Question

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

• A. Nerve fibre 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

Answer: (D)

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

Unidirectional transmission of a nerve impulse through nerve fibre is due to the fact that neurotransmitters are released by the axon endings and not by dendrites. Transmission of nerve impulses along the synapse comes through the ends of axons the nerve endings, through which electrical impulses are transmitted from one neuron to another. Transmission of nerve impulses is an electrochemical process. The mechanism of chemical transmission of nerve impulses across the synapse: the contents of synaptic vesicles comes in small portions in the synaptic cleft and interacts with receptor proteins of postsynaptic membrane. This causes membrane depolarization and excitation of the next neuron. Ultrastructural features of the synapse and the mechanism of transmission of impulses determine the strict unidirectional transmission of impulses that underlies the transmit of impulses.