Question

How are neurons structurally adapted to chemically transmit impulses to neighbouring neurons?
A) The trigger zone is near the cell body.
B) Axon terminals contain neurotransmitter substances within synaptic vesicles.
C) Schwann cells surround axons.
D) They have numerous dendrites.

Answer 1

Hint:
When a nerve impulse arrives at the terminal of the presynaptic neuron transmission occurs by chemical synapses. Depending on which ions pass the channels, the postsynaptic potential may be depolarization or hyperpolarization.

Complete step by step answer:
A nerve impulse arrives at the axon terminal of a presynaptic axon. The change in membrane potential caused by the arrival of action potential leads to the opening of voltage-gated calcium channels in the presynaptic membrane. Calcium moves inside by the open channels as calcium concentration is more in the extracellular fluid. An increase in the concentration of calcium inside the presynaptic neuron serves as a signal that triggers exocytosis of the synaptic vesicles. A vesicle membrane merges with the plasma membrane, and neurotransmitter molecules within the vesicles are released into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and bind to the neurotransmitter receptors in the postsynaptic neuron’s plasma membrane.
The binding of neurotransmitter molecules to their receptor causes the opening of channels and the movement of ions across the membrane. When the ions go through the channels that are opened, the voltage across the membrane changes. This change in membrane voltage is postsynaptic potential. Through this process, a typical chemical synapse transmits the signal.

Option ‘B’ is correct

Note:
A single postsynaptic neuron receives input from many presynaptic neurons, some of which release excitatory neurotransmitters and some of which release inhibitory neurotransmitters. The effect on the postsynaptic neuron Is determined by the total excitatory and inhibitory signals.
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