Question 1

A muscle cell cannot be depolarized again during which phases of an action potential?
A) End of 0 to the beginning of 2
B) Beginning of 1 to the end of 3
C) End of 1 to the beginning of 4
D) Beginning of 0 to the middle of 3

Accepted Answer

The period from the beginning of phase 0 to the middle of phase 3 is referred to as the absolute refractory period or effective refractory period,because regardless of the strength of the stimulus,the myocyte cannot be depolarized again.

Question 2

The time required for the atrial impulse to travel through the atrioventricular node is defined as which of the following?
A) P-R segment
B) P-R interval
C) QRS interval
D) ST segment

Accepted Answer

The P-R interval ranges from 0.12 to 0.2 second and is the time it takes for the impulse initiated in the atria to travel through the atrioventricular node.The P-R segment occurs between the end of the P wave and the beginning of the QRS interval,corresponds to the 0.1-second delay that occurs within the atrioventricular node.The P-R segment is included in the P-R interval.The QRS interval represents ventricular depolarization,and the ST segment represents ventricular depolarization.

Question 3

The QRS complex represents which of the following?
A) Atrial depolarization
B) Ventricular depolarization
C) Ventricular repolarization
D) Threshold potential

Accepted Answer

Ventricular depolarization is represented on the electrocardiogram as the QRS complex.The P wave represents atrial depolarization.The T wave represents ventricular repolarization.Threshold potential is the critical level of electrical excitation reached by any cell,causing an action potential to occur.

Question 4

When a cell membrane of an excitable cell is exposed to a depolarizing current,which of the following occurs?
A) Increased influx of calcium into the cell
B) Rapid influx of sodium ions into the cell
C) Increased efflux of potassium out of the cell
D) Rapid efflux of protein molecules out of the cell

Accepted Answer

An action potential begins when the cell membrane of the excitable cell is exposed to a depolarizing current and eventually reaches its excitation threshold potential.The initial phase of this type of action potential consists of a rapid upstroke or depolarization.This change in membrane potential to a more positive value occurs because of a rapid influx of sodium ions into the cell.

Question 5

Which of the following cardiac cells has the slowest action potential?
A) Atrial
B) Ventricular
C) Purkinje fiber
D) Sinoatrial node

Accepted Answer

The slope of phase 0 of the sinoatrial node (pacemaker)is less than those of the atrial,ventricular,and Purkinje fiber action potentials,and the former often is referred to as a slow action potential,whereas the latter are called fast action potentials.

Question 6

The paper speed of an electrocardiographic machine should be set at a speed of ____ mm/s.
A) 10
B) 15
C) 20
D) 25

Accepted Answer

When an ECG is recorded,the paper speed is set at 25 mm/s,the equivalent of 1500 mm/min.

Question 7

Each millimeter on electrocardiographic recording paper represents _____ seconds.
A) 0.02
B) 0.04
C) 0.20
D) 0.40

Accepted Answer

Time is recorded on the x-axis,with each millimeter representing 0.04 second.

Question 8

Automatic electrical discharges in the myocardium normally begin within which of the following?
A) Bundle of His
B) Sinoatrial node
C) Bachmann's bundle
D) Atrioventricular node

Accepted Answer

The sinoatrial node ,as well as the atrioventricular node,normally have action potentials that differ from those of other excitable cells of the heart.Depolarization of the sinoatrial node initiates the heartbeat by triggering a wave of excitation that spreads through the right and left atria as it moves toward the atrioventricular node.

Question 9

The fourth intercostal space at the left sternal margin is the site for which of the following electrocardiogram leads?
A) V1
B) V2
C) V3
D) V4

Accepted Answer

V₂ is placed in the fourth intercostal space,at the right sterna margin.

Question 10

The fifth intercostal space on the anterior axillary line is the site for which of the following electrocardiogram leads?
A) V3
B) V4
C) V5
D) V6

Accepted Answer

V₅ is located at the same level as V₄ (fifth intercostal space)on the anterior axillary line.

Question 11

On an electrocardiogram,the time between atrial and ventricular contraction is known as the:
A) P-R segment
B) ST segment
C) QRS interval
D) Q-T interval

Accepted Answer

The P-R segment represents the time delay that occurs within the atrioventricular node and therefore represents the time between atrial and ventricular contractions.The ST segment occurs during ventricular depolarization,the QRS interval represents ventricular polarization,and the Q-T interval represents the time required for ventricular depolarization and repolarization to occur.

Question 12

Which of the following is defined as "the ability of a cell to respond to an electrical stimulus"?
A) Conductivity
B) Rhythmicity
C) Excitability
D) Automaticity

Accepted Answer

Excitability is defined as the ability of a cell to respond to an electrical stimulus.Conductivity refers to the ability of cardiac tissue to propagate an action potential.Automaticity describes the ability of certain specialized cells of the heart to depolarize.Rhythmicity refers to the heart's pacemaker action potential.

Question 13

The ability of cardiac tissue to propagate an action potential is the definition of:
A) excitability.
B) automaticity.
C) conductivity.
D) depolarization.

Accepted Answer

Conductivity is defined as the ability of cardiac tissue to propagate an action potential.Excitability refers to the ability of a cell to respond to an electrical stimulus.Automaticity describes the ability of certain specialized cells of the heart to depolarize.Polarization occurs when a cell becomes electrically activated.

Question 14

A specialized high-speed conduction system begins at which of the following points?

A) A
B) C
C) D
D) H

Accepted Answer

Electrical impulses move through a series of high-speed internodal conduction pathways between the sinoatrial and atrioventricular nodes.

Question 15

Which letter in the figure identifies the anterior internodal pathway?

A) A
B) C
C) E
D) F

Accepted Answer

The anterior internodal pathway is located anteriorly in the right atrium and is responsible for transmitting impulses from the sinoatrial node to the atrioventricular node. In the figure, pathway B connects the sinoatrial node to the atrioventricular node and is located anteriorly, therefore it identifies the anterior internodal pathway.

Question 16

Which letter in the figure identifies the cardiac cells through which there is a 100-ms delay?

A) A
B) B
C) C
D) D

Accepted Answer

As the electrical impulse travels through the atrioventricular node,there is a 100-ms delay in the conduction.This allows the atria to become fully depolarized and contract before ventricular excitation begins.This allows the atrial contraction and emptying to contribute optimally to ventricular filling.

Question 17

The ability of certain specialized cells of the heart to depolarize spontaneously is known as which of the following?
A) Diastasis
B) Excitability
C) Automaticity
D) Conductivity

Accepted Answer

Automaticity describes the ability of certain specialized cells of the heart to depolarize.Diastasis refers to the long period of reduced ventricular filling that follows the rapid-filling period.Excitability is defined as the ability of a cell to respond to an electrical stimulus.Conductivity is defined as the ability of cardiac tissue to propagate an action potential.

Question 18

How many millimeters are between each heavy vertical line on electrocardiographic paper?
A) 1.0
B) 2.0
C) 4.0
D) 5.0

Accepted Answer

The area between the heavy vertical lines on the electrocardiographic paper represents 5.0 mm.

Question 19

The QRS vector appears downward in which of the following electrocardiogram leads?
A) II
B) V5
C) aVL
D) aVR

Accepted Answer

The QRS vector will normally be upward in leads I,II,aVL,and V₅ and is usually downward in leads aVR and V₁.

Question 20

Electrical stimulation of a cardiac muscle cell is the definition of which of the following?
A) Contraction
B) Refraction
C) Polarization
D) Depolarization

Accepted Answer

The action potential begins when the cell membrane of the excitable cell is exposed to a depolarizing current and eventually reaches its excitation threshold potential.This is known as depolarization.

Quiz 9: Assessment of Cardiovascular Function

A muscle cell cannot be depolarized again during which phases of an action potential?

The time required for the atrial impulse to travel through the atrioventricular node is defined as which of the following?

The QRS complex represents which of the following?

When a cell membrane of an excitable cell is exposed to a depolarizing current,which of the following occurs?

Which of the following cardiac cells has the slowest action potential?

The paper speed of an electrocardiographic machine should be set at a speed of ____ mm/s.

Each millimeter on electrocardiographic recording paper represents _____ seconds.

Automatic electrical discharges in the myocardium normally begin within which of the following?

The fourth intercostal space at the left sternal margin is the site for which of the following electrocardiogram leads?

The fifth intercostal space on the anterior axillary line is the site for which of the following electrocardiogram leads?

On an electrocardiogram,the time between atrial and ventricular contraction is known as the:

Which of the following is defined as "the ability of a cell to respond to an electrical stimulus"?

The ability of cardiac tissue to propagate an action potential is the definition of:

A specialized high-speed conduction system begins at which of the following points?

Which letter in the figure identifies the anterior internodal pathway?

Which letter in the figure identifies the cardiac cells through which there is a 100-ms delay?

The ability of certain specialized cells of the heart to depolarize spontaneously is known as which of the following?

How many millimeters are between each heavy vertical line on electrocardiographic paper?

The QRS vector appears downward in which of the following electrocardiogram leads?

Electrical stimulation of a cardiac muscle cell is the definition of which of the following?