Hall: Guyton and Hall Textbook of Medical Physiology, 12th Edition
Chapter 10: Rhythmical Excitation of the Heart
Test Bank
1. If the sinus node stops discharging, what is the expected heart rate (in beats/minute) if the
A-V node takes over as the cardiac pacemaker?
A. 15
B. 20
C. 35
D. 50
E. 72
2. If the S-A node discharges at 0.00 seconds, when will the action potential normally arrive
at the A-V node?
A. 0.03 seconds
B. 0.09 seconds
C. 0.12 seconds
D. 0.16 seconds
E. 0.80 seconds
3. Which of the following conditions at the S-A 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
4. In which phase of the ventricular muscle action potential is the potassium permeability
the highest?
A. 0
B. 1
C. 2
D. 3
E. 4
Test Bank
10-2
5. If the S-A node discharges at 0.00 seconds, when will the action potential normally arrive
at the A-V bundle?
A. 0.80 seconds
B. 0.16 seconds
C. 0.12 seconds
D. 0.09 seconds
E. 0.03 seconds
6. A patient entered the local emergency room and had an EKG taken. The attending
physician stated that the patient had an A-V nodal rhythm. What is the likely heart rate?
A. 30/min
B. 50/min
C. 65/min
D. 75/min
E. 85/min
7. Which of the following conditions at the S-A 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
8. Which of the following conditions at the A-V 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
9. If the S-A 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
Test Bank
10-3
10. What is the normal total delay of the cardiac impulse in the A-V node + bundle?
A. 0.22 seconds
B. 0.18 seconds
C. 0.16 seconds
D. 0.13 seconds
E. 0.09 seconds
11. Which of the following are caused by acetylcholine?
A. Hyperpolarization of the S-A node
B. Depolarization of the A-V node
C. Decreased permeability of the S-A node to potassium ions
D. Increased heart rate
E. Increased permeability of the cardiac muscle to calcium ions
12. If the sinus node stops discharging, what is the expected heart rate (in beats/minute) if the
A-V node takes over as the cardiac pacemaker?
A. 5
B. 30
C. 50
D. 70
E. 90
13. 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