Question

What event directly triggers the release of neurotransmitter shown in a?

Answer 1

An action potential at the presynaptic neuron's axon terminal triggers the opening of voltage-gated calcium channels. This leads to the release of neurotransmitters through exocytosis. The neurotransmitters then bind to the postsynaptic receptors, possibly triggering a new action potential.

Step-by-step explanation:

The event that directly triggers the release of neurotransmitters, such as acetylcholine (ACh), is the arrival of an action potential at the axon terminal of the presynaptic neuron. This action potential causes voltage-gated calcium channels to open, leading to an influx of Ca²⁺ ions. These calcium ions facilitate the fusion of synaptic vesicles containing neurotransmitters with the presynaptic membrane, ultimately causing the release of neurotransmitters through exocytosis into the synaptic cleft.

Once in the synaptic cleft, the neurotransmitter, like ACh, binds to receptors on the postsynaptic membrane. This binding opens ion channels, such as ligand-gated Na⁺ channels in the case of ACh at the neuromuscular junction, which leads to depolarization of the postsynaptic neuron and a possible generation of a subsequent action potential.

Neurotransmitter release is triggered by the opening of voltage-gated calcium channels in the presynaptic neuron. When an action potential reaches the axon terminal, these channels open, allowing calcium ions to enter the presynaptic cell. The increase in calcium concentration inside the cell triggers the fusion of neurotransmitter vesicles with the presynaptic membrane, leading to the release of neurotransmitters into the synaptic cleft.

Answer 2

The event that directly triggers the release of the neurotransmitter is THE DIFFUSION OF CALCIUM IONS INTO THE AXONAL TERMINUS.
Neurotransmitters are chemical messengers which relay information throughout the entire body system. There are many neurotransmitters and different events are responsible for triggering them up.