Question 1

Which structure in the cardiac conduction system is responsible for setting the normal heart rhythm under physiological conditions?

Accepted Answer

Sinoatrial (SA) node

Question 2

If the SA node fails to function, which part of the cardiac conduction system can take over as the pacemaker, and how does the heart rate compare to normal?

Accepted Answer

The AV node; the heart rate will be slower than normal

Question 3

During the cardiac cycle, which event immediately follows the closure of the atrioventricular (AV) valves?

Accepted Answer

Isovolumetric contraction

Question 4

Which of the following best describes the function of gap junctions in cardiac muscle tissue?

Accepted Answer

They allow for the rapid spread of action potentials between adjacent cardiac cells.

Question 5

A patient has a mutation that increases the number of gap junctions between atrial cells. What is the most likely effect on the conduction of action potentials?

Accepted Answer

Conduction will be faster due to decreased resistance.

Question 6

Which phase of the cardiac cycle is characterized by all four heart valves being closed and no change in ventricular volume?

Accepted Answer

Isovolumetric contraction

Question 7

The formula for cardiac output is given by $$CO = HR 	imes SV. If a $$patient has a heart rate ($$HR) of$$ $$80\ 	ext{beats/min}$$ and a stroke volume ($$SV) of$$ $$70\ 	ext{mL/beat}$$, what is their cardiac output?

Accepted Answer

$$5600\ 	ext{mL/min}$$

Question 8

Which of the following would most likely increase stroke volume ($$SV) $$according to the Frank-Starling law of the heart?

Accepted Answer

Increased end-diastolic volume ($$EDV)$$

Question 9

A drug that blocks muscarinic receptors in the heart would have which of the following effects?

Accepted Answer

Increase heart rate by inhibiting parasympathetic activity

Question 10

Which of the following best explains why cardiac muscle cannot undergo tetanus like skeletal muscle?

Accepted Answer

The absolute refractory period in cardiac muscle is much longer, preventing summation of contractions.

Question 11

A patient with chronic hypertension has an increased afterload. What is the most likely effect on their stroke volume ($$SV) $$and end-systolic volume ($$ESV$$)?

Accepted Answer

$$SV$$ decreases and $$ESV$$ increases

Question 12

Which of the following events occurs during the ventricular ejection phase of the cardiac cycle?

Accepted Answer

Semilunar valves open

Question 13

Which of the following would most likely cause a positive inotropic effect on the heart?

Accepted Answer

Increased sympathetic nervous system stimulation

Question 14

A patient is given a drug that increases the permeability of cardiac pacemaker cells to potassium ions ($$K^+). $$What is the expected effect on heart rate?

Accepted Answer

Heart rate will decrease due to slower depolarization

Question 15

Which of the following best describes the effect of increased preload on cardiac output ($$CO$$), assuming all other factors remain constant?

Accepted Answer

Increased preload increases $$CO by $$increasing stroke volume

Question 16

Which of the following is the correct sequence of structures that an action potential passes through in the cardiac conduction system?

Accepted Answer

SA node → AV node → AV bundle → bundle branches → Purkinje fibers

Question 17

A patient with a mutation that decreases the number of gap junctions in the AV node would most likely experience which of the following?

Accepted Answer

Slower conduction of action potentials through the AV node

Question 18

Which of the following best explains why the AV node delays the conduction of action potentials?

Accepted Answer

To allow the atria to finish contracting before the ventricles contract

Question 19

If a patient’s end-diastolic volume ($$EDV) is$$ $$120\ 	ext{mL}$$ and their end-systolic volume ($$ESV) is$$ $$50\ 	ext{mL}$$, what is their stroke volume ($$SV$$)? Use the formula $$SV = EDV - ESV.$$

Accepted Answer

$$70\ 	ext{mL}$$

Question 20

Which of the following would most likely decrease cardiac output ($$CO$$), assuming all other factors remain constant?

Accepted Answer

Decreased venous return

Cardiovascular Physiology: The Conduction System, Electrophysiology, The Cardiac Cycle, and Regulation of Cardiac Output

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