SSC MTS EXAM

Detailed explanation-1: -The depolarization, also called the rising phase, is caused when positively charged sodium ions (Na+) suddenly rush through open voltage-gated sodium channels into a neuron. As additional sodium rushes in, the membrane potential actually reverses its polarity.

Detailed explanation-2: -The correct answer is (d): neurotransmitters into the axon. The action potential is the reversal of the membrane potential brought about by the influx of sodium ions through voltage-gated sodium channels. These channels are activated by the depolarization of nearby membranes and let sodium ions in.

Detailed explanation-3: -In fact, more sodium entered during the falling phase of the action potential than during the rising phase. The sodium current during the upstroke reaches a maximum shortly before the peak of the action potential.