Deck 10: Rhythmical Excitation of the Heart

Question 1

Which of the following conditions at the sinoatrial node will cause a decrease in heart rate?

A)Increased sodium permeability
B)Increased acetylcholine levels
C)Increased norepinephrine levels
D)Decreased potassium permeability
E)Increased calcium permeability

Answer 1

B

Question 2

If the sinoatrial node discharges at 0.00 seconds, when will the action potential normally arrive at the atrioventricular node?

A)0.03 seconds
B)0.09 seconds
C)0.12 seconds
D)0.16 seconds
E)0.80 seconds

Answer 2

A

Question 3

If the sinus node stops discharging, what is the expected heart rate (in beats per minute) if the ventricular Purkinje fibers take over as the cardiac pacemaker?

A)5
B)30
C)55
D)60
E)72

Answer 3

B

Question 4

A patient was admitted to the local emergency department and had an electrocardiogram taken. The attending physician stated that the patient had an atrioventricular nodal rhythm. What is the likely heart rate?

A)30 beats/min
B)50 beats /min
C)65 beats /min
D)75 beats /min
E)85 beats /min

Question 5

Which of the following is caused by acetylcholine?

A)Hyperpolarization of the sinoatrial node
B)Depolarization of the atrioventricular node
C)Decreased permeability of the sinoatrial node to potassium ions
D)Increased heart rate
E)Increased permeability of the cardiac muscle to calcium ions

Question 6

Which of the following is correct regarding sympathetic stimulation of the heart?

A)Releases acetylcholine at the sympathetic endings
B)Decreases sinus nodal discharge rate
C)Decreases excitability of the heart
D)Releases norepinephrine at the sympathetic endings
E)Decreases cardiac contractility

Question 7

What is the normal total delay of the cardiac impulse in the atrioventricular node and bundle?

A)0.22 seconds
B)0.18 seconds
C)0.16 seconds
D)0.13 seconds
E)0.09 seconds

Question 8

Which of the following conditions at the atrioventricular node will cause a decrease in heart rate?

A)Increased sodium permeability
B)Decreased acetylcholine levels
C)Increased norepinephrine levels
D)Increased potassium permeability
E)Increased calcium permeability

Question 9

If the sinoatrial node discharges at 0.00 seconds, when will the action potential normally arrive at the ventricular septum?

A)0.22 seconds
B)0.16 seconds
C)0.12 seconds
D)0.09 seconds
E)0.03 seconds

Question 10

In which of the following conditions at the atrioventricular node would you expect a decrease in heart rate?

A)Increased sodium permeability
B)Increased acetylcholine levels
C)Increased norepinephrine levels
D)Decreased potassium permeability
E)Increased calcium permeability

Question 11

If the sinus node stops discharging, what is the expected heart rate (in beats per minute) if the atrioventricular node takes over as the cardiac pacemaker?

A)5
B)30
C)50
D)70
E)90

Question 12

In which phase of the ventricular muscle action potential is the sodium permeability the highest?

A)0
B)1
C)2
D)3
E)4