Q: A patient has a heart rate of 90 beats per minute and a stroke volume of 70 ml/beat. What is their cardiac output?

Cardiac output = $$SV \times HR = 70 \text{ ml/beat} \times 90 \text{ beats/min} = 6300 \text{ ml/min}$$

Question 1

Which structure is responsible for initiating the electrical impulse that sets the rhythm of the heart?

Accepted Answer

Sinoatrial (SA) node

Question 2

During the plateau phase of the cardiac action potential in contractile cells, which ion is primarily responsible for maintaining the membrane potential near 0 mV?

Accepted Answer

Calcium ($$Ca^{2+})$$

Question 3

What is the formula for stroke volume (SV) and what does it represent?

Accepted Answer

SV = EDV - ESV; amount of blood ejected by a ventricle in one heartbeat

Question 4

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

Accepted Answer

They allow ions and action potentials to pass directly from cell to cell, enabling the myocardium to contract as a unit

Question 5

A patient has a heart rate of 90 beats per minute and a stroke volume of 70 ml/beat. What is their cardiac output?

Accepted Answer

Cardiac output = $$SV 	imes HR = 70 	ext{ ml/beat} 	imes 90 	ext{ beats/min} = 6300 	ext{ ml/min}$$

Question 6

Which event occurs during ventricular systole (late phase) in the cardiac cycle?

Accepted Answer

Semilunar valves open and blood is ejected from the ventricles

Question 7

What is the primary advantage of the long absolute refractory period in cardiac muscle cells?

Accepted Answer

It prevents tetanus, ensuring alternating contraction and relaxation for effective blood pumping

Question 8

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

Accepted Answer

Increased preload

Question 9

Which heart sound is associated with the closing of the AV valves?

Accepted Answer

S1: 'lubb'

Question 10

A patient with a damaged AV node may experience which of the following changes in their ECG?

Accepted Answer

Prolonged P-Q interval

Question 11

Which of the following best describes the Frank-Starling principle?

Accepted Answer

Increased end-diastolic volume (EDV) results in increased stroke volume (SV)

Question 12

Which of the following is a consequence of ventricular fibrillation?

Accepted Answer

Ventricles quiver and stop pumping blood, leading to cardiac arrest

Question 13

Which of the following would most likely occur if the vagus nerve was cut?

Accepted Answer

Heart rate would increase due to loss of parasympathetic inhibition

Question 14

Which phase of the cardiac action potential is characterized by the opening of voltage-gated fast $$Na^+$$ channels?

Accepted Answer

Rapid depolarization

Question 15

Which of the following is a positive ionotropic agent that increases contractility of cardiac muscle?

Accepted Answer

Epinephrine

Question 16

Which of the following best describes the sequence of excitation in the heart?

Accepted Answer

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

Question 17

Which of the following would most likely result in an increased afterload?

Accepted Answer

Atherosclerosis causing arterial narrowing

Question 18

Which ECG wave corresponds to ventricular depolarization?

Accepted Answer

QRS complex

Question 19

Which of the following is true regarding cardiac muscle metabolism?

Accepted Answer

Cardiac muscle adapts to different nutrient supplies, including fatty acids, glucose, and lactic acid

Question 20

A well-trained athlete has a higher stroke volume and lower heart rate at rest compared to a sedentary person. What happens to their cardiac output at rest?

Accepted Answer

It is the same as a sedentary person

Comprehensive Study Notes: The Heart and Cardiac Physiology

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