Question 1

Which of the following best describes the sequence of electrical conduction through the heart during a normal cardiac cycle?

Accepted Answer

Sinoatrial (SA) node → Atrioventricular (AV) node → Bundle of His → Purkinje fibers

Question 2

A patient presents with a heart rate of 45 beats per minute and an ECG showing absent P waves but normal QRS complexes. Which part of the conduction system is most likely acting as the pacemaker?

Accepted Answer

Atrioventricular (AV) node

Question 3

During which phase of the cardiac cycle does isovolumetric contraction occur, and what is the status of the heart valves during this phase?

Accepted Answer

Ventricular systole; all heart valves are closed

Question 4

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

Accepted Answer

Increases heart rate and contractility by releasing norepinephrine

Question 5

A sudden drop in blood pressure is detected by baroreceptors. Which of the following is the most likely immediate response mediated by the autonomic nervous system?

Accepted Answer

Increased sympathetic activity leading to vasoconstriction and increased heart rate

Question 6

Which component of the ECG corresponds to ventricular depolarization?

Accepted Answer

QRS complex

Question 7

Calculate the cardiac output ($CO$) for a patient with a stroke volume ($SV$) of $70\ \mathrm{mL}$ and a heart rate ($HR$) of $80\ \mathrm{beats/min}$. Use the formula $CO = SV 	imes HR$.

Accepted Answer

$5600\ \mathrm{mL/min}$

Question 8

A patient stands up quickly from a lying position and experiences dizziness. Which physiological mechanism is primarily responsible for restoring blood pressure in this scenario?

Accepted Answer

Baroreceptor reflex increases sympathetic output to the heart and vessels

Question 9

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

Accepted Answer

Decreases heart rate by releasing acetylcholine at the SA node

Question 10

Which of the following changes would you expect to see in the ECG during hyperkalemia (elevated serum potassium)?

Accepted Answer

Peaked T waves

Question 11

A patient has a blood pressure of $120/80\ \mathrm{mmHg}$. What is the mean arterial pressure ($MAP$)? Use the formula $MAP = \dfrac{1}{3} (Systolic - Diastolic) + Diastolic$.

Accepted Answer

$93\ \mathrm{mmHg}$

Question 12

Which of the following is a direct effect of increased firing of baroreceptors in the carotid sinus?

Accepted Answer

Increased parasympathetic activity to the heart

Question 13

During heavy exercise, which organ receives a significantly increased proportion of cardiac output compared to rest?

Accepted Answer

Skeletal muscle

Question 14

Which of the following best describes the function of the AV node in the cardiac conduction system?

Accepted Answer

Delays the electrical impulse to allow ventricular filling

Question 15

A patient with a mutation causing nonfunctional baroreceptors would most likely experience which of the following?

Accepted Answer

Large fluctuations in blood pressure with postural changes

Question 16

Which of the following best explains why the QRS complex is larger than the P wave on an ECG?

Accepted Answer

Ventricular muscle mass is greater than atrial muscle mass

Question 17

If a drug blocks muscarinic acetylcholine receptors in the heart, what is the expected effect on heart rate?

Accepted Answer

Heart rate will increase due to reduced parasympathetic inhibition

Question 18

Which of the following best describes the baroreceptor reflex response to a sudden increase in arterial blood pressure?

Accepted Answer

Increased baroreceptor firing, increased parasympathetic output, decreased heart rate

Question 19

A patient with a heart rate of $100\ \mathrm{beats/min}$ and a stroke volume of $50\ \mathrm{mL}$ has a cardiac output of:

Accepted Answer

$5000\ \mathrm{mL/min}$

Question 20

Which of the following is a correct statement about the effect of the diving reflex on heart rate and blood pressure?

Accepted Answer

Heart rate decreases and peripheral vasoconstriction increases blood pressure

The Heart, ECG, and Baroreceptor Reflex: Regulation by the Autonomic Nervous System

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