Question

Assertion: A synaptic knob contains many mitochondria and small granules, like synaptic vesicles filled with the chemicals, that transmits impulses to post synaptic neurons.
Reason: The chemical transmitters from the posterior pituitary are also called 'neurohormones', their release is proportionate to Calcium ions influx.
a. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
b. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
c. Assertion is correct but Reason is incorrect.
d. Assertion is incorrect but Reason is correct

Answer 1

Hint: Calcium fluxing in by mitochondria is a key feature in cell life. It is involved in energy production for cell activity in buffering and shaping cytosolic calcium rises and also in determining cell fate by actually preventing apoptosis so basically. The calcium is the source for the mitochondrial matrix to develop energy.

Complete answer:
The nerve impulses are the electrical signals along the dendrites to produce a nerve impulse or action potential.
When an action potential arrives at the end of the presynaptic neuron, it causes the release of neurotransmitter molecules that open ion channels in the postsynaptic neuron. The combined potentials of the influx from both the synaptic ends can start a new action potential in the postsynaptic neuron.

The presynaptic knob contains many mitochondria to provide ATP for the synthesis of neurotransmitters. When a nerve impulse passes through a neuron and reaches the axon terminal many vesicles containing neurotransmitters are stimulated.
The arrival of an action potential at the synaptic knob opens Calcium ions channels in the plasma membrane. The influx of Calcium ions triggers the exocytosis of some of the vesicles. Then Their neurotransmitter is released into the synaptic cleft.

Hence, the correct answer is option (a).

Note: Neurotransmitters are chemical messengers that transmit a message from a nerve cell across the synapse to a target cell. The target can be another nerve cell, or a muscle cell, or a gland cell. They are chemicals made by the nerve cell specifically to transmit the message.