cardiac physio - charming

[ArchivalUser]

Ventriular muscle action potential

Development of plateau phase is dependent on:
a. voltage gated Ca channels
b.Voltage gated K channels iKi
c.voltage gated K channels iK
d.voltage gated Na channels

[ArchivalUser]

A..

[ArchivalUser]

its B

Development of plateau is dependent on closure of voltage gated K channels
If they dint close early repolarization occur ,preventing full development of plateau

[ArchivalUser]

Thank you...good point

[ArchivalUser]

What is the difference between c option and b option?

Thank you so much

[ArchivalUser]

two types of K channels (voltage gated )
1.Inward rectifying
2.delayed rectifying

inward rectifying r open under resting conditions
depolarization is the signal to close these channels

Delayed rectifier open with depolarization n close when cell is replolarized . they contribute to relative refractory period

[ArchivalUser]

ok unless my concept is wrong, I still don't get this.

During the plateau phase the fast K channels are open pushing K out and making the cell more negative. The only thing stopping it from repolarizing is the inward Ca current which keeps the cell at a steady state.

Wouldn't Ca be the main cause of the plateau as without it the cell goes straight into repolarization??????

makes sense to me.

[ArchivalUser]

The cardiac action potential plateau, or phase 2, is primarily determined by the influx of Ca2+ through the L-type Ca2+ channels. In addition, a counterbalancing outward K+ current flows through the "anomalous" K+ rectifier. Both of these channels are activated during the upstroke of the action potential and reach peak current concurrently during the plateau phase. L-type Ca2+ channels are intimately involved in excitation-contraction coupling, which will be discussed in a later section.

http://jtcs.ctsnetjournals.org/cgi/conte.../118/2/375

[ArchivalUser]

Thank you so much for the explanation.