QuestionSBA
QuestionChoice
This is incorrect as once the cell has depolarised, potassium moves outward (not inward) to begin repolarisation. At that point, L-type calcium channels open causing calcium influx, which balances the potassium efflux to bring about the plateau phase.
10026247
c
Balanced calcium efflux and potassium influx
QuestionChoice
This is incorrect as this unopposed potassium efflux describes the ion movement during repolarisation. This occurs briefly after depolarisation (during the partial rapid repolarisation phase) and after the plateau phase during terminal repolarisation. The plateau phase is caused by the balanced outward movement of potassium ions with the inward movement of calcium ions through L-type calcium channels.
10026249
e
Potassium efflux
QuestionChoice
This is incorrect as once the cell has depolarised, sodium channels are deactivated so sodium influx stops. The plateau phase is caused by the balanced outward movement of potassium ions with the inward movement of calcium ions through L-type calcium channels.
10026246
b
Balanced sodium influx and potassium efflux
QuestionChoice
Rapid depolarisation is first brought about by sodium influx. sodium channels are then inactivated and initial repolarisation begins to occur due to potassium efflux. At the same time, calcium influx occurs through L-type calcium channels. This potassium efflux and calcium influx are balanced, giving a plateau phase and prolonging the action potential. The L-type calcium channels are eventually inactivated, giving unopposed potassium efflux and hence repolarisation of the cell.
10026245
a
Balanced calcium influx and potassium efflux
QuestionChoice
This is incorrect as this describes the ion movement during the rapid depolarisation phase. Once the cell has depolarised, sodium channels are deactivated so sodium influx stops. The plateau phase is caused by the balanced outward movement of potassium ions with the inward movement of calcium ions through L-type calcium channels.
10026248
d
Sodium influx
Concept
Chapter
2693
3962
Cardiac Action Potential Generation and Conduction
Topic
159
Cardiovascular physiology
17647
Which of the following is the correct explanation for the plateau phase of the ventricular myocyte action potential?
a