Wed24November0743AM 8

Which one of the following ionic changes is associated with the initial repolarisation phase of the ventricular myocyte action potential?

(Please select 1 option)

Increased Na+ and decreased K+ conductances Incorrect answer selected

Ceased Na+ and increase K+ conductances This is the correct answer

Increased Ca2+ conductance

Increased K+, decreased Na+ and decreased Ca2+ conductances

Decreased Ca2+ and increased K+ conductances

Explanation

The action potential (AP) of ventricular and atrial myocytes, as well as the Purkinje system have the same characteristic ionic changes. The duration is approximately 200 ms and has a resting membrane potential with fast depolarisation and plateau phases.

There are five phases:

Phase 0 (rapid depolarisation) - Increased Na+ and decreased K+ conductances

Phase 1 (initial repolarisation) - Ceased Na+ and increased K+ conductances

Phase 2 (plateau phase) - Increased Ca2+ conductance

Phase 3 (repolarisation phase) - Decreased Ca2+ and increased K+ conductances

Phase 4 (resting membrane potential) - Increased K+ and decreased Na+ and decreased Ca2+ conductances.

Answer Statistics

1

12%

2

24%

3

11%

4

30%

5

26%

Times answered: 242