Chapter 14 concept questions

Question 1

A cardiovascular system has what three major components?

Answer 1

A cardiovascular system has tubes (blood vessels), fluid (blood), and a pump (heart)

Question 2

What is the difference between
(a) the pulmonary and systemic circulations,
(b) an artery and a vein,
(c) an atrium and a ventricle?

Answer 2

(a) pulmonary circulation takes blood to and from the lungs; systemic circulation takes blood to and from the rest of the body
(b) arteries carry blood away from the heart; veins carry blood blood to the heart
(c) atrium - upper heart chamber that receives blood entering the heart. Ventricle - lower heart chamber that pumps blood out of the heart.

Question 3

Which is more important for determining the flow through a tube: absolute pressure or the pressure gradient?

Answer 3

The pressure gradient is more important

Question 4

The two identical tubes below have the pressures shown at each end. Which tube has the greater flow? Defend your choice.

Answer 4

The bottom tube has a greater flow because it has a larger pressure gradient (50 mm Hg versus 40 mm Hg for the top tube)

Question 5

All four tubes below have the same driving pressure.

Which tube has the greatest flow?

Which has the least flow? Defend your choices.

Answer 5

Tube C has the highest flow because it has the largest radius of the four tubes (less resistance) and the shorter length (less resistance).

Tube B has the same radius as tube C but a longer length and therefore offers greater resistance to flow.

Tube D, with the greatest resistance due to its longer length & narrow radius, has the lowest flow.

Question 6

Two canals in Amsterdam are identical in size, but the water flows faster through one than through the other. Which canal has the higher flow rate?

Answer 6

If the canals are identical in size and therefore in cross-sectional area A, the canal with the higher velocity of flow v has the higher flow rate Q. (Q = v x A)

Question 7

What prevents electrical signals from passing through the connective tissue in the heart?

Answer 7

connective tissue is not excitable and is therefore unable to conduct action potentials

Question 8

Trace a drop of blood from the superior vena cava to the aorta, naming all structures the drop encounters along its route

Answer 8

superior vena cava –> right atrium —> tricuspid (right AV) valve –> right ventricle –> pulmonary (right semilunar) valve —> pulmonary trunk —> pulmonary vein –> left atrium –> mitral (bicuspid, left AV) valve –> left ventricle –> aortic (left semilunar) valve –> aorta.

Question 9

What is the function of the AV valves?

What happens to blood flow if one of these valves fails?

Answer 9

The AV valves prevent the backward flow of blood. If one fails, blood leaks back into the atrium.

Question 10

Compare the receptors and channels involved in cardiac EC coupling to those found in skeletal muscle EC coupling

Answer 10

skeletal muscle L-type Ca2+ channels (DHP receptors) are mechanically linked to sarcoplasmic reticulum RyR Ca2+ release channels.

Myocardial L-type Ca2+ channels open to allow Ca2+ into the cell. In both muscles, sarcolemma Ca2+ channels are associated with RyR Ca2+ release channels on the SR.

Question 11

If a myocardial contractile cell is placed in interstitial fluid and depolarized, the cell contracts. If Ca2+ is removed from the fluidsurrounding the myocardial cell and the cell is depolarized,it does not contract. If the experiment is repeated with a skeletal muscle fiber, the skeletal muscle contracts when depolarized, whether or not Ca2+ is present in the surrounding fluid. What conclusion can you draw from the results of this experiment?

Answer 11

It is possible to conclude that myocardial cells require extracellular Ca2+ for contraction but skeletal muscle cells do not.

Question 12

A drug that blocks all Ca2+ channels in the myocardial contractile cell membrane is placed in the solution around the cell. What happens to the force of contraction in that cell?

Answer 12

If all Ca2+ channels in the muscle cell membrane are blocked, there will be no contraction. If only some are blocked, the force of contraction will be smaller than the force created with all channels open.

Question 13

Which ions moving in what directions cause the depolarization and repolarization phases of a neuronal action potential?

Answer 13

Na+ influx causes neuronal depolarization, and K+ efflux causes neuronal repolarization

Question 14

At the molecular level, what is happening during the refractory period in neurons and muscle fibers?

Answer 14

The refractory period represents the time required for the Na+ channel gates to reset (activation gate closes, inactivation gate opens)

Question 15

Lidocaine is a molecule that blocks the action of voltage-gated cardiac Na+ channels. What happens to the action potential of a myocardial contractile cell if lidocaine is applied to the cell?

Answer 15

If cardiac Na+ channels are completely blocked with lidocaine, the cell will not depolarize and therefore will not contract. Partial blockade will decrease electrical conduction

Question 16

What does increasing K+ permeability do to the membrane potential of the cell?

Answer 16

Increasing K+ permeability hyperpolarizes the membrane potential.

Question 17

A new cardiac drug called ivabradine selectively blocks If channels in the heart. What effect would it have on heart rate and for what medical condition might it be used?

Answer 17

Ivabradine slows heart rate and is used to lower abnormally high heart rates.

Question 18

Do you think that the Ca2+ channels in autorhythmic cells are the same as the
Ca2+ channels in contractile cells? Defend your answer.

Answer 18

The Ca2+ channels in autorhythmic. cells are not the same as those in contractile cells.

Autorhythmic Ca2+ channels open rapidly when the membrane potential reaches about -50mV and close when it reaches about +20mV.

Question 19

What happens to the action potential of a myocardial autorhythmic cell if tetrodotoxin, which blocks voltage-gated Na+ channels, is applied to the cell?

Answer 19

If tetrodotoxin is applied, nothing will happen bc there are no voltage-gated Na+ channels in the cell.

Question 19

In an experiment, the vagus nerve, which carries parasympathetic signals to the heart, was cut. The investigators noticed that heart rate increased. What can you conclude about the vagal neurons that innervate the heart?

Answer 19

cutting the vagus nerve increased heart rate, so parasympathetic fibers in the nerve must slow heart rate

Question 20

Name two functions of the AV node. What is the purpose of AV node delay?

Answer 20

The AV node conducts action potentials from the atria to the ventricles. It also slows down the speed at which those action potentials are conducted, allowing atrial contraction to end before ventricular begins.

Question 21

Where is the SA node located?

Answer 21

The SA is in the upper right atrium

Question 22

Occasionally an ectopic pacemaker {ektopos, out of place} develops in part of the heart’s conducting system. What happens to heart rate if an ectopic atrial pacemaker depolarizes at a rate of 120 times per minute?

Answer 22

The fastest pacemaker sets the heart rate, so the heart rate increases to 120 beats/min

Question 23

During atrial filling, is pressure in the atrium higher or lower than the pressure in the venae cavae?

Answer 23

The atrium has lower pressure than the venae cavae.

Question 24

Which chamber—atrium or ventricle—has higher pressure during the following phases of the cardiac cycle?

a. ventricular ejection
b. isovolumic ventricular relaxation
c. atrial and ventricular diastole
d. isovolumic ventricular contraction

Answer 24

(a) ventricle, (b) ventricle, (c) atrium, (d) ventricle

Question 25

Murmurs are abnormal heart sounds caused either by blood forced through a narrowed valve opening or by backward flow (regurgitation) through a valve that has not closed completely. Valvular stenosis {stenos, narrow} may be an inherited condition or may result from inflammation or other disease processes. At which step(s) in the cardiac cycle (Fig. 14.18a) would you expect to hear a murmur caused by the following pathologies?

a. aortic valvular stenosis
b. mitral valve regurgitation
c. aortic valve regurgitation

Answer 25

a. ventricular ejection
b. isovolumic ventricular contraction and ventricular ejection
c. from isovolumic ventricular relaxation until ventricular contraction begins again.

Question 26

In Figure 14.19, at what points in the cycle do EDV and ESV occur?

Answer 26

EDV occurs in step 3, and ESV occurs in step 5.

Question 27

On the Wiggers diagram in Figure 14.19, match the following events to the lettered boxes:
a. end-diastolic volume,
b. aortic valve opens,
c. mitral valve opens,
d. aortic valve closes,
e. mitral valve closes,
f. end-systolic volume

Answer 27

(a) E, (b) A, (c) D, (d) B, (e) C, (f) F

Question 28

Why does atrial pressure increase just to the right of point C in Figure 14.19? Why does it decrease during the initial part of ventricular systole, then increase? Why does it decrease to the right of point D?

Answer 28

Atrial pressure increases because pressure on the mitral valve pushes the valve back into the atrium, decreasing atrial volume. Atrial pressure decreases during the initial part of ventricular systole as the atrium relaxes. The pressure then increases as the atrium fills with blood. Atrial pressure begins to decrease at point D, when the mitral valve opens and blood flows down into the ventricles.

Question 29

Why does ventricular pressure shoot up suddenly at point C in Figure 14.19?

Answer 29

Ventricular pressure shoots up when the ventricles contract on a fixed volume of blood.

Question 30

If the stroke volume of the left ventricle is 250 mL/beat and the stroke volume of the right ventricle is 251 mL/beat, what happens to the relative distribution of blood between the systemic and pulmonary circulation after 10 beats?

Answer 30

After 10 beats, the pulmonary circulation will have gained 10 mL of blood and the systemic circulation will have lost 10 mL

Question 31

Using the myocardial cell in Figure 14.10 as a model, draw a contractile cell and diagram how catecholamines increase myocardial contractility.

Answer 31

Your drawing should show a Bbeta1- receptor on the cell membrane activating intracellular cAMP, which should have an arrow drawn to Ca2+ channels on the sarcoplasmic reticulum. Open channels should be shown increasing cytoplasmic A second arrow should go from cAMP to Ca2+ on the SR and the cell membrane, showing increased uptake in the SR and increased removal of Ca2+ from the cell.

Question 32

A person’s aortic valve opening has become constricted, creating a condition known as aortic stenosis. Which ventricle is affected by this change? What happens to the afterload on this ventricle?

Answer 32

The aortic valve is found between the left ventricle and the aorta. A stenotic aortic valve would increase afterload on the ventricle.