Question

Which of the following is the CORRECT order of events for a chemical synapse? (not all events included in each option)

A. Action potential invades presynaptic cell, Synaptic vesicles bind to presynaptic membrane, Ca2+ channels open, Transmitter released into synaptic cleft.
B. Ca2+ channels open, Action potential invades presynaptic cell, Transmitter moves out through Ca 2+ channels.
C. Action potential invades postsynaptic cell, Synaptic vesicles fuse with postsynaptic cleft, Transmitter is released into synaptic cleft.
D. Action potential invades presynaptic cell, Ca2+ channels open, Ca2+ begins to move into cell, vesicle fuses with presynaptic membrane, transmitter released into synaptic cleft.
E. Opening/closing of presynaptic channels, Synaptic vesicle fuses with presynaptic membrane, Ca2+ moves into the cell, Neurotransmitter released into synaptic cleft.

Answer 1

Option D is the correct order of events in a chemical synapse, starting with an action potential in the presynaptic cell, followed by the opening of Ca²⁺ channels, the fusion of synaptic vesicles with the membrane, and the release of neurotransmitter into the synaptic cleft.

Step-by-step explanation:

The correct order of events for a chemical synapse is represented by option D, which describes the sequence in the following way: An action potential invades the presynaptic cell, which depolarizes the membrane and leads to the opening of voltage-gated calcium channels. As Ca²⁺ channels open, Ca²⁺ begins to move into the cell. This influx of calcium ions triggers the fusion of synaptic vesicles with the presynaptic membrane, followed by the release of neurotransmitter into the synaptic cleft.

This sequence starts with the arrival of the action potential at the presynaptic terminal, causing the voltage-gated Na+ channels and subsequently Ca²⁺ channels to open. The calcium ions then facilitate the binding of synaptic vesicles to the membrane, allowing them to release their neurotransmitter contents into the synaptic cleft. Finally, the neurotransmitter diffuses across the cleft and binds to receptors on the postsynaptic neuron, potentially initiating a new action potential.