Answer:
Opening of sodium channels
Explanation:
Sodium channels play important roles in transmission of nerve impulse as well in the releasing of neurotransmitter (Acetylcholine). Both of these are dependent on sodium channels. As for the transmission of impulse the first step is depolarization of nerve cells and for depolarization the opening of sodium channels is necessary.
So the neurotransmitter released from on neuron and binds to receptors on other neuron causes the opening of sodium channels. These channels cause the influx of sodium into the neuron and alternatively cause the depolarization by making the inside of cell less negative. During this process a minor amount of potassium also move out of the membrane.
