How does the membrane potential inside a neuron change during an action potential?
First negative, then positive and again back to negative
Before the generation of an action potential, the neuron is in resting state that is -70mV, inside the cell. During action potential or transmission of nerve impulse, the membrane potential inside the neuron rises upto 30mV. After the action potential has passed the neuron returns back to its resting state i.e. at -70mV.