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
Correct Answer: A
Solution :
Neurotransmitters are chemical messengers secreted by the axon terminals for transmitting impulses to the next neuron. At most synapses information is passed from the transmitting neuron (pre-synaptic cell) to the receiving (post synaptic cell) by neurotransmitters. The membrane of presynaptic terminal contains large number of voltage gated calcium channels. The quantity of neurotransmitter that is released from the terminal into the synaptic left is directly related to number of calcium ions that enter. When the calcium ion enters the presynaptic terminal, it is believed that they bind with special protein molecules, on the inside surface of presynaptic membrane called release sites. This binding in turn couses the release site to open through the membrane, allowing a few transmitter vesicles to release their transmitter into the cleft.
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