AP in the heart

action potential

tension

absolute refractory period

plateau

time (ms)

tension (g)

membrane potential (mV)

1

2

3

1. Depolarization: \(Na^+\) influx through voltage gated channels, which increases the slightly positive charge of the membrane.
2. Plateau: a useful technique to avoid tetanus (which would prevent the heart from being a pump) that is caused by slow \(Ca^2+\) channels with an influx of calcium as most \(K^+\) channels are closed.
3. Repolarization: occurs as \(Ca^2+\) channels inactivate. \(K^+\) channels open, which increase the slight negativity of the membrane potential; \(K^+\) efflux returns to resting potential.

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