Question

Conduction of nerve impulse is a wave of followed by .

• A. depolarisation
• B. repolarisation
• C. hyperpolarisation
• D. polarisation

Answer 1

Answer: (A), (B)

repolarisation

In the normal resting condition, the outer side of the nerve fibre carries positive charge. This is called polarised state. This polarisation is due to more ${\mathrm{Na}}^{+}$ions outside the axon membrane. On stimulation the axon membrane at a spot becomes more permeable to ${\mathrm{Na}}^{+}$ which moves inwards and causes loss of polarisation (depolarised). This depolarisation becomes a stimulus for the next neighbouring area of the membrane which in turn becomes depolarised. Meanwhile, the previous area becomes repolarised due to the active transport of ${\mathrm{Na}}^{+}$ions again to the outside. So the conduction of a nerve impulse or action potential is a wave of depolarisation followed by repolarisation.