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Multiple Choice
When a nerve signal arrives at a synaptic knob, which of the following events occurs first?
A
Voltage-gated calcium channels open, allowing Ca^{2+} to enter the cell.
B
The postsynaptic cell generates an action potential.
C
Postsynaptic receptors bind to the neurotransmitter.
D
Neurotransmitter is released into the synaptic cleft.
Verified step by step guidance
1
Understand the structure of a synapse: A synapse is the junction between two neurons where the transmission of a nerve signal occurs. It consists of the presynaptic neuron (sending the signal), the synaptic cleft (gap between neurons), and the postsynaptic neuron (receiving the signal).
Recognize the sequence of events in synaptic transmission: When a nerve signal reaches the synaptic knob of the presynaptic neuron, it triggers a cascade of events leading to neurotransmitter release and signal transmission to the postsynaptic neuron.
Identify the role of voltage-gated calcium channels: The arrival of the nerve signal causes depolarization of the synaptic knob, which opens voltage-gated calcium channels. This allows calcium ions (Ca^{2+}) to enter the presynaptic neuron.
Understand the importance of calcium ions: The influx of Ca^{2+} into the synaptic knob is crucial because it stimulates the synaptic vesicles to fuse with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.
Clarify the subsequent steps: After neurotransmitters are released, they bind to receptors on the postsynaptic neuron, which may lead to the generation of an action potential in the postsynaptic cell, depending on the type of neurotransmitter and receptor involved.