Phase 2; Ca\textsuperscript{2+} influx

$CO = 80 \times 75 = 6000\ \text{ml/min}$

SERCA pump and Na\textsuperscript{+}-Ca\textsuperscript{2+} exchanger remove Ca\textsuperscript{2+} from the cytoplasm.

Question 1

Which of the following best describes the role of the SA node in cardiac physiology?

Accepted Answer

It initiates and distributes impulses to coordinate heart rhythm as part of the intrinsic cardiac conduction system.

Question 2

During the pacemaker potential in SA node cells, which ion's influx is primarily responsible for the slow depolarization phase?

Accepted Answer

Na	extsuperscript{+}

Question 3

Which phase of the cardiac contractile cell action potential is responsible for the plateau, and which ion is mainly involved?

Accepted Answer

Phase 2; Ca	extsuperscript{2+} influx

Question 4

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

Accepted Answer

AV node

Question 5

Which equation correctly represents cardiac output?

Accepted Answer

$CO = HR 	imes SV$

Question 6

If a patient’s heart rate is 80 bpm and their stroke volume is 75 ml/beat, what is their cardiac output?

Accepted Answer

$CO = 80 	imes 75 = 6000\ 	ext{ml/min}$

Question 7

Which of the following would most likely increase stroke volume?

Accepted Answer

Increased end-diastolic volume (EDV)

Question 8

Which homeostatic imbalance is characterized by rapid, irregular electrical activity in the ventricles, rendering them useless for pumping blood?

Accepted Answer

Ventricular fibrillation

Question 9

Which mechanism is responsible for the relaxation of cardiac muscle cells after contraction?

Accepted Answer

SERCA pump and Na	extsuperscript{+}-Ca	extsuperscript{2+} exchanger remove Ca	extsuperscript{2+} from the cytoplasm.

Question 10

Which of the following best explains the Frank-Starling Law of the Heart?

Accepted Answer

Increased myocardial stretch leads to increased contraction strength.

Question 11

Which of the following would most likely result in bradycardia?

Accepted Answer

Increased parasympathetic stimulation to the SA node

Question 12

A patient with left-sided heart failure is most likely to experience which of the following symptoms?

Accepted Answer

Pulmonary congestion

Question 13

Which of the following is true regarding the absolute refractory period in cardiac muscle cells?

Accepted Answer

It prevents tetanus by overlapping with the contraction period.

Question 14

Which of the following would most likely decrease cardiac output?

Accepted Answer

Persistent high blood pressure increasing afterload

Question 15

Which heart sound is associated with the closing of the semilunar (SL) valves?

Accepted Answer

Second sound (dup)

Question 16

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

Accepted Answer

Increases heart rate and contractility

Question 17

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

Accepted Answer

Increased end-diastolic volume (EDV) leading to increased stroke volume

Question 18

Which of the following is NOT a factor that increases venous return?

Accepted Answer

Decreased blood volume

Question 19

Which of the following ECG findings is most consistent with second-degree AV block?

Accepted Answer

Prolonged P-R interval with some dropped QRS complexes

Question 20

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

Accepted Answer

The absolute refractory period overlaps with the contraction period, preventing summation.

Cardiac Physiology: Electrical Activity and the Cardiac Cycle

Study Guide - Practice Questions