ANATOMY

Detailed explanation-1: -When an action potential reaches the axon terminal it depolarizes the membrane and opens voltage-gated Na+ channels. Na+ ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated Ca2+ channels to open.

Detailed explanation-2: -Action potential (AP) induces presynaptic membrane depolarization and subsequent opening of Ca2+ channels, and then triggers neurotransmitter release at the active zone of presynaptic terminal.

Detailed explanation-3: -One axon terminal may contain a million such vesicles. When an action potential arrives at the presynaptic axon terminal, it depolarizes the membrane, opening its voltage-gated calcium ion channels for a short time. Extracellular calcium ions enter through these calcium channels.

Detailed explanation-4: -Changes in voltage due to the action potential cause the voltage-gated calcium ion channels to open, allowing calcium ions to move into the cell.

Detailed explanation-5: -In neurons, calcium channels open in response to the binding of neurotransmitters to cell surface receptors that are permeable to calcium, such as NMDA and AMPA receptors.