MCAT BIO CH. 9 PART 1 Flashcards
What is perfusion?
The flow of blood through a tissue
What is ischemic?
Inadequate blood flow resulting in tissue damage due to shortage of oxygen and nutrients and buildup of metabolic waste
What is hypoxia tissue?
Adequate circulation is present but the supply of oxygen is reduced
What is the difference between ischemia and hypoxia?
Waste build up in ischemia but removed in hypoxia
What is the difference between arteries and veins?
Arteries: Carry blood away from the heart at high pressure
Veins: Carry blood back toward the heart at low pressure
What do arteries branch into?
Arterioles; lower blood pressure
What do the arterioles lead to?
Capillaries
What important component do arterioles have in their walls and what does that allow?
Smooth muscle in their walls that can act as a control valve to restrict or increase the flow of blood into the capillaries of tissues
What important component do capillaries have in their walls and what does that allow?
Thin walls made of a single layer of cells; designed to allow the exchange of material between the blood and tissues
Where does blood go after it passes through capillaries?
Venules, small veins that lead into veins back to the heart
What do veins lack in their walls?
Lack a muscular wall
The inner lining of all blood vessels is formed by what?
A thin layer of endothelial cells
What are the four most important roles of endothelial cells?
- Vasodilation/constriction
- Inflammation
- Angiogenesis
- Thrombosis
What substances regulate vessel diameter?
Nitric oxide and endothelia
What is the important of vaso control?
Maintaining blood pressure, tissue oxygenation and thermoregulation
What does the release of inflammatory chemicals stimulate endothelial cells to do?
Increase there expression of adhesion molecules
What does the increase of adhesion molecules by endothelial cells allow?
Molecules allow white blood cells to adhere to the endothelial cells and enter the injured tissue
What is angiogenesis?
Formation of new blood vessels
What do angiogenesis growth factors stimulate?
Endothelial cells to break from an existing vessel and proliferate in surrounding tissues, creating new vessels
What does angiogenesis allow based on supply?
Increase supplies oxygen and nutrients to help sustain cell division and growth
What is thrombosis?
Blood clotting
How do endothelial cells prevent blood clots?
Secrete substances that inhibit the coagulation cascade
Which side of the heat has the pulmonary circulation? What about the systemic circulation?
Right side; left side
What is an exception to the rule of blood passing through only one set of capillaries before returning to the heart?
Portal systems
What happens in the hepatic portal system?
Blood goes through capillaries in intestine, collects in veins to travel to the liver, passes through capillaries again
What happens in the hypothalamic portal system?
Blood passes through capillaries in the hypothalamus to the portal veins then to the capillaries in the pituitary
Why do portal systems exist?
To transport nutrients or hormones without passing through the entire body
What happens in the atria?
Blood collects from the veins before getting pumped into the ventricles
What do the ventricles do?
Muscular ventricles pump blood out of the heart at high pressures into the arteries
The right atrium receives deoxygenated blood from which circulation and from which large veins?
The systemic circulation; inferior vena cava and superior vena cava
Where is the oxygenated blood from the lungs sent?
Return through the pulmonary veins to the left atrium and is pumped into the left ventricle
Which artery pumps the blood out of the left ventricle?
Aorta
What do the aorta branch into?
Coronary arteries
What do the coronary arteries do?
Branch to supply blood to the wall of the heart
Deoxygenated blood from the heart collects where?
Coronary veins
What do the coronary veins lead into?
Coronary sinus
Where is the coronary sinus located?
Beneath a layer of fat not he outer wall of the heart
What happens to the blood in the coronary sinus?
Drains directly into the right atrium
Why are valves necessary?
To ensure one-way flow through the circulatory system
What are the differences in pressures in the heart?
Ventricular pressure is very high and atrial pressure is low
What does the AV Valve stand for and what does it do?
Atrioventricular valve and its between each ventricle and its atrium; necessary to prevent backflow
Where are the bicuspid valve or mitral valve located?
Between the left atrium and the left ventricle
What would happen if the mitral valve ruptured?
Ventricle would pump blood in both directions, out the aorta and back into the left atrium
Where are the tricuspid valve?
AV Valve between the right atrium and right ventricle
What are the valve between the large arteries and the ventricles?
The pulmonary and aortic semilunar valves
Why are valves important throughout the venous system?
Necessary because in passing through capillaries, blood loses its pressure
What happens when the venous valves fail?
Varicose veins
What happens to the ventricles and atria during diastole?
Ventricles relax to allow blood in; atria contract to propel blood into the ventricles
What happens to the ventricles and atria during systole?
The ventricles contract
What happens during the initial contraction of systole to the valves?
The buildup pressure causes the AV valves to shut
What happens to the ventricles while the AV valve shut?
The pressure in the ventricles increase rapidly until the semilunar valves fly open
What happens when the semilunar valves fly open?
Blood rushes into the aorta and pulmonary artery
What is ejection fraction?
End of systole, the ventricles are nearly empty
What sound does the systole cycle make?
Ventricles contract; starts with the lub sound ending at the dup
What happens when the ventricles stop contracting at the end of systole?
Blood begins to flow backwards from pulmonary artery into the right ventricle and from aorta into the left ventricle
Even though back flow enters the ventricle, how much and why?
Very little back flow occurs because semilunar valves slam shut when the pressure in the ventricles becomes lower than the pressure in the great arteries
What causes the lub sound?
The lub sound results from the closure of the AV valves at the beginning of systole
What causes the dup sound?
The dup sound results from the semilunar valves closing at the end of systole
What is the heart rate/pulse?
The number of time the “Lub-dup” cardiac cycle is repeated per minute
What is the normal pulse rate (HR)?
One beat per second ranging from 45 beats per minute in athletes to 80 or more in elderly and children
What is the stroke volume (SV)?
The amount of blood pumped with each systole
What is the cardiac output (CO)?
The total amount of blood pumped per minute
What is the equation of cardiac output (CO)?
CO = SV X HR
What is the Frank-Starling mechanisms?
The heart muscled will contract more forcefully if its stretched
How does the heart muscle get more stretched out to increase contract?
Increasing venous return
How can the body increase venous return?
- Increase blood volume
2. Contract on of large veins
How can the body increase venous return through increasing blood volume?
Retaining water and urinating less
From what is the force of contraction in the ventricles and the atria generated by?
The cardiac muscle cells that form the muscular walls the chambers of the heart
What do muscles cells have that allow them to contract?
Share with neurons the ability to propagate an action potential across their surface
Do ligand-gated ion channels propagate action potentials in cardiac muscle?
No, propagation of action potentials requires voltage-gated ion channels
What is a syncytium?
A tissue in which the cytoplasm difference cells can communicate via gap junctions
Where are the gap junctions found in cardiac muscles?
There intercalated disks
How is the action potential in the heart transmitted from the atrial syncytium to the ventricles?
Cardiac conduction system
What allows the atria to contract first before the ventricles?
Transmission of the action potential is delayed slightly as it passes through the A-V node
What two channels are important in cardiac muscle action potential?
- Fast sodium channels
2. Slow calcium channels
What is the effect of the slow calcium channel in the cardiac muscle?
Stay open longer; causes membrane depolarization to last longer in cardiac muscle than neurons, producing plateau phase
What do cardiac muscles have to maximize the entry of calcium in the cell?
T-tubules
What is the purpose of T-tubules in cardiac muscles?
Action potentials travel down along it and allow the entry of calcium from extracellular environment and induced sarcoplasmic reticulum to release some Ca2+
What does the combination of intracellular and extracellular calcium causes in cardiac muscles?
Contraction of actin-myosin fibers
What is the initiation of each action potential that asters each cardiac cycle that its is occur automatically?
Sinoatrial node (SA) in the right atrium
Under normal circumstances, the SA nodes cells act as what?
Pacemaker of the heart
What are the three phases of the SA node?
Phase 0, Phase 3 and Phase 4
The SA node is unique that it is an u…?
Unstable resting potential
What is Phase 4 of the SA node?
Automatic slow depolarization caused by special sodium leak channels that are responsible for rhythmic, automatic excitation
What does Phase 4 from the sodium leak channels allow based on the SA node?
Inward sodium leak brings cell potential to the threshold for voltage-gated calcium channels
What does the opening of the voltage-gated calcium channels occur in Phase 4, what does it case based on SA node?
Phase 0, the upstroke of the pacemaker potential
What is the upstroke of the pacemaker potential in Phase 0 caused by?
Caused by an inward flow of Ca 2+
Skeletal muscle cells and other myocytes depolarize because due to what instead of the inward flow of Ca 2+?
Because of a Na+ influx
What does the influx of Ca 2+ in Phase 0 of the SA node cause?
Drives the membrane potential of the SA nodal cells towards the positive Ca 2+
How are the CA 2+ channels compared to the Na + channels based on SA node Phase 0?
Phase 0 Ca 2+ channels open more slowly, leading to a more gradual upsweep in the action potential
What is Phase 3 of the SA node phases?
Repolarization
What happens during Phase 3 of the SA node?
Closure of the Ca 2+ channels and opening of the K+ channels
What does the opening of the K+ channels cause during the Phase 3 Sa node?
Drives the membrane potential back down towards the negative K+ equilibrium potential
Based on the phases, summarize what the SA node does based on action potential?
Transmits action potential through intercalated discs, repolarize and starts process again
What regions of the earth can spontaneously depolarize?
the Av node, Purkinje fibers, SA node
Why is the SA node called the pacemaker of the heart?
It has more NA+ leak channels, reaching threshold before any other region of the heart does
What is the resting potential of the cardiac muscle cells?
Resting membrane potential of about -90 mV and a long duration of 300 mms
What is the resting membrane potential of the SA node?
-50 and self-depolarizes right away
What are the phases of cardiac muscle cells?
Phase 0-4
What is the name of the phase 0 of cardiac muscle cells?
Depolarization
What happens during phase 0 of cardiac muscle cells?
Upstroke of the action potential; caused by transient increase in Na+ conductance
What happens when there an upstroke of the action potential in one of the intercalated disks, based on Phase 0?
Intercalated disks stimulate myocytes to reach threshold for voltage-gated Na+ channels
What happens when threshold is reached in Phase 0 of the cardiac muscle cell?
Na+ channels open and Na+ rushes into the cell
What is the name of the phase 1 of cardiac muscle cells?
Initial depolarization
What happens during phase 1 of cardiac muscle cells?
The Na+ channels inactivate and K+ channels open
What does the opening of K+ channels cause in phase 1 of cardiac muscle cells?
Efflux of K+ and a slight drop in cell potential
What in phase 1 leads into phase 2 of the cardiac muscle cells?
Increase potential due to initial Na+ influx causing the Ca 2+ channels to open
What is the name of the phase 2 of cardiac muscle cells?
Plateau phase
What happens during phase 2 of cardiac muscle cells?
The influx of Ca2+ ions balance the K+ efflux from phase 1, leading to an equilibrium in cell potential
What is the name of the phase 3 of cardiac muscle cells?
Repolarization
What happens during phase 3 of cardiac muscle cells?
The Ca2+ channels close and the K+ channels stay open
What happens during phase 4 of cardiac muscle cells?
Inward and outward current equal, dictated also by action of Na+/K+ ATPase and slow K+ leak channels
What is the name of the phase 3 of cardiac muscle cells?
The resting membrane potential
What is the internodal tract?
Pathway connecting the SA node to the AV node
Why does the AV node spreads through the atria more slowly when there’s conductance?
Contracting heart muscle cells pass the impulse more slowly than specialized conduction fibers
Where does the impulse go after it is slightly delayed through the AV node?
Tot he ventricles via the conduction pathway known as the AV bundle of bundle of His
What does the AV bundle divide in and what is it called?
Left and right bundle branches and then into the Purkinje fibers
The Purkinje fibers spread across the…..of the heart?
Inferior portion the ventricles, apex of the heart.
The autonomic nervous system regulates the action potentials in the heart. T/F
False: Regulates the rate of contraction
Why is the heart rate only 60-80 beats per minute?
Parasympathetic nervous system continually inhibits depolarization of the SA node
What part of the parasympathetic nervous system inhibits depolarization of the SA node?
The vagus nerve contains preganglionic axons which synapse in ganglia near the SA node
What do the preganglionic axons cause to the SA node?
Postganglionic neurons innervate the SA node and release acetylcholine (ACh)
What does the acetylcholine in the SA node do, based on the vagus nerve?
Inhibits depolarization by binding to receptors on the cells of the SA node
What is the vagal tone?
The constant level of inhibition caused by the vagus nerve
The role of the parasympathetic system in controlling the heart is to modulate the rate by….?
Inhibiting rapid automaticity
When does the sympathetic nervous system affect the heart?
When increased cardiac output is needed during a flight or fight response
What are the two neurotransmitters related to the effect of the sympathetic nervous system onto the heart and how are the released?
- Norepinephrine released by postganglionic neurons
2. Epinephrine secreted by the adrenal medulla binds to receptor on cardiac muscle cells
What is the effect of sympathetic activation?
Stimulatory and increases the heart rate
What are the three components required in regulatory system?
- Input
- Integration
- Output
What is another term for the input in regulatory system?
Afferent informaton
What is another term for the output in regulatory system?
Efferent information
What is another term for the integration in regulatory system?
Function of the central nervous system
What is the key element in the regulation input of the heart rate?
Baroreceptors
What do baroreceptors monitor?
Blood pressure
Based on input, what happens when the baroreceptors send information the pressure is too high?
CNS increase vagal tone and decreases sympathetic input
What is hemodynamic?
Study of blood flow
What is the equation for Ohm’s Law?
Δ P = Q X R
In the Ohm’s Law equation, what does delta P stand for?
Pressure gradient in mmHg
In the Ohm’s Law equation, what does Q stand for?
Blood flow (or cardiac output in L/min)
In the Ohm’s Law equation, what does delta R stand for?
Denotes resistance
Based on blood flow, what is the resistance?
Opposing force of flow, friction
Pressure is directly proportional to…?
Cardiac output and peripheral resistance
If we want to change blood pressure, what are the only ways we can?
Changing pressure or the resistance
What are the two ways pressure can vary, based on heart?
By changing the force (stroke volume) or rate (beats per minute)
What is the precapillary sphincters?
Arteriolar smooth muscle
What is the principal determinant of resistance in blood pressure?
Degree of constriction of precapillary sphincters
The result of R = ΔP/Q, what does it give?
Peripheral resistance
What controls the peripheral resistance?
The sympathetic nervous system controls the peripheral resistance
A basal level of pressure is provided by what?
A constant level of norepinephrine released by sympathetic postganglionic axons innervating precapillary sphincters
The constant nervous input from the sympathetic nervous system allowing for a basal level of pressure is called what?
Adrenergic tone
When physician measure blood pressuring, they are actually measuring what?
Systemic arterial pressure
What is the systemic arterial pressure?
Force per unit area exerted by blood upon the walls of arteries
What are the two numbers from a blood pressure reading, such as 120/80?
120 mm Hg is the systolic pressure and 80 mm Hg is the diastolic pressure
What is the pulse pressure?
The difference between systolic and diastolic pressures
What is the blood pressure measured by?
Taken using a sphygmomanometer
What is the pressure in the vena cava?
Blood pressure is negligible and valves must prevent back flow
Why is there high diastolic aterial pressure as high as it is?
When the heart contracts, the arteries distend like balloons and during diastole, they exert pressure on the blood
What is local autoregulation?
When a tissue is under-refused, wastes build up and vasodilation occurs automatically
What are the three components of blood?
Plasma, leukocytes, hematocrit
What are the three key components of plasma?
- Electrolytes
- Buffers
- Lipoproteins
What are electrolytes?
Na+ K+ Cl- Ca2+ and Mg 2+ ions
What do buffers achieve in the blood?
Maintain constant pH of 7.4
What is the principal blood buffer?
Bicarbonate HCO3-
What is the principal sugar in the blood?
Glucose
What are the blood proteins?
Albumin, Immunoglobin, Fibrinogen, Lipoproteins
What is albumin, based on protein?
Essential for maintenance of oncotic pressure
What is oncotic pressure?
Osmotic pressure in the capillaries due to only plasma proteins
What is the purpose of immunoglobulins?
Key part of the immure system
What is fibrinogen important for?
Blood clotting
What are lipoproteins?
Large particles consisting of fats, cholesterol and carrier proteins
What is the role of lipoproteins?
Transports lipids in the bloodstreams
What is the principal metabolic waste product?
Urea
What is Urea?
A breakdown product of amino acid, carrier of excess nitrogen
What is bilirubin?
A breakdown product of heme (oxygen-binding moiety of hemoglobin)
What is the hemacrotit of blood?
Volume occupied by erythrocytes
All the formed elements of the blood develop from special cells called what?
Bone marrow stem cells
What is serum?
Liquid left when the blood clots; plasma that lacks proteins
What hormone stimulates RBC production and where?
Erythropoeitin and in the bone marrow
What happens aged RBCs?
Eaten by phagocytes in the spleen and liver
What are features of erythrocytes?
Cell with no nucleus or other organelles such as mitochondria
How long do RBCs live for?
120 day
What do RBC rely on since they do not have mitochodria?
Rely on glycolysis for ATP synthesis
What is the purpose of RBC?
Transport oxygen from lungs to the tissues and CO2 from the tissues to the lungs
What from the RBC allows for a surface area large enough for gas exchange?
Flat, biconcave shape
Why is the RBC able to carry oxygen?
Contains millions of molecules of hemoglobin
What are the two most important blood group antigens?
ABO blood group and the Rh blood group
What is the Rh blood group classification?
RR, Rr and rr
What genotypes of Rh positive and which are Rh negative?
+: RR and Rr
-: rr
What is a transfusion reaction?
Blood transfusions with the wrong antigen
What is sensitization based on blood transfusion?
A person with Rh- blood for example is exposed to Rh+ blood and produces antibodies
What is hemolytic disease of the newborn?
When the mother produces antibodies against a different blood and now her antibodies can cross placental barrier and destroy the baby’s RBC
Why are AB+ and O- special blood types?
They do not make antibodies to any of the blood group antigens; universal recipients
Why are AB+ know as universal recipients?
They can receive any of the other blood types without complication
Why are O- know as universal donors?
Can donate blood to any of the other blood types without complication
What are two ways a white blood cell move around?
- Amoeboid motility (Crawling)
2. Chemotaxis
Why is white blood cells moving in crawling motion important?
Squeeze out of capillary intercellular junctions and can roam free in the tissues
What is chemotaxis based on leukocytes movement?
Movement directed by chemical stimuli
What can be the chemical stimuli to move leukocytes?
Toxins and waste products released by pathogens or chemical signals released by other white blood cells
What are the six types of white blood cells?
- Monocytes
- Macrophages
- Lymphocytes
- B and T cell
- Granulocytes
- The -phils
What are the three types of the -phil leukocytes?
Neutrophil, eosinophil and basophil
What is the purpose of macrophages?
Phagocytose debris and microorganisms, amoeboid motility and chemotaxis
What is the purpose of B cell?
Mature into plasma cell and produce antibodies
What is the purpose of T cell?
Kill virus-infected cells, tumor cells and reject tissue grafts, also control immune response
What is the purpose of neutrophil?
Phagocytose bacteria reusing in pus; amoeboid motility and chemotaxis
What is the purpose of eosinophil?
Destroy parasites, allergic reactions
What is the purpose of basophil?
Store and release histamine; allergic reactions
What are platelets derived from?
Large bone marrow cells called megakaryotypes
What is the purpose of the platelets?
Aggregate at the site of damage to the blood vessel wall and form a platelet plug
What is hemostasis?
Preventing bleeding
What is the hemostatic response of fibrin?
Fibrin mesh becomes a scab and seals and protects the wound
What is the structure of the fibrin?
Threadlike protein which forms a mesh that holds the platelet plug together
What is converted into fibrin and with the help of what?
Fibrinogen plasma protein is converted into fibrin by throbbing
What is thrombus?
A blood clot; scar circulating the blood stream
What is hemophilia?
Excessive bleeding
What does each hemoglobin contain?
Heme, a large multi-ring structure that has a single iron atom bound at its center
What is the role of heme with its iron atom?
Bind to O2
What happens when none of the subunits have oxygen bound?
All four subunits of hemoglobin assume a tense conformation; low affinity for oxygen
What happens to hemoglobin the one oxygen binds?
Conformation changes to a relaxed state that has higher affinity to oxygen
What factors caused the hemoglobin to have ten conformation, which has a low O2 affinity?
- Decreased pH
- Increased PCO2 (level of Co2 in the blood)
- Increased tempoerature
What is the Bohr effect?
Certain factors stabilize tense hemoglobin and thus reduce its oxygen affinity
Why does the hemoglobin get a tense conformation in decreased pH?
Active tissue leads to more metabolizing glucose, elevated PCo2, cells run low on oxygen, performing lactic acid which dropsH
Why does the hemoglobin get a tense conformation when temperature increases?
Temperature increases when there is a lot of metabolic activity
How is most of the Co2 transport accomplished?
Conversion of CO2 to carbonic acid
What can carbonic acid dissociate into?
Bicarbonate and a proton
What is the advantage of bicarbonate and a proton being the dissociative components of carbonic acid?
Compound are extremely water-soluble and easily carried in the blood
The conversion of CO2 into carbonic acid is catalyzed by an RBC enzyme called…?
Carbonic anhydrase
How is 20% of CO2 is transported in the blood?
Being stuck Ono hemoglobin
Why is binding of CO2 to hemoglobin important for hemoglobin?
Based on the Bohr effect, it further stabilizes tense Hb
What is the least percentage of the way Co2 is transported in the blood and how?
7% - Dissolved in the blood and carried from the tissues to the lungs since its water soluble
What are intercellular clefts of capillary walls?
Spaces between endothelial cells that make up the capillary walls
What are the three substances that must be able to pass through the intercelluar clefts?
Nutrients, wastes, and white blood cells
Is it necessary for O2and CO2 to pass through the clefts?
No, they can pass through by simple diffusion
What are the main three types of nutrients?
Amino acids, glucose and lipids
What is the purpose of the hepatic portal vein based on exchange of substances across the capillary wall?
Amino acids and glucose are absorbed from the digestive tract and carried through the special vein to the liver
Why the hepatic portal vein called a portal vein?
Connects two capillary beds; the one in the intestinal wall and the one inside the liver
What happens to the amino acid and glucose when they’re released into the blood streamy the liver?
They can pass through capillary clefts into the tissues
What happens after fats are absorbed from the intestine?
Packaged into chylomicrons
What do the chylomicrons do?
Enter tiny lymphatic vessels in the intestinal wall called lacteals
What is lipemia?
A person’s blood appearing milky, lips flowing in the blood
What happens when lacteals have been filled by chylomicrons?
Empty into large lymphatics which eventually drain into a large vein near the neck
Where do lipoproteins carry fats for storage?
Adipocytes - fat cells
What happens to waste produced during cellular metabolism?
- Diffuse through the capillary walls into the bloodstream
- Liver passes it into gut as bile
- Excreted by kidney
What are the types of white blood cells that can squeeze through the clef of capillaries?
- Macrophages
2. Neutrophils
Why are the two reasons as to why water has a great tendency to flow out of capillaries?
- Hydrostatic pressure created by the heart
2. High osmolarity of tissues drawing out water of the bloodstream
How is the plasma osmolarity created?
Plasma osmolarity is provided by high concentrations of large plasma proteins, mainly albumin
Why can albumin be used to create plasma osmolarity?
Its too large and rigid to pass through the clefts so it remains in the capillaries and keeps water there too
What is oncotic pressure?
Osmotic pressure provided by plasma proteins
How are the capillaries in general?
Hydrostatic pressure is high; water squeezes out into the tissues
What happens to the capillaries when water continues to leave the capillary?
Concentration of plasma proteins increases
What happens when the hydrostatic pressure is low in capillaries?
Blood very concentrated so oncotic pressure is high; water flows back into the capillary from the tissues
Why is more water lost during inflammation?
Capillaries dilate, increasing the size of the intercellular clefs to let the white blood cells migrate into the tissues
What is the result of inflammation since the capillaries dilate?
Edema; swelling as a result of water in the tissues
What does the lymphatic duct have in their walls?
Smooths muscles in their walls
What is the behavior of the lymphatic system; how does it act?
Acts like a suction pump to retrieve water, proteins and white blood
What is the lymph?
The fluid inside the lymphatic vessels
What do lymph nodes do?
Filters the lymph
Why is the lymph nodes an important part of the immune system?
They contain white blood cells that can initiate an immune response against anything foreign
What is the largest lymphatic vessel and where is it located?
The thoracic duct; located in the chest
What does the thoracic duct dump into?
A large vein located in the neck
Where does the lymphatic vessels dump dietary fats from the intestines into?
Dump dietary fats in the form of chylomicrons into the thoracic duct
