Physiology I- Cardiac Physiology Practice Questions Exam 3

Question 1

An abnormality that causes a sustained decrease in left ventricular compliance is most likely to result in an increased:

a. Left ventricular stroke volume
b. Left atrial volume and pressure
c. Left ventricular afterload
d. Pulmonary blood low
e. Left ventricular end-diastolic volume

Answer 1

B. Left atrial volume and pressure

Question 2

Intrinsic control of blood flow is most likely to predominate over extrinsic control of blood flow in:

a. The splanchnic circulation
b. The kidneys
c. Resting skeletal muscle
d. Exercising skeletal muscle
e. Skin

Answer 2

D . Exercising skeletal muscle

Question 3

Compared with the systemic circulation, the pulmonary circulation:

a. Carries more blood low per minute.
b. Has a lower perfusion pressure.
c. Has a higher resistance to blood low.
d. Carries blood that has a lower hematocrit.
e. Contains a higher blood volume.

Answer 3

B. Has a lower perfusion pressure.

Question 4

In response to an increase in perfusion pressure, the arterioles
of an autoregulating organ _______________, and the vascular
resistance of the organ _______________.
a. constrict; increases
b. constrict; decreases
c. dilate; increases
d. dilate; decreases

Answer 4

A. constrict; increases

Question 5

Blood low to skeletal muscle increases dramatically during dynamic exercise (e.g., running or swimming, during which
the exercising muscles alternate between contraction and relaxation). The increase in muscle blood low is much smaller during static exercise (e.g., pushing hard against an immovable object, during which the exercising muscles maintain a forceful,
steady contraction). he limited increase in muscle blood low during static exercise is best explained by:
a. Mechanical compression of muscle blood vessels.
b. Metabolic control of muscle blood low, leading to arteriolar vasodilation.
c. Metabolic control of muscle blood low, leading to arteriolar vasoconstriction.
d. Autoregulation of blood flow, leading to arteriolar vasoconstriction.
e. The release of histamine and bradykinin by the contracting
muscle cells.

Answer 5

A. Mechanical compression of muscle blood vessels.

Question 6

The rate of diffusion of glucose molecules from capillary blood to interstitial fluid is most directly affected by the:

a. Capillary plasma oncotic pressure.
b. Interstitial fluid hydrostatic pressure.
c. Size and number of capillary pores.
d. Amount of oxygen in the blood.
e. Hematocrit.

Answer 6

C. Size and number of capillary pores

Question 7

During which phase of a normal ventricular action potential is it most likely that fast Na+ channels are in an inactivated state, slow Ca2+ channels are open, and most K+ channels are closed?

a. Phase 0 (rapid depolarization)
b. Phase 1 (partial repolarization)
c. Phase 2 (plateau)
d. Phase 3 (repolarization)
e. Phase 4 (rest)

Answer 7

C. Phase 2 (plateau)

Question 8

When a young dog with a PDA attempts vigorous exercise:

a. Arterioles in the exercising skeletal muscle constrict.
b. Oxygen concentration in the skeletal muscle interstitial fluid decreases.
c. Left ventricular output decreases.
d. Right ventricular output decreases.
e. Mean arterial pressure increases to very high levels.

Answer 8

B. Oxygen concentration in the skeletal muscle interstitial fluid decreases.

Question 9

A patient with a form of protein-losing kidney disease has a plasma colloid osmotic pressure of 10 mm Hg. The patient has edema but is not getting any worse. Blood pressure and heart rate are normal. Which of the following is probably preventing further edema?

a. Increased capillary hydrostatic pressure
b. Decreased lymph low
c. Decreased concentration of plasma proteins in the plasma
d. Increased interstitial fluid oncotic pressure
e. Increased interstitial fluid hydrostatic pressure

Answer 9

E. Increased interstitial fluid hydrostatic pressure

Question 10

Which of the following would cause mean aortic pressure to increase?

a. Stroke volume increases from 30 to 40 mL, and heart rate decreases from 100 to 60 beats/min.
b. Arterial compliance decreases.
c. Cardiac output decreases.
d. Arterioles throughout the body dilate.
e. TPR increases.

Answer 10

E. TPR increases

Question 11

The metabolic control mechanism serves to match blood low
in a tissue to the tissue’s metabolic activity. Which of the following variables is actually being regulated (i.e., held constant) by the metabolic control mechanism?
a. Perfusion pressure applied to the tissue.
b. Blood low to the tissue.
c. Arteriolar resistance in the tissue.
d. Oxygen concentration in the tissue interstitial fluid.
e. The number of open capillaries (i.e., the number of capillaries carrying blood low at any one time).

Answer 11

D. Oxygen concentration in the tissue interstitial fluid.

Question 12

Which of the following intervals on an ECG most closely corresponds to the time required for propagation of a cardiac action potential through the AV node?

a. RR interval
b. PR interval
c. ST interval
d. PP interval
e. QT interval

Answer 12

B. PR interval

Question 13

The normal pathway followed by a cardiac action potential is to begin in the SA node and then propagate:

a. Across the atria in the bundle of His.
b. Through the connective tissue layers that separate the atria and ventricles.
c. Across the atria and into the AV node.
d. From the left atrium to the right atrium.
e. From the left atrium to the left ventricle and from the right atrium to the right ventricle.

Answer 13

C. Across the atria and into the AV node.

Question 14

Which of the following cause-and-effect statements is true for a normal heart?

a. Sympathetic activation causes end-systolic ventricular volume to increase.
b. An increase in ventricular preload causes end-diastolic ventricular volume to decrease.
c. Pacing the heart at a high rate causes stroke volume to decrease.
d. An increase in ventricular contractility causes systolic duration to increase.
e. An increase in ventricular contractility causes the external work of the heart to decrease.

Answer 14

C. Pacing the heart at a high rate causes stroke volume to decrease.

Question 15

For the dog described in Question 6, the perfusion pressure for the systemic circulation is approximately _________ the
perfusion pressure for the pulmonary circulation.
a. Half as much as
b. Equal to
c. Twice as high as
d. Four times higher than
e. Nine times higher than

Answer 15

D. Four times higher than

Question 16

Starting at the open circle in Fig. 21.12, which point would be reached after the contractility decreased and the preload increased?

a. Point A
b. Point B
c. Point C
d. Point D
e. Point E

Answer 16

E. Point E

Question 17

The blood low through the brain of a resting dog would be decreased most by a 20% decrease in the:

a. Mean arterial pressure
b. Heart rate
c. Systemic perfusion pressure
d. Radius of arteries in the brain
e. Radius of arterioles in the brain

Answer 17

E. Radius of arterioles in the brain

Question 18

A transfusion of normal plasma into a normal dog would:

a. Decrease the hematocrit of the recipient’s blood.
b. Increase the viscosity of the recipient’s blood.
c. Decrease the mean corpuscular hemoglobin concentration (MCHC) in the recipient’s plasma.

d. Increase the number of cells in the recipient’s blood.
e. Decrease the concentration of proteins in the recipient’s plasma.

Answer 18

A. Decrease the hematocrit of the recipient’s blood.

Question 19

Fig. 21.11 shows a plot of the changes in pressure and volume that occur in the left ventricle during one normal cardiac cycle.
Which of the following is true regarding this plot?
a. Point D marks the beginning of isovolumetric relaxation.
b. Point B marks the closure of the aortic valve.
c. Point C marks the opening of the mitral valve.
d. Point A marks the beginning of isovolumetric contraction.
e. Point D marks the beginning of ventricular systole.

Answer 19

D. Point A marks the beginning of isovolumetric contraction.

Question 20

During a normal cardiac cycle, which of the following events
happens soonest after the first heart sound is heard?
a. Atrial contraction begins.
b. he mitral valve opens.
c. Atrial depolarization begins.
d. Ventricular ejection begins.
e. The aortic valve closes.

Answer 20

D. Ventricular ejection begins.

Question 21

Which of the following characteristically acts as a paracrine to cause vasoconstriction in systemic arterioles?

a. Carbon dioxide
b. Nitric oxide
c. Endothelin-1 (ET1)
d. Prostacyclin (PGI2)
e. Bradykinin

Answer 21

C. Endothelin-1 (ET1)

Question 22

The increase in coronary blood low during exercise is:

a. Called Starling’s law of the heart.
b. Called reactive hyperemia.
c. Caused by activation of parasympathetic nerves to the heart.
d. Caused by compression of the coronary blood vessels during systole.
e. Closely matched to the increased metabolic requirements of the heart muscle.

Answer 22

E. Closely matched to the increased metabolic requirements of the heart muscle.

Question 23

Which of the following is true for both cardiac muscle and skeletal muscle?

a. The muscle forms a functional syncytium.
b. An action potential in the muscle cell membrane is required to initiate contraction.
c. Pacemaker cells spontaneously depolarize to threshold and initiate action potentials.
d. Frequent action potentials in motor neurons can cause a sustained (tetanic) muscle contraction.
e. Extracellular Ca2+ enters the muscle cell during an action potential and triggers the release of additional Ca2+ from the sarcoplasmic reticulum

Answer 23

B. An action potential in the muscle cell membrane is required to initiate contraction.

Question 24

Which of the following will NOT cause pulmonary edema?

a. An increase in pulmonary capillary permeability to protein
b. A blockage of pulmonary lymph vessels c. An increase in left atrial pressure
d. A constriction of pulmonary arterioles
e. Left-sided heart failure

Answer 24

D. Constriction of pulmonary arterioles

Question 25

The volume of blood pumped by the left ventricle in 1 minute would equal:

a. The volume of blood that lowed through the coronary circulation (in the same minute).
b. The volume of blood that lowed through all organs of the systemic circulation, except for coronary blood flow.
c. The volume of blood that lowed through the lungs.
d. One-half of the cardiac output.
e. Two times the cardiac output.

Answer 25

C. The volume of blood that lowed through the lungs.

Question 26

Suppose that the following conditions exist in a particular blood vessel: blood pressure (BP) inside vessel at inlet = 60 mm Hg, BP inside vessel at midpoint = 50 mm Hg, and BP inside vessel at outlet = 40 mm Hg. Pressure in the tissue fluid (interstitial fluid) immediately outside vessel = 5 mm Hg. Under these conditions:
a. Perfusion pressure for blood low through this vessel = 20 mm Hg.

b. Perfusion pressure for blood low through this vessel =15 mm Hg.
c. Distending pressure at the vessel midpoint = 55 mm Hg.
d. Distending pressure at the vessel midpoint = 45 mm Hg.
e. Both a and d are correct.

Answer 26

E. Both a and d are correct.

Question 27

What would the lead I ECG look like if an ectopic pacemaker in the free wall of the left atrium subsumed the role of the SA node (i.e., “took over” the initiation of atrial action potentials)?

a. The ECG would appear normal.
b. The order of waves would be reversed (i.e. T-QRS-P, instead of P-QRS-T).

c. The P waves and T waves would appear normal, but there would be no R waves.
d. The P wave would be negative and the R wave would be positive.
e. The P wave would be negative and the R wave would be
negative.

Answer 27

d. The P wave would be negative and the R wave would be positive.

Question 28

During a 30-minute hemorrhage, a horse loses a substantial volume of blood. The horse’s mean arterial pressure decreases
from 90 to 75 mm Hg, and the heart rate increases from 40 to 90 beats/min. The skin becomes cool and the mucous membranes become pale, suggesting marked vasoconstriction. Because hemorrhage involves the loss of whole blood (both plasma and cells), you might expect that, soon after such a hemorrhage, the horse’s remaining blood would still have a
normal composition. However, you take a blood sample and discover that the hematocrit is abnormally low (only 28%). Which of the following would most likely account for the decrease in hematocrit observed after the hemorrhage?
a. Excessive capillary filtration has caused interstitial fluid pressure to increase above normal.
b. Excessive capillary filtration has caused capillary colloid osmotic pressure to increase above normal.
c. Arteriolar constriction has caused capillary hydrostatic pressure to increase above normal.
d. Low capillary hydrostatic pressure has caused interstitial fluid to be reabsorbed into the bloodstream.
e. Many blood cells have been filtered out of capillaries and into the interstitial fluid.

Answer 28

D. Low capillary hydrostatic pressure has caused interstitial fluid to be reabsorbed into the bloodstream.

Question 29

In which of the following arrhythmias will there be more atrial beats per minute than ventricular beats?

a. Complete (third-degree) AV block
b. Frequent premature ventricular contractions
c. Sick sinus syndrome (sinus bradycardia)
d. First-degree AV block
e. Ventricular tachycardia

Answer 29

A. Complete (third-degree) AV block

Question 30

Which of the following is a correct comparison between segments of the systemic circulation?

a. The aorta and large arteries have a higher resistance to blood low than the capillaries.
b. The arterioles have a higher resistance to blood low than the capillaries.
c. The veins have a higher resistance to blood low than the capillaries.
d. The aorta and large arteries have a higher compliance than the veins.
e. The aorta and large arteries contain a greater volume of blood than the veins and venae cavae.

Answer 30

B. The arterioles have a higher resistance to blood low than the capillaries.

Question 31

If aortic compliance decreases while heart rate, cardiac output, and total peripheral resistance (TPR) remain unchanged:

a. Pulse pressure will be unchanged.
b. Pulse pressure will increase.
c. Pulse pressure will decrease.
d. One cannot know the effect on pulse pressure because stroke volume may have changed.
e. One cannot know the effect on pulse pressure because mean aortic pressure may have changed.

Answer 31

B. Pulse pressure will increase.

Question 32

At the moment when an action potential begins propagating slowly through the AV node in a normal resting dog, the ventricular muscle cells are:

a. At their resting membrane potential.
b. Depolarizing slowly toward threshold for formation of an action potential.
c. Undergoing rapid depolarization at the beginning of an action potential.
d. At the plateau of an action potential.
e. Just ending their action potential (i.e., repolarizing back toward resting membrane potential

Answer 32

A. At their resting membrane potential.

Question 33

For continuous capillaries, such as those found in skeletal muscle, the capillary surface area available for diffusion is greatest for which of the following?

a. Glucose
b. Dissolved oxygen
c. Ions, such as Na+, K+, and Cl−
d. Amino acids
e. Plasma proteins

Answer 33

B. Dissolved O2

Question 34

An increase in heart rate could result from:

a. An increase in sympathetic nerve activity to the heart.
b. A decrease in parasympathetic nerve activity to the heart.
c. An abnormally rapid decrease in permeability of SA node cells to K+ during diastole.
d. An abnormally rapid increase in permeability of SA node cells to Na+ during diastole.
e. All the above are correct.

Answer 34

E. All of the above are correct

Question 35

Which of the following sequences of capillary beds might a red blood cell encounter in a normal circulation?

a. Lungs, skin, lungs, brain
b. Spleen, liver, mesentery, lungs
c. Coronary, kidney (glomerular), kidney (tubular), lungs
d. Lungs, coronary, stomach, liver
e. Brain, lungs, liver, coronary

Answer 35

A. Lungs, skin, lungs, brain

Question 36

A dog with an arterial blood pressure of 120/80 mm Hg has a cerebral blood low of 100 mL/min. When blood pressure is
increased to 130/100 mm Hg, the cerebral blood low increases
to 105 mL/min. his is an example of:
a. Active hyperemia
b. Autoregulation
c. Reactive hyperemia
d. The blood-brain barrier
e. Hypoxic vasoconstriction

Answer 36

B. Autoregulation

Question 37

In which of the following arrhythmias will the ECG characteristically show the same number of P waves and QRS complexes?

a. Complete (third-degree) AV block
b. First-degree AV block
c. Ventricular tachycardia
d. Atrial flutter
e. All the above are correct.

Answer 37

B. First degree AV block

Question 38

In the normal cardiac cycle:

a. The P wave in the electrocardiogram coincides with the beginning of ventricular ejection.
b. The second heart sound coincides with the beginning of isovolumetric relaxation.
c. Left ventricular pressure reaches its highest level just as the aortic valve closes.
d. Aortic pressure reaches its highest level at the beginning of ventricular systole.
e. The mitral valve is open throughout ventricular diastole.

Answer 38

B. The second heart sound coincides with the beginning of isovolumetric relaxation.

Question 39

What is the name of the condition when blood low to a tissue is inadequate to meet the metabolic needs of the tissue?

a. Anemia
b. Edema
c. Necrosis
d. Ischemia
e. Infarction

Answer 39

D. Ischemia

Question 40

The walls of most capillaries have pores or clefts in them, which are approximately 4 nm (4 × 10–9 m) in diameter. According to Fig. 18.7:

a. A capillary pore is many times larger in diameter than a sodium ion.
b. A capillary pore is many times larger in diameter than a glucose molecule.
c. The diameter of a red blood cell is many times greater than the diameter of a capillary pore.
d. A molecule of β globulin or γ globulin could just about squeeze through a capillary pore if it were lined up exactly right.
e. All of the above are correct.

Answer 40

E. All of the above are correct.

Question 41

Which of the following types of drugs would be the best choice to treat a patient with both supraventricular tachycardia and inadequate cardiac contractility?

a. Local anesthetic (fast Na+ channel blocker)
b. Muscarinic cholinergic antagonist
c. Beta-adrenergic agonist
d. Cardiac glycoside (inhibits Na+, K+ pump)
e. Calcium channel blocker

Answer 41

D. Cardiac glycoside (inhibits Na+, K+ pump)

Question 42

If the heart suddenly stops beating in an otherwise normal dog,
which of the following would be most likely to increase?
a. Mean circulatory filling pressure
b. Mean aortic pressure
c. Vena caval pressure
d. Perfusion pressure for the systemic circulation
e. Perfusion pressure for the pulmonary circulation

Answer 42

C. Vena caval pressure

Question 43

The magnitude of pulsations in blood pressure (caused by the pulsatile ejection of blood from the heart) is greatest in the:

a. Arteries
b. Arterioles
c. Capillaries
d. Veins
e. Venae cavae

Answer 43

A. Arteries

Question 44

The following parameters exist in the microcirculation of a skeletal muscle during a period of vigorous exercise:
Pc (capillary hydrostatic pressure) = 34 mm Hg
Pi (interstitial fluid hydrostatic pressure) = 10 mm Hg
πc (capillary plasma oncotic pressure) = 24 mm Hg
πi (interstitial fluid oncotic pressure) = 3 mm Hg
Which of the following is true?
a. These conditions favor filtration.
b. These conditions favor reabsorption.
c. These conditions favor neither filtration nor reabsorption.
d. It is not clear what these conditions favor because the concentration of plasma protein is not specified.
e. It is not clear what these conditions favor because the rate of lymph low is not specified.

Answer 44

A. These conditions favor filtration

Question 45

Histamine and bradykinin cause edema by increasing BOTH:

a. Capillary permeability to plasma protein AND interstitial hydrostatic pressure.
b. Interstitial colloid osmotic pressure AND lymph low.
c. Capillary hydrostatic pressure AND capillary permeability to plasma protein.
d. Capillary hydrostatic pressure AND plasma colloid osmotic pressure.
e. Lymph low AND interstitial hydrostatic pressure.

Answer 45

A. Capillary permeability to plasma protein AND interstitial hydrostatic pressure.

Question 46

An increase in the venous resistance (e.g., too tight a bandage on an extremity) causes edema because:

a. Lymph low increases.
b. Pinocytosis cannot remove excess interstitial fluid fast enough.
c. Capillary hydrostatic pressure increases. d. The interstitial proteins block up lymph channels.
e. The interstitial fluid pressure decreases

Answer 46

C. Capillary hydrostatic pressure increases.

Question 47

The following measurements are made on a dog exhibiting distress following surgery: heart rate, 80 beats/min; stroke volume, 30 mL; mean aortic pressure, 96 mm Hg; mean pulmonary artery pressure, 26 mm Hg; left atrial pressure, 5 mm Hg; and right atrial pressure, 12 mm Hg. Which of the following is the best estimate for the TPR of this dog?

a. 8.75 mm Hg/L/min
b. 10.83 mm Hg/L/min
c. 29.17 mm Hg/L/min
d. 35.00 mm Hg/L/min
e. 40.00 mm Hg/L/min

Answer 47

D. 35.00 mm Hg/L/min