air remaining in the lungs after normal exhalation; expressed as ERV + RV
Total lung capacity (TLC)
Maximum amount of air that the lungs can accommodate; expressed as IC + FRC
Circulation in Invertebrates - Protozoans (unicellular animal-like [due to movement] protists)
Rely on the movement of gas via simple diffusion within the cell
Circulation in Invertebrates - Cnidarians
Body walls are 2 cells thick, so all cells are in direct contact with either internal or external environment
i. Example: hydra
Circulation in Invertebrates - Arthropods (includes most insects and mollusks)
i. Open circulatory systems - pump blood into an internal cavity called the hemocoel (has smaller cavities called sinuses), which bathes tissues in oxygen and nutrient containing fluid called hemolymph
ii. Hemolymph returns to the pumping mechanism (heart) through holes called ostia
Circulation in Invertebrates - Arthropods (includes most insects and mollusks) - Mollusks
Most have open circulatory systems except for cephalopods, which have closed circulatory systems
a. Cephalopods have closed systems due to large oxygen demands, and have gill hearts
Circulation in Invertebrates - Arthropods (includes most insects and mollusks) - Annelids (Include earthworms)
a. Have closed circulatory systems in which blood is confined to vessels (also seen in certain mollusks and vertebrates
Path of circulation in closed system
System Away from heart: aorta —> arteries —>
arterioles —> capillaries
Back to heart: capillaries —> venules —> veins
The dorsal vessel functions as the main heart or pump; aortic loops link the dorsal and ventral vessels together which function in pumping blood
Number of heart chambers in different animals
Human and bird hearts have 4 chambers, reptiles and amphibians have 3 chambers, fish have 2 chambers, and crocodiles and alligators have 4 chambers
Pericardium
A fluid filled sac that surrounds the heart in order to protect and lubricate it for proper function
Right atrium
Chamber where deoxygenated blood enters via the superior and inferior vena cava
Right ventricle
Blood is squeezed into this chamber through the right AV (atrioventricular)/tricuspid valve, which contracts and pumps blood into the pulmonary artery via the pulmonary semilunar valve
i. When the ventricle contracts, the AV valve closes to prevent back flow, which produces the ‘lub’ sound
ii. When the ventricle relaxes, the semilunar valve prevents back flow from pulmonary artery back into ventricles by closing, thus creating the ‘dub’ sound
Pulmonary circuit
The blood pathway from the right side of the heart to the lungs, and eventually to the left side of the heart
Systemic circuit
The circulation pathway through the body between left and right sides of the heart
Left atrium
After traveling through the lungs, oxygenated blood enters the left atrium via the pulmonary veins
Left ventricle
After traveling through the left AV/mitral/bicuspid valve, blood from the left ventricle enters the aorta through the aortic semilunar valve into the rest of the body:
i. Aorta (largest vessel) —> arteries —> arterioles —> capillaries —> tissues get the nutrients they need —> venules —> veins —> superior and inferior vena cava —> the cycle repeats
ii. The left AV valve prevents back flow into the atrium, and the aortic semilunar value prevents back flow into the ventricle
Ejection fraction
The percentage of blood that leaves the ventricles when the heart pumps. Not all blood leaves the ventricles when the heart pumps.
Cardiac Cycle
This cycle is the rate regulated cycle by auto- rhythmic cells of the autonomic nervous system, but contractions are initiated independently of the autonomic nervous system. Instead, the heart contracts automatically:
- SA (sinoatrial) node / pacemaker
- AV node
- Ventricular contraction
SA (sinoatrial) node / pacemaker
Part of cardiac cycle.
Located in upper wall of the right atrium, the SA node is a group of specialized cardiac muscle cells that initiate by contracting both atria and sending an impulse that stimulates the AV node.
i. At the AV node, the impulse is briefly delayed to allow the atria to completely empty, and to allow the ventricles to fill with blood.
ii. The impulse spreads the contraction to surrounding cardiac muscles via electrical synapses made from gap junctions
iii. The pace of the SA node is faster than the normal heartbeat, but the parasympathetic vagus nerve innervates the SA node and slows contractions
a. The vagus nerve also increases digestive activity of intestines
AV node
Part of cardiac cycle.
Located in the lower wall of the right atrium / interatrial septa; sends impulse through the Bundle of His —> passes between both ventricles —> branches into ventricles via the purkinje fibers which results in contraction of both ventricles simultaneously
Ventricular contraction
Part of cardiac cycle.
When the ventricles contract (ventricular systole phase), blood is forced through the pulmonary arteries and aorta.
Papillary muscles and chordae tendinae
Papillary muscles and chordae tendinae are attached to cardiac valves and force them closed during systole
Ventricles vs atria
Ventricles have thicker walls than atria and generate higher blood pressure because ventricles must pump blood throughout the body and lungs, while atria only need to generate enough pressure to fill the ventricles.
Left vs right ventricle
Left ventricle is thicker than the right because the left ventricle pumps blood to most of the body, but the right ventricle only pumps to the lungs
Systole
Occurs when the atria or ventricles contract
Diastole
Occurs during relaxation of atria or ventricles
Semilunar valves
Aortic and pulmonary valves
Atrioventricular valves
Tricuspid/right AV valves and bicuspid/left AV/mitral
Blood pressure
Hydrostatic pressure from the heart contracting causes blood to move through the arteries. Blood pressure drops as it reaches the capillaries, and reaches near zero in the venules
Blood moves through the veins due to
- Pumping of the heart assisted by movements of adjacent skeletal muscles
- Expansion of atria each time the heart beats
- Falling pressure in the chest when a person breathes
Valves in the veins
Prevent back flow
Closed circulatory system
Blood is transported via arteries, veins, and capillaries
Open circulatory system
Soaking the organs in a bath of blood
Arteries
Thick-walled, muscular, elastic vessels that pump oxygenated blood away (except for pulmonary arteries that transport deoxygenated blood from the heart to lungs). Wrapped in smooth muscle, arteries are typically innervated by the sympathetic nervous system.
Large vs medium-sized arteries
Large arteries have less smooth muscle (per volume) than medium sized ones; larger arteries are also less affected by the sympathetic nervous system, but medium sized arteries can constrict enough to re-route blood.
Layers of arteries
Arteries have three layers (tunics)
a. Endothelial lining (inner)
b. Smooth muscle and elastic tissue (middle)
c. Connective tissues (outer)
Arterioles
Very small vessels wrapped in smooth muscle, and constrict or dilate to regulate blood pressure or re-route blood. Are a major determinant of blood pressure as they have the greater resistance to blood flow
Capillaries
Have the smallest diameter and have a single layer of endothelial cells across which gases, nutrients, enzymes, hormones, and waste diffuse
Methods for materials to cross capillary wall
a. Endo or exocytosis (proteins)
b. Diffusion through capillary cell membrane (O2 and CO2)
c. Movement through pores called fenestrations
d. Movement through space
between the cells (ions)
Pericytes
Sometimes you will see pericytes (contractile cells) around the capillaries and venules throughout the body
Capillary exchange
Capillaries exchange with the interstitial fluid that surrounds tissue cells.
Blood hydrostatic pressure
The pressure from the flow of blood pushing outward
Blood colloid osmotic pressure
Osmotic pressure exerted by blood proteins, usually in the plasma, and wants to pull water into the capillary (oncotic pressure)
Net filtration and net absorption
Blood flowing in from the capillaries has a high blood hydrostatic pressure — so high that it overcomes the blood colloid osmotic pressure working against it.
Net filtration at the capillary end of the bed is, therefore, fluid moving outward. But, towards the end of the capillary bed, blood hydrostatic pressure has decreased enough that blood colloid osmotic pressure overcomes it, and fluid flows back inward (net reabsorption) at the venous end
Pre-capillary sphincters
Regulate the passage of blood into capillary beds
Venules
Small blood vessels that lead back to veins and are very thin and porous
i. Drain blood from capillary bed —> venules combine —> veins
Veins
Larger veins often have valves to aid in the transport of deoxygenated blood back to the heart due to fighting gravity (except for pulmonary veins and umbilical veins that carry oxygenated blood)
Cross sectional areas
The cross-sectional area of veins is about 4x higher than that of arteries, and the total cross-sectional area of capillaries is far greater than that of arteries of veins. While capillaries are the narrowest vessels, there are far more capillaries
Blood velocity
Because blood volume flow rate is approximately constant, blood velocity is inversely proportional to total cross-sectional area. Blood pressure drops as we go from aorta —> capillaries because of energy loss due to increased resistance and decreased vessel diameter.
Blood pressure equation
Blood pressure = cardiac output * systemic vascular resistance (resistance controlled by vasoconstriction/dilation). If resistance increases, why does pressure decrease?
The blood pressure formula above applies to MAP (mean arterial pressure}, which is measured at the arteries by a sphygmomanometer. When a blood vessel constricts (increased resistance), the blood pressure is indeed higher in the part of the tube before the constriction (which is presumably where we measure blood pressure).
The pressure after the constriction is what is lowered, hence why blood pressure effectively decreases as we go through smaller diameter vessels. By the time we hit venules/veins, the original source of the blood pressure/flow (the beating of the heart) is virtually gone, which is why the pressure continues to decrease further.
Vessel with greatest resistance to flow (highest ability to constrict)
Arterioles
Location of most blood
At any given time, most blood is in the veins/venules/venus sinuses
Lymphatic system
An open secondary circulatory system that transports excess interstitial fluids (lymph) through the contraction of adjacent muscles, and some walls of larger lymph vessels have smooth muscle
Lymphatic system - Proteins and large particles
Proteins and large particles that can’t be taken up by the capillaries are removed to the lymph, which also monitors blood for infection. Also transports absorbed fat from small intestine to the blood
Lymphatic system - Valves
Has valves to prevent back flow - fluid returns to the blood circulatory system through two ducts located in the shoulder region (thoracic duct and right lymphatic duct) which empty into the left and right subclavian vein, respectively. This fluid eventually rejoins the blood as plasma.
Lymphatic system - Nodes
Contains lymph nodes - these cotton phagocytic cells (leukocytes) that filter the lymph and serve as immune response centers. Swollen glands during sickness are actually lymph nodes filled with white blood cells!
Lymphatic system - Organs
The thymus and bone marrow are the primary central lymphoid organs that can replenish immune cells (T-Cells in thymus, B-cells in bone marrow).
i. The lymph nodes, spleen, adenoids, appendix, Peyer’s patches (found in small intestine), and tonsils are peripheral lymphoid tissues [TALAPS]
a. These house immune system cells but can’t replenish them
b. The thymus technically doesn’t make new T-cells, but T-cells mature there so it houses fresh ones
Blood
There are 4-6 liters in the human body, and is a connective tissue. The heart pumps ~7000 L of blood a day
Percentage components of blood
55% liquid (plasma) and 45% cellular components.
Plasma, blood serum, RBC, leukocytes (WBC), platelets/thrombocytes
Plasma
Component of blood.
Aqueous mixture of nutrients, salts, gases, wastes, hormones, and blood proteins (immunoglobulins, albumin, fibrinogen, clotting factors)
Blood serum
Component of blood.
The same as plasma minus any clotting factor components
Erythrocytes (RBCs)
Component of blood.
a. Transports oxygen on
hemoglobin
b. Catalyzes conversion of CO2 and H2O to H2CO3
c. Lacks a nucleus and organelles to maximize hemoglobin content
d. Do not undergo mitosis
e. Contain spectrin, which enables them to resist strong shearing forces
f. If the tissues do not receive enough oxygen, the kidneys can synthesize and secrete a hormone called erythropoietin (EPO) to stimulate generation of more erythrocytes in bone marrow
g. Derive energy from glycolysis
Leukocytes (WBCs)
Component of blood.
Are larger than RBCs and phagocytize foreign matter and organisms
a. Contain organelles but no
hemoglobin
b. Undergo diapedesis - a process by which WBCs become part of the interstitial fluid and slip through the endothelial lining
Platelets/thrombocytes
Component of blood.
Cell fragments involved in blood clotting
a. Lack nuclei and stick to damaged epithelium in order to attract more platelets
b. Convert fibrinogen (inactive) to fibrin (active)
c. Are formed from small portions of membrane-bound cytoplasm torn
from megakaryocytes
d. Can produce prostaglandins and some important enzymes
Process of Blood Clotting
- Formation of platelet plug
- Release of thromboplastin
- Conversion of prothrombin to thrombin
- Conversion of fibrinogen to fibrin
- Clot formation
First step of blood clotting
Formation of platelet plug - platelets contact exposed collagen of damaged vessel and cause neighboring platelets to form a platelet plug
Second step of blood clotting
Release of thromboplastin - both the platelets and damaged tissue release the clotting factor thromboplastin
Third step of blood clotting
Conversion of prothrombin to thrombin - thromboplastin converts inactive plasma protein prothrombin to thrombin (active)
Fourth step of blood clotting
Conversion of fibrinogen to fibrin - thrombin converts fibrinogen into fibrin
Fifth step of blood clotting
Clot formation - fibrin threads coat the damaged area and trap blood cells to form a clot
Thrombus
A thrombus (blood clot that forms in a vessel abnormally) can cause a heart attack or stroke (if the clot causes death of nervous tissue in the brain)
Fetal circulation
Occurs both inside of the mother and her fetus that essentially temporarily re-wires the cardiovascular systems.
The process occurs as follows: Oxygenated, nutrient-rich blood from placenta carried to fetus via umbilical vein —> half of the blood enters the ductus venosus, which allows blood to bypass the liver —> blood is carried to the inferior vena cava —> right atrium —> right ventricle —> ductus arteriosus (conducts some blood from the pulmonary artery to the aorta [bypassing the lungs/fetal pulmonary circulation]) —> aorta
The other half of the blood that didn’t enter the ductus venosus enters the live/portal vein —> right atrium —> foramen ovale (a small opening in the heart which allows blood to bypass pulmonary circulation by entering the left atrium directly from the right atrium since there is no gas exchange in the fetal lung) —> left atrium — > left ventricle —> aorta
Baby’s first breath
CO2 stimulates a baby’s first breath as receptors in the nose detect it and acts as a respiratory stimulant. The temperature change from leaving the womb also stimulates the first breath. Surfactant is especially important here because the first breath is difficult — newborn lungs are collapsed and the airways are small, leading to lots of resistance to air movement.
Cardiac output (CO) equation
Cardiac output (CO) = stroke volume (SV) x heart rate (HR)
Stroke volume
Volume of blood discharged from the ventricles with each contraction
Cardiac output
Volume discharged from the ventricle each minute
Stroke volume equation
Stroke volume = end diastolic volume (EDV) - end systolic volume (ESV)
End diastolic volume (EDV)
Volume of blood in the ventricle just before contraction
End systolic volume (ESV)
Blood in the ventricle at the
end of the contraction/systole
Mean atrial pressure (MAP) equation
Blood pressure (BP) / Mean atrial pressure (MAP) = CO x Systemic Vascular Resistance (SVR)
Systemic Vascular Resistance (SVR)
Resistance controlled by
vasoconstriction/dilation — the larger the diameter, the less resistance
Rh factor; Erythroblastosis fetalis
Another blood antigen; a mother might attack Rh+ antigens in her second fetus, which is a condition known as erythroblastosis fetalis. This condition is also known as Rh incompatibility. The first child that is Rh+ while the mother is Rh- is fine, but during the first childbirth, the blood exposure leads to antibodies that attack the Rh+ fetus during the second childbirth, and can be fatal
Double capillary beds (portal systems)
Occur in the hepatic portal system (stomach/intestines/spleen drain via the hepatic portal vein to capillaries of the liver), and the hypophyseal portal system between the hypothalamus and anterior pituitary gland. Non-mammals also possess a renal portal system.
Movement across capillary beds occurs as follows: Capillary bed pools into another capillary bed (1) —> drains into portal vein —> capillary bed (2) —> drains into vein that returns blood to the heart without first going to the heart (which is beneficial since products are transported in a high concentration to a targeted part of the body without spreading to the entire body. For example, the liver can screen for harmful substances picked up from digestion before the heart pumps these substances everywhere)
Phosphate buffer system
Maintains pH of internal fluids of all cells; H2PO4(-) and HPO4(2-) act as acid and base (amphoteric), and bicarbonate acts as an extracellular buffer!
Hemorrhage (excessive bleeding)
Results in a decrease in arterial pressure which is sensed by arterial baroreceptors. The body wants to compensate for this reduced blood pressure, and does so by increasing the heart rate and system vascular resistance.
i. This makes sense logically: blood pressure has fallen —> the body wants to raise it —> cardiac output and heart rate increase —> this increases stroke volume and system vascular resistance
Blood-brain barrier (BBB)
The blockade of cells that prevents or slows the passage of drugs, ions, and pathogens into the central nervous system. This is permeable to O2, CO2, glucose, and general anesthetics
Osmoregulation
Maintenance of osmotic pressure of fluids by control of water and salt concentrations
Osmoregulation - Marine fish
This body is hypotonic to the environment —> water is constantly lost by osmosis, so these fish are constantly drinking water, rarely urinating, and secreting accumulated salts through gills
Osmoregulation - Fresh water fish
Body is hypertonic to the environment —> water moves in, so the fish are rarely drinking water, constantly urinating, and absorbing salt though gills
Invertebrate Excretion - Protozoans and Cnidarians
All cells are in contact with external, aqueous environment.
i. Have water soluble wastes (ammonia, CO2) that exit via simple diffusion
ii. Protists such as paramecium and amoebas possess contractile vacuoles for excess H2O excretion via active transport
Invertebrate Excretion - Annelids
Excrete CO2 directly through moist skin
Invertebrate Excretion - Annelids - Nephridia (metanephridia)
Functional unit of excretion that occur in pairs within each segment of annelids (earthworms).
a. Interstitial fluids enter a
nephridium through a ciliated opening called a nephrostome and concentrate through a collecting tubule due to selective secretion into surrounding coelomic fluid. Blood that surrounds the tubule reabsorbs the fluid. Water, salts, and urea are excreted through an excretory pore.
Invertebrate Excretion - Platyhelminthes
Possess flame cells/ flame bulbs, which are bundles of flame cells that combine to form protonephridia, that are distributed along a branched tube system that permeates the flatworm
i. Body fluids are filtered across flame cells, whose cilia move fluids through the tube system; wastes exit through pores of the tube (these are also found in Rotifera)
Invertebrate Excretion - Arthropods
CO2 is released from tissue via trachea, which lead to the external air via spiracles
Invertebrate Excretion - Arthropods - Malpighian tubules
Found in arthropods (terrestrial insects) and are tubules that attach to the mid digestive tract (midgut) and collect body fluids from the hemolymph that bathes the cells. The fluids are deposited into the midgut
a. Fluids include nitrogenous wastes including uric acid crystals (formed from water and retained salts). As fluids pass through the hind-gut, retained materials pass out of walls and wastes continue down the tract for excretion through the anus
b. Aquatic crustaceans use green glands instead, which function similar to malpighian tubules
Nitrogenous waste
Nitrogenous waste is usually converted to ammonia, which is also toxic. Excretion handling is varied depending on the organism.
Excretion in Humans - Lungs
CO2 and H2O (gas) diffuse from the blood and are continually exhaled
Excretion in Humans - Liver
Largest internal organ that processes nitrogenous wastes, blood pigment wastes, other chemicals, produces urea via the urea cycle
Excretion in Humans - Skin
Sweat glands in the skin excrete water and dissolved salts to regulate body temperature
i. Is the largest organ overall
ii. Sweat gland function decreases as we age
Excretion in Humans - Kidney regions
i. The outer cortex
ii. Inner medulla
iii. Renal pelvis which drains to the ureter
Nephrons
Each kidney has many nephrons, the functional unit of the kidney. Composed of a renal corpuscle and renal tubule, and function to reabsorb nutrients, salts, and water
Kidney functions
i. Excrete waste via the path - kidneys —> ureter —> bladder —> urethra
ii. Maintain homeostasis of body fluid volume and solute composition
iii. Regulate blood pressure
Renal corpuscle
Contains the glomerulus, which acts as a sieve, and Bowman’s capsule, which encloses the glomerulus. Bowman’s capsule also contains two arterioles: an afferent arteriole that leads into the glomerulus, and an efferent arteriole that leads out of the glomerulus
Hydrostatic pressure in renal corpuscle
Hydrostatic pressure forces plasma through the fenestrations (small pores) of the glomerular endothelium, and into Bowman’s capsule. These fenestrations screen out blood cells and large proteins from entering Bowman’s capsule
a. The fluid that does get in is called the filtrate/primary urine.
b. Podocytes are cells in Bowman’s capsule that filter blood and hold back large molecules (proteins) and allow smaller molecules (sugars, water, salts) through
Efferent arteriole
After the efferent arteriole passes back out of the glomerulus, it webs around the entire nephron structure as the peritubular capillaries (which surround the proximal convoluted tubule and distal convoluted tubule and reabsorb materials) and vasa recta (which surrounds the Loop of Henle in the kidney’s medulla and maintains the concentration gradient) before dumping back into the renal branch of the renal vein
Renal tubule
Contains Proximal convoluted tubule (PCT), Loop of Henle, Distal convoluted tubule
(DCT), Collecting duct
Proximal convoluted tubule (PCT)
Where active reabsorption of almost all glucose, amino acids, and some NaCl, as well as passive reabsorption of K+ and HCO3- begins. Water follows these ions out so the cortex is not salty. Most reabsorption takes place here
a. Drugs, toxins, NH3 also get secreted into the filtrate; H+ ions are secreted in as well as via anti- port with Na+
b. The net result of the PCT is to reduce the amount of filtrate, but the concentration stays roughly the same
c. PCT cells have a lot of mitochondria due to all of the active reabsorption that takes place here
Loop of Henle
Makes up a majority of the nephron
Descending loop of Henle
Is only permeable to water (but this water is picked up by the vasa recta so the medulla stays salty) via lots of aquaporins. The solute concentration in the tube increases as a result
Ascending loop of Henle
Makes the renal medulla salty: first passively and then actively by pumping out NaCl. The ascending loop is also impermeable to water! Solute concentration in the tube decreases as a result.
Distal convoluted tubule
DCT
More reabsorption of glucose, ions and water occurs here so the cortex isn’t salty. The filtrate (NaCl and HCO3-) get actively pulled out and reabsorbed into the body, and K+/H+ are actively secreted into the tubule. Some water passively gets pulled out, but overall, the filtrate concentration is lowered.
Aldosterone, and to a lesser extent ADH, can act on the end of the distal tubule to increase its permeability to water, which is normally not permeable. Aldosterone increases the amount of Na+/K+ antiport — more K+ gets secreted into the tubule as more Na+ is resorbed from the tubule. Water follows the Na+ out and the concentration of the filtrate increases.
Collecting duct
Collects the remaining filtrate. What happens here (concentrated or dilute urine) is highly dependent on what hormones are acting on it.
a. We can have resorption of NaCl at the upper part of the medulla, and the collecting duct is largely impermeable to water unless ADH acts on it. The body uses ADH to control how much water we retain.
b. Urea is also resorbed here which maintains the medulla’s osmolarity (although sometimes it can re- enter the tubule at the Loop of Henle — a phenomenon known as urea recycling)
Path of urea through collecting duct
- Urea first descends to the medulla (salty part) where antidiuretic hormones (ADH/vasopressin) can make more water leave from urine by increasing permeability of the collecting duct (via increased aquaporins) —> urine is even more concentrated. Note that one collecting duct is shared by many nephrons.
- Aldosterone can also act on the collecting duct by increasing Na+ reabsorption, resulting in water passively following Na+
- By the time urine emerges, it usually has varying amounts of: H2O, urea, NaCl, K+, and creatinine
Alcohol
Alcohol blocks the creation of vasopressin and leads to more urine output since less H2O is resorbed by the body!
Urine formation
Filtration, reabsorption, secretion, and concentration
Filtration
The fluid that goes through the glomerulus (afferent arteriole —> glomerulus —> efferent arteriole) to the rest of the nephron is called filtrate, which is pushed into Bowman’s capsule. Particles that are too large to filter through the glomerulus (such as blood cells or albumin) remain in the circulatory system. This is a passive process that is driven by the hydrostatic pressure of blood.
Reabsorption
Glucose, salts, and amino acids are reabsorbed from filtrate and return to the blood. This process takes place primarily in the PCT via active transport.
The only passive transport here is the movement of water and the leaving of bicarbonate
At the DCT, NaCl and bicarbonate are actively reabsorbed, allowing water to passively follow
To reabsorb something means to bring it back into the blood
Secretion
Substances such as acids, bases, ammonia, drugs, and ions are secreted by both passive and active transport from the peritubular capillaries and into the nephron.
To secrete is to remove a substance from the blood
Concentration
When we’re dehydrated, the volume of fluid in the bloodstream is low, so we need to make small amounts of concentrated urine (and increase our blood fluids).
ADH prevents water loss by making the collecting duct more permeable to water. When blood pressure is low, aldosterone increases reabsorption of Na+ by the DCT and collecting duct, which increases water retention
Excretion equation
Excretion = Filtration - Reabsorption + Secretion
Excretion Recap
- Filtration occurs in the renal corpuscle
- Reabsorption/secretion occurs mostly in the PCT
- Filtrate becomes more concentrated as it moves down the Loop of Henle (passive movement of water out of the tube)
- Filtrate becomes more dilute as it moves up the up (passive and active transport of salts out of the Loop, but no movement of water)
- DCT dumps into the collecting duct
- Filtrate becomes more concentrated again as it descends the collecting duct because the surrounding medulla is salty, causing water to leave
- The collecting duct leads to the multiple renal calyces (singular: renal calyx)
- The renal calyx empties into the renal pelvis
- Drains to ureter
- Drains to urinary bladder
- Urethra
Juxtaglomerular Apparatus
The macula densa, an area of closely packed specialized cells lining the DCT, monitor the filtrate pressure in the DCT. If the blood pressure is low, then via the granular cells —> secrete renin —> angiotensin cascade —> tells adrenal cortex to synthesize aldosterone —> more water is reabsorbed from the DCT and the blood pressure rises and is restored to normal
Selective permeability of the tubules establishes an osmolarity gradient in the surrounding interstitial fluid. Urine is hypertonic to the blood and contains a high urea and solute concentration.
Osmolarity Gradient
Created by the entering and exiting of solutes, and increases from the cortex to the medulla
Counter Current Multiplier
Because the descending loop is permeable to water and the ascending loop is permeable to salts and ions, the medulla is very salty and facilitates water reabsorption.
The innervations of the sympathetic nervous system primarily affects the afferent arterioles (constrict it —> reduces urine output)
Amount of fluid filtered, reclaimed and excreted per day by humans
Humans filter and reclaim a lot of fluid from the bloodstream through the kidney each day (~180 liters!) and 1-2 L are excreted per day
Nitrogen
Waste product
Nitrogenous Waste Products - Aquatic animals
Excrete NH3 and NH4 directly into the water
Nitrogenous Waste Products - Mammals, sharks, and amphibians
Convert NH3 into urea
Nitrogenous Waste Products - Birds, insects, reptiles
Secrete uric acid (is insoluble in water and is excreted as a solid to conserve water)
Allantois
A special sac in bird eggs that keeps nitrogenous waste in the form of uric acid away from the embryo
Excretion in Plants
Excess CO2, waste O2, and H2O (gas) leave via diffusion through the stomata and lenticels via transpiration (recall: woody stems have lenticels)
4 main feeding mechanisms of animals
Filter feeding, substrate feeding, fluid feeding, and bulk feeding
Intracellular digestion
Takes place within the cells and occurs in amoeba, paramecium, and porifera. Food is usually phagocytized, and fuses with food vacuoles and lysosomes to break down nutrients
Extracellular digestion
Takes place outside the cells usually in a food compartment continuous with the animal’s body
Platyhelminthes and Cnidaria digestion
Platyhelminthes and Cnidaria, which have two-way gastrovascular cavities rather than one-way canals, use a combination of extracellular (enzymes secreted into gastrovascular cavity, food particles broken down) and intracellular (food particles engulfed and digested in food vacuoles) digestion.
Digestion in unicellular organisms - Amoeba
Food capture via phagocytosis —> food vacuoles —> fuse with lysosomes
Digestion in unicellular organisms - Paramecium
Cilia sweep food into the cytopharynx. Food vacuoles form and move toward the anterior end of the cell
Invertebrate Digestion
Rely on either physical breakdown, which occurs via cutting and grinding in the mouth and churning in the digestive tract, and/or chemical breakdown, which involves enzymatic hydrolysis —> smaller nutrients —> pass through semi-permeable membrane of gut cells to be further metabolized.
Invertebrate Digestion - Cnidarians
Hydra rely on intracellular and extracellular digestion
Invertebrate Digestion - Annelids
Earthworms have a one-way digestive tract
i. Crop - food storage
ii. Gizzard - grind food
iii. Intestine - contains typhlosole to increase surface area for absorption
Invertebrate Digestion - Arthropods
Have jaws for chewing and salivary glands
Invertebrate Digestion -
Molluscs
Have radula, and tongue/ tooth structure that located in the mouth and breaks down food
4 groups of molecules encountered in digestive system in humans
- Starches —> glucose
- Proteins —> amino acids
- Fats —> fatty acids
- Nucleic acids —> nucleotides
Mouth
Salivary amylase breaks down starch into maltose by breaking starch’s alpha-glycosidic bonds. Chewing creates a bolus which is swelled, and also increases the surface area of food, thus exposing it to more enzymes
Pharynx (throat)
Area where food and air passages cross; epiglottis, a flap of tissue that blocks the trachea so only solid and liquid enter, is located here
Esophagus
Tube leading to stomach, food travels by contractions (wave motion peristalsis via smooth muscle), and saliva lubricates this
Stomach
Secretes gastric juice (digestive enzymes and HCl) and food enters the stomach through the lower esophageal/cardiac sphincter. The stomach contains exocrine glands (local secretion by way of duct) within gastric pits (indentation in stomach that denote entrance to the gastric glands) which contain secreting chief cells, parietal cells, G cells, and mucous cells (secrete mucus to prevent backwash)
Stomach - Storage
Stomach contains accordion-like folds that allow 2-4 liters of storage
Stomach - Mixing
Mixes food with H2O and gastric juice, forming chyme, a creamy medium
Stomach - Physical breakdown
Muscles are activated to break down food; HCl denatures proteins and kills bacteria
Stomach - Chemical breakdown
Pepsin (secreted by chief cells) digests proteins; pepsinogen —> pepsin activated by HCl, which is secreted by parietal cells
Stomach - Peptic ulcers
Caused by failure of mucosal lining to protect stomach. Ulcers can also be caused by excess stomach acid or H. Pylori, which can be treated with antibiotics.
Stomach - Controlled release
Chyme enters the small intestine via the pyloric sphincter
Stomach - Mucous cells
A type of stomach cell.
Secretes mucus that lubricates and protects stomach’s epithelial lining from acid environment. Mucus is mainly composed of sticky glycoproteins and electrolytes, and some cells also secrete a small amount of pepsinogen.
Stomach - Chief cells
A type of stomach cell.
Secrete pepsinogen (zymogen precursor to pepsin). Pepsinogen is activated to pepsin by the low pH in stomach, and once active, it begins protein digestion
Stomach - Parietal cells
A type of stomach cell.
Secrete HCl; intrinsic factor that assists ileum’s B-12 absorption. Possess many mitochondria for energy to establish proton gradient
Stomach - G cells
A type of stomach cell.
Secrete gastrin, a large peptide hormone which is absorbed into blood and stimulates parietal cell to secrete HCl
Stomach - ECL cells
A type of stomach cell.
Neuroendocrine cells in the digestive tract; gastrin stimulates them to release histamine which in turn stimulates parietal cells to produce gastric acid
Stomach cells in general
All cell types are affected by acetylcholine, which increases secretion of each cell. Gastrin and histamine also increase HCl secretion
Stomach pH
A full stomach has a pH of 2, which is extremely acidic and beneficial for killing ingested bacteria, and is the optimal pH for pepsin!
Stomach - Rugal folds
Stomach contains these folds / rippled areas to increase the surface area of the stomach lumen
Absorption in the stomach
Protein digestion begins in the stomach, but no absorption occurs in the stomach
Small Intestine
Food goes from the stomach to the small intestine through the pyloric sphincter. The small intestine has 3 portions: the duodenum, jejunum, and the ileum.
Duodenum
Continues breakdown of starches and proteins as well as remaining food types (fats and nucleotides)
Majority of digestion occurs in duodenum
Jejunum
Absorption of nutrients.
Majority of absorption occurs in jejunum
Ileum
Absorption of nutrients, longest portion and contains Peyer’s patches, which are large aggregates of lymphoid tissue
Amount of digestion and absorption in small intestine
90% of digestion and absorption occurs in the small intestine
Ileocecal valve
Small intestine is connected to the large intestine via the ileocecal valve
Structure of small intestine
Wall has finger-like projections called villi that increase the surface area to allow for greater digestion and absorption. Each villi has a lacteal, a lymph vessel surrounded by a capillary network that functions for nutrient absorption. Villi have microvilli, allowing for greater surface area.
Globet Cells
Goblet cells are found in small intestine and secrete mucus to lubricate and protect from mechanical or chemical damage
pH of duodenum
Duodenum has a pH of ~6 mainly due to bicarbonate ions secreted by pancreas.
Small intestine - Enzyme origin
Proteolytic enzymes like proteases, disaccharadidases, lipases, nucleotidades, phosphatases, and nucleosidases
Pancreas
Secretes bicarbonate and acts as an exocrine gland releasing major enzymes from acinar cells via pancreatic duct —> duodenum
Key enzymes of pancreas
The key enzymes of the pancreas include trypsin, chymotrypsin, lipase, pancreatic amylase, and deoxy/ribonucleases.
These enzymes exist as zymogens/ proenzymes (inactive)
Pancreas - Trypsin
Trypsin gets activated by enterokinases (produced by cells of the duodenum) located in the brush border, then activated trypsin activates the other enzymes
Pancreatic juice
Activated enzymes are secreted into the pancreatic juice, an alkaline solution due to the bicarbonate secreted by the pancreas
Pancreas - Enzyme flow
Enzymes flow from the pancreatic duct —> duodenum and the alkaline fluid helps neutralize the acidic chyme in the stomach, providing a better environment to activate pancreatic enzymes
Liver
Produces bile
The liver’s bile and pancreatic digestive enzymes all come together with food in the duodenum; opening is the sphincter of oddi
Bile
Contains no enzymes but emulsifies fats and contains sodium bicarbonate that helps neutralize stomach acid
Storage and flow of bile
Bile is stored in the gall bladder, and will flow out via the cystic duct (which merges with the hepatic duct of the liver) into the common bile duct, which then merges with the pancreatic duct that secretes into the duodenum (biliary flow). Not all bile is stored in the gall bladder, though, as some flows directly out to the duodenum.
Intestinal fluid
Intestinal fluid is aqueous, which causes fat to clump up. Emulsification (due to bile) breaks up the fat into small particles (without chemically modifying it) which exposes a greater surface area for lipase to work on.
Absorption of breakdown products in small intestine
Remainder of small intestine (6m) absorbs breakdown products (villi and microvilli) i. Amino acids and sugars —> capillaries ii. Fatty acids and glycerol —> lymphatic system —> bloodstream
Chyme in intestines
Chyme moves through intestines via peristalsis - segmentation of the small intestine mixes chyme with digestive juices
Large Intestine (colon)
Where water and salts are reabsorbed to form feces; is 1.5 m long, and has four parts: ascending, transverse, descending, and sigmoid.
Major functions are water and electrolyte absorption
Feces storage
Feces stored at the end of large intestine in the rectum —> excreted through the anus.
Diarrhea
Malfunction of large intestine often leads to diarrhea
Healthy feces breakdown
75% water and solid mass containing 30% dead cells, 10-20% fat, 10-20% organic matter, 2-3% protein, 30% roughage (cellulose), and undigested matter (sloughed cells)
Beginning of large intestine
The beginning of the large intestine is the cecum (before the ascending colon), it has an offshoot of unknown function known as the appendix
Large cecum in herbivores
In herbivores, the large cecum functions in cellulose digestion with the help of bacteria
Bacteria (like E. Coli) a symbiont in large intestine
Main source of vitamin K (also produce Vitamin B12, thiamin, riboflavin)
Gastrin
Hormone produced by stomach lining when food reaches or upon sensing of food
Secretin
Local peptide hormone from SI, produced by cells lining duodenum in response to HCl; stimulates pancreas to produce bicarbonate (neutralizes the chyme)
Cholecystokinin
Hormone secreted by small intestine in response to fat digestates; stimulates gallbladder to release bile and pancreas to release its enzymes. Also decreases motility of stomach —> more time for duodenum to digest fat
Gastric Inhibitory Peptide
Hormone produced in response to fat/protein digestates in duodenum; effect = mild decrease of stomach motor activity
Enterogastrone
Enterogastrone is any hormone secreted by the duodenum in response to lipids that inhibits forward movement of chyme. Includes secretin, CCK, GIP, etc. Inhibits peristalsis and acid secretion by the stomach.
Grehlin
Hormone secreted from stomach wall, initiates hunger
Leptin
Hormone secreted from adipose tissue, inhibits hunger
Peptide YY
Hormone secreted from small intestine and is concerned with hunger and lack of hunger
Insulin
Hormone secreted from pancreas, encourages storage of glucose as glycogen in the liver
Epinephrine
Hormone that suppresses hunger
Digestion in Plants and Fungi
Plants have no digestive system, but intracellular processes similar to animals do occur.
Digestion in Plants and Fungi - Intracellular digestion
Store primarily starch in seeds, stems, and roots; when nutrients are required, polymers are broken down (into glucose, fatty acid, glycerol, and amino acids) by enzymatic hydrolysis
Digestion in Plants and Fungi - Extracellular digestion - Fungi (rhizoids of bread molds)
Secrete enzymes into bread, producing simple digestive products which are then absorbed by diffusion into rhizoid
Digestion in Plants and Fungi - Extracellular digestion - Venus flytrap
Enzymes digest trapped fly (serves as nitrate source) still autotrophic though
Liver functions
The liver receives blood from capillary beds of intestines, stomach, spleen, and pancreas via hepatic portal vein —> liver “works on” this blood. The liver is oxygenated by a second blood supply (via hepatic artery). All blood received from liver —> flattened hepatic sinusoids —> hepatic vein —> vena cava.
The liver functions are: Blood storage, blood filtration, carbohydrate metabolism, fat metabolism, protein metabolism, detoxification, erythrocyte destruction, vitamin storage, glycogenesis and glycogenolysis, mobilizes fat or protein for energy, digestive function
All carbohydrates absorbed into the blood are carried by the portal vein to the liver
Liver function - Blood filtration
Kupfer cells (specialized macrophages in liver) phagocytize bacteria picked up in intestines
Liver function - carbohydrate metabolism
Liver maintains normal blood glucose levels via glujconeogeneis (production of glycogen and glucose from noncarbohydrate precursors), glycogenesis, and storage of glycogen (not glucose, it stores as glycogen!)
i. All carbohydrates absorbed into blood are carried by portal vein to the liver
ii. Absorbed galactose + fructose converted to glucose, then stored as glycogen
Liver function - Fat metabolism
Liver synthesizes bile from cholesterol and converts carbohydrates and proteins —> fat. Fat metabolism oxidizes fatty acids for energy, and also forms lipoproteins
Liver function - Protein metabolism
Liver deaminates amino acids, forms urea from ammonia in blood, synthesizes plasma proteins and nonessential amino acids
Urea
Major end product of nitrogen metabolism and is produced here and later transported to the kidneys for excretion
Liver function - Detoxification
Detoxifies chemicals which are excreted by the liver as part of bile (or polarized to be excreted by the kidneys)
Liver function - Erythrocyte destruction
Kupfer cells destroy irregular erythrocytes (but most are destroyed by the spleen)
Liver function - Vitamin storage
Stores vitamin A, D, and B12. The liver also stores iron by combining it with apoferritin —> ferritin
Liver function - Glycogenesis and glycogenolysis
Glycogenesis (formation of glycogen) and glycogenolysis (if blood glucose levels decrease —> glycogen broken down to glucose for release)
Liver function - mobilizes fat or protein for energy
When the liver mobilizes fat or protein for energy, blood acidity increases (ketone bodies are produced —> ketosis/ acidosis results)
Liver function - digestive function
Has digestive function (produces bile), transportation (synthesizes blood plasma proteins like albumin which is important in clotting)
Jaundice
Liver malfunction can lead to jaundice, yellow pigmentation from excess bilirubin (a byproduct of erythrocyte breakdown). Liver malfunction also fails to remove it so it builds up in the blood
Nervous system vs endocrine system
nervous system is responsible fro rapid, direct, and specific communication while the endocrine system relies on slower, more spread out, and long lasting communication via hormones that affect many cells and tissues
Neuron
Consists of several dendrites, a single branched axon, and cell body (soma). Neurons are highly specialized, aren’t able to divide, and are highly dependent on glucose for chemical energy.
i. Use facilitated transport to move glucose from the blood into the cell, but is not uniquely dependent on insulin for this transport.
ii. Contain low stores of glycogen and oxygen, and rely on the blood supply for these nutrients.
Axon hillock
Where the soma connects to the axon; action potentials are generated here
Dendrites
Receive information and transfer it to the cell body
Axon
Transfers impulses away from the cell body
Myelinated axons
Appear white (referred to as white matter)
Neuronal cell bodies
Gray and are not myelinated (gray matter)
Glial cells
Nervous tissue support cells that are capable of cell division
Oligodendrocytes
A type of glial cell
Produce myelin in the central nervous system (CNS)
Schwann cells
A type of glial cell
Produce myelin in the peripheral nervous system (PNS)
Myelin Sheath
Fatty sheaths that act as insulators and are separated by Nodes of Ranvier that allow the action potential to travel continuously down the axon jumping from node to node, a process known as saltatory conduction, that speeds up the impulse
Only vertebrates have myelinated axons
Microglia
A type of glial cell
Phagocytes of the CNS
Ependymal cells
A type of glial cell
Use cilia to circulate cerebrospinal fluid
Satellite cells
A type of glial cell
Groups of cell bodies in the PNS that serve as support cells
Astrocytes
A type of glial cell
Provide physical support to neurons of the CNS and maintain the mineral and nutrient balance
Sensory (afferent) neurons
Receive the initial stimulus from the brain (ex: neurons in the retina of the eye)
Association (interneuron) neurons
Located in the spinal cord and brain, and receive impulses from sensory neurons and send impulses to motor neurons.
i. Are integrators as they evaluate impulses for the appropriate response
ii. 99% of nerves are interneurons
iii. Are found in reflex arcs but some do
not require an interneuron
Motor (efferent) neurons
Travel from the brain and stimulate effectors, which are target cells that elicit some response
i. May stimulate muscles, sweat glands,
or cells in the stomach to secrete gastrin
Nerve impulse
An electrical signal that is transmitted along a nerve fiber, allowing us to send signals to perform actions
Resting membrane potential is negative for the following reasons…
- Neuron membranes are selectively permeable to K+, but only minimally permeable to Na+, which helps maintain the polarization. There are many K+ channels open, allowing the ion to freely flow outward, creating a charge differential across the membrane
- There are negatively charged proteins and nucleic acids residing in the cell
- An Na+/K+ ATPase pump maintains the resting potential; 3Na+ are pumped out for every 2K+ brought in, resulting in the net removal of one positive charge from the intracellular space
Steps of Nerve Impulse Transmission
- Resting potential
- Action potential
- Repolarization
- Hyperpolarization
- Refractory period
Steps of Nerve Impulse Transmission - Resting potential
The normal polarized state of neuron, -70 mV
Steps of Nerve Impulse Transmission - Action potential
a stimulus causes gated ion channels to open and Na+ ions enter the axon, depolarizing the neuron. If the threshold level is reached (-50 mV), an action potential is caused that will result in the opening of voltage gated Na+ channels down the entire length of the neuron All or nothing event!
Steps of Nerve Impulse Transmission - Repolarization
in response to the Na+ flow in, more gated ion channels let K+ out of the cell, restoring polarization
1. Note that Na+ are now IN and the K+
are OUT!
Steps of Nerve Impulse Transmission - Hyperpolarization
by the time channels close, too much K+ is released (~ -80 mV)
Steps of Nerve Impulse Transmission - Refractory period
a period where the neuron will not respond to a new stimulus until Na+/K+ pumps return the ions to their resting potential locations.
Absolute refractory period
where Na+ channels are inactivated and there is no chance of responding to a new stimulus; sets upper limit to action potential frequency
Relative refractory period
an abnormally large stimulus can create an action potential
Refractory period in general
prevents an action potential from moving backwards, even though ions are theoretically rushing in and diffusing in both directions.
K-ATP sensitive channel
will close in the presence of ATP, causing K+ to be unable to escape, thus resulting in depolarization. In beta cells, this depolarization leads to the voltage dependent calcium channel (VDCC) to open, causing the exocytosis of insulin
Electrical Transmission Across a Synapse
a bidirectional action potential that travels along membranes of gap junctions; is less common in the body, fast, and found in cardiac and visceral smooth muscle
Chemical Transmission Across a Synapse
a unidirectional action potential that is most typical in animal cells
Steps of Transmission Across Chemical Synapse
- Ca2+ gates open
- Synaptic vessels release neurotransmitter
- Neurotransmitter binds with postsynaptic receptors
- Postsynaptic membrane is excited or inhibited
- Neurotransmitter is degraded/ recycled/diffused away
Steps of Transmission Across Chemical Synapse - Ca2+ gates open
depolarization allows Ca2+ to enter the cell via VDCC’s (are also found in beta cells!)
Steps of Transmission Across Chemical Synapse - Synaptic vessels release neurotransmitter
influx causes release of neurotransmitters into the synaptic cleft
Steps of Transmission Across Chemical Synapse - Neurotransmitter binds with postsynaptic receptors
diffusion via Brownian motion and binding
Steps of Transmission Across Chemical Synapse - Postsynaptic membrane is excited or inhibited - Excitatory postsynaptic potential (EPSP)
Na+ gates open and membrane is depolarized; if threshold potential is succeeded, an action potential is generated
Steps of Transmission Across Chemical Synapse - Postsynaptic membrane is excited or inhibited - Inhibitory postsynaptic potential (IPSP)
K+ gates open and membrane is hyperpolarized; it becomes more difficult to generate an action potential
Steps of Transmission Across Chemical Synapse - Neurotransmitter is degraded/ recycled/diffused away
neurotransmitters are broken down by enzymes in the cleft, reuptaken, or diffused
Factors that alter the rate at which impulses travel
- Diameter - greater diameter allows an impulse to propagate faster since a larger diameter results in a less resistance to the flow of ions (think of passing water through a large pipe vs a small one)
- Myelination - heavily myelinated axons allow impulses to propagate faster since Na+ ions can’t leak out, thereby driving saltatory conduction to occur faster
Acetylcholine (Ach)
A neurotransmitter
Secreted at neuromuscular junctions and cause muscle contraction or relaxation
i. In parasympathetic nervous system,
and are released from pre and post
ganglionic nerves
ii. Broken down by acetylcholinesterase
and is located on post-synaptic membrane and found in nerve + muscle tissues, central and peripheral tissues, and sensory + motor fibers. Ach binds to Ach receptors on post-synaptic membrane for nerve transmission – acetylcholinesterase breaks down Ach to terminate the signal
Glutamate
An amino acid neurotransmitter
neurotransmitter at the neuromuscular junction in invertebrates, and is the most common CNS neurotransmitter in vertebrates
Gamma aminobutyric acid (GABA)
An amino acid neurotransmitter
inhibitory neurotransmitter among brain neurons
Glycine
An amino acid neurotransmitter
inhibitory neurotransmitter among synapses of the CNS outside the brain
Epinephrine, norepinephrine,
dopamine, and serotonin (5HT)
Amino acid derived (biogenic amines) neurotransmitter
secreted between neurons of the CNS
Epinephrine/norepinephrine act
in the sympathetic nervous system and are released from post ganglionic nerves
Neuropeptides
A neurotransmitter
Short chains of amino acids and are a diverse group including substance P and endorphins
Gases
Unlike most neurotransmitters, these
are not stored in vesicles and are actually synthesized and released on demand! Example: nitric oxide (NO)
Somatic nervous system
Has sensory components which convey sensations from the eyes, nose, and other sensory organs to the brain + motor components transmitting impulses to the skeletal muscles
Autonomic nervous system
Conveys sensory impulses form the blood vessels, heart, organs in the chest, abdomen, and pelvis via nerves to the brain. The motor component transmits signals to end organs.
Central Nervous System (CNS)
Consists of the interneurons, brain, and spinal cord.
Meninges
Part of CNS
Covers the brain and spinal cord
It is a three-layer protective covering
Meninges - Dura mater
Part of CNS
outermost layer; thick, protects brain and spinal cord, has vein-like structures to carry blood from brain back to heart
Meninges - Arachnoid mater
Part of CNS
middle layer with a spiderweb-like appearance
Meninges - space between arachnoid and pia mater
Part of CNS
space filled with cerebrospinal fluid (CSF) which is produced by tissue called choroid plexus in fluid-filled compartments in the CNS called ventricles
a. Brain floats in CSF, which acts as a cushion and shock absorber; CSF also circulates chemical substances throughout the brain and into the spinal cord
Meninges - Pia mater
Part of CNS
a delicate innermost membrane covering the brain and spinal cord
Brain
Part of CNS
has outer grey matter (cell bodies) and inner white matter (axons); consists of forebrain, midbrain, and hindbrain
Brain - Forebrain
Part of CNS
largest and most important brain region; contains the cerebrum
Brain - Forebrain - Cerebral cortex
Part of CNS
Processes sensory input, important for perception, memory, voluntary movement, and learning
Brain - Forebrain - Olfactory bulb
Part of CNS
smell
Brain - Forebrain - Thalamus
Part of CNS
Relays sensory information between spinal cord and cerebral cortex
Brain - Forebrain - Hypothalamus
Part of CNS
responsible for visceral function such as water balance, blood pressure regulation, temperature regulation, hunger, thirst, sex, circadian rhythms — circadian rhythms coordinated suprachiasmatic nucleus
Brain - Forebrain - Basal ganglia
Part of CNS
Centers for planning/learning movement sequences
Brain - Forebrain - Hippocampus
Part of CNS
memory consolidation and spatial navigation
Brain - Midbrain
Part of CNS
relay center for visual and auditory impulses, and motor control
Brain - Hindbrain
Part of CNS
posterior part of the brain
Brain - Hindbrain - Cerebellum
Part of CNS
maintains balance, hand-eye coordination, timing of rapid movements, and motor skills
The cerebellum doesn’t initiate movement, but it does help to coordinate it
Brain - Hindbrain - Pons
Part of CNS
relay center to allow communication between the cortex and cerebellum
Brain - Hindbrain - Medulla oblongata
Part of CNS
regulates breathing, heart rate, and gastrointestinal activity
Brain - Hindbrain - Brainstem
Part of CNS
consists of the midbrain, medulla oblongata, and pons; connects the cerebrum with the spinal cord and is part of the reticular formation, which is a network of neurons within the brainstem that regulates sleep and arousal
Spinal cord
Part of CNS
a bundle of nerves (does not include the bony spine/ vertebral column) with the outer area of the cord consisting of white matter, and the inner consisting of gray matter; contains two horns:
i. Dorsal horn - sensory info enters
here
ii. Ventral horn - motor information exists here
Brain lobes in general
Part of CNS
The cerebrum, the largest part of the brain with two hemispheres and connected by the corpus collosum (thick nerve bundle) is divided by lobes
Frontal lobe
Part of CNS
responsible for conscious though (attention), initiates voluntary skeletal muscle movement via motor cortex, contains olfactory bulb for smell, Broca’s area for forming speech is found here, and contains the prefrontal cortex for decision making and planning
Parietal lobe
Part of CNS
contains the sensory areas
Parietal lobe - Somatosensation
Part of CNS
temperature, touch, pressure, and pain
Parietal lobe - Proprioception
Part of CNS
orientation of body parts in space
Parietal lobe - Somatosensory cortex
Part of CNS
receives and processes sensory information from entire body
Temporal lobe
Part of CNS
processes and interprets sounds
Temporal lobe - Wernicke’s area
Part of CNS
understanding speech
Temporal lobe - Hippocampus
Part of CNS
memory formation
Temporal lobe - Auditory cortex
Part of CNS
processes auditory information in humans
Occipital lobe
Part of CNS
processes and interprets visual input, responsible for object recognition, responds to visual stimuli
Occipital lobe - Visual association cortex
Part of CNS
processes vision
cerebrum
Part of CNS
has an outer portion (cerebral cortex made of gray matter) and an inner portion (white matter) and basal ganglia. The cerebrum contains sensory, motor, and association areas
Amygdala
Part of CNS
The base of the cerebrum contains the amygdala, a mass of nuclei responsible for emotional memory
Peripheral Nervous System (PNS)
Consists of the somatic and autonomic branches, both of which have sensory and motor sub- branches
Sympathetic
Part of PNS
Responsible for fight or flight response by doing the following:
a. Increasing blood pressure and heart rate
b. Ejaculating
c. Generating energy (liver converts glycogen —> glucose)
d. Inhibiting digestion, urination, and salivary secretion
Parasympathetic
Part of PNS
Responsible for rest and digest activities by doing the following:
a. Lowering heart rate
b. Increasing digestion, relaxation, and sexual arousal
Nerves of sympathetic nervous system
Part of PNS
a. Preganglionic - originate in and exit the CNS midway through the spinal cord and form synapses in ganglia (with postganglionic nerves) just outside the spinal cord; release acetylcholine. Short preganglionic neuron
b. Postganglionic - release epinephrine/norepinephrine. Long postganglionic fiber
(Be sure to note the differences in length of the pre and postganglionic nerves of each system!)
Nerves of parasympathetic nervous system
Part of PNS
a. Preganglionic - originate and
exit the CNS from the base of the brain and upper spinal cord and form synapses with ganglia in or near effectors; release acetylcholine. Long preganglionic neuron
b. Postganglionic - release acetylcholine as well (sometimes nitric oxide)
(Be sure to note the differences in length of the pre and postganglionic nerves of each system!)
Acetylcholine receptors
Part of PNS
are called cholinergic receptors and have two types
Nicotinic
Part of PNS. An acetylcholine receptor
found on skeletal muscle and on postganglionic nerves at the ganglia
Muscarinic
Part of PNS. An acetylcholine receptor
found on effectors for the parasympathetic nervous system
Epinephrine and norepinephrine receptors
Part of PNS.
are called adrenergic receptors
Reflex arc
A rapid, involuntary response to a stimulus involving two or three neurons, but the brain does NOT integrate the sensory and motor activities - instead a synapse is made in the spinal cord. Example: knee jerk (patellar) reflex
Mechanoreceptors
A sensory receptor
touch
Thermoreceptors
A sensory receptor
temperature
Nociceptors
A sensory receptor
pain
Electromagnetic receptors
A sensory receptor
light
Chemoreceptors
A sensory receptor
Taste, smell, blood chemistry
Cranial and spinal nerves
They originate in the CNS, but their axons extend beyond the brain and spinal cord, and are thus considered part of the PNS.
There are 12 pairs of cranial nerves and are categorized as sensory, motor, or mixed. There are 31 pairs of spinal nerves divided among the sections of the vertebral column
Vagus nerve
extends from medulla oblongata and innervates parts of the heart, lungs, stomach, intestines, and liver
Sciatic nerve
innervates lower limbs and pelvis
Abducens nerve
serves the somatic muscles surrounding the eyes
Supraorbital nerve
serves structures surrounding the eyes and scalp
Path of Vision
Cornea (focuses light) —> pupil (diameter controlled by the pigmented iris) —> lens (thickness controlled by ciliary muscles; responsible for focusing images) —> retina (light sensitive cells that)
Sclera
Surrounds the eye. Is a connective tissue layer
Choroid
Beneath sclera. Is a vascular layer providing blood and nutrition to the retina
Retina - Cones
responsible for perceiving high-
intensity illumination and are sensitive to color
Retina - Rods
receptive to low-intensity light; are important in night vision and do not perceive color
i. Rods perceive light via the pigment
rhodopsin which, when struck by photons of light, causes hyperpolarization transduced into a neural action potential sent to the brain
ii. Photoreceptor cells synapse to bipolar cells —> ganglion cells —> axons of ganglion cells bundle to form the optic nerve
a. The point at which optic nerve exits is the blind spot, at which no photoreceptors are found
Retina - Fovea
Area with the most dense concentration of cones and is important for high acuity vision
Vitreous humor
jelly-like liquid between the lens and retina that maintains eye shape and has optical properties; makes up most of the eye volume
Aqueous humor
watery liquid that fills anterior chamber between the lens and cornea; the eye produces this in order to maintain intraocular pressure and provide nutrients to the avascular ocular tissues
Myopia
nearsightedness
Hyperopia
farsightedness
Astigmatism
irregularly shaped cornea
Cataracts
lens becomes opaque and light cannot enter
Glaucoma
an increase in pressure of the eye due to blocking of outflow of aqueous humor
Ear
three main parts: the outer, middle, and inner, and functions to transduce sound energy into impulses
Outer ear
contains the auricle/pinna (what we think of as the ear) and auditory canal; directs sound into the external auditory canal —> middle ear
Middle ear
amplifies sound; the tympanic membrane (eardrum) begins in the middle eat and vibrates at the same frequency as the incoming sound —> three tiny bones, ossicles, (malleus, incus, and stapes) —> inner ear
Inner ear
waves move through the cochlea (vibration of ossicles exert pressure on the fluid). As the wave moves through alternating pressures, motion is creating along the basilar membrane. This movement is detected by hair cells (not actual hair cells, but specialized stereocilia cells) of the organ of Corti —> transduced neural signal —> action potential
a. The inner ear also contains semicircular canals which are responsible for balance (fluid + hair cells sense orientation and motion)
olfaction
smell
gustation
taste
papillae
Papillae of the tongue contain the taste buds
Unicellular Locomotion - Protozoans and primitive algae
use cilia or flagella by means of a power stroke and recovery stroke
Unicellular Locomotion - Amoeba
extend pseudopodia, in which the advancing cell membrane extends forward
Invertebrate Locomotion - Flatworms
contain longitudinal and circular bi-layered muscles that contract agains the hydrostatic skeleton
Contraction causes the hydrostatic skeleton to flow longitudinally, lengthening the animal
Invertebrate Locomotion - Annelids (segmented worms)
advance by action of muscles on hydrostatic skeletons
a. Bristles in the lower part of each
segment, known as setae, anchor worm in the earth while muscles push ahead
b. Worms also use peristalsis of longitudinal and circular muscles to worm
Muscle contractions result in…
movement, stabilization of position, movement of substances throughout the body, and generation of body heat
Muscular System
Consists of contractile fibers held together by connective tissue, and muscles covered by a loose connective tissue known as fascia.
There are 3 types of muscles: skeletal, cardiac, and smooth.
Skeletal muscle (striated muscle)
involved in voluntary movement and contain fibers with multinucleate cells.
Skeletal muscle (striated muscle) - Myofibrils
filaments are divided into sarcomeres
Skeletal muscle (striated muscle) - Sarcomeres
individual contractile units separated by a border (Z-line)
structure unit of a myofibril in striated muscle and is composed of thin filaments (made of actin polymers) and thick filaments (made of the protein myosin)
- Z line - boundary of a single sarcomere and anchors thin filaments
- M line - center of sarcomere
- I band - region containing thin
filaments (actin) only (on the ends) - H zone - region containing thick filaments (myosin) only (in middle)
- A band - area where actin and myosin overlap
Note that H and I reduce during contraction, while A does not
Striations are the result of alternating thin actin + thick myosin (I bands and A bands)
Skeletal muscle (striated muscle) - Sarcoplasm reticulum
stores Ca2+ and surrounds myofibrils
Skeletal muscle (striated muscle) - Sarcoplasm
same thing as cytoplasm, but referred to as
sarcoplasm in muscles
Skeletal muscle (striated muscle) - Sarcolemma
plasma membrane of muscle cells that can propagate action potentials
specialized cell membrane which surrounds striated muscle fiber cells
a. Invaginated by T-tubules - these
are channels for ion flow
b. Muscle cell/muscle fiber - Sarcolemma wraps several myofibrils together to form this
Skeletal muscle (striated muscle) - Mitochondria
Present in large amounts in myofibrils
Contraction of skeletal muscles
squeeze blood and lymph vessels, aiding in circulation. Occurs via the sliding filament model
All steps of contraction - skeletal muscles
- Action potential of a neuron releases acetylcholine when it meets a neuromuscular junction
- An action potential is then generated on the sarcolemma and travels throughout T- tubules
- The sarcoplasmic reticulum releases Ca2+
- Myosin cross bridges form, resulting in Ca2+ binding to troponin on an actin helix
- At the end of each contraction cycle, Ca2+ is actively pumped back into the sarcoplasmic reticulum
Sliding Filament Model steps
- ATP binds to the myosin head
- Ca2+ exposes binding sites on actin
- Cross bridges between myosin heads and actin filaments form
- ADP + Pi are released
- New ATP attaches to the myosin head, causing cross bridges to unbind
Sliding Filament Model steps - 1. ATP binds to the myosin head
- ATP binds to the myosin head - initially, the myosin head is bound to the actin filament from the previous contraction. When ATP binds to the myosin head, myosin and actin unbind. When ATP is converted to ADP + Pi, the myosin head is cocked back
i. Note that after death, ATP production ceases. The cross bridges remain locked in place because no ATP is available to bind to the myosin head and make it unbind!
Sliding Filament Model steps - 2. Ca2+ exposes binding sites on actin
- Ca2+ exposes binding sites on actin - Ca2+ binds to troponin —> pulls back tropomyosin —> exposes attachment sites of actin
Sliding Filament Model steps - 4. ADP + Pi are released
- ADP + Pi are released - the sliding motion of actin brings Z lines together (contraction, power stroke)
Sliding Filament Model steps - 5. New ATP attaches to the myosin head, causing cross bridges to unbind
- New ATP attaches to the myosin head, causing cross bridges to unbind - new phosphorylation breaks cross bridge
Strength of contraction
The strength of contraction of a single muscle fiber cannot be increased, but the strength of overall contraction can be increased by recruiting more muscle fibers. Muscle fibers of a single muscle don’t all contract at once.
The force of contraction depends on the number and size of active motor units and frequency of action potentials.
Motor Unit
A motor unit is a neuron and the muscle fibers it innervates. Each muscle fiber (cell) forms synapses with only one motor neuron, but each motor neuron typically synapses with many muscle fibers
Smaller motor units tend to be activated first, and larger ones are recruited as needed.
Intricate movements tend to use smaller motor units (such as in the finger) whereas muscles requiring greater force (like the back) have larger motor units.
Twitch
There is a smooth increase in force generated — from slow twitch to fast twitch. A twitch occurs when one muscle fiber contracts in response to a stimulus.
Recruitment
Recruitment occurs when a greater quantity of muscle fibers are activated by the brain rather than an increase in frequency of action potentials that stimulate muscle fiber contraction.
Simple twitch
response of a single muscle fiber to brief stimulus; the steps are the latent phase, contraction, and relaxation
Simple twitch - Latent period
time between stimulation and onset of contraction; lag
An action potential spreads on the sarcolemma and Ca2+ ions are released
Simple twitch - Contraction
Muscle contracts following sliding filament model
Simple twitch - Relaxation (absolute refractory period)
Time where the muscle in unresponsive to a stimulus
Summation
contractions combine and become stronger and more prolonged (repeated action potentials summate)
Repeated twitch contractions, where the previous twitch has not relaxed completely
See graph
Tetanus
continuous sustained contraction where a muscle cannot relax and will release if maintained
a. In tetanus, the rate of muscle
stimulation is so fast that twitches blend together into one smooth constant
See graph
Tonus
State of partial contraction where the muscle is never completely relaxed
Sub-threshold stimuli
no motor units respond
Threshold
one motor unit responds
Sub-maximal
an increasing number of motor units respond
Maximal
all motor units respond
Supra-maximal
all motor units respond
a stimulus having strength significantly above that required to activate all the nerve or muscle fibers
Speed and amplitude during action potential, and intensity.
Speed and amplitude remain constant during an action potential
As stimulus intensity increases, the number of action potentials increases.
Type I muscle
i. Slow twitch
ii. Lots of myoglobin
iii. Lots of mitochondria
iv. Aerobic endurance - they split ATP at
a slow rate, causing type I fibers to be slow to fatigue but have slow contraction velocity
v. Appear red
vi. Small diameter
Type IIA muscle
i. Fast twitch
ii. Lots of myoglobin
iii. Less endurance than type I - can use
aerobic and anaerobic unequally; split ATP at a high rate and contract rapidly; faster to fatigue
iv. Appear reddish pink
v. Intermediate in diameter
Type IIB muscle
i. Fast twitch
ii. Low myoglobin - use glycolysis
(primarily use anaerobic)
iii. Lots of glycogen - generates power
iv. Split ATP at fast rate
v. Fastest to fatigue
vi. Appear white
vii. Large diameter
Adult human skeletal muscle
Adult human skeletal muscle generally doesn’t undergo mitosis to create new muscle cells (hyperplasia), but it will increase in size (hypertrophy) which results in an increase in: diameter of muscle fibers, number of sarcomeres and mitochondria, and sarcomere length
Smooth Muscle
Is mainly involuntary, contains one central nucleus, lacks striation, stimulated by the autonomic nervous system (lining of bladder, uterus, digestive tract, blood vessel walls, etc), are slow to contract.
Does not rely on sarcomere organization: intermediate filaments are attached to dense bodies spread throughout the cell.
Can respond to hormones, changes in pH, O2, CO2 levels, temperature, and ion concentration
Does not have T-tubules, striations, troponin, or tropomyosin. It instead uses myosin light change kinase to overcome lack of troponin
Smooth muscle contraction
Thick and thin filaments are attached to intermediate filaments, which contract —> intermediate filaments pull dense bodies together —> smooth muscle length shrinks
Single-unit smooth muscle
visceral; connected by gap junctions, contract as a single unit (found in stomach, uterus, and urinary bladder)
Multi-unit smooth muscle
Each fiber is directly attached to the neuron; can contract independently (found in iris and bronchioles)
Cardiac Muscle
Has a striated appearance due to sarcomeres, has one or two central nuclei, has cells separated by intercalated discs that have gap junctions to allow action potentials to chain flow via electrical synapse, contract involuntarily, and have lots of mitochondria.
Cardiac muscle is not connected to bone, rather it forms a net that contracts upon itself and grows via hypertrophy.
Both smooth and cardiac muscle
Both smooth and cardiac muscle are myogenic, or capable of contracting without stimuli from nerve cells
Exoskeleton
A hard covering on the outer surface
Insects and other arthropods have a jointed exoskeleton (cuticle) composed of hard chitin, which necessitates molting for growth. In this process, a non-living coat is secreted by the epidermis, and the hormone ecdysone is involved in insect molting and metamorphosis.
Endoskeleton
the vertebrate skeleton is comprised of an internal skeleton under soft tissue. The two major components are cartilage and bone
Cartilage
Part of endoskeleton
an avascular connective tissue that is soft and flexible, and can be found in the ear, nose, larynx, trachea, and joints
3 types of cartilage
hyaline (most common, reduces friction and absorbs shock in joints), fibrocartilage (fibrous), and elastic
Development of cartilage
arises from mesenchyme tissue that differentiates into chondrocytes. Chondrocytes secrete molecules that form a cartilaginous matrix made of collagen and proteoglycans.
Collagen
present in tissue as a triple helix with special amino acids hydroxyproline and hydroxylysine, ground substance, and elastin fibers
Collagen is the most abundant protein in vertebrates
Composition of cartilage
cartilage is composed primarily of collagen fibers embedded in chondroitin sulfate, and receive nutrients via diffusion.
Surroundings of cartilage
Cartilage is surrounded by a dense fibrous connective tissue called perichondrium
Bone
living connective tissue that is hard and strong while also elastic and lightweight
Bone functions
support soft tissue, protect internal organs, assist in body movement, mineral storage, blood cell production, and energy storage in the form of adipose cells in bone marrow
Bone types
bone can be mature or immature. Woven bone is immature and weak, and is the first bone to form during development and in fracture repair. Woven bone is replaced by lamellar bone which is mature and strong. Spongey and compact bone are types of lamellar bone
Axial skeleton
basic framework of the skeleton that includes the skull, vertebral column, and rib cage
Appendicular skeleton
Bones of appendages, pectoral and pelvic girdles, and everything else that isn’t in the axial skeleton
Sutures
immoveable joins that hold together the bones of the skull
Moveable joints
bones that move relative to each other
Ligaments
A moveable joint.
bone to bone connectors that strengthen joints (the ACL ligament connects the femur to the tibia and limits rotational knee movement)
Tendons
A moveable joint.
Dense connective tissue that connects muscle to bone and bends skeleton at moveable joints
Ball and socket joint
A moveable joint.
The joint at the shoulder is a ball and socket joint (movement in all planes)
Hinge joint
A moveable joint.
The knee is a hinge joint (movement in one plane only)
Origin
Point of attachment of muscle to stationary bone
Insertion
Point of attachment of muscle to bone that moves
Extension
Straightening of joint
Flexion
bending of joint
Foramen
An opening in the bone that allows for the passage of nerves (foramen magnum in the skull allows for the passage of the spinal cord)
Osteoarthritis
Disorder - the cartilage that covers the bone ends of freely moveable joints begins to wear away due to aging
Rheumatoid arthritis
A degenerative disorder with a genetic basis
Male vs female skeletons
The male and female skeletons differ - pelvic bones are lighter and wider in females, and males have more defined features on the skull (prominent jaw and eyebrows)
Fibrous joint
Connects bones without allowing any movement (ex: skull, pelvis, spinous process, and vertebrae)
Cartilaginous joint
Bones are attached by cartilage and allow little movement (ex: spine and ribs)
Synovial joint
Most common type of joint that allows for much more movement as it is filled with synovial fluid that acts as a lubricant
Bone Composition
Bone has four types of cells surrounded by an extensive matrix:
- Osteoprogenitor/osteogenic
- Osteoblasts
- Osteocytes
- Osteoclasts
Osteoprogenitor/osteogenic cells
Cells that are part of the mesenchymal stem cell lineage that differentiate into osteoblasts
Osteoblasts
Secrete collagen and organic compounds upon which bone is formed. These cells are incapable of mitosis. As these cells release matrix materials around themselves, they become enveloped by the metric and differentiate into osteocytes
Osteocytes
Are incapable of mitosis and exchange nutrients and waste material with the blood
Osteoclasts
Resorb (destroy) bone matrix and release minerals back to the blood. These have carbonic anhydrase, and develop from WBC’s called monocytes (hematopoietic stem cell lineage)
Osteoblasts vs osteoclasts
osteoBlasts BUILD bone while osteoClasts CUT (breakdown) bone.
Neither can carry out mitosis
Compact bone
Highly organized, dense bone that doesn’t appear to have cavities from outside. This bone constantly remodels
Compact bone - Haversian canals
Osteoclasts burrow tunnels that form these
canals
Compact bone - Lamellae
Osteoclasts are followed by osteoblasts, which lay down new matrix onto tunnel walls, forming concentric rings or lamellae
Compact bone - Lacunae
Osteocytes trapped between the lamellae reside in a space called the lacunae and exchange nutrients via small canals (canaliculi)
Compact bone - Volkmann’s canals
the Haversian canal contains nerves, blood vessels, and lymph vessels which are connected by Volkmann’s canals
Compact bone - Osteon
The entire system of lamellae + Haversian canals
Compact bone - Medullary cavity
Compact bone surrounds the medullary cavity which is filled with yellow bone marrow that contains adipose cells for fat storage
Spongey (cancellous) bone
less dense bone that consists of an interconnecting lattice of bony spicules called trabeculae.
Spongey bone is filled with red bone marrow, which is the site of hemopoiesis, or RBC development
Long bone
Typically has a long shaft (diaphysis) and two ends, each composed of a metaphysis and epiphysis. A sheet of cartilage is found between the metaphysis and epiphysis, called the epiphyseal plate, which is also the location of bone growth. Bone increases in both length and diameter along the diaphysis as well
Mineral homeostasis
bones function in mineral homeostasis. In the blood, calcium salts are only slightly soluble, and most of the Ca2+ in the body is stored in bone matrix as hydroxyapatite (a calcium phosphate mineral). This matrix, alongside collagen fibers, provides great tensile and compressive strength
i. Calcium phosphate (CaHPO4) is the main calcium compound in bone. 99% of calcium in the body is contained in bones and teeth!
ii. If stress is put on the bone, osteoblasts deposit collagen and release calcium phosphate to strengthen the bone — the mineral hydroxyapatite is produced.
iii. Bones can be made from a combination of compact and spongey bone
Bone Formation
There are two routes for bone formation, both of which occur during the fetal stage of development
- Endochrondral ossification
- Intramembranous ossification
Endochrondral ossification
Cartilage turns into bone (ex: long bones, limbs, fingers, toes)
Intramembranous ossification
Undifferentiated connective tissue is replaced by bone (ex: flat bones, skull, sternum, mandible, clavicles)
Periosteum membrane
Bone is surrounded by the periosteum membrane, which is highly vascularized. Tendons associated with powerful movements highly integrate with it
Osteoporosis
Causes bone density to decrease, and the bone becomes easier to break and fracture. Estrogen can help maintain bone density, but it can increase a female’s risk of blood clots, heart disease, and cancer. To prevent the disease, ensure high calcium and vitamin D intake, and regular exercise
Functions of Skin
- Thermoregulation
- Protection
- Environmental sensory input
- Excretion
- Immunity
- Blood reservoir
- Vitamin D synthesis
Functions of Skin - Thermoregulation and goosebumps
helps regulate body temperature. Blood can be shunted away from the capillaries of the skin to reduce hair loss, hairs can be erected (piloerection) via sympathetic stimulation to trap insulating air next to skin
goosebumps, the piloerection reflex, can occur when cold in response to stress/emotion. The response is believed to be a vestigial reflex that may have been used to make ancestors appear larger to scare off predators.
Functions of Skin - Protection
Skin is a physical barrier to abrasion, bacteria, dehydration, many chemicals, and UV radiation
Functions of Skin - Environmental sensory input
Skin gathers information about the environment by sensing temperature, pressure, pain, and touch
Functions of Skin - Excretion
Water and salts are excreted through the skin, and independent of sweating, we diffuse water out via insensible fluid loss
Functions of Skin - Immunity
Specialized cells of the epidermis are components of the immune system
Functions of Skin - Blood reservoir
Vessels in the dermis hold up to 10% of the blood in a resting adult
Functions of Skin - Vitamin D synthesis
UV radiation activates skin molecules that are precursors to vitamin D
Epidermis
The superficial, avascular epithelial tissue that relies on the dermis for oxygen and nutrients. Exposure of the epidermis to pressure/friction will result in thickening to form a callus.
The epidermis is divided into 5 layers, which are listed here from the top down:
i. Stratum corneum
ii. Stratum lucidum
iii. Stratum granulosum
iv. Stratum spinous (spinosum)
v. Stratum basale (germinativum)
Epidermis - Stratum corneum
25-30 dead layers of variable thickness; filled with keratin and surrounded by lipids. This layer contains lamellar granules to make it water repellant
Epidermis - Stratum lucidum
Only in palms and soles of feet and finger tips, consists of 3-5 layers, and appears clear/dead
Epidermis - Stratum granulosum
3-5 layers of dying cells; lamellar bodies release hydrophobic lipids
Epidermis - Stratum spinous (spinosum)
Contribute to strength and flexibility; 8-10 layers held together by desmosomes which are keratin involving adhesion proteins
Epidermis - Stratum basale (germinativum)
Deepest layer of skin, contains Merkel cells and stem cells that divide to produce keratinocytes; is attached by the basement membrane and melanocytes are found here
a. The keratinocytes are pushed to the top layer and as they rise, they accumulate keratin and die by losing cytoplasm/nucleus/ other organelles. As they move to the outermost layer of the body, they slough off.
Cells of the Epidermis
Keratinocytes, Melanocytes, Langerhans cells, Merkel cells
Keratinocytes
Produce the protein keratin that helps waterproof the skin. As these are pushed to the top layer of skin, they accumulate keratin and die, losing their organelles along the way. Keratin is also the most abundant protein in the epidermis
Melanocytes
Transfer skin pigment melanin to keratinocytes
Langerhans cells
Interact with helper T cells of the immune system
Merkel cells
Attach to sensory neurons and function in touch sensation
Dermis
the second layer of the skin that consists primarily of connective tissue, collagen and elastic fibers, and contains hair follicles, glands, nerves, and blood vessels. The dermis is also highly vascularized and is tightly connected to the epidermis above via the basement membrane
Dermis - Papillary region (top 20%)
Thin vascular network within upward projecting papillae that helps supply nutrients to epidermis and regulates temperature. Papillae also contain Meisner’s corpuscles (sensory touch receptors) and their upward projection is what creates fingerprint ridges (not to be confused with tongue papillae that have taste buds on their surface)
Dermis - Reticular region
Region with dense connective tissue, collagen, and elastic fibers; packed with glands, sweat gland ducts, fat, and hair Follicles; provides strength and elasticity (stretch marks are dermal tears)
Dermis - Tattoos
Tattoos are injected here in the dermis - macrophages eat the ink up and as the wound heals, the dermal fibroblasts lock the ink containing macrophages into a collagen network just beneath the dermis/ epidermis junction
Chameleons
Chameleons can use color change for camouflage and finding a mate. Camouflage cells are located in the dermis in cells called dermal chromatophores
Hypodermis (subcutaneous)
technically not a part of skin, but it is a part of the integumentary system; consist of areolar and adipose tissue, and function in fat storage, act as a heat insulator, and serves as a shock absorber. The hypodermis also contains pressure sensing nerve endings and passages for blood vessels
Sebaceous (oil) glands
glands that are connected to hair follicles and are absent in palms and soles. These glands secrete oil (sebum) that keeps skin relatively acidic to discourage microbial growth, and acne is caused by these glands getting clogged
Sudoriferous (sweat) glands
Eccrine (most of body) and Apocrine
Sudoriferous (sweat) glands - Eccrine
most of body, regulate temperature through perspiration and eliminate urea; open directly to skin
produce your watery sweat
Sudoriferous (sweat) glands - Apocrine
found in armpits, pubic region, and nipples; secretions are more viscous and open to hair follicles
produce your stinky sweat
Ceruminous (wax) glands
found in ear canal and produce a wax-like material that acts as a barrier to entrance
Mammary (milk) glands
secrete milk for breastfeeding
Hair
a column of keratinized cells held tightly together, and stand up via contraction of smooth muscles (arrector/ erector pili)
First degree burn
affects the epithelial layer
Second degree burn
affects the epithelial and part of the dermal layers
Third degree burn
affects both skin layers (epithelial and dermal) and extended into the subcutaneous layer
Centrifuging blood
centrifuging blood results in three parts: plasma, buffy coat (WBC’s), and RBC’s
Hematocrit level
The percentage of blood by volume of RBC’s is referred to as the hematocrit level, and is higher in men
Plasma
Plasma contains matrix (liquid portion) of blood, and includes water, ions, urea, ammonia, and proteins
55% of total blood
Composition:
92% water
1% electrolytes, nutrients, wastes
7% plasma proteins called albumins, clotting factors and immunoglobulins
most plasma proteins are formed in the liver, although gamma globulin that make antibodies are formed in lymph tissue. Plasma proteins act as a source of amino acids for tissue protein replacemen
Albumins
A plasma protein
transport fatty acids and steroids, help regulate osmotic pressure, and the most abundant
Clotting factors
A plasma protein
help control bleeding
Buffy coat
leukocytes and platelets (<1% of total blood)
Erythrocytes
RBC, 45% of total blood
Serum
plasma minus fibrinogen results in serum
Origin of blood cells
All blood cells arise from stem cell precursors in bone marrow; erythrocytes lose their nucleus while still there, and then exit to blood and lose rest of their organelles soon after
First line of defense
surface barriers that prevent the entry of pathogens into the body
nonspecific immunity, and is called innate immunity, which is generalized protection
Second line of defense
the non-specific phagocytes and other internal mechanisms that comprise innate immunity
nonspecific and is also innate.
Innate immunity - skin
physical and hostile barrier covered with oily and acidic (pH 3-5) secretions from sweat glands
Innate immunity - Antimicrobial proteins
lysozyme (saliva, tears) which break down the cell wall of bacteria
Innate immunity - Cilia
line the lungs and serve to sweep invaders out
Innate immunity - Gastric juice
stomach kills most of the microbes we ingest
Innate immunity - Symbiotic bacteria
the bacteria found in the digestive tract and vagina outcompete many other organisms
WBC origin
All WBC’s originate from stem cells in bone marrow, but some multiply and become non- naive in the lymph node. Lymph drainage acts as a sewer system of antigens: cell recognizes antigen, goes from naive —> activated. Be sure to know the relative amounts of leukocytes in the blood: erythrocytes > platelets > leukocytes.
WBC - Phagocytes
Engulf foreign particles, bacteria, dead or dying cells via phagocytosis. Macrophages are the largest phagocytes
Neutrophils, Monocytes, Eosinophils, Dendritic cells, Mast cells
WBC - Phagocytes - Neutrophils
function in destruction of pathogens in infected tissues; are drawn to infected/injured areas by chemicals via the process of chemotaxis
a. Neutrophils slip between endothelial cells of capillary and into tissues via diapedesis.
WBC - Phagocytes - Monocytes
Circulate in blood until they move into tissues via diapedesis where they develop into macrophages that phagocytize cell debris and pathogens, which are professional antigen-presenting cells. Monocytes can also give rise to dendritic cells.
WBC - Phagocytes - Eosinophils
Work collectively to surround and destroy multicellular parasites. These are not phagocytes.
WBC - Phagocytes - Dendritic cells
Responsible for the ingestion of pathogens and stimulate acquired immunity. Their main function is to process antigen material and present it on the cell surface to the T cells (T-lymphocytes) of the immune system. They act as messengers between the innate and the adaptive immune systems. Dendritic cells can also have myeloid (from monocyte) or lymphoid lineage
WBC - Phagocytes - Mast cells
Function in allergic response, inflammatory response (histamine release), and anaphylaxis. These reside in tissues
WBC - Lymphocytes
lymphocytes are WBC’s, but are not part of the non-specific second line of defense
WBC - Basophils
Release histamines for inflammatory response, found circulating the blood, and are recruited into tissue when needed. Contain histamine and heparin (which works as an anticoagulant) and several cytokines
WBC - Natural killer cells
other WBCs are called natural killer cells (NK cells) and attach abnormal body cells such as tumors or pathogen-infected tissues
i. After neutrophils and macrophages engulf necrotic tissue + bacteria, they die; these dead leukocytes + necrotic tissue = pus
Complement System
contains ~30 complement proteins that circulate the body and assist in activating the immune response. The proteins circulate in an inactive state and are activated by a substance on microbe surfaces. This activation results in a cascade that attracts phagocytes to foreign cells and helps destroy them by promoting cell lysis.
Complement System - Interferons
secreted by cells invaded by viruses/pathogens that stimulate neighboring cells to produce proteins to defend against the virus. These are also believed to be regulators of the complement system
Inflammatory Response
A series of non-specific events that occur in response to injury or pathogens.
Inflammatory Response - Histamine
secreted by mast cells, which are white blood cells in connective tissue, and cause vasodilation
Inflammatory Response - Vasodilation
stimulated by histamine and increases blood supply to the area, which causes a subsequent increase in temperature that stimulates WBCs that can kill pathogens
Inflammatory Response - Phagocytes
Attracted to injury by chemical gradients of the complement system, and engulf pathogens and damaged cells
Inflammatory Response - Complement
helps phagocytes engulf foreign cells, stimulate basophils to release histamine, and lyse foreign cells
Prostaglandins
Causative agent of the inflammatory response
controls inflammation and blood flow
Lymphokines
Causative agent of the inflammatory response
Activate macrophages
Some pathogens can invade the innate immune system
Some bacteria have an outer capsule preventing molecular recognition and phagocytosis, while others resist breakdown within lysosomes.
Acquired/Adaptive Immunity
Adaptive immunity is the specific third line of dense that develops after the body has been attacked. Here, the immune response targets specific antigens, rather than doing a broad sweep like in the complement system or inflammatory response
Acquired/Adaptive Immunity - Major histocompatibility complex (MHC)
the mechanism by which the immune system is able to differentiate between self and non self. A foreign MHC triggers a T-cell attack.
i. MHC is a collection of glycoprotein that exists on membranes of all body cells. The proteins of a single individual cell are unique (20 genes, each with 50+ alleles, and we are unlikely to have the same cells with the same MHC set as someone else)
ii. MHC also assists with antigen presentation, and is involved in organ transplant or graft rejection.
Acquired/Adaptive Immunity - Lymphocyte
Primary agents of the immune response. Are leukocytes that originate in bone marrow and concentrate in lymphatic tissue such as the lymph nodes, thymus gland, and spleen
Acquired/Adaptive Immunity - B cells (produce antibodies)
originate and mature in the bone marrow, and are activated in response to antigens. The plasma membrane of B cells contain antigen-receptor antibodies, the soluble form of these receptors are antibodies (or immunoglobulins).
Acquired/Adaptive Immunity - B cells (produce antibodies) - Antibodies
Proteins that are specific to each antigen, and have 5 classes: IgA, IgD, IgE, IgG, and IgM. These are Y-shaped proteins with constant and variable regions, and disulfide bonds connect heavy chains to each other, and to light chains.
Antigen vs antibody
antigens are ANTibody GENerators, and are therefore the foreign object in the body. Antibodies are produced in response to antigens
Acquired/Adaptive Immunity - B cells (produce antibodies) - Antibodies - IgG
A class of antibodies
Gross - gross quantities are produced, most abundant antibody (lg) in serum and extravascular spaces. Can cross placenta and are most important in protecting the fetus
the protection of the fetus by the mother’s IgG antibodies is considered passive immunity, because the antibodies in the recipient (fetus) are produced by another individual.
B-cells in fetuses
In fetuses, B-cells mature in the liver and not the bone marrow.
Acquired/Adaptive Immunity - B cells (produce antibodies) - Antibodies - IgA
A class of antibodies
BreAst milk - found in breast milk and other bodily secretions (most abundant Ig in secretions)
Acquired/Adaptive Immunity - B cells (produce antibodies) - Antibodies - IgM
A class of antibodies
Mono - first antibodies produced after initial exposure to antigen
Acquired/Adaptive Immunity - B cells (produce antibodies) - Antibodies - IgE
A class of antibodies
SneEze - related to allergies
Acquired/Adaptive Immunity - B cells (produce antibodies) - Antibodies - IgD
A class of antibodies
Diminished - very few are produced, and the function is not well known
Acquired/Adaptive Immunity - B cells (produce antibodies) - Proliferation
when an antigen binds to a B cell, proliferation, or expansion of the B cell population occurs, thus forming daughter B cells.
Acquired/Adaptive Immunity - B cells (produce antibodies) - Proliferation - Plasma cells
B cells that circulate in blood and release specific free antibodies that dispose of antigens by:
- Preventing virus from blocking to host cell
- Marking the antigen for phagocytosis via macrophage, neutrophil, or natural killer cell (opsonization)
- Lysis by complement proteins (pore formation)
- Agglutination of antigenic substance
- Chemical inactivation (if a toxin)
- Free antibodies may also attach their base to mast cells, and if it encounters an antigen, it releases histamine
Acquired/Adaptive Immunity - B cells (produce antibodies) - Proliferation - Memory cells
long-lived B cells that do not release antibodies in response to immediate antigen invasion. Instead, they circulate the body, proliferate, and respond quickly (via antibody synthesis) to eliminate subsequent invasion by the same antigen.
• The secondary response takes less time (~5 days) thanks to the memory cells which are able to quickly spring into action and release antibodies
Acquired/Adaptive Immunity - T cells
originate in the bone marrow but mature in the thymus. Have antigen receptors but do not make antibodies.
T cells check molecules displayed by non-self cells, and if a T cell binds to a self antigen in the thymus, it is destroyed (negative selection). If not, it is released to circulate in lymphoid tissue, blood or lymph
Acquired/Adaptive Immunity - T cells - Discrimination of self and non-self
i. MHC markers on plasma membrane of cells
ii. When body cell is invaded by a non- self pathogen, it displays a combination of self and non-self markers, and the T cell interprets this as a non-self cell
iii. Cancer cells or tissue transplant cells are often recognized as non-self cells by T cells due to the combination of self and non self markers
Acquired/Adaptive Immunity - T cells - When a T cell encounters a non-self cell, it divides and produces four kinds of cells
i. Cytotoxic T cells
ii. Helper T cells
iii. Suppressor T cells
iv. Memory T cells
Acquired/Adaptive Immunity - T cells - Cytotoxic T cells
A cell type produced when T cell encounters a non-self cell
killer T cells that recognize and destroy by releasing perforin protein that punctures cells (lysis). These can attack many cells because they do not phagocytize their victims
Acquired/Adaptive Immunity - T cells - Helper T cells
A cell type produced when T cell encounters a non-self cell
stimulate activation of B cells, cytotoxic T cells, and suppressor T cells. Are also the target for the virus that causes AIDs (HIV)
Acquired/Adaptive Immunity - T cells - Suppressor T cells
A cell type produced when T cell encounters a non-self cell
play a negative feedback role in the immune system
Acquired/Adaptive Immunity - T cells - Memory T cells
A cell type produced when T cell encounters a non-self cell
similar in function to Memory B cells, which says that: long-lived B cells that do not release antibodies in response to immediate antigen invasion. Instead, they circulate the body, proliferate, and respond quickly (via antibody synthesis) to eliminate subsequent invasion by the same antigen. The secondary response takes less time (~5 days) thanks to the memory cells which are able to quickly spring into action and release antibodies
Acquired/Adaptive Immunity - Natural killer cells
attach virus- infected cells or abnormal body cells (tumors). These cells are part of innate immunity, not specific, and they attack infected body cells, not the microorganisms directly
Acquired/Adaptive Immunity - Clonal selection
occurs when an antigen binds to a B cell, or when a non- self cell binds to a T cell, and the B or T cells divide into daughter cells that bear a “selected” effective antigen receptor. This cell with the selected copy of the receptor reproduces repeatedly to make clones
Responses of Acquired/Adaptive Immune System
- Cell-mediated response
2. Humoral Response (antibody mediated response)
Responses of Acquired/Adaptive Immune System - Cell-mediated response
effective against infected cells, uses mostly T cells and responds to any non-self cells, including cells invaded by pathogen. When the non-self cell binds to a T cell, clonal selection occurs, as well as the following chain of events
i. Produce cytotoxic T cells and helper T cells
ii. Helper T cells bind macrophages, and macrophages engulf pathogens
iii. Helper T cells produce interleukins to stimulate proliferation of T cells, B cells, and macrophages
Responses of Acquired/Adaptive Immune System - Humoral Response (antibody mediated response)
responds to antigens or pathogens that circulate in lymph or blood (such as bacteria, fungi, parasites, viruses, or blood toxins). The following events occur:
i. Macrophage and helper T cells stimulate B cell production
ii. B cells produce plasma cells
iii. B cells produce memory cells
iv. General progression of B cells :
naive —> mature —> plasma —> antibody
v. Note that antibodies are released from plasma cells, are specific for an antigen, and a single B-lymphocyte produces only one antibody type
Comparing B cells and T cells
- B cells can directly bind intact antigens at their receptor sites, but T cells must have the antigen presented as fragments from other cells
- Both T cells (developing in thymus) and B cells (develop in bone marrow) undergo negative selection, as if they bind to self cells too tightly, they are eliminated. T cells also undergo positive selection, which ensures T cells can recognize self cells to some extent
Human Supplements to Immune System - Antibiotics
chemicals derived from bacteria and fungi that are harmful to other microorganisms
Human Supplements to Immune System - Vaccines
stimulate production of memory cells from inactivated viruses or weakened bacteria (artificially active immunity)
vaccines are not just used against viruses, they can be made against bacteria as well (tuberculosis is a bacterial disease whereas chicken/smallpox, rabies, and hepatitis are viral diseases)
Human Supplements to Immune System - Vaccines - Inactivated vaccine
consist of an inactivated pathogen that has been destroyed
Human Supplements to Immune System - Vaccines - Attenuated vaccine
contain live pathogens but are disabled in some way to prevent virulence
Human Supplements to Immune System - Vaccines - Toxoid vaccine
can be made from inactivated toxic compounds that cause illness
does not contain the pathogen in any form
Human Supplements to Immune System -
Passive immunity
occurs when antibodies are transferred from another individual (for ex: newborns from mother)
i. Acquired immediately, but short- lived and non-specific
ii. Gamma globulin (blood containing antibodies) can confer temporary protection against hepatitis and other diseases
This is natural
Primary response
Primary Immune Response is the reaction of the immune system when it contacts an antigen for the first time.
primary response requires ~20 days to reach its full potential
Recap of Humoral Response
Imagine you get a bacterial infection. First, the area of the infection becomes inflamed, and macrophages and neutrophils engulf the bacteria. Interstitial fluid is flushed into the lymphatic system where lymphocytes are waiting in lymph nodes. Macrophages process and present the bacterial antigen to B-lymphocytes. With the help of helper T cells, B cells differentiate into plasma and memory cells. Memory cells prepare for the chance that the same bacteria could attack again, in which case a secondary response would be launched. Plasma cells produce antibodies that are released into the blood to attack the bacteria.
Paracrine System
consists of local mediators that function in the immediate area around the cell from which they were released. These mediators can be proteins, amino acid derivatives, or fatty acids
Mediators include Prostaglandins, growth factors and lymphokines, which are a subset of cytokines produced by T cells
Paracrine System - Prostaglandins
locally acting autocrine/paracrine lipid messenger molecule that has physiological effects such as:
i. Contraction and relaxation of smooth muscle
ii. Platelet aggregation
iii. Inflammation
iv. Fever
v. Pain sensation
Aspirin
Aspirin inhibits prostaglandin synthesis, and is thus considered anti-inflammatory and decreases blood clotting
Cytokines
Cytokines are chemical signaling molecules used in the immune response for immune cells to communicate with one another.
Interleukins
Interleukins are specific types of cytokines.
Interleukin-2
Interleukin-2 primarily triggers the immune system to produce T cells and activates the clonal expansion of B cells; they are made by helper T cells.
Interleukin-1
Interleukin-1 is involved with the acute-phase response that accompanies inflammatory reactions. IL-1, made by macrophages, causes neurons in the hypothalamus to raise the body temperature several degrees above normal to impede growth of microorganisms.
Macrophages also release other types of cytokines that activate T helper cells or activate B cells.
Endocrine
synthesizes and secretes hormones into the bloodstream
Exocrine
secretes enzymes into ducts (ex: gallbladder)
i. Sudoriferous, sebaceous, mucus,
digestive, and mammary glands are examples
Paracrine
Cell signaling where the target is nearby
Autocrine
cell signaling via hormone or chemical messenger that binds to receptors on the same cell
Hormone
are transported throughout the body in blood, a small amount has a large impact, and compared to the nervous system, the endocrine system is slower, indirect, and longer lasting
3 hormone categories
Peptide hormones, Steroid hormones, Tyrosine derivatives
Peptide hormones - synthesis and modification
synthesized in the rough ER and modified in Golgi (requires vesicles to cross membrane)
Manufactured in rough ER as a larger pre-prohormone —> cleaved in ER lumen to prohormone —> cleaved again and modified with carbohydrates in Golgi to final form —> packaged by Golgi into secretory vesicles for release via exocytosis
Peptide hormones - solubility
Peptide hormones are water soluble, and can move freely though blood but can’t diffuse well through cell membrane of effector (target cell). Instead they attach to membrane- bound receptor —> can trigger one of several effects
a. Receptor may act as an ion channel, increasing membrane permeability to specific ions
b. Receptors may activate or deactivate other intrinsic membrane proteins to act as ion channels
c. Receptor may activate intracellular second messenger systems (hormone is the ‘first’ messenger, and other chemicals act as the ‘second’ messenger) that can create cascade of effects
Peptide hormones act on surface receptors typically via secondary messengers (ex: cyclic AMP)
Peptide hormones - Receptor mediated endocytosis example
protein stimulates production of second messengers (G protein —> cAMP produced from ATP; IP3 produced from membrane phospholipids which triggers Ca release from ER)
a. Note that a G protein doesn’t phosphorylate GDP —> GTP; GDP is swapped for GTP, which activates the G protein
Pancreas - Endocrine or exocrine?
The pancreases is both an exocrine and endocrine gland - it releases digestive enzymes via the pancreatic duct, and insulin + glucagon into blood
Peptide hormones in Anterior pituitary
follicle stimulating hormone (FSH), luteinizing hormone (LH), adrenocorticotropic hormone (ACTH), human growth hormone (hGH), thyroid stimulating hormone (TSH), prolactin
Peptide hormones in Posterior pituitary
anti-diuretic hormone (ADH), parathyroid hormone (PTH)
Peptide hormones in Pancreas
glucagon, and insulin
Steroid hormones
synthesized from cholesterol in the smooth ER; are hydrophobic, which means they freely diffuse but require a protein transport molecule to dissolve in blood; have intracellular receptors
Steroid hormones - Direct stimulation
steroid hormone diffuses past the plasma membrane and binds to receptors in the cytoplasm —> hormone + receptor are transported to the nucleus —> binding activates a portion of DNA, acting at the transcription level
Steroid hormones in adrenal cortex
glucocorticoids and mineralocorticoids (cortisol and aldosterone)
Steroid hormones in Gonads
estrogen, progesterone, testosterone (estrogen and progesterone are also produced by the placenta)
Tyrosine derivatives
hormone type formed by enzymes in cytosol or on the rough ER
Tyrosine derivatives - Thyroid hormones
lipid soluble, require a protein carrier in the blood, and bind to receptors in the nucleus. The response has a latent period and increased duration. These hormones increase transcription of many genes in nearly all cells of the body
Tyrosine derivatives - Catecholamines
hormones made by your adrenal glands, which are located on top of your kidneys
examples are epinephrine and norepinephrine, which are tyrosine derivatives that are water soluble, dissolve in blood, bind receptors on target tissue, and mainly act via second messenger cAMP
Tyrosine derivatives - Thyroid hormones
T3 and T4 (thyroxine)
Receptor Specificity of hormones
All hormones bind to receptors highly specific to them. Some hormones have receptors on almost all cells, while some have receptors only on specific tissue
Receptor Specificity of hormones - Receptor location varies
receptors can be on the membrane or inside the cell, and hormone regulation can occur by increasing or decreasing the number of receptors in response to hormone amount.
Hypothalamus
monitors the external environment and internal conditions of the body. The hypothalamus contains neurosecretory cells that link the hypothalamus to the pituitary gland, and is therefore considered the link between the endocrine and nervous system.
The hypothalamus helps to regulate the pituitary via negative feedback mechanisms and by the secretion of releasing and inhibiting hormones.
Hypothalamus - Hormones secreted
ADH (vasopressin) and oxytocin to
be stored in the posterior pituitary
Gonadotropin releasing hormone
(GnRH) from neurons, which stimulates the anterior pituitary to secrete FSH and LH
Anterior Pituitary
mainly regulates hormone production by other glands, and is regulated itself by the hypothalamus
Anterior Pituitary - Direct (non-tropic) hormones
directly stimulate target organs
hGH, Prolactin, Melanocyte stimulating hormone (MSH), Endorphins
Anterior Pituitary - Direct (non-tropic) hormones - hGH
aka somatotropin. stimulates bone and muscle growth
Stimulates growth in almost all cells of the body, and does by increasing episodes of mitosis, cell size, rate of protein synthesis, and use of fatty acids for energy.
hGH also mobilizes fat stores, decreases use of glucose, increases protein transcription/translation, and decreases protein/amino acid breakdown
Anterior Pituitary - Direct (non-tropic) hormones - Prolactin
stimulates milk production in females from mammary gland cells. The hypothalamus can inhibit prolactin release. Suckling stimulates the hypothalamus, which stimulates the anterior pituitary —> release of prolactin. There is no milk production before birth due to inhibitory effects on it by progesterone and estrogen
Anterior Pituitary - Direct (non-tropic) hormones - Melanocyte stimulating hormone (MSH)
stimulates melanocytes to produce and release melanin
Anterior Pituitary - Direct (non-tropic) hormones - Endorphins
inhibit perception of pain (is technically a neurohormone)
Anterior Pituitary - Tropic hormones
stimulate other endocrine glands
ACTH, TSH, LH, FSH
Anterior Pituitary - Tropic hormones - ACTH
stimulates adrenal cortex —> release glucocorticoids via second messenger cAMP. Release of ACTH is stimulated by many types of biological stress, and glucocorticoids are stress hormones
Anterior Pituitary - Tropic hormones - TSH
Stimulates thyroid gland which in turn increases in size, cell number, and rate of secretion of hormones T3 and T4. T3 and T4 concentrations have a negative feedback effect on TSH release at both the anterior pituitary and hypothalamus.
Anterior Pituitary - Tropic hormones - LH
in females, stimulates formation of corpus luteum, and in males, it stimulates interstitial cells of testes to produce testosterone
Anterior Pituitary - Tropic hormones - FSH
in females, stimulates maturation of ovarian follicles to secrete estrogen, and in males, stimulates maturation of seminiferous tubules and sperm production
Posterior Pituitary
composed mainly of support tissue from nerve endings extending from the hypothalamus. Does not synthesize hormones, but stores ADH and oxytocin produced by the hypothalamus.
Posterior Pituitary - ADH/vasopressin
increases reabsorption of water by increasing permeability of the nephron’s collecting duct —> water reabsorption and increased blood volume and pressure. Coffee and alcohol block ADH, therefore increasing urine volume
Posterior Pituitary - Oxytocin
secreted during childbirth, increases strength of uterine contractions and stimulates milk ejection by stimulating contraction of smooth muscle cells in the uterus and mammary glands
Pineal gland
Secretes melatonin which plays a role in the circadian rhythm
i. Note that the hypothalamus, pituitary gland, and pineal gland are the endocrine glands in the human brain
Thyroid
located on the ventral surface of the trachea, just in front of the trachea
The thyroid is the only gland that produces more than one type of hormone (the adrenal cortex and adrenal medulla are considered separate glands)
Thyroid - Thyroxine (T4) and triiodothyronine
T3
are lipid soluble tyrosine derivatives
Derived from tyrosine and necessary for growth and neurological development in children, as well as increasing basal metabolic rate (BMR) in the body (negative feedback on TSH)
These hormones contain iodine
Thyroid - Thyroxine (T4) and triiodothyronine
(T3) - Hypothyroidism
under secretion
—> low heart rate, respiratory
rate, and BMR
Thyroid - Thyroxine (T4) and triiodothyronine
(T3) - Hyperthyroidism
over secretion
—> increased BMR and sweating (both hypo and hyperthyroidism lead to goiter, or enlargement of thyroid gland)
Thyroid - Calcitonin
peptide hormone that ‘tones down’ Ca2+ in blood
a. Stimulates osteoblast activity, which builds up bone by using up the Ca2+ in the blood b. Decreases plasma Ca2+ by inhibiting its release from bone c. Decreases osteoclast activity and number
Thyroid - Disorders of thyroid - Achondroplasia
results in dwarfism
Thyroid - Progeria
premature aging, wrinkled skin, arthritis, and arteriosclerosis
Parathyroid
four pea-shaped structures attached to the back of the thyroid
Parathyroid - Parathyroid hormone (PTH)
antagonistic to calcitonin
a. Raises Ca2+ concentrations in
blood by stimulating relate from bone. This increases osteocyte absorption of Ca2+ phosphate from bone, and stimulates osteoclast proliferation
b. Increases renal Ca2+ reabsorption and renal phosphate excretion
c. Increases Ca2+ phosphate uptake from gut by increasing renal production of vitamin D- derived steroid
d. Secretion is regulated by Ca2+ plasma concentration, and parathyroid glands grow or shrink accordingly
Thymus
involved in immune response, secretes thymosins that stimulate WBCs to become T cells that identify and destroy infected body cells
Adrenal gland
rest on top of the kidneys
Adrenal gland - Adrenal cortex (outer portion)
secretes only steroid hormones
Adrenal gland - Adrenal cortex (outer portion) - Glucocorticoids (cortisol and
cortisone)
raise blood glucose levels, which stimulates glujconeogeneis in the liver, and degrades adipose tissue to fatty acids for use as energy
- Also causes degradation of non hepatic proteins and decrease in non-hepatic amino acids. This results in a corresponding increase in liver/plasma proteins, and amino acids
- Cortisol is a stress hormone
Adrenal gland - Adrenal cortex (outer portion)
- Mineralocorticoids (aldosterone)
- increases reabsorption of Na+ and excretion of K+ in kidneys
• Acts on the distal convoluted
tubule and collecting duct of nephron to increase Na/Cl reabsorption and K+/H+ secretion.
- This net gain in particles in the plasma causes passive reabsorption of water in the nephron —> rise in blood
- Volume/pressure (secondary effect)
- Has the same effect, but to a lesser extend, on sweat/ salivary glands and intestines
Adrenal gland - Adrenal cortex (outer portion) - Cortical sex hormones
androgens are male sex hormones; a small amount is secreted, which is significant in females but not in males, since they have testes producing much more
Adrenal medulla (inner portion) - Epinephrine and norepinephrine (adrenaline and noradrenaline)
fight or flight catecholamines
a. The “fight or flight” response effects target tissue similar to the role in the sympathetic NS, but lasts longer; considered stress hormones
b. Glycogen —> glucose, vasoconstrictor to internal organs + skin, but vasodilator to skeletal muscle; increases heartbeat and blood pressure
c. Increase metabolic activities (glycogenolysis, lipolysis)
d. Increase blood flow to the brain
Pancreas
has bundles of cells called Islet of Langerhans which contain two cell types: alpha and beta cells
Pancreas - Alpha cells
Alpha cells secrete glucagon - catabolic, and released when energy is low, thus raising blood glucose levels
a. Stimulates liver to convert glycogen
—> glucose
b. Stimulates gluconeogenesis in liver
c. Adipose tissue —> blood lipids
Pancreas - Beta cells
Beta cells secrete insulin - anabolic, released when blood levels of carbohydrates/proteins are high, thus lowering blood glucose levels
a. Stimulates levels (and most other body cells) to absorb glucose
b. Liver and muscle cells convert glucose —> glycogen
c. Fat cells convert blood lipids —> adipose tissue storage
d. Works on most body cells (except for neurons of brain and a few others) to become highly permeable to glucose
e. Insulin is derived from pre-proinsulin and pro-insulin. These precursor molecules undergo hydrolysis reaction that modify them to active insulin. Specific protease enzymes cleave two peptide bonds —> allows mature insulin to form
Pancreas - Somatostatin
released by delta cells of pancreas; inhibits both insulin and glucagon; possibly increases nutrient absorption time. Suppresses release of GI hormones, which decreases the rate of gastric emptying and rate of blood flow to intestines
Testis - Testosterone
spermatogenesis, secondary sex characteristics
Ovaries - estrogen
menstrual cycle, secondary sex characteristics
Ovaries - Progesterone
menstrual cycle, pregnancy, regulates formation of internal reproductive structures
Ovaries - Male and female development
in XX organism, the Mullerian duct
differentiates into oviduct, and Wolffian ducts degenerate. In XY, Wolffian develops into male reproductive structures, and Mullerian duct degenerates.
Ovaries - Male and female development - SRY genes
SRY genes are present on Y chromosomes; in its absence, ovaries develop. In its presence, sertoli cells form, which produce a signal that inhibits formation of Mullerian ducts.
Ovaries - Male and female development - Leydig cells
The Leydig cells that form from the presence of the Y chromosome produce testosterone that causes Wolffian duct to further develop
Gastrointestinal hormones - gastrin
breaks down food in stomach, stimulates secretion of HCl
Gastrointestinal hormones - Secretin
small intestine; when acidic food enters from stomach, these neutralizes acidity of chyme by stimulating the release of alkaline bicarbonate from the pancreas
Gastrointestinal hormones - Cholecystokinin
small intestine; presence of fats causes contraction of gall-bladder and release of bile, which is involved in the digestion of fats and tells pancreas to relate enzymes for digestion
