Q: If a patient has an end diastolic volume (EDV) of 130 mL and an end systolic volume (ESV) of 60 mL, what is their stroke volume (SV)?

$$SV = EDV - ESV = 130\,\text{mL} - 60\,\text{mL} = 70\,\text{mL}$$

Question 1

Which of the following best describes the sequence of electrical excitation in the heart's intrinsic conduction system?

Accepted Answer

Sinoatrial node → Atrioventricular node → Atrioventricular bundle → Right and left bundle branches → Subendocardial conducting network (Purkinje fibers)

Question 2

During the pacemaker potential phase in cardiac pacemaker cells, which ion channels are primarily responsible for the slow depolarization?

Accepted Answer

Slow Na$$^+$$ channels open and K$$^+$$ channels close

Question 3

Which event is represented by the QRS complex on an ECG?

Accepted Answer

Ventricular depolarization and atrial repolarization

Question 4

A patient presents with a heart rate of 45 beats per minute and absent P waves on their ECG. Which of the following is the most likely explanation?

Accepted Answer

The SA node is nonfunctional and the AV node is pacing the heart (junctional rhythm)

Question 5

Which of the following equations correctly represents cardiac output (CO)?

Accepted Answer

$$CO = HR 	imes SV$$

Question 6

If a patient has an end diastolic volume (EDV) of 130 mL and an end systolic volume (ESV) of 60 mL, what is their stroke volume (SV)?

Accepted Answer

$$SV = EDV - ESV = 130\,	ext{mL} - 60\,	ext{mL} = 70\,	ext{mL}$$

Question 7

Which of the following best explains why the action potential in cardiac contractile cells has a plateau phase?

Accepted Answer

The plateau is due to Ca$$^{2+}$$ influx through slow Ca$$^{2+}$$ channels, keeping the cell depolarized

Question 8

A patient with persistent high blood pressure has an increased afterload. What effect does this have on stroke volume (SV) and end systolic volume (ESV)?

Accepted Answer

Increased afterload increases ESV and decreases SV

Question 9

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

Accepted Answer

Increased heart rate and increased contractility

Question 10

Which of the following best describes the Frank-Starling law of the heart?

Accepted Answer

The greater the preload (stretch), the greater the force of contraction

Question 11

A patient is diagnosed with ventricular fibrillation. What is the most immediate risk associated with this condition?

Accepted Answer

The heart cannot pump blood effectively, leading to cessation of circulation and risk of brain death

Question 12

Which of the following would most likely cause a heart murmur due to backflow of blood?

Accepted Answer

An incompetent (insufficient) valve

Question 13

Which of the following is the correct formula for stroke volume (SV)?

Accepted Answer

$$SV = EDV - ESV$$

Question 14

Which of the following would most likely be seen in a patient with left-sided heart failure?

Accepted Answer

Pulmonary congestion due to blood backing up in the lungs

Question 15

Which of the following is a likely effect of hyperkalemia on the heart?

Accepted Answer

It can lead to heart block and cardiac arrest

Question 16

Which of the following best explains why the heart cannot undergo tetanic contractions like skeletal muscle?

Accepted Answer

The long absolute refractory period in cardiac muscle prevents tetanus

Question 17

A patient has a heart rate of 100 beats/min and a stroke volume of 60 mL/beat. What is their cardiac output?

Accepted Answer

$$CO = HR 	imes SV = 100\,	ext{beats/min} 	imes 60\,	ext{mL/beat} = 6000\,	ext{mL/min}$$

Question 18

Which of the following is true regarding the effect of the parasympathetic nervous system on the heart?

Accepted Answer

It decreases heart rate by hyperpolarizing pacemaker cells via K$$^+$$ channels

Question 19

Which of the following is a direct result of the Bainbridge (atrial) reflex?

Accepted Answer

Increased heart rate in response to increased venous return

Question 20

Which of the following congenital heart defects involves both mixing of oxygen-poor and oxygen-rich blood and narrowed valves or vessels?

Accepted Answer

Tetralogy of Fallot

Electrical and Mechanical Events of the Heart: ANP Study Guide

Study Guide - Practice Questions

Study Guide - Flashcards