Question

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

• A. The neuron is insulated by a medullary sheath
• B. Sodium pump starts operating only at the cyton and then continues into the nerve fibre
• C. Neurotransmitters are released by dendrites and not by axon endings
• D. Neurotransmitters are released by the axon endings and not by dendrites.

Answer 1

The correct option is D

Neurotransmitters are released by the axon endings and not by dendrites.

A synapse occurs where the axon of one neuron (the pre-synaptic neuron) meets the dendrite of another (the post-synaptic neuron). At the tip of the pre-synaptic axon is a button-shaped swelling called a synaptic knob, inside which are numerous mitochondria and vesicles packed with a substance called a neurotransmitter. This chemical, at the time of nerve impulse conduction, diffuses across space and bind to receptors in the membrane of the post-synaptic cell. This binding leads to transmission of the nerve impulse to the next neuron.