Unidirectional transmission of a nerve impulse through nerve fibre is due to the fact that

Options

A. Nerve fibre is insulated by a medullary sheath
B. Sodium pump starts operating only nerve fibre
C. Neurotransmitters are relesed by dendrites and not by axon endings
D. Neurotransmitters are released by the axon endings and not by dendrites.

Answer

D

Explanation

A synapse occurs where the dendrite or the cell body of another(the post-synaptic neurone).At the tip of the pre-synaptic axon is a button shaped swlling called a synaptic and vesicles packed with a substance called a neutransmitter is present.This neurotransmitters at the time of nerve impulse diffuse across the space and bind to receptors in the membrane of the post-synaptic cell.This open ion channels in the post-synaptic membrane of the post-synaptic cell resulting in a change in the post-synaptic cell's membrane potential and(if the cell is sufficiently excited)in the consequent generation of a nerve impulse.