Question

A neuron is at rest. A millisecond later, an action potential travels along its axon. What happened in the interim?

Answer 1

A neuron develops an action potential only when there is a stimulus. Stimulus is a change in the internal or immediate external environment.

Explanation:

Resting membrane potential of -70mv is maintained by Na-K pump across neuronal cell membrane. A stimulus will disrupt the pump by opening of sodium channels. Entry of positively charged sodium ions inside neuron through the simulated area changes the membrane potential:- a phenomenon known as depolarisation.

An action potential develops when membrane potential becomes about +30mv. This initiates impulse transmission along neuron, which is unidirectional.