Question 1

Which of the following best describes the role of the SA node in the cardiac conduction system?

Accepted Answer

It initiates the action potential that sets the pace for the heart rate.

Question 2

During the plateau phase of a cardiac contractile cell action potential, which ion movement is primarily responsible for maintaining the membrane potential?

Accepted Answer

Influx of Ca$$^{2+}$$

Question 3

A patient presents with bradycardia. Which of the following is the most likely physiological explanation?

Accepted Answer

Increased parasympathetic stimulation of the SA node

Question 4

Which of the following equations correctly calculates stroke volume (SV)?

Accepted Answer

$$SV = EDV - ESV$$

Question 5

Which event occurs immediately after the QRS complex on an ECG?

Accepted Answer

Ventricular depolarization

Question 6

A patient with coronary artery disease experiences chest pain during exercise. What is the most likely physiological cause?

Accepted Answer

Decreased ATP production due to hypoxia

Question 7

Which of the following best explains why tetany does not occur in cardiac muscle?

Accepted Answer

Cardiac muscle has a long absolute refractory period.

Question 8

If the left ventricle's end-diastolic volume (EDV) is 140 mL and the end-systolic volume (ESV) is 60 mL, what is the stroke volume (SV)?

Accepted Answer

$$SV = 140\,mL - 60\,mL = 80\,mL$$

Question 9

Which of the following would most likely increase cardiac output (CO)?

Accepted Answer

Increased end-diastolic volume (EDV)

Question 10

Which of the following is a direct effect of sympathetic stimulation on the heart?

Accepted Answer

Increased heart rate

Question 11

Which phase of the cardiac cycle is associated with the closure of the AV valves and the first heart sound ('lubb')?

Accepted Answer

Ventricular systole (isovolumetric contraction)

Question 12

Which of the following best describes the Bainbridge (atrial) reflex?

Accepted Answer

An increase in heart rate in response to increased venous return

Question 13

Which of the following is true regarding the energy metabolism of cardiac muscle?

Accepted Answer

Cardiac muscle stores oxygen in myoglobin and uses aerobic metabolism.

Question 14

Which of the following would most likely result from a blockage in the left coronary artery?

Accepted Answer

Ischemia of the left ventricle

Question 15

Which of the following best describes the function of intercalated disks in cardiac muscle?

Accepted Answer

They allow for chemical and electrical coupling between cells.

Question 16

A patient has an ectopic pacemaker in the ventricles. What is the most likely effect on the heart rhythm?

Accepted Answer

The ventricles will contract at a faster, abnormal rate.

Question 17

Which of the following is the correct formula for cardiac output (CO)?

Accepted Answer

$$CO = HR 	imes SV$$

Question 18

Which of the following changes would most likely decrease stroke volume (SV)?

Accepted Answer

Increased end-systolic volume (ESV)

Question 19

Which of the following best explains why the left and right sides of the heart have equal cardiac output?

Accepted Answer

Both sides must pump the same volume to maintain continuous circulation.

Question 20

Which of the following is a feature of nodal (pacemaker) cells but NOT contractile cardiac cells?

Accepted Answer

Ability to spontaneously depolarize

Ch. 20 pt.2: Cardiac Physiology: Structure, Function, and Dynamics of the Heart

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