Depolarization of the neuronal membrane

Question

Explain how depolarization of the neuronal membrane begins?

Answer 1

The main cause of neuronal depolarization is the binding of neurotransmitters liberated in the synapse (that is, by the axon of neuron which sent the signal) to specific receptors in the membrane of neuron which receive the stimulus. The binding of neurotransmitters to such receptors is a reversible phenomenon which modifies the membrane permeability of the area as the binding causes sodium channels to open. Whenever positive sodium ions enter the cell in the favor of their concentration gradient, the membrane voltage rises, therefore lessening the negative polarization. When this depolarization reaches the excitation threshold (around –50 mV) the depolarization continues, the action potential is reached and the impulse is transmitted all along the cell membrane.