Week 16: (C) Action Potential in cardiac contractile cell

Question 1

What moves into cell?

Answer 1

Na+ infast

Question 2

What channels open and close at the early depolarisation phase?

Answer 2

Na open
K closed (transient)

Question 3

What move in and out during plateau phase?

Answer 3

K out fast

Ca in slowly

Question 4

What channels open and close in the plateau phase?

Answer 4

open Ca L
close K (both transient and leaky)

Question 5

What moves out of cell during late repolarisation phase?

Answer 5

k out fast

Question 6

What channels open and close during late repolarisation?

Answer 6

open Ca L
increase K (v gated)

Question 7

What channels are opened and closed in resting potential?

Answer 7

decrease K (v gated)
increase K (leaky)

Question 8

When can a second action potential be triggered?

Answer 8

until the excitable cell membrane has recovered from the preceding AP
cannot initiate another AP during refractory period

Question 9

How long does the refractory period last?

Answer 9

~250 ms

Question 10

What is the factor responsible for the long refractory period?

Answer 10

is inactivation of the na channels responsible for the initial Na influx of the rising phase of the AP