Question 1

Which of the following best describes the primary function of the intercalated discs in cardiac muscle tissue?

Accepted Answer

They allow synchronized contraction of the heart by connecting cells mechanically and electrically.

Question 2

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

Accepted Answer

Ventricular depolarization

Question 3

Which of the following is TRUE regarding the source of calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$for contraction in cardiac muscle cells?

Accepted Answer

Calcium comes from both the sarcoplasmic reticulum and the extracellular fluid.

Question 4

Which phase of the cardiac cycle is responsible for the 'lub' sound heard during auscultation?

Accepted Answer

Closure of the AV valves at the start of ventricular systole

Question 5

If a person’s heart rate is 80 beats per minute and their stroke volume is 70 mL/beat, what is their cardiac output ($$CO$$)?

$$CO = SV 	imes HR$$

Accepted Answer

$$CO = 5600\ \mathrm{mL/min}$$

Question 6

Which of the following best explains why tetanus (sustained contraction) cannot occur in cardiac muscle?

Accepted Answer

Cardiac muscle has a long refractory period due to the plateau phase of the action potential.

Question 7

Which structure acts as the pacemaker of the heart, initiating each heartbeat?

Accepted Answer

Sinoatrial (SA) node

Question 8

During which phase of the cardiac cycle does most ventricular filling occur?

Accepted Answer

Ventricular diastole (passive filling)

Question 9

Which of the following is a key difference between skeletal muscle and cardiac muscle contraction?

Accepted Answer

Cardiac muscle contracts as a unit due to gap junctions.

Question 10

A patient has a blockage in their right coronary artery. Which of the following is most likely to be affected first?

Accepted Answer

Oxygen supply to the right side of the heart, impairing ATP production in cardiomyocytes

Question 11

Which event is represented by the T wave on an ECG?

Accepted Answer

Ventricular repolarization

Question 12

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

Accepted Answer

It increases heart rate and force of contraction.

Question 13

Which of the following is the correct sequence of electrical conduction in the heart?

Accepted Answer

SA node → AV node → AV bundle → Purkinje fibers

Question 14

Which of the following statements about cardiac muscle energy metabolism is correct?

Accepted Answer

Cardiac muscle relies almost exclusively on aerobic respiration and has many mitochondria.

Question 15

Which of the following best explains why the AV node delays the electrical signal?

Accepted Answer

To allow the atria to fully contract and the ventricles to fill with blood

Question 16

Which of the following is a function of desmosomes in cardiac muscle?

Accepted Answer

They mechanically anchor cells together to prevent separation during contraction.

Question 17

Which of the following would most likely result from a failure of the Purkinje fibers?

Accepted Answer

The ventricles would not contract in a coordinated manner.

Question 18

Which of the following best describes the effect of the parasympathetic nervous system on the heart?

Accepted Answer

It decreases heart rate via the vagus nerve.

Question 19

Which of the following is the correct formula for cardiac output ($$CO$$)?

Accepted Answer

$$CO = SV 	imes HR$$

Question 20

Which of the following best explains why an ECG is a useful diagnostic tool?

Accepted Answer

It provides a non-invasive snapshot of the heart’s electrical activity, helping to diagnose heart conditions.

The Cardiovascular System: Cardiac Muscle and Conduction

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