Repolarisation
A fraction of second after the sodium gates open, depolarisation of membrane causes opening of potassium gates therefore potassium diffused out of the axon. This causes less positive charge inside with respect to outside. Thus due to repolarisation, potential changes from 30 mV to -65 mV. The neuron is now prepared for receiving another stimulus and to conduct as described before. Now it’s necessary to restore normal resting potential by expelling sodium ions out and taking potassium ions inside. The time taken for restoration is called refractory period because during this period membrane can’t receive another impulse. All the three state of neuron is shown in Figure 13.4.

 

Figure 13.4: The three states of neuron.