Question 1

Which structural feature allows cardiac muscle cells to contract as a functional syncytium, unlike skeletal muscle cells?

Accepted Answer

Intercalated discs containing gap junctions and desmosomes

Question 2

A patient has a mutation that prevents the opening of Ca$$^{2+}$$ channels in pacemaker cells. Which phase of the pacemaker action potential would be most affected?

Accepted Answer

Depolarization phase

Question 3

Which of the following best describes the difference in contraction initiation between skeletal and cardiac muscle?

Accepted Answer

Cardiac muscle contracts automatically due to autorhythmic cells, while skeletal muscle requires neural input

Question 4

During the cardiac cycle, which event immediately follows ventricular depolarization as seen on an ECG?

Accepted Answer

Ventricular repolarization (T wave)

Question 5

If the sinoatrial (SA) node fails to function, which pacemaker center will set the heart rate, and what is the expected rate?

Accepted Answer

AV node; \u003e50 bpm

Question 6

Which equation correctly calculates cardiac output (CO)?

Accepted Answer

$$CO = SV 	imes HR$$

Question 7

A patient with hypertension has increased afterload. What is the expected effect on stroke volume (SV) and end-systolic volume (ESV)?

Accepted Answer

SV decreases, ESV increases

Question 8

Which of the following is responsible for the pacemaker potential in SA node cells?

Accepted Answer

Opening of Na$$^+$$ 'funny' channels and closing of K$$^+$$ channels

Question 9

Which of the following statements about the volumes pumped by the left and right sides of the heart is correct?

Accepted Answer

Both sides pump equal volumes of blood

Question 10

Which phase of the contractile cardiac muscle cell action potential is responsible for the plateau, and what ion movement causes it?

Accepted Answer

Phase 2; Ca$$^{2+}$$ influx

Question 11

Which of the following best explains why tetanus cannot occur in cardiac muscle?

Accepted Answer

The long refractory period prevents summation of contractions

Question 12

Which of the following is a direct effect of increased venous return on the heart?

Accepted Answer

Increased stretch of ventricular muscle fibers (preload)

Question 13

Which of the following is true regarding the source of Ca$$^{2+}$$ for contraction in cardiac muscle?

Accepted Answer

From both the sarcoplasmic reticulum and extracellular fluid

Question 14

A patient’s ECG shows an abnormal QRS complex. Which cardiac event is most likely affected?

Accepted Answer

Ventricular depolarization

Question 15

Which of the following correctly describes the effect of sympathetic stimulation on the heart?

Accepted Answer

Increases heart rate and contractility

Question 16

Which equation correctly calculates stroke volume (SV)?

Accepted Answer

$$SV = EDV - ESV$$

Question 17

Which of the following is NOT a similarity between skeletal and cardiac muscle?

Accepted Answer

Both have intercalated discs

Question 18

Which component of the cardiac conduction system is responsible for the fastest rate of depolarization?

Accepted Answer

Sinoatrial (SA) node

Question 19

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

Accepted Answer

They allow ions to pass between cells, enabling coordinated contraction

Question 20

A patient is experiencing heart failure due to chronic high blood pressure. Which of the following best explains the underlying mechanism?

Accepted Answer

Increased afterload leads to increased workload and pathological changes in the heart

Chapter 18: The Cardiovascular System – The Heart (BIO 221 Human Physiology Study Notes)

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