Chapter 11: Animal Form and Function Flashcards
Tissues
=a group of similar cells performing a common function.
- epithelial= outer skin and internal protective coverings
- connective= bone, cartilage, blood
- nervous
- muscle
homeostasis
animal systems contributing toward maintaining stable, internal conditions within narrow limits
negative feedback
original condition is canceled so that conditions are returned to normal
positive feedback
an action intensifies a condition so that it is driven further beyond normal limits (labor contraction,
lactation, and sexual orgasm).
Thermoregulation
Ectotherms – obtain body heat from environment (aka poikilotherms/cold-blooded)
o Invertebrates, amphibians, reptiles, fish
Endotherms – generate their own body heat (aka homeotherms/warm-blooded)
Regulatory mechanisms
o Evaporation – body heat is removed as liquid evaporates (endergonic)
o Metabolism – muscle contraction and other metabolic activities generate heat
o Surface Area – Vasodilation or vasoconstriction of extremity vessels results in heat retention or removal (blood
flow to ears reduce body temp, countercurrent exchange keeps central parts of body warm)
respiration
Respiration: movement of gases in and out; also means cellular respiration producing ATP within mitochondria.
gas exchange mechanisms
Invertebrate Respiration:
Cnidaria: Protozoa and Hydra
o Direct with environment: large surface areas and every cell is either exposed to environment or close to it simple diffusion of gases directly
with outside environment (e.g. flatworms). Small animals only.
Annelids:
o Mucus secreted by earthworm provides moist surface for gaseous exchange by diffusion
o Circulatory system bring O2 to cells and waste products (CO2) back to skin for excretion
Arthropods (80% of all living species – insects, spiders, crustaceans (crabs), etc…
o Grasshopper
Series of chitin-lined respiratory tubules called trachae open to surface in openings called spiracles through with O2 enters, CO2
exits. No oxygen carrier is needed due to direct distribution and removal of respiratory gases between air and body cells; diffusion
across moistened tracheal endings.
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o Spider
Book lungs: stacks of flattened membranes enclosed in internal chamber
Fish
o Water enters mouth, passes over gills (evaginated structures, create large SA, take O2 and deposit CO; can be external/unprotected or
internal/protected), exits through operculum (gill cover). Countercurrent exchange between opposing movements of water and underlying
blood maximizes diffusion of O2 into blood and CO2 into water
4. lungs=invaginated structures
gas exchange in humans
in the plasma (liquid portion of blood), catalyzed by carbonic
anhydrase (CO2 + H2O ↔ H2CO3 ↔ H
+ + HCO3
-
) located in the RBC. Some CO2 mixes direct w/ plasma as gas, or binds with
hemoglobin in RBCs
Alveoli – where gas exchange between the circulatory system and the lungs occurs; surfactant reduces the surface tension (prevents H2O from
collapsing alveoli). There are two types of epithelial cells in human alveoli: type 1 (structural support) and type 2 (produce surfactant)
Nose (filter, moisten, warms incoming air – mucus secreted by goblet cells traps large dust particles here), pharynx (throat – passageway
for food and air; dust/mucus swept back here by cilia for disposal via spitting or swallowing), larynx (voice box- if non-gas enters, cough
reflex activates)
Trachea (epiglottis covers the trachea during swallowing) – ringed cartilage (C-shaped) covered by ciliated mucus cells
Bronchi, Bronchioles: Two 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 across moist, sac membranes of alveoli. O2 diffuses through alveolar wall,
through pulmonary capillary wall, into blood, and into red blood cells. (CO2 is opposite)
Bulk flow of O2: O2 transported through body within hemoglobin containing red blood cells (RBCs)
Diffusion between blood and cells: Oxygen diffuses out of RBCs, across blood capillary walls, into interstitial fluids, and across cell
membranes (CO2 opposite)
Bulk flow of CO2: CO2 mainly transported as HCO3
-
ions in plasma, liquid portion of blood. Produced by carbonic anhydrase in RBCs. CO2
can also directly mix with plasma (as CO2 gas), or bind hemoglobin inside RBCs
Bulk flow of air into and out of the lungs:
a. Inhalation – diaphragm (under lungs) and intercostal muscles (between ribs) contract/ flattens; increase in volume / decrease in
pressure in lungs bulk flow of air into lungs.
b. Exhalation – passive process; decrease in lung volume/ increase in air pressureair rushes out; diaphragm relaxes and expands
open circulatory system
Arthropods- most insects and molluscs o Open circulatory system- pump blood into internal cavity called hemocoel (cavities called sinuses), which bathe tissues in oxygen and nutrient containing fluid (hemolymph). This fluid returns to pumping mechanism (heart) through holes called ostia.
closed circulatory system
Annelids- earthworm
o Closed circulatory system- blood is confined to vessels.
Also seen in certain mollusks (octopus and squid) and vertebrates
Away from heart: aorta arteries arterioles capillaries
Back to heart: capillaries venules veins
Note: human and bird hearts have 4 chambers, reptiles+amphibians 3, fish 2 (but crocs+gators have 4 chambers)
Blood flow in closed system
o Right atrium – deoxygenated blood enters via superior and inferior vena cava
o Right ventricle – blood is squeezed through right AV/tricuspid valve into right ventricle which contracts and
pumps blood into pulmonary artery through the pulmonary semilunar valve.
When the ventricle contracts, AV valve closes to prevent backflow
When ventricle relaxes, semilunar valve prevents backflow from pulmonary artery back into ventricles
o Pulmonary circuit: blood pathway from right side of heart to lungs to left side of heart
Blood flows from pulmonary artery arterioles capillaries of the lungs collects in venules veins
pulmonary veins left atrium
o Systemic circuit is the circulation pathway through the body between left and right sides of heart
o Left atrium – after lungs the oxygenated blood enters left atrium via pulmonary veins
o Left ventricle – after going through left AV(aka mitral or bicuspid) valve, blood from left ventricle goes to aorta
through the aortic semilunar valve into rest of body:
Aorta arteries arterioles capillaries tissues get what they want venules veins superior
and inferior vena cava cycle repeats
As above: left AV valve prevents backlow into atrium, aortic semilunar valve prevents it into ventricle
o So: right/left AV valves and pulmonary/aortic SL valves
cardiac cycle
– regulated (in terms of rate)by autorhythmic cells of the autonomic NS, but contractions are intiated
independently of the autonomic NS. Instead the heart contracts automatically:
o SA (sinoatrial) node, or pacemaker (located in upper wall of right atrium) is a group of specialized cariac muscle
cells that initiates by contracting both atria and sending delayed impulse to stimulate AV (atrioventricular) node.
Spreads contraction to surrounding cardiac muscles via electrical synapses made from gap junctions
Pace of SA node is faster than normal heartbeat but parasympathetic vagus nerve innervates SA node
(also increases digestive activity of intestines); slows contractions
o AV node – located in lower wall of the right atrium/interatrial septa; sends impulse through bundle of His
passes between both ventricles branches into ventricles via the purkinje fibers which results in contraction
o When the ventricles contract (systole phase), blood is forced through pulmonary arteries and aorta
– When they relax (diastole phase), backflow into ventricles causes semilunar valves to close.
Cardiac output: Heart Rate * Stroke Volume. The volume of blood pumped by the ventricle (per min)
Heart rate: number of beats per minute
Stroke volume = EDV - ESV. Volume of blood pumped out of the heart with each beat. Formula subtracts
the End-systolic Volume (blood in the ventricle at the end of the contraction/systole) from the Enddiastolic
Volume (volume of blood in the ventricle just before contraction)
Heart contraction
Heart contraction: heart is a large muscle, but unlike skeletal, not anchored to bone. Its fibers form a net and the net contracts upon itself, which squeezes blood
into arteries.
Systole: occurs when ventricles contract. Diastole: occurs during relaxation of the entire heart and then contraction of the atria.
Hydrostatic pressure from heart contracting causes blood to move through arteries. Blood pressure drops as it reaches the capillaries, and reaches
near zero in the venules. Blood continues to move through veins because of pumping of the heart assisted by movements of adjacent skeletal
muscles, expansion of atria each time heart beats, and falling pressure in chest when a person breathes.Valves in the veins prevent backflow.
lymph vessels
Lymphatic system is an open secondary circulatory system- transports excess interstitial fluids (lymph) through the contraction of adjacent
muscles & some walls of larger lymph vessels have smooth muscle
o Proteins & large particles that can’t be taken up by capillaries removed to lymph; also monitors blood for infxn
o Valves prevent backflow- fluid returns to blood circulatory system through two ducts located in shoulder region (thoracic&right lymphatic duct)
o Lymph nodes contain phagocytic cells (leukocytes) that filter the lymph and serve as immune response centers
excretory system
help maintain homeostasis in organisms by regulating water balance and by removing
harmful substances
osmoregulation
is the absorption and excretion of water and dissolved substances (solutes) so that proper water balance
(and osmotic pressure) is maintained between the organism and its surroundings
a. Marine fish: body is hypotonic to environment water is constantly lost by osmosis, constant drinking, rarely
urinate, and secrete accumulated salts through gills.
b. Fresh water fish: body is hypertonic to environment; water moves in => rarely drink, constantly urinate, and
absorb salts through gills.
nephrons
composed of renal corpuscle and renal tubule; reabsorbs nutrients, salts, and water (image summary here)
Renal corpuscle – glomerulus (sieve) surrounded by Bowman’s capsule; afferent arteriole=into glomerulus; efferent
arteriole=out of glomerulus
o After efferent arteriole passes back out of the glomerulus is just webs around the entire nephron structure
(see above) as the peritubular capillaries (surround PCT and DCT; reabsorb stuff) and vena cava (surround
LOH in medulla, maintain cxn gradient) before dumping back in to the renal branch of renal vein. Meanwhile,
Bowman’s capsule leads to…
Renal tubule –
o Proximal convoluted tubule – active reabsorption of glucose, ions, amino acids begins (water follows
cortex not salty)
Drugs, toxins, etc secreted into filtrate; H+ ions secreted in as well via antiport with Na+
o Loop of Henle (majority of nephron)
DESCENDING – only permeable to water (but this water is picked up by vasa recta medulla stays
salty)
ASCENDING makes renal medulla salty–actively pumps out Na+,K+,Cl-
; impermeable to water!
This process allows reabsorption of 99% of filtrate conc. urine
o Distal convoluted tubule – more reabsorption of glucose, ions, water, etc (cortex not salty).Filtrate: Na+ and
Ca2+ get resorbed into body, K+/H+/HCO3- secreted out via tubule. Distal tubule empties to…
o Collecting duct – collects remaining filtrate. Is ordinarily impermeable to water unless ADH acts on it
Descends to medulla (salty part), where antidiuretic hormones (ADH / vasopressin) can make MORE
water leave from urine by increasing permeability of collecting duct urine even more
concentrated. 1 CD shared by many nephrons
Also, aldosterone acts on DCT and CD: increase Na+ resorbtion, K+ secretion water passively
follows Na+
urine formation
Filtration – The fluid that goes through glomerulus (afferent arteriole => glomerulus => efferent) to the rest of the
nephron is called filtrate; particles that are too large to filter through (blood and albumin) remain in circulatory
system; passive process; driven by hydrostatic pressure of blood. So Glomerulus filtrate pushed into Bowman’s.
Secretion – substances such as acids, bases, and ions (K+) are secreted by both passive / active transport; secreted
from peritubular capillaries
Reabsorption – glucose, salts, AA, and water are reabsorbed from filtrate & return to blood; takes place namely in
PROXIMAL convoluted tubule (active)
Concentration – when dehydrated volume of fluid in bloodstream is low so you need to make small amounts of
concentrated urine => ADH prevents water loss by making distal tubule permeable to water /// when Blood Pressure
is low => aldosterone increases reabsorption of Na+ by distal nephron which increases water retention (serum [Na+]
increases BP)
Antidiuretic hormone (ADH)
- increases the reabsorption of water by the body and increases the concentration of salts in urine.
- it does this by increasing the permeability of the collecting duct to water
- result= urine becomes more concentrated as water diffuses out of the collecting duct as filtrate descents into renal pelvis
aldosterone
- increases both reabsorption of water and the reabsorption of Na+
- increases the permeability of distal convoluted tubule and collecting duct to Na+
- result= more Na+ diffuses out of this tubule and duct, Since Na+ increases as salt concentration outside the tubule, water passively follows
Nitrogen as waste product
- Aquatic animals excrete NH3 or NH4 directly into water,
- mammals convert NH3 to urea,
- Birds/insects/reptiles convert urea to uric acid (insoluble in water, water conservation, excreted as solid)
- Allantois = special sac in bird egg that keeps N waste away from embryo
Four groups of molecules encountered in human digestion
- Starches glucose
- Proteins amino acids
- Fats fatty acids
- Nucleic acids nucleotides
Digestion in humans
gestion follows a specific series of events ***Note – All digestive enzymes cleave SPECIFIC bonds
1. Mouth - salivary a-amylase breaks down (starchmaltose), chewing creates bolus which is swallowed
2. Pharynx (throat) – this is where food and air passages cross; the epiglottis, flap of tissue, blocks trachea so only solid and liquid enter…
3. Esophagus – tube leading to stomach, food travels by contractions (peristalsis),
4. Stomach – secretes gastric juice (digestive enzymes and HCl) – food enters stomach through lower esophageal/cardiac sphincter. The
stomach contains exocrine glands (local secretion by way of duct) within gastric pits (indentations in stomach that denote entrance to the
gastric glands, which contain secreting chief cells, parietal cells, and mucous cells (secrete mucus to prevent backwash)
a. Storage – accordion-like folds allow 2-4 liters of storage
b. Mixing – mixes food w/ H2O and gastric juice chyme (creamy medium)
c. Physical breakdown – muscles break food; HCl denatures proteins & kills bacteria
d. Chemical breakdown – pepsin (secreted by Chief cells) digests proteins; (pepsinogen activated by HCl, which is secreted by
parietal cells)
i. Peptic ulcers – caused by failure of mucosal lining to protect stomach
– Ulcers can be caused by excess stomach acid or H.pylori as well
e. Controlled release – chyme small intestine; controlled by pyloric sphincter
f. Stomach cells
i. Mucous Cells – secrete mucus that lubricates & protects stomach’s epithelial lining from acid environment
ii. Chief Cells – ex.gl. secrete pepsinogen (zymoegn precursor to pepsin).
– Pepsinogen activated to pepsin by low pH in stomach; once active begins protein digestion
iii. Parietal Cells – Secrete HCl; intrinsic factor (B-12 absorption)
iv. G cells – secrete gastrin, a large peptide hormone which is absorbed into blood stims parietal cell to secrete HCl
v. Affected by: A-chol increases secretion of all cell types, gastrin and histamine increase HCl secretion
5. Small intestine – food goes from stomach to small intestine through the pyloric sphincter - first 25cm (duodenum), continues breakdown
of starches and proteins as well as remaining food types (fats and nucleotides); ileocecal valve between it and large intestine. Structure is
duodenum (most digestion), jejunum, then ileum (jej and il mostly absorption). 90% of digestion and absorption occurs in SI; completes.
a. Structure – Wall has finger-like projections called villi that increase the surface area for greater digestion/absorption. Each villi
has a lacteal (lymph vessel surrounded by capillary network; both fxn for nutrient absorption). Villi have microvilli, more SA.
i. Goblet cells secrete mucus to lubricate and protect from mech/chem damage
ii. Duodenum has a ph ~6 mainly due to bicarbonate ions secreted by pancreas
b. Enzyme origin
i. Small intestine – proteolytic enzymes: proteases, maltase and lactase, phosphatases/nucleosidases (nucleotides); lipase
c. Pancreas – secretes bicarbonate; also acts as exocrine gland releasing major enzymes from acinar cells via pancreatic duct
duodenum
- Trypsin & chymotrypsin (proteases), lipase, pancreatic amylase, deoxy&ribonucleases
- All exist as zymogens/proenzymes (inactive) first. Trypsin gets activated, then activates the other enzymes
- These enzymes in alkaline solution (pancreatic duct duodenum)
d. Liver – produces bile (no enzymes, emulsifies fats) stored in gall bladder, flows thru bile duct which merges with pancreatic duct
e. Remainder of small intestine (6m) absorbs breakdown products (villi and microvilli)
i. Amino acids and sugarscapillaries ; fatty acids and glycerol lymph. System
f. Chyme moves through intestines via peristalsis as well. Segmentation (2nd type of intestinal motion) mixes chime w/ dig. juices
6. Large intestine (colon) – reabsorption of water and salts to form feces; 1.5m long
a. Feces stored at end of L.I. in the rectum excreted through anus
b. At beginning is appendix, which in herbivores is large cecum (cellulose digestion) with the help of bacteria
c. Bacteria (e.g. E.Coli) a symbiont in large intestine = main source of vitamin K (also Vitamin B)
ECL cells are neuroendocrine cells in the digestive tract; gastrin stimulates them to release histamine which in turn stimulates parietal cells to
produce gastric acid
hormones involved in digestive process
Hormones involved in the digestive process
- Gastrin – produced by stomach lining when food reaches or upon sensing of food; more above
- Secretin – produced by cells lining duodenum when food enters; stimulates pancreas to produce bicarbonate (neutralizes the chime)
- Cholecystokinin – produced by S.I. in response to fats; stimulates gallbladder to release bile and pancreas to release its enzymes
- Gastric Inhibitory Peptide – produced in response to fat/protein digestates in duodenum; mild decrease of stomach motor activity
neuron structure
Neuron – consists of several dendrites, single (branched) axon, and cell body
Dendrites – receive information and transfer it TO CELL body
Axon – transfers impulses AWAY from cell body
Glial Cells – nervous tissue support cells; capable of cellular division
• Oligodendrocytes – produce myelin in CNS; wrap many times around axons
• Schwann cells – produce myelin in PNS. Myelin sheaths act as insulators and are separated by nodes of Ranvier. Instead of
traveling continuously down axon, action potential jumps from node to node (salutatory conduction), speeding up impulse
- Only vertebrates have myelinated axons. Myelinated axons appear white (white matter); neuronal cell bodies
gray (gray matter).
three types of neurons
- Sensory (Afferent)- receive initial stimulus (Ex: neurons in retina of eye) ABRAIN
- Motor (Efferent)- stimulate effectors, target cells that elicit some response (Ex: neurons may stimulate the muscles, sweat
glands, or cells in the stomach to secrete gastrin. BRAIN M - Association (Interneuron)- located in spinal cord & brain- receive impulses from sensory and send impulses to motor
neurons. They are integrators, as they evaluate impulses for appropriate response. ~99% of nerves are interneurons.
transmission of a nerve impulse
The membrane of an unstimulated neuron is polarized, although a high concentration of Na+
is present outside the cell and a high
concentration of K+
is present inside the cell (the inside is actually negative due to the negatively charged proteins and nucleic acids
residing in the cell). Additionally, neuron membranes are selectively permeable to K+ as opposed to Na+
, which helps to maintain the
polarization.*
1. Resting potential. Normal polarized state of neuron, -70 mV.
2. Action potential. Stimulus gated ion channels let Na+
into the cell, depolarizing it. If the threshold level is reached (~ -
50mV), it will cause an action potential that will result in opening of (voltage gated) Na+ channels down the entire length of
the neuron. All or nothing event!
3. Repolarization. In response to Na+ flow in, more gated ion channels let K+ out of the cell, restoring polarization- but the Na+
are IN and the K+ are OUT
4. Hyperpolarization. By the time the channels close, too much K+
is released (-80 millivolts)
5. Refractory period. Neuron will NOT respond to new stimulus until Na+
/K+ pumps return the ions to their resting potential
locations (outside/in, respectively) if absolute. If relative, abnormally large stimuli can create an AP. Note that refractory
period is what prevents an AP from moving backwards, even though ions are theoretically rushing in and diffusing in both
directions.
Note that from -70 up to threshold (or -70 downward) is the graded potential that cannot travel, but it can potentially (if it surpasses threshold) open the voltage
gated channels and this part is the action potential, that travels by opening other voltage gated. The other gated types cannot spread unless they trigger this AP. Also
note that AP is all or nothing, so strength of a neural signal is based on other factors (frequency of AP firing or how many nervous cells contribute AP’s, etc).
Note in case you encounter it, the K-ATP sensitive channel will close in the presence of ATP K+ can’t escape depolarization occurs. In beta cells, this
depolarization leads to the voltage dependent calcium channel (VDCC) opening, which itself causes the exocytosis of insulin.
transmission across synapse
presynaptic cell postsynaptic cell
I. Electrical- action potential travels along membranes of gap junctions (less common); fast; cardiac and visceral smooth muscle.
II. Chemical- most typical in animal cells; unidirectional (unlike electrical) [Isn’t electrical conduction unidirectional too?]
1. Ca2+ gates open- depolarization allows Ca2+ to enter the cell via VDCC’s (also found in beta cells!)
2. Synaptic vessels release neurotransmitter- influx causes release into cleft
3. Neurotransmitter binds with postsynaptic receptors. Diffusion (via Brownian motion) and binding
4. Postsynaptic membrane is excited or inhibited. Two possible outcomes:
i. Na+ gates open, membrane is depolarizedexcitatory postsynaptic potential (EPSP), if threshold potential
is succeeded, action potential is generated
ii. K+ gates open, membrane becomes hyperpolarized inhibitory postsynaptic potential (IPSP)… it becomes
more difficult to generate action potential
5. Neurotransmitter is degraded and recycled. Broken down by enzymes in cleft and recycled
common neurotransmitters
- Acetylcholine- secreted at neuromuscular junctions muscle contraction/relaxation. Inhibitory everywhere else.
a. parasympathetic nervous system - Epinephrine, norepinephrine, dopamine, and serotonin (5HT)- AA derived, secreted between neurons of CNS
a. sympathetic nervous system - Gamma aminobutyric acid (GABA)- inhibitory neurotransmitter among brain neurons
central nervous system
consists of the brain and spinal cord
Brain – outer grey matter (cell bodies) and inner white matter (axons); forebrain, midbrain, hindbrain
- Forebrain – largest & most important brain region. contains cerebral cortex (processes sensory input / important for memory
and creative thought), olfactory bulb (smell), thalamus (relay for spinal cord and cerebral cortex), hypothalamus- visceral
function (water balance, blood pressure, and temp regulation, hunger, thirst, sex)
- Midbrain – relay center for visual/ auditory impulses; motor control
- Hindbrain – posterior part of brain; cerebellum (maintenance of balance, hand-eye coord, timing of rapid movements), pons
(relay center to allow communication b/w cortex and cerebellum), medulla oblongata (breathing, heart rate, gastrointestinal
activity) -
o The brainstem consists of midbrain + medulla oblongata + pons. Connects the cerebrum with the spinal cord.
Spinal cord- out white/inner gray(cell bodies). Sensory info enters through dorsal horn. All motor info exits through the ventral
horn.
Cerebrum is largest part of brain w/ two hemispheres connected by corpus callosum (thick nerve bundle). Divided by lobes: frontal (conscious thought; voluntary
skeletal muscle movement), partietal (sensory areas – temperature, touch, pressure, pain), temporal (sensory – hearing and smelling), occipital (sensory – vision).
Cerebrum has outer portion (cerebral cortex – gray matter) +inner portion (medulla – white matter) see ↑. Cerebrum contains sensory, motor, association areas
peripheral nervous system
Peripheral Nervous System (PNS) – consists of sensory branch and motor branch. Motor consists of somatic and autonomic nervous systems
Somatic – responsible for VOLUNTARY movement of skeletal muscles
Autonomic – involuntary movement; innervates cardiac and smooth muscle
o Sympathetic – fight or flight (higher BP and HR)
o Parasympathetic – rest and digest; non-emergency (lower HR, digestion, relaxation, sexual arousal)
reflex arc
A reflex arc is a rapid, involuntary response to a stimulus involving two or three neurons, but brain DOES NOT integrate the
sensory and motor activities… instead synapse in spinal cord**
Ex: Knee-jerk (patellar) reflex
muscular system
- Skeletal muscle (striated muscle) – voluntary movement, fibers are multinucleated cells
a. Myofibrils – filaments divided into sarcomeres
b. Sarcomeres – individual contractile units separated by a border (Z-line)
c. Sarcoplasmic reticulum – stores Ca2+; surrounds myofibrils
d. Sarcoplasm – cytoplasm
e. Sarcolemma – plasma membrane of muscle cells; can propagate action potential
i. Invaginated by T-tubules- channels for ion flow
ii. Wraps several myofibrils together to form a muscle cell/muscle fiber
f. Mitochondria – present in large amounts in myofibrils
sarcomere
– is composed of thin filaments (actin) and thick filaments (myosin)
- Z line – boundary of a single sarcomere; anchor thin filaments
- M line – center of sarcomere
- I band – region containing thin filaments (actin) only (on ends, only purple above)
- H zone – region containing thick filaments (myosin) only (in middle, only green above)
- A band – actin and myosin overlapping (one end of overlap to the other end of overlap)
o H and I reduce during contraction, while A does NOT
contraction
Stimulation Process of Sliding Filament Model – “all-or-nothing” response
- Action potential of neuron releases acetylcholine when meets neuromuscular jxn
- Action potential then generated on sarcolemma and throughout T-tubules
- Sarcoplasmic reticulum releases Ca2+
- Myosin cross bridges form – result of Ca2+ binding to troponin on actin helix
sliding filament model
- ATP binds to myosin head – converted to ADP + Pi, which remain attached to head
- Ca2+ exposes binding sites on actin – binds troponintropomyosin exposes attachment sites
- Cross bridges between myosin heads and actin filaments form
- ADP + Pi are released sliding motion of actin bring Z lines together (contraction, power stroke)
- New ATP attaches to myosin head, causes cross bridges to unbind – new phosphorylation breaks cross bridge
Without new ATP, the cross bridges remain attached to myosin head… this is why corpses are stiff
Strength of contraction of single muscle fiber cannot be increase, but strength of overall contraction can be increased by recruiting more muscle
fibers
Types of muscles
- skeletal= attached to bones and causes, striated, multinucleated, movements… voluntary
- smooth muscle=is spindle-shaped, nonstriated… uninucleated… occurs in walls of internal organs… involuntary
- cardiac= has striated, branched, uninucleated fibers… occurs in walls of heart.. involunatry
immune system: 1st line of defense
- Nonspecific 1st line of defense: innate immunity – generalized protection
- Skin: physical and hostile barrier covered with oily and acidic (pH 3-5) secretions from sweat glands.
- Antimicrobial proteins: lysozyme (saliva, tear) which breaks down cell wall of bacteria.
- Cilia: line the lungs serve to sweep invaders out. - Gastric juice: stomach kills most microbes.
- Symbiotic bacteria: digestive tract and vagina outcompetes many other organisms.
2nd line of defense
also innate
Types of WBCs (leukocytes) – see image here – all WBC’s originate from bone marrow but some multiply + become non-naive in the
lymph node (lymph drainage acts as a sewer system of antigens; cell recognizes antigen, goes from naïve activated; multiplies).
Phagocytes – engulf foreign particles/bacteria/dead or dying cells
o Neutrophils – fxn in destruction of pathogens in infected tissues; drawn to infected or injured areas by chemicals
in process called chemotaxis; slip between endothelial cells of capillary (into tissue) via diapedesis
o Monocytes – move into tissues (diapedesis) where they develop into macrophages (which phagocytize cell
debris + pathogens, are a professional antigen-presenting cell)
o Eosinophils – work collectively to surround and destroy multicellular parasites
o Dendritic Cells – responsible for the ingestion of pathogens and stimulate acquired immunity (“main function as
APCs that activates T-lymphocytes”)
o Mast Cells – fxn in allergic response, inflammatory response (histamine release), anaphylaxis
Lymphocytes – covered below
Basophils – release histamines for inflammatory response
- Phagocytes: leukocytes (WBC’s) engulf pathogens by phagocytosis (neutrophils and monocytes [enlarge into
macrophages]). Other WBCs called natural killer cells (NK cells) attack abnormal body cells-tumors or pathogen-infected.
- Complements: 20 complement proteins; help attract phagocytes to foreign cells and help destroy by promoting cell lysis.
- Interferons: secreted by cells invaded by viruses/pathogens that stimulate neighboring cells to produce proteins defend
against virus.
- Inflammatory: series of non-specific events that occur in response to pathogens. EX: when skin is damaged and bacteria enter the body
1. Histamine is secreted by basophils (white blood cells found in CT) causes vasodilation.
2. Vasodilation- stimulated by histamine, increases blood supply to area- increase in temperature that stimulates WBCs
and can kill pathogens
3. Phagocytes attracted to injury by chemical gradients of complement, engulf pathogens and damaged cells.
4. Complement helps phagocytes engulf foreign cells, stimulate basophils to release histamine, and help lyse foreign cells
3rd line of defense
Specific 3rd line of defense (Immune response-targets specific antigen) (acquired immunity – develops after body has been attacked)
- Major histocompatibility complex: mechanism by which immune system is able to differentiate between self and nonself.
MHC is a collection of glycoprotein that exists on membranes of all body cells. The proteins of single individual are unique
(20 genes, each w/ 50+ alleles, unlikely to have same cells w/ same MHC set as someone else). Antigen presentation.
- Lymphocytes: primary agents of immune response, leukocytes that originate in bone marrow but concentrate in lymphatic
tissues such as lymph nodes, thymus gland, and spleen.
B cells
- B cells (antibodies): originates and mature (?) in bone marrow (B cell for bone); response to antigens. Plasma
membrane of B cells contains antigen receptor-antibodies (immunoglobulins).
- are proteins; specific to each antigen, five classes (IgA, IgD, IgE, IgG, IgM-variation in Y-shaped protein-constant
region and variable regions). Insert antibody structure picture for IgG; note that disulfide bonds connect the heavy
chains to each other and to light chains. Include fxn of each Ig?
- Antibodies inactivate antigens upon binding mark for macrophage or natural killer cell phagocytosis, lysis by
complement proteins, agglutination of antigenic substance, or chemical inactivation (if a toxin)
- When antigen bound to B cell proliferation (2 copies) into daughter B cells (assisted by helper T)
a. Plasma cells: B cells that release specific antibodies that circulate in blood
b. Memory cells: long-lived B cells that do not release antibodies in response to immediate antigen invasion;
instead, they circulate the body, proliferate, and response quickly (via antibody synthesis) to eliminate subsequent invasion
by same antigen. (2ndary response – takes less time, ~5 days)
T cells
- T cells (foreign): originates in bone marrow but mature in thymus gland (T for thymus). T cells have antigen receptors
but do not make antibodies; they check molecules displayed by nonself cells. In the thymus, if a T cell binds to a selfantigen,
it is destroyed. If not, released for work in lymphoid tissue. Discrimination of self and nonself are as follow:
- MHC markers on plasma membrane of cells distinguish between self and nonself cells.
- When body cell is invaded by pathogen (nonself), it displays a combination of self and nonself markers. T cells
interpret this as nonself.
- Cancer cells or tissues transplant cells are often recognized as nonself by T cells due to the combination.
+ When T cells encounter nonself cells: they divide and produce four kinds of cells:
a. Cytotoxic T cells: killer T cells recognize and destroy by releasing perforin protein to puncture them (lysis).
b. Helper T cells: stimulate activation of B cells, cytotoxic T cells, and suppressor T cells
c. Suppressor T cells: play negative feedback role in immune system
d. Memory T cells: similar fxn to memory B cells
natural killer cells
- Natural killer cells: attack virus-infected cells or abnormal body cells (tumors)
clonal selection
n: when antigen bind to B cell or when nonself binds to T cell divide into daughter cells, only B or T
cells that bears effective antigen receptor is “selected” and reproduces to make clones.
cell mediated response
- Cell-mediated response: Effective against infected cells. Uses mostly T cells and responds to any nonself cell, including
cells invaded by pathogens. Nonself cell binds T cell clonal selection chain of events:
a. Produce cytotoxic T cells (destroy) and helper T cells.
b. Helper T cells bind macrophages (macrophages engulf pathogens = whole is nonself).
c. Helper T cells then produce interleukins to stimulate proliferation of T cells and B cells and macrophages
humoral response (antibody mediated response)
: responds to antigens or pathogens that circulate in lymph or blood
(bacteria, fungi, parasites, viruses, blood toxins). Basically the B-cell stuff. Humor is body fluid and the following events:
a. B cells produce plasma cells. b. B cells produce memory cells.
c. Macrophage and helper T cells (in cell-mediated of macrophages engulf-nonself) stimulate B cell production.
d. General progression: Naïve Mature Plasma antibody
Note that antibodies are released from plasma cells, are specific for an antigen, and a single B lymphocyte produces only
one antibody type
human supplements natural body defenses by:
Antibiotics: are chemicals derived from bacteria/fungi that are harmful to other microorganisms.
- Vaccines: stimulate production of memory cells from inactivated viruses or weakened bacteria (artificially active immun)
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- Passive immunity: transferred antibodies from another individual- EX: newborns from mother
a. Acquired immediately, but short-lived and non-specific
b. Gamma globulin (blood containing antibodies) – can confer temporary protection against hepatitis and other
endocrine system
Endocrine – synthesize and secretes hormones into bloodstream
Exocrine – secrete substances into ducts (ex. gall bladder) (Pancreas is both exo and endo)
- Sudoriferous (sweat), sebaceous (oil), mucous, digestive, mammary glands are examples
Paracrine – cell signalling where target is nearby; Autocrine is cell signaling via hormone/chemical messenger that binds to receptors on same cell
Prostaglandins – locally acting autocrine/paracrine lipid messenger molecules that have physiological effect (e.g. contract/relax smooth muscle)
- General characteristics of hormone: are transported throughout body in blood; small amount = large impact; slower effect
hormone types
o Peptide – synth’d in rough ER and modified in Golgi (requires vesicle to cross membrane), acts on surface receptors typically via
secondary messengers (ex. Cyclic AMP)
Manufactured in rough ER as larger preprohormone cleaved in ER lumen to prohormone cleaved again (possibly modified w/
carbs) in Golgi to final form
Receptor-mediated endocytosis: protein stimulates production of 2nd messengers (G-protein cAMP-produced from ATP; IP3-
produced from membrane phospholipids which triggers Ca release from ER).
Include (AP) FSH, LH, ACTH, hGH, TSH, prolactin; (PP) ADH & oxytocin; (PT) PTH; (PANCR) glucagon & insulin
o Steroid – synth’d from cholesterol in smooth ER; hydrophobic = freely diffuse but require protein transport molecule to dissolve in
blood; intracellular receptors
Direct stimulation: “steroid” diffuses past plasma membrane and binds receptor in cytoplasm hormone+receptor transported to
nucleus binds activate portion of DNA.
Incudes glucocorticoids and mineralicorticoids of the Adrenal Cortex: cortisol & aldosterone; the gonadal hormones: estrogen,
progesterone, and testosterone (estrogen & progesterone are also produced by placenta)
o Tyrosine Derivatives – formed by enzymes in cytosol or on rough ER
Thyroid hormones: lipid soluble; require protein carrier in blood; bind to receptors in nucleus
Catecholamines: (epi and norepi) water soluble; dissolve in blood; bind to receptors on target tissue and mainly act via 2nd messenger
Includes thyroid hormones (T3 and T4 aka thyroxine) and catecholamines formed in adrenal medulla: epi and norepi
All hormones bind to receptors highly specific to them. Some hormones have receptors on almost all cells, some have receptors only on specific tissues. Hormone
regulation can occur by increasing/decreasing # of these receptors in response to hormone amount.
hypothalamus
monitors external environment and internal conditions of the body; Contains neurosecretory cells that link the
hypothalamus to the pituitary gland. Regulation of the pituitary = negative feedback mechanisms and by secretion of releasing and
inhibiting hormones; secretes ADH (vasopressin) and oxytocin to be stored in posterior pituitary; also secretes GnRH (gonadotropin
releasing hormone) from neurons, which stimulates anterior pituitary to secrete FSH and LH
anterior pituitary gland
mainly regulates hormone production by other glands – itself regulated by hypothalamus
1. Direct hormones: directly stimulate target organs
o Growth hormone (HGH)- aka somatotropin; stimulates bone and muscle growth
o Prolactin- stimulates milk production in females
o Endorphins- inhibit perception of pain (technically a neurohormone)
2. Tropic hormones: stimulate other endocrine glands
o Adrenocorticotrophic hormone (ACTH)- stimulates adrenal cortex release glucocorticoids- involved in regulation
of metabolism of glucose
o Thyroid-stimulating hormone (TSH)- stimulates thyroid gland (↑ size, cell #) to release thyroid hormone (T4 and T3)
o Luteinizing hormone (LH): females-stimulates formation of corpus luteum / males- stimulates interstitial cells of
testes to produce testosterone
o Follicle-stimulating hormone (FSH): females- stimulates maturation of ovarian follicles to secrete estrogen / malesstimulates
maturation of seminiferous tubules and sperm prod
posterior pituitary gland
does not synthesize hormones, stores ADH and oxytocin produced by hypothalamus
- Antidiuretic hormone (ADH/vasopressin)- increases reabsorption of water by increasing permeability of nephron’s
collecting duct water reabsorption and increased blood volume and pressure. Coffee blocks ADH.
- Oxytocin- secreted during childbirth- increases strength of uterine contractions and stimulates milk ejection
pineal gland
secretes melatonin- plays role in circadian rhythm
thyroid gland
located on ventral surface of trachea
- Thyroxine (T4) and Triiodothyronine (T3)
o Derived from tyrosine and necessary for growth and neurological development in children and increase basal
metabolic rate in body (negative feedback on TSH)
o Hypothyroidism- undersecretionlow heart rate and respiratory rate
o Hyperthyroidism- oversecretion increased metabolic rate and sweating
Both lead to GOITERS
- Calcitonin (“tones down” Ca2+) in blood
o Decreases plasma Ca2+ by inhibiting its release from bone
o Decreases osteoclast activity and number
Disorders of the thyroid include anchondroplasia (AD; dwarfism) and progeria (AR; premature aging)
parathyroid
- four pea-shaped structures attached to back of thyroid
- Parathyroid hormone (PTH)- antagonistic to calcitonin
o Raises Ca2+ concentrations in blood by stimulating release from bone
Increases osteocyte absorption of Ca + P from bone; stimulates osteoclast proliferation
o Increases renal Ca reabsorption
thymus
involved in immune response
- Secretes thymosins that stimulate lymphocytes (WBCs) to become T-cells (identification and destroying of infected body
cells)
adrenal gland
on top of kidneys and consist of:
- Adrenal cortex – secretes only steroid hormones
o Glucocorticoids (cortisol and cortisone)- raise blood glucose levels (stimulates gluconeogenesis in the liver);
affect fat and protein metabolism; stress hormones
o Mineralcorticoids (aldosterone)- increases reabsorption of Na+ and excretion of K+
Causes passive reabsorption of water in nephron rise in blood volume/pressure
o Cortical sex hormones (androgens=male sex hormones)- effect is small due to testis
- Adrenal medulla
o Epinephrine and Norepinephrine (adrenaline and noradrenaline)- “fight or flight” – the catecholamines
“fight or flight”(sympathetic N.S.); considered stress hormones
glycogenglucose, vasoconstrictor to internal organs+skin but vasodilator to skeletal muscle, increased
heartbeat
pancreas
both exocrine and endocrine; has bundles of cells called islet of Landerhans which contains two cell types:
- Alpha cells secrete glucagon (α “active”): catabolic, released when energy charge low; raises blood glucose levels
- Stimulates liver to glycogen glucose
- Beta cells secrete insulin (β “bumming”): anabolic, released when energy charge is high; lower blood glucose levels
- Stimulates liver (and most other body cells) to absorb glucose
- Liver +muscle cells: glucose glycogen; fat cells: glucose fat
- Somatostatin is released by delta cells of pancreas; inhibits both insulin and glucagon; possibly increases nutrient
absorption time
testis
testosterone- spermatogenesis, secondary sex characteristics
ovaries
Estrogen- menstrual cycle, secondary sex characteristics
- Progesterone- menstrual cycle, pregnancy
gastrointestinal hormones
Gastrin- food in stomach, stimulates secretion of HCl
- Secretin- small intestine- when acidic food enters from stomach neutralize acidity of chime by secretion of alkaline
bicarbonate
- Cholecystokinin- small intestine- presence of fats causes contraction of gall-bladder and release of bile(involved in
digestion of fats)
