Q: A 25-year-old endurance athlete has a resting heart rate (HR) of 50 bpm and a stroke volume (SV) of 100 ml/beat. What is their resting cardiac output ($$Q$$)? $$Q = HR \times SV$$

$$Q = 50 \times 100 = 5000 ml/$$min = 5 L/min

Q: A person has a heart rate of 120 bpm and a stroke volume of 60 ml/beat during maximal exercise. What is their cardiac output ($$Q$$)? $$Q = HR \times SV$$

$$Q = 120 \times 60 = 7200 ml/$$min = 7.2 L/min

Question 1

A 25-year-old endurance athlete has a resting heart rate (HR) of 50 bpm and a stroke volume (SV) of 100 ml/beat. What is their resting cardiac output ($$Q$$)?

$$Q = HR 	imes SV$$

Accepted Answer

$$Q = 50 	imes 100 = 5000 ml/$$min = 5 L/min

Question 2

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

Accepted Answer

The greater the stretch of cardiac muscle cells before contraction, the greater the force of contraction and stroke volume.

Question 3

A patient with hypertension is likely to experience which of the following changes in stroke volume ($$SV$$)?

Recall: $$SV = EDV - ESV$$

Accepted Answer

Increased afterload leads to increased ESV and decreased SV.

Question 4

Which factor is most important in determining preload?

Accepted Answer

Venous return

Question 5

During exercise, which organ receives the greatest increase in absolute cardiac output compared to rest?

Accepted Answer

Skeletal muscle

Question 6

Which of the following would most likely cause a decrease in end-systolic volume ($$ESV$$)?

Accepted Answer

Increased contractility due to sympathetic nervous system activation

Question 7

A patient is given a drug that blocks beta-1 adrenergic receptors. What is the expected effect on heart rate and contractility?

Accepted Answer

Both heart rate and contractility will decrease.

Question 8

Which hormone, released from the adrenal medulla, increases both heart rate and contractility?

Accepted Answer

Epinephrine

Question 9

A person has a heart rate of 120 bpm and a stroke volume of 60 ml/beat during maximal exercise. What is their cardiac output ($$Q$$)?

$$Q = HR 	imes SV$$

Accepted Answer

$$Q = 120 	imes 60 = 7200 ml/$$min = 7.2 L/min

Question 10

Which of the following best explains why endurance training lowers resting heart rate?

Accepted Answer

Increased vagal tone from the parasympathetic nervous system

Question 11

Which of the following is a direct effect of acetylcholine on the heart?

Accepted Answer

Hyperpolarization of pacemaker cells, slowing heart rate

Question 12

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 ($$SV$$)?

$$SV = EDV - ESV$$

Accepted Answer

$$SV = 130 - 60 = 70 ml$$

Question 13

Which of the following scenarios would most likely trigger the Bainbridge (atrial) reflex?

Accepted Answer

Rapid intravenous infusion increasing venous return

Question 14

Which of the following is NOT a direct regulator of heart rate?

Accepted Answer

Venous return

Question 15

Which of the following best describes afterload?

Accepted Answer

The pressure the ventricles must overcome to eject blood

Question 16

A 60-year-old male has a persistent heart rate of 110 bpm at rest. Which term best describes his condition?

Accepted Answer

Tachycardia

Question 17

Which of the following would most likely result from cutting the vagus nerve to the heart?

Accepted Answer

Resting heart rate would increase to approximately 100 bpm.

Question 18

Which of the following is a normal and desirable adaptation in endurance athletes?

Accepted Answer

Bradycardia due to increased stroke volume

Question 19

Which of the following would increase both heart rate and contractility?

Accepted Answer

Epinephrine release from the adrenal medulla

Question 20

Which of the following best explains why females, on average, have a higher resting heart rate than males?

Accepted Answer

Females generally have a smaller heart size, resulting in a higher heart rate to maintain cardiac output.

Heart Part 4 Cardiac Output and Heart Rate Regulation: ANP Study Guide

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