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An investigator places as isolated neuro...

An investigator places as isolated neuron in a calcium-free medium, gives the neuron a suprathreshold stimulus and then performs an assay to test whether neurotransmitter is released into the medium. Which of the following outcomes would you predict ?

A

No neurotransmitter is detected since influx of calcium into the synaptic knob is required for neurotransmitter release

B

No neurotransmitter is detected since influx of calcium is required in order for the neuron to conduct an action potential

C

Neurotransmitter is detected since calcium is not required for action potential conduction and the initial stimulus was suprathreshold

D

We cannot predict the outcome without knowing whether the neuron was myelinated

Text Solution

Verified by Experts

The correct Answer is:
A
No neurotransmitter is detected since influx of calcium into the synaptic knob is required for neurotransmitter release
(i) A nerve impulse arrives at synaptic end bulb of a pre-synaptic axon.
(ii) The depolarization phase of nerve impulse opens voltage gates `Ca^(2+)` channels so `Ca^(2+)` flows inward through the opened channels.
(iii) The concentration of `Ca^(2+)` inside the pre – synaptic neuron increases. This trigger release of neurotransmitter molecules with in the vesicles from the pre-synaptic neuron into the synaptic cleft.
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