$$CO = HR \times SV = 90 \times 60 = 5400\ \text{mL/min}$$

$$\text{Cardiac Reserve} = \text{Maximal CO} - \text{Resting CO} = 35 - 5.25 = 29.75\ \text{L/min}$$

Question 1

Which event marks the beginning of ventricular systole in the cardiac cycle?

Accepted Answer

Closure of the atrioventricular (AV) valves

Question 2

A patient has a heart rate (HR) of 90 beats/min and a stroke volume (SV) of 60 mL/beat. What is their cardiac output (CO)?

Accepted Answer

$$CO = HR 	imes SV = 90 	imes 60 = 5400\ 	ext{mL/min}$$

Question 3

Which of the following best describes preload in the context of stroke volume regulation?

Accepted Answer

The degree of stretch of cardiac muscle cells before they contract

Question 4

During vigorous exercise, which factor primarily increases stroke volume?

Accepted Answer

Increased preload due to greater venous return

Question 5

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

Accepted Answer

Epinephrine

Question 6

A patient with persistent high blood pressure is at risk for which change in stroke volume?

Accepted Answer

Increased afterload and reduced stroke volume

Question 7

Which of the following is a positive inotropic agent that increases contractility?

Accepted Answer

Epinephrine

Question 8

If a person’s heart rate decreases due to increased parasympathetic stimulation, which neurotransmitter is responsible?

Accepted Answer

Acetylcholine

Question 9

Which of the following conditions is most likely to cause a feeble heartbeat and arrhythmias due to low potassium levels?

Accepted Answer

Hypokalemia

Question 10

A 25-year-old athlete has a resting cardiac output of 5.25 L/min and a maximal cardiac output of 35 L/min. What is their cardiac reserve?

Accepted Answer

$$	ext{Cardiac Reserve} = 	ext{Maximal CO} - 	ext{Resting CO} = 35 - 5.25 = 29.75\ 	ext{L/min}$$

Question 11

Which phase of the cardiac cycle is associated with the 'lub' sound heard during auscultation?

Accepted Answer

Closure of the AV valves

Question 12

Which of the following would most likely result in congestive heart failure (CHF)?

Accepted Answer

Coronary atherosclerosis

Question 13

A patient with hypercalcemia is likely to experience which effect on the heart?

Accepted Answer

Increased heart rate and contractility

Question 14

Which of the following best explains why the heart rate increases during exercise?

Accepted Answer

Increased sympathetic stimulation and release of norepinephrine

Question 15

Which ion’s extracellular concentration must be maintained for normal heart function, and if elevated, can cause heart block and cardiac arrest?

Accepted Answer

Potassium ($$K^+)$$

Question 16

Which of the following is a negative chronotropic factor?

Accepted Answer

Parasympathetic stimulation

Question 17

A patient’s ECG shows a prolonged QRS complex and they present with bradycardia. Which electrolyte imbalance is most likely responsible?

Accepted Answer

Hyperkalemia

Question 18

Which of the following would most likely increase venous return to the heart?

Accepted Answer

Slow heartbeat and exercise

Question 19

Which of the following is true regarding the effect of thyroxine on the heart?

Accepted Answer

It increases heart rate and enhances the effects of norepinephrine and epinephrine

Question 20

Which of the following best describes the effect of acetylcholine on pacemaker cells?

Accepted Answer

It hyperpolarizes pacemaker cells by opening potassium channels

The Heart: Cardiac Cycle, Cardiac Output, and Regulation

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