MedicoPlexus
Cardiovascular Physiology practice mcq’s
Q1. The major regulatory proteins of the thin filament of Skeletal muscle are
- Actin and Myosin
- The myosin Light Chains
- The Myosin Light Chain Kinase and Myosin Light Chain Phosphatase
- Troponin and Tropomyosin
Answer – d. Troponin and Tropomyosin
Tropomyosin covers the myosin binding sites on actin when the muscle is at rest. With activation, calcium binds to troponin which moves tropomyosin deep into the groove of actin filaments exposing the myosin binding sites on thin filament’s actin molecules
Q2. Which of the following mechanisms does not contribute to gradation of force in smooth muscle?
- Regulation of the availability of calcium
- Frequency of activation
- Regulation of no. of active smooth muscle cells in unitary smooth muscle
- Alterations of cAMP and cGMP levels
Answer – c. Regulation of no. of active smooth muscle cells in unitary smooth muscle
The cells are well coupled with gap junctions such that if one cell is activated then all cells will become activated by conduction from cell to cell
Q3. If Lead 1 in ECG records a net positive potential of 0.5mV at the same instant that Lead 3 records a net positive potential of 0.7mV what would be recorded in Lead 2?
- +1.2mV
- -1.2mV
- +0.2mV
- -0.2mV
Answer- a. +1.2mV
Using a tri-axial diagram the point of intersection of the first and second lead axis’ is the voltage that would be measured in that lead. Roughly this would be +1.2mV
Q4. The major determinants of Resting Membrane Potential in muscle cells is
- The Potassium gradient and high resting membrane potassium permeability
- The Sodium gradient and low resting membrane sodium permeability
- The chloride gradient and high resting membrane chloride permeability
- The Calcium gradient and low resting membrane calcium permeability
Answer – a. The Potassium gradient and high resting membrane potassium permeability
The equilibrium potentials for potassium and sodium are -90mV and +65mV, respectively. These gradients are maintained by Na/k ATPase. The gradients and permeability of these ions then determine the RMP because potassium is most permeable and it the major determinant.
Q5. Which of the following Cardiac Tissues have the most rapid conducting velocity?
- SA node
- Atrial Muscle
- AV node
- Purkinje Fibers
Answer- d. Purkinje Fibers
These are the tissues of the heart that are specialized for conduction and due to this they have large number of gap junctions between the cells and fairly large size and comparatively little branching of cells
Q6. Simultaneous recordings of Leads 1,2 and 3 reveals that component vector amplitudes are negative in leads 1 and 2, and positive in lead 3. The axis of depolarization for this heart would therefore be between _______ degrees.
- 0 and 60
- 90 and 120
- 90 and 180
- 150 and 210
Answer- d. 150 and 210
(calculate summated vector)
Q7. The Calcium released channel in the sarcoplasmic reticulum of skeletal muscle requires which of the following to open?
- The change in intracellular Na+ concentration occurring as a result of the AP
- Binding of ACh to the channel
- Mechanical interaction with DHP-receptor in the t-tubule as it undergoes a voltage induced conformational change
- A change in intracellular calcium concentration as a result of calcium entry through DHP-receptor
Answer- c. Mechanical interaction with DHP-receptor in the t-tubule as it undergoes a voltage induced conformational change
DHPR in the t-tubular membrane is physically connected to the calcium release channel in the SR. When the muscle cell depolarizes, the DHPR Ca-channel undergoes a voltage dependent conformational change. This change is transmitted mechanically to release the Ca-release channel in the SR and induces the later channel to open.
Q8. Sliding Filament model of muscle contraction predicts which of the following?
- Maximum contracted force will be generated when thick and thin filaments overlap is maximal between 2 and 2.2 microns
- Contractile force is proportional to the no. of active cross bridges
- Contractile force is diminished at sarcomere lengths greater than 2.5 microns
- Contractile force is diminished at very short sarcomere lengths -less than 1.5 microns due to steric hinderance
- All of the above
Answer- e. All of the above
Q9. Decrease in the velocity of impulse conduction through the AV node will usually cause:
- The PR interval to increase
- The PR interval to decrease
- Disappearance of T wave
- Increased Heart rate
Answer- a. The PR interval to increase
The PR interval contains AV node depolarization information, so if conduction through AV node is slowed, because this represents the only pathway for conduction to the ventricle, the PR interval will lengthen.
Q10. Which of the following statements regarding length-tension relationships in skeletal muscles is false?
- The active tension is that tension resulting from maximal stimulation of the muscle
- The sub-cellular basis for the length-tension relationship is optimization of thick and thin filament overlap at the level of sarcomere
- Passive tension is a measure of the force required to stretch an activated muscle
Answer- c. Passive tension is a measure of the force required to stretch an activated muscle
Q11. The CNS controls force production in skeletal muscle in which of the following ways?
- Motor unit recruitment
- Elevation of IP3
- Frequency of activation
- Elevation of cGMP
- A and C are correct
Answer- e. A and C are correct
Q12. The Standard ECG Lead 1 consists of electrodes recording the potential difference between the _______ (A arms, L Legs, or AL arms and legs) so arranged as to normally yield an upright deflection of the p-wave when the right extremity is __________ (P positive or N negative) with respect to the other.
- A, arms; P, Positive
- L, legs; P, Positive
- AL, arms and legs; P, Positive
- A, arms; N, negative
Answers- d. A, arms; N, negative
Lead 1 is positive on the left arm and records between the left and right arms
Q13. The Phenomenon of summation of force in skeletal muscle involves:
- Response of the muscle to increased frequency of stimulation
- Recruitment of additional motor units
- Optimization of thick and thin filaments to overlap
- Phosphorylation of troponin to enhance its sensitivity to calcium
Answer- a. Response of the muscle to increased frequency of stimulation
Summation of force occurs when a muscle receives additional stimuli before the force transient from a previous stimulus has dissipated.
Q14. Which of the following regarding length-tension relationships in smooth muscles is true?
- Smooth muscles can produce near maximum tension over a broad range of initial lengths
- The basis of the length-tension relationship is smooth muscle lies in the sacromeric arrangement of thick and thin filaments
- The passive tension curve rises steeply over the range of lengths wherein active tension declines
- Steric hinderance accounts for loss of force production at short muscle lengths
Answer- a. Smooth muscles can produce near maximum tension over a broad range of initial lengths
Q15. A 55-year-old patient of yours begins a vigorous exercise program. As a precaution you assess his family history and noting that he is at a high risk for cardiac disease perform a routine ECG. You note in his ECG that not every P-wave is followed by a QRS complex and that the PR intervals lengthens with each successive beat until there is a dropped beat. The arrhythmia exhibited by this patient is:
- First degree block
- Second degree block
- Third degree block
- Mobitz II Block
Answer- b. Second degree block
This ECG observation is characteristic of WENCKEBACH phenomenon. This is a type of second-degree block also known as Mobitz I.
Q16. Which of the following is a determinant of myocardial function?
a. Afterload
b. Preload
c. Heart Rate
d. contractility
e. all of the above
Correct answer: E.) All of the above,
Reasoning: The four determinants of myocardial function are: Preload, Afterload, Heart
Rate and Contractility
Q17. Which of the following is true bout Frank-Starling’s Law of the Heart
a. Ensures sufficient calcium is available for each contraction
b. Ensures that are Output (CO) for the right and left ventricles are equal
- Has its basis in optimization of thick and thin filament overlap
- Has its basis in the rate and quantity of calcium delivered to the myofilaments
e. Both Band C are correct
f. Both A and D are correct
Correct answer: E. Both B and C are correct.
Q18. Heterometric Regulation occurs on a beat-to-heat basis. Homeometric Regulation
occurs over the course of many beats
A True
B. False
Correct answer: A.) True
Q19. At high heart rates __________ time is compromised, which initially (over a few heats)
compromises Stroke Volume (SV), and consequently, Cardin Output (CO) and mean
arterial pressure. Through intrinsic Regulatory strategies, the heart compensates for these
efforts with increased:
A. Filling Contractility
B. Contraction Filling Pressure
C. Filling Length-Dependent Force Development
D. Contraction: Blood Volume
Correct answer: A.) Filling: Contractility
Q20. If the aortic valve were stenotic (calcified such that it does not open fully during the
ejection phase), in what ways would you expect the Wiggers Diagram to be different
from normal control conditions?
A Peak systolic pressure in the aorta would be elevated
B. Peak systolic pressure in the ventricle would be cleated,
C End systolic volume in the ventricle would be reduced
D. End systolic volume in the ventricle would be elevated,
E. Both B and D are true.
Correct answer: E.) Both B and D are true.
Reasoning. If the aortic valve fails to open completely, the ventricle has to eject through a
narrowed orifice. Like the nozzle on a hose when it is narrowed, a higher water pressure
is required to achieve the same flow. Thus, ventricular pressure will rise to a much higher
value than is observed in the aorta. The worse the stenosis, the greater the pressure
difference across the valve must be to develop the same amount of output. Ejection
fraction will likely decrease in the case, causing End Systolic Volume (ESV) and End
Diastolic Volume (EDV) to rise.
Q21. The first heart sound occurs when the ________ and ____________ valves _______
A. Mitral; Tricuspid; Close
B. Aortic; Pulmonic: Close
C. Mitral; Tricuspid; Open
D. Aortic; Pulmonic: Open
Correct answer: A.) Mitral; Tricuspid; Close
Reasoning: Valves make sounds only when they close, not when they open, unless when
they are diseased. In that regard, they are like doors. The cardiac cycle begins when the
SA node fires. At this point in time the aortic and pulmonic valves are already closed.
The mitral and tricuspid valves close as the ventricle is activated. They cause the first
heart sound in the cardiac cycle.
Q22. Put the following events in their proper order.
1. c-wave
2. a-wave
3. V-wave
4. P-wave
5. QRS complex
6. T-wave
A. 4, 2, 5, 1, 6,3
B.4, 1, 5, 2, 6,3
C. 4, 2, 5, 3, 6,1
Correct answer: A.) 4, 2, 5, 1, 6,3
Reasoning. The a-wave results from atrial contraction which is preceded by electrical
activation of the atrium, the signature of which is the P-wave. The c-wave results from
the AV valves ballooning back into the atrium as they slam shut due to the pressure rising
in the ventricle. Pressure rises in the ventricle due to contraction of the ventricle which is
initiated by the QRS complex. The v-wave results from the accumulation of blood in the
atrium while the AV valves are closed. The peak of this wave occurs when the AV valves
open, which occur when the ventricle is nearly completely relaxed. Ventricular relaxation
occurs due to repolarization which is represented by the T-wave. Thus, the proper order of
events are: P-wave, a-wave, QRS complex, c-wave, T-wave, V-wave.
Q23. During the isovolumetric contraction phase of the cardiac cycle, the A-V valves are ________
(C, closed; 0, open) and the aortic and pulmonic valves are _________ (C, closed; O, open)
A. O, open; O, open
B. O, open; C, close
C. C, close; O, open
D. C, close; C, close
Correct answer: D.) C, closed; C, closed
Reasoning: In order for the volume of the ventricles to be constant, all the valves must be
closed. Also, because the blood is incompressible, when the ventricles attempts to
contract, the pressure in the ventricles will rise but the volume will not change until the
valves open
Q24. A normal systolic / diastolic blood pressure of 22 / 14 is most likely measured in the:
A. Left Ventricle
B. Right Ventricle
C. Aorta
D. Pulmonary Artery
Correct answer: D.) Pulmonary Artery
Reasoning Pressures on the left side of the heart are significantly larger than the right
with typical pressures in the left ventricle being 120/10 and the aorta being 120/80
Corresponding pressures on the right side of the heart are for the ventricle 22/5 and the
pulmonary artery 22/14.
Q25. Ischemia of local areas of cardiac muscle caused by coronary thrombosis results in
localized partial ___________(D, depolarization; H, hyperpolarization) of cell
membranes and localized extracellular ____________ (EP, electro positivity, EN,
electronegativity).
A. D, depolarization; EP, electro positivity
B.D, depolarization; EN, electronegativity
C. H, hyperpolarization; EP, electro positivity
D. H, hyperpolarization; EN, electronegativity
Correct answer: B.) D, depolarization; EN, electronegativity
Reasoning: Ischemia reduces the availability of ATP in cardiac cells which has an
immediate and significant impact on resting membrane potential with a depolarizing
effect. Compared to normal conditions this depolarized tissue is relatively electronegative
in the extracellular space.
Q26. Hemorrhage leads to hypovolemic hypotension in an effort to compensate for the loss
of blood, the reflex response to hemorrhage includes
A. Increased heart rate, increased cardiac contractility and demand total
peripheral resistance
B. Increased heart rate, decreased cardiac contractility and increased total
peripheral resistance
C. Decreased heart rate, decreased cardiac contractility and increased total
peripheral resistance
D. Increased heart rate, increased cardiac contractility and licensed total
peripheral resistance
Correct answer: D.) Increased heart rate, increased cardiac contractility and
increased total peripheral resistance.
Reasoning: Hypovolemic hypotension means that the systemic blood pressure is
decreased due to blood loss. Reflex compensatory mechanisms will attempt to return
blood pressure back to normal. Because the pressure is decreased and because MAP =
CO x TPR, the reflex response will be to increase both the cardiac output (CO) and the
total peripheral resistance (TPR). Thus, heart rate, contractility and total peripheral
resistance will all increase.
Q27. Increased sympathetic efferent activity in response to hemorrhage will cause
increase in venous tone, which will
A. Increase venous compliance and mores venous return
B. Decrease venous compliance and mobilize’ venous blood
C Decrease venous return and reduce pulmonary arterial pressure
D. Increase venous tone and decrease venous return
Correct answer: B.) Decrease venous compliance and ‘mobilize’ venous blood.
Reasoning: Increasing venous vascular tone will cause venoconstriction and decrease
venous compliance. The venous reservoir will be reduced, ‘mobilizing’ and redistributing
venous blood to the arterial side of the vasculature to help compensate for the loss of total
blood volume.
Q28. Cardiovascular mums may be caused by
A. Increased velocity of flow through a narrowed vessel
B. Significant irregularities in a vessel wall
C. Turbulent flow through a damaged cardiac valve
D. All of the above
Correct answer is: D.) All of the above.
Reasoning: Cardiovascular murmurs occur due to turbulent blood flow. Turbulent flow
occurs when 1.) the laminar flow of blood is disrupted by irregularities in the flow path,
or 2.) the velocity of flow is very high.
Q29. Flow of fluid through the lymphatic vessels will be decreased if there is an increase
A. capillary hydrostatic pressure
B. capillary permeability
C. interstitial protein concentration
D. capillary oncotic pressure
Correct answer: D.) Capillary oncotic pressure.
Reasoning: Lymph flow is related directly to the amount of fluid filtered out of the
capillaries. Fluid exchange depends on the capillary permeability and the Starling Forces
of hydrostatic and oncotic pressures. Increasing the plasma oncotic pressure will tend to
decrease fluid filtration from blood to tissue and thus will reduce lymph flow.
Q30. The Nucleus Tractus Solitarius (NTS) integrates information is receives from Cranial
Nerves (CN) IX and X. The NTS sends signals to the cardiovascular brain stem centers
Which of the three centers are stimulated in response to increased IX and X input to the NTS?
A Cardiac Accelerator
B. Vasoconstrictor
C. Cardiac Decelerator.
D. All of the above.
Correct answer: C.) Cardiac Decelerator.
Reasoning: The input to the NTS, via Cranial Nerves IX and X, is increased when blood
pressure is increased. In response, input to the cardiac decelerator center is increased.
Heart rate is reduced which will reduce cardiac output and return blood pressure back to normal levels
Q31. If there is inadequate blood flow to the brain, the body quickly responds by:
A. Inducing vasodilatation of cerebral arterioles by producing nitric oxide.
B. Causing sympathetic vasoconstriction and sympathetic cardiac stimulation
C. Increasing heart rate and inhibiting sympathetic stimulation of cerebral arterioles.
D. Causing release of epinephrine into the blood stream which binds to B- receptors of smooth muscle cells in cerebral arteries and causes their vasodilatation
Correct answer: B.) causing sympathetic vasoconstriction and sympathetic cardiac
stimulation.
Reasoning: An extremely strong autonomic response, called the cerebral ischemic
response, is triggered by inadequate brain blood flow, which can produce a more intense
sympathetic vasoconstriction and cardiac stimulation than is elicited by any other
influence on the cardiovascular control centers.
Q32. The enzyme ultimately responsible for the formation of fibrin monomers is:
A. Heparin
B. Thrombin
C. Plasminogen.
D. Kininogen.
Correct answer: B.) Thrombin
Reasoning: Thrombin is generated from pro-thrombin by activating factor X. Activation
of factor X occurs by both the extrinsic and intrinsic pathways, Kininogens are enzymes
responsible for the production of peptides (kinins) associated with inflammation
Plasminogen is the inactive precursor of plasmin, the proteolytic enzyme involved in clot
dissolution. Heparin is an anticlotting agent that is found on endothelial cell surfaces.
Q33 .Which of the following signs is observed in a patient who has lost a significant amount
of blood?
A. Respiratory acidosis.
B. Dry skin
C. Polyuria.
D. Low hematocrit.
Correct answer: D.) Low Hematocrit.
Reasoning: Blood loss causes the blood pressure to fall. The baroreceptor reflex will
cause arteriolar resistance to increase, decreasing capillary hydrostatic pressure. The
decrease in capillary pressure will cause a net fluid reabsorption from tissue to blood,
decreasing the hematocrit. Arteriolar constriction will lower blood flow to the kidney,
lowering urine output. The sympathetic outflow will increase sweating, causing cold,
damp skin
Q34. The renin-angiotensin-aldosterone system regulates blood pressure primarily by
Regulating __________. A decrease in blood pressure causes _____________ to be converted to _____
in the juxtaglomerular cells of the kidneys.
A. blood volume; prorenin; renin
B. red cell production; angiotensinogen; angiotensin
C. vasomotor tone; proadrenaline; adrenaline
D. blood volume; prothrombin; thrombin
Correct answer: A.) blood volume; prorenin; renin
Reasoning: The renin-angiotensin system is involved in long-term regulation of blood
pressure. The system influences blood pressure principally by regulating blood volume.
The decrease in perfusion pressure is sensed by mechanoreceptors in the afferent
arterioles in the kidney. The next step in the response is conversion of prorenin to renin in
the juxtaglomerular cells. Renin catalyzes the conversion of angiotensinogen to
angiotensin I. In the presence of angiotensin converting enzyme, angiotensin I is
converted to angiotensin II, which acts on the adrenal cortex, vascular smooth muscle, the
central nervous system, and the kidneys.
Q35. Mechanisms to regulate a long-term increase in arterial pressure would cause:
A. a decrease in urine output rate and an increase in blood volume.
B. no change in urine output rate
C. an increase in urine output rate and a decrease in blood volume.
D. a decrease in total peripheral resistance.
Correct answer: C.) an increase in urine output rate and a decrease in blood
volume.
Reasoning: Increased arterial pressure leads to increased urine output rate and hence fluid
volume depletion, and thus blood volume depletion. A reduced blood volume leads to a
decreased cardiac output, and hence a reduced arterial pressure. This is a negative
feedback mechanism. A decrease in total peripheral resistance arises from the baroreceptor response to an acute increase in arterial pressure.
Q36. According to Poiseuille’s Equation, blood flow through a blood vessel is directly
proportional to
A Vessel Length
B. Blood Viscosity
C. Vessel Radius, squared
D. Pressure Gradient along the vessel length:
Correct answer: D.) Pressure Gradient along the vessel length
Reasoning Upon examination of Poiseuille’s equation, it should be clear that blood flow
is inversely proportional to vessel segment length ( ) and Viscosity, but directly
proportional to the fourth power of the radius (R), and to the PRESSURI GRADUNT
(PL)
Q37. Arteries can withstand higher pressures than veins of similar diameter because:
A. A greater circumferential stress for a given pressure is generated in arteries than in veins.
B. Arteries do not contain valves.
C. Arteries have thicker media than veins of similar diameter
D. Arteries are more compliant than veins
Correct answer: C.) arteries have thicker media than veins.
Reasoning Stress (Pressure x Radius/Wall Thickness, so a thicker wall means loss
stress for a given pressure
Q38. Warfarin (coumarin) is an anti-coagulant that is often given to patients following a
heart attack. However, it too much warfarin is administered, the patient can have
episodes of bleeding. The bleeding produced by warfarin can be overcome by administering
A. Aspirin
B. Heparin.
C. Vitamin K
D. I-PA (tissue plasminogen activator)
Correct answer: C) Vitamin K.
Reasoning Warfarin is often prescribed for patients at risk for thromboembolic events,
Vitamin K is necessary for the conversion of prothrombin to thrombin. Thrombin
converts fibrinogen to fibrin and activates platelets Warfarin interferes with the activity
of Vitamin K and therefore reduces the likelihood of clot formation. Heparin prevents
clotting by inhibiting thrombin. Aspirin inhibits platelet aggregation Tissue plasminogen
activator is a thrombolytic agent
Q39. What type of blood vessel has the lowest mean blood velocity?
A. Arteries
B. Arterioles
C. Capillaries
D. Venules
E. Veins
Correct answer: C.) Capillaries
Q40. If total volumetric flow through a microvascular bed is 100 cubic centimeters per
second and mean velocity is 1 centimeter per second, what is the best estimate of the total
cross-sectional area of the microvascular bed?
A. I centimeter squared
B. 10 centimeters squared
C. 50 centimeters squared
D. 100 centimeters squared
Correct answer: D.) 100 centimeters squared.
Reasoning: Blood Flow – Velocity x Cross-Sectional Area
Q41. Vessel B has twice the length and double the radius of vessel A. Which vessel has the highest resistance to flow?
A Vessel A
B. Vessel B
Correct answer: A.) Vessel A
Reasoning: The resistance of vessel A is INVERSELY proportional to it’s radius raised
to the fourth power, whereas the resistance of vessel B, relative to vessel A, is
INVERSELY proportional to 8 times it’s radius raised to the fourth power. Hence, the
resistance of vessel A is 8 times greater than vessel B.
Q42. If the plasma protein concentration is suddenly decreased, the net filtration through the
capillary wall will:
A. Decrease
B. Increase
C. Stay the same
D. Change direction so that there is a net fluid absorption.
Correct answer: B. Increase
Reasoning Plasma colloid osmotic pressure in decreased so less fluid in reabsorbed into
the capillary from the tissue
Q43. A small molecule will tend to diffuse from the blood, across the capillary wall, and
into the tissue only if.
A. Hydrostatic pressure in the capillary is greater than the plasma colloid osmotic pressure.
B. The rate of blood flow is not too high.
C. The concentration of the molecule is higher in the blood than in the tissue
D. The capillaries contain fenestrae.
Correct answer C. the concentration of the molecule is higher in the blood than in the tissue
Reasoning : The driving force for the DIFFUSION of any molecule is its concentration gradient
Q44. If an organ’s metabolic activity increases, which one of the following events will most
likely occur?
A. Mean arterial pressure will increase and blood flow to the organ will increase
B. Parasympathetic nerves are stimulated and arterioles serving the organ dilate.
C. Epinephrine is released from the adrenal medulla and arterioles dilate.
D. Arterioles serving the organ dilate in response to local chemical changes
Correct answer: D.) Arterioles serving the organ dilate in response to local chemical
changes
Reasoning Arteriolar dilation is the response to increased accumulation of metabolites in
the tissue It leads to an increase in blood flow. This local response does not have to be
accompanied by an increase in mean arterial pressure
Q45. Venous return (VR) will increase if:
A. Central venous pressure (CVP) increases.
B. Venous resistance (Rv) increases,
C. Peripheral venous pressure (PVP) decreases.
D. Peripheral venous pressure (PVP) increases.
Correct answer: D. peripheral venous pressure (PVP) Increases
Q50. Turbulent flow can occur in:
A. veins
B. capillaries
C. arteries
D. lymphatics
Correct answer: C.) Arteries.
Reasoning: Inertial forces are too low in other vessels.
Q51. A high arterial pulse pressure together with a normal mean arterial pressure indicates:
A. arterial compliance is low.
B. total peripheral resistance is high.
C. cardiac output is low.
D. arterial compliance is high.
Correct answer: A.) arterial compliance is low.
Reasoning: The two determinants of pulse pressure are stroke volume and arterial
compliance. The two determinants of mean arterial pressure are cardiac output and total
peripheral resistance. If mean arterial pressure is normal, then it is fair to assume that
cardiac output and hence stroke volume are normal. It follows, then, that the high arterial
pulse pressure must be the result of a low arterial compliance. In other words, the arteries
are rigid and one should suspect problems with atherosclerosis.
Q52. Most of the total blood volume in the body is contained in:
A. systemic arteries
B. systemic veins
C. capillaries
D. pulmonary circulation.
Correct answer: B.) systemic veins.
Q53. During exercise, arterioles in the coronary circulation relax, while those in the
gastrointestinal circulation constrict because:
A. coronary arteriolar smooth muscle cells do not possess alpha-receptors.
B. coronary arterioles do not possess adrenergic nerves.
C. cardiac metabolism increases and functional hyperemia occurs.
D. gastrointestinal metabolism increases causing vasoconstriction,
Correct answer: C.) cardiac metabolism increases and functional hyperemia occurs.
Reasoning: During exercise, the total body oxygen demand increases, largely due to
increased skeletal muscle metabolism. To meet the increased demand, the total body
oxygen delivery, and thus the cardiac output, must increase. Increased cardiac work and
increased cardiac metabolism are required to increase the cardiac output. Functional
hyperemia in the heart means that the coronary blood vessels reflexly vasodilate,
increasing blood flow, nutrient delivery and removal of waste products to meet the
increased cardiac demand. This response is localized and does not require central control
mechanisms
Q54. When a subject is frightened, blood flow through skin arterioles is reduced. This is
caused by:
A. release of nitric oxide.
B. stimulation of the sympathetic nervous system.
C. decreased production of norepinephrine.
D. increased concentration of Potassium in tissues.
Correct answer: B.) stimulation of the sympathetic nervous system.
Reasoning: A, C and D would all result in arteriolar dilation and increased flow through
the skin.
Q55. Small (less than 1 nm diameter) lipid insoluble molecules, such as glucose, may cross
the endothelium by passing through:
A. the cell membrane.
B. junctions between cells.
C. fenestrae.
D. pinocytotic vesicle channels.
E. A and B above.
F. B and D above.
G. B, C and D above.
H. C and D above.
Correct answer: G.) B (junctions between cells), C (through fenestrae), and D
(through pinocytotic vesicle channels).
Reasoning: Lipid insoluble molecules do not pass through the cell membrane.
Q56. Plasma colloid osmotic pressure is dependent on:
A. the number of protein molecules per unit volume of plasma.
B. plasma viscosity.
C. temperature.
D. blood flow rate.
E. A only
F. A and C above.
G. C and D above
H. A, B and C above.
Correct answer: F.) A (the number of protein molecules per unit volume of plasma),
and C (the absolute temperature).
Reasoning: The Plasma Colloid Osmotic Pressure = sigma * R*T*(Ci – Co).
Q57. When a person lies down horizontally after standing for a long period of time, their
venous blood will be redistributed more evenly between their leg veins and their thoracic
veins. This will immediately result in which of the following responses:
A. a decrease in central venous pressure (CVP).
B. a decrease in cardiac output (CO).
C. an increase in central venous pressure (CVP).
D. an increase in resistance of the peripheral veins.
Correct answer: C.) An increase in central venous pressure (CVP).
Reasoning: Veins contain the greatest percentage of blood in the body and they are very
compliant. When a person stands, the combined effects of gravity and venous compliance
cause blood to pool in the leg veins. Assuming a horizontal position will shift some of
this blood to the vena cava because gravity no longer exerts its downward force on this
volume of blood. The volume of blood that shifts into the vena cava is large enough to
increase the pressure in the thoracic vena cava so that central venous pressure (CVP) will
increase
Q58. Which of the following statements is FALSE. The myogenic response is associated
with:
A. a change in smooth muscle cell membrane potential.
B. opening of calcium channels in smooth muscle cell membrane.
C. stimulation of G-protein by norepinephrine.
D. stretching of the arteriolar wall.
Correct answer: C.) stimulation of G-protein by norepinephrine.
Reasoning: The myogenic response is thought to act by opening stretch-sensitive cation
channels. Sodium ions then enter the cell and depolarize the membrane gradually, which
will subsequently open voltage-dependent calcium channels.
Q59. Which of the following statements is FALSE. The net rate at which water filters
across capillary walls from blood to tissue depends on:
A. capillary pressure.
B. sodium pumps.
C. capillary filtration coefficient,
D. reflection coefficient to albumin.
Correct answer: B.) sodium pumps.
Reasoning: See the Starling Equation for transcapillary fluid flow.
Open resource