Deck 12: Electrophysiology of the Heart

Question 1

Which phase of the action potential represents the nonrefractory period?

A) last half of Phase 3
B) first half of Phase 3
C) Phase 4
D) Phase 5

Answer 1

C

Question 2

What is the term for the unique ability of cells in the SA node to generate an action potential without being stimulated?

A) excitability
B) conductivity
C) automaticity
D) contractility

Answer 2

C

Question 3

Which phase of the action potential represents the relative refractory period?

A) First half of Phase 4
B) Last half of Phase 4
C) First half of Phase 3
D) Last half of Phase 3

Answer 3

D

Question 4

Which phase of the action potential prolongs the contraction of the myocardial cells?

A) Phase 3
B) Phase 4
C) Phase 2
D) Phase 5

Question 5

What is the term for the ability of cardiac muscle fibers to shorten in response to an electrical stimulus?

A) conductivity
B) contractility
C) automaticity
D) excitability

Question 6

What is the term for the time in which cells cannot respond to a stimulus?

A) partial resistance period
B) nonrefractory period
C) absolute refractory period
D) relative refractory period

Question 7

What are the three primary electrolytes responsible for the electrical difference across the resting membrane potential?

A) potassium sodium, and chloride
B) sodium, chloride, and potassium
C) sodium, chloride, and bicarbonate
D) potassium, sodium, and calcium

Question 8

Which phase of the action potential represents initial repolarization of the myocardial cells?

A) Phase 1
B) Phase 3
C) Phase 2
D) Phase 0

Question 9

Which phases of the action potential represent the absolute refractory period?
I. Phase 0
II. Phase 1
III. Phase 2
IV. First half of Phase 3
V. First half of Phase 4

A) II, III, and IV only
B) I, II, and III only
C) IV and V only
D) I, II, III, and IV only

Question 10

Of the phases of the action potential, which phase represents rapid depolarization of the myocardial cells?

A) Phase 4
B) Phase 0
C) Phase 5
D) Phase 1

Question 11

What is another term for "pacemaker cells"?

A) autorhythmic cells
B) sympathetic neural fibers
C) contractile muscle fibers
D) atrial muscle fibers

Question 12

What does the RMP of the myocardial cells equal?

A) -30 mV
B) -50 mV
C) -90 mV
D) -15 mV

Question 13

At the end of Phase 0, what does the voltage inside the myocardial cell equal?

A) +30 mV
B) +15 mV
C) -30 mV
D) -90 mV

Question 14

What is the term for the ability of a cell to reach its threshold potential and respond to a stimulus?

A) contractility
B) conductivity
C) automaticity
D) excitability

Question 15

During which phase of the action potential do the voltage-sensitive ion channels return to their pre-depolarization permeability?

A) Phase 0
B) Phase 4
C) Phase 3
D) Phase 5

Question 16

What is the term for a transmitted action potential?

A) conduction
B) nerve impulse
C) stimulus
D) action potential

Question 17

What is the basic term for the phase in which the heart is not generating an action potential?

A) polarized
B) contractile
C) depolarized
D) conductive

Question 18

Which portion of the conductive system is considered to be the pacemaker of the heart?

A) arteriovalvular node
B) sinoatrial node
C) sinoarterial node
D) atrioventricular node

Question 19

After the electrical impulse leaves the atrioventricular junction, where does it travel next?

A) Purkinje fibers
B) bundle of His
C) Bachmann's bundle
D) bundle branches

Question 20

What is the term for the ability of the heart cells to transmit electrical current from cell to cell?

A) irritability
B) contractility
C) automaticity
D) conductivity

Question 21

What effect does stimulation of the parasympathetic neural fibers have on the contactility and AV conduction of the heart?

A) Contractility would increase and AV conduction would decrease
B) Both contractility and AV conduction would increase
C) AV conduction would decrease and contractility would not be affected
D) Both contractility and AV conduction would decrease

Question 22

Where does the electrical impulse travel after leaving the AV bundle?

A) Purkinje fibers
B) bundle of His
C) SA node
D) left and right bundle branches

Question 23

What are indications for synchronized cardioversion?
I. Unstable atrial fibrillation
II. Atrial flutter
III. Atrial Tachycardia
IV. Ventricular fibrillation

A) I, II, and III only
B) I and III only
C) IV only
D) I, II, II, and IV only

Question 24

Which structure transmits the electrical impulse from the SA node to the left atrium?

A) AV junction
B) Bachmann's bundle
C) Purkinje fibers
D) bundle of His

Question 25

In a healthy adult at rest, approximately how much time is required for the entire heart to depolarize?

A) 0.002 seconds
B) 0.02 seconds
C) 2.2 seconds
D) 0.22 seconds

Question 26

What effect will stimulation of sympathetic neural fibers have on heart rate and excitability?

A) both will be increased
B) heart rate will increase and excitability will be unaffected
C) heart rate will increase and excitability will decrease
D) both will be decreased

Question 27

At what point do the internodal tracts of the right atrium merge?

A) AV junction
B) SA junction
C) Purkinje fibers
D) Bachmann's bundle