Cellular Control Voltage-dependent sodium channels
At the cellular level the refractory period of an action potential prevents abnormal repetitive firing. During this refractory period the sodium channels are inactivated and the efflux of potassium ions restores the membrane potential. (see also action potential 1-4). The voltage-dependent sodium channels are responsible for propagation of an action potential along the neuronal membrane.
During an action potential the sodium channel exists in 3 different conformations:
- Closed resting state before the depolarisation
- Open activated state during depolarisation (grey area)
- Closed inactivated state after the peak
The sodium channel cannot be opened/activated and cause another action potential until the membrane is sufficiently repolarised. This is an intrinsic mechanism to prevent uncontrolled firing of neurons.
Depolarisation of a neuron cell membrane will shift the membrane potential toward
If the resting membrane potential is -70 mV and the threshold is -55 mV, a membrane potential of -60 mV will