Question 1

Which of the following best describes the primary function of the membrane pump in cardiac cells?

Accepted Answer

It maintains the electrical polarity of the cell by actively transporting ions across the membrane.

Question 2

During the process of depolarization in cardiac cells, which of the following occurs?

Accepted Answer

There is a loss of internal negativity as positive ions enter the cell.

Question 3

Which type of cardiac cell is primarily responsible for initiating the heartbeat and why?

Accepted Answer

Pacemaker cells, because they can spontaneously depolarize without external stimulation.

Question 4

A patient’s EKG shows a prolonged PR interval. Which of the following best explains what is happening physiologically?

Accepted Answer

There is delayed conduction through the atrioventricular (AV) node.

Question 5

Which of the following best describes the QRS complex on an EKG?

Accepted Answer

It represents ventricular depolarization.

Question 6

If the depolarization wave in the heart moves toward a positive electrode, what will be seen on the EKG?

Accepted Answer

A positive deflection.

Question 7

Which of the following statements about pacemaker cells is correct?

Accepted Answer

They can spontaneously depolarize and generate action potentials.

Question 8

A wave of repolarization moving away from a positive electrode will produce which of the following on the EKG?

Accepted Answer

A negative deflection.

Question 9

Which of the following best explains why the amplitude of the QRS complex is greater than that of the P wave?

Accepted Answer

The ventricles have a greater muscle mass than the atria.

Question 10

A patient’s EKG shows tall R waves in leads V5 and V6. Which region of the heart is most likely being recorded by these leads?

Accepted Answer

Lateral left ventricle

Question 11

Which of the following best describes the physiological significance of the refractory period in cardiac muscle?

Accepted Answer

It prevents tetanic contractions by making the cell temporarily unresponsive to further stimulation.

Question 12

If the limb leads are reversed during EKG recording, what is the most likely consequence?

Accepted Answer

The EKG results will be reversed, potentially leading to misinterpretation.

Question 13

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

Accepted Answer

SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers

Question 14

Which of the following best explains why the PR interval is clinically important?

Accepted Answer

It reflects the time required for the electrical impulse to travel from the atria to the ventricles.

Question 15

A patient is found to have a heart rate of 150 beats per minute. How would this affect the QT interval on the EKG?

Accepted Answer

The QT interval would be shorter than normal.

Question 16

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

Accepted Answer

It delays the electrical impulse to allow the atria to contract before the ventricles.

Question 17

Which of the following is true regarding the direction of the depolarization wave in the atria?

Accepted Answer

It moves from the right atrium (SA node) to the left atrium and slightly inferiorly.

Question 18

Which of the following best explains why the T wave is typically positive in the same leads that have tall R waves?

Accepted Answer

Repolarization moves in the opposite direction to depolarization, but the electrical effect is reversed.

Question 19

A patient’s EKG shows a biphasic wave in lead V3. What does this indicate about the electrical activity in that region?

Accepted Answer

The depolarization wave is moving perpendicular to the electrode, resulting in equal positive and negative deflections.

Question 20

Which of the following best describes the clinical importance of proper electrode placement during an EKG?

Accepted Answer

Improper placement can lead to erroneous interpretation and missed or false diagnoses.

Electricity and the Heart: Cellular Basis and Types of Cardiac Cells

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