Electrophysiology - QUIZ

Question 1

Which portion of the ECG corresponds to repolarization of the atria?

a) P Wave
b) QRS complex
c) T wave
d) None of the above

Answer 1

d) None of the above

Question 2

Which component of the heart conduction system would have the slowest rate of firing?

a) Atrioventricular node
b) Purkinje fibers
c) Atrioventricular bundle
d) Bundle branches

Answer 2

b) Purkinje fibers

Question 3

Conductive cells contain a series of sodium ion channels that allow a normal and slow influx of sodium ions that causes the membrane potential to rise slowly from an initial value of −60 mV up to about –40 mV. This results in which of the following:
Select all that apply.
a) Spontaneous depolarization
b) Spontaneous repolarization
c) Autorhythmicity
d) Delayed conduction

Answer 3

a) Spontaneous depolarization

c) Autorhythmicity

Question 4

How do gap junctions and intercalated disks aid contraction of the heart?

a) Gap junctions allow impulses to spread from one cardiac muscle cell to another, whereas intercalated disks prevent the movement of ions in undesirable directions.
b) Intercalated disks allow impulses to spread from one cardiac cell to another, whereas gap junctions prevent the movement of ions in undesirable directions.
c) Intercalated disks join adjacent cardiac cells. Gap junctions within the intercalated disks allow impulses to spread from one cardiac muscle cell to another.
d) None of the above

Answer 4

c) Intercalated disks join adjacent cardiac cells. Gap junctions within the intercalated disks allow impulses to spread from one cardiac muscle cell to another.

Question 5

The duration of the effective refractory period in cardiac cells can be increased by:

a) Inhibiting potassium channels
b) Opening L-type calcium channels
c) Shortening Phase 2
d) Shortening Phase 3

Answer 5

a) Inhibiting potassium channels

Question 6

Conduction velocity in non-nodal cardiac cells is decreased by:

a) Activation of fast sodium channels
b) Sympathetic nerve activation
c) Decreasing the slope of Phase 0
d) Supressing sodium “funny” currents.

Answer 6

c) Decreasing the slope of Phase 0

Question 7

According to the length-tension relationship for cardiac muscle, an increase in muscle sarcomere length within its normal operating range increases active tension development. True or False?

Answer 7

True

Question 8

Binding of calcium to __________ is a primary mechanism involved in regulating cardiac muscle tension development.

a) Actin
b) Myosin
c) Troponin-C
d) Tropomyosin

Answer 8

c) Troponin-C

Question 9

If the QRS in Lead III is biphasic and Lead II is positive, then the mean electrical axis is:

a) -60 degrees
b) -150 degrees
c) +30 degrees
d) +60 degrees

Answer 9

c) +30 degrees

Question 10

Which lead is represented by a negative electrode on the right arm and a positive electrode on the left leg?

a) Lead I
b) Lead II
c) Lead III
d) Lead aVR

Answer 10

b) Lead II

Question 11

If the mean electrical axis is 90o, then the net amplitude of the QRS will be greatest in:

a) Lead I
b) Lead III
c) aVF
d) aVL

Answer 11

c) aVF

Question 12

In a Lead I ECG recording, the first small negative deflection of the QRS (the Q-wave) represents:

a) Atrial repolarization
b) Depolarization of the interventricular septum from left to right
c) A wave of depolarization traveling towards the left leg
d) Ventricular repolarization

Answer 12

b) Depolarization of the interventricular septum from left to right