Chemical transmission

Presynaptic membrane

Not homogeneous; contains specialized regions of neurotransmitter release called active zones.

Active zones

Specialized regions within the presynaptic membrane where neurotransmitter release occurs.

Vesicles

Contain neurotransmitter and are located near active zones in the presynaptic terminal, protecting NT against degradation.

SNAREs

Scaffold proteins that are Ca2+ sensitive and facilitate vesicle docking at active zones.

Calcium dependency

Vesicle fusion allowing neurotransmitter release is Ca2+ dependent, while vesicle docking is Ca2+ sensitive but not dependent.

Voltage-sensitive Ca2+ channels

Channels that are voltage-gated and selectively allow Ca2+ influx, especially concentrated near active zones.

Glutamate

An excitatory neurotransmitter, most common single amino acid neurotransmitter.

GABA

An inhibitory neurotransmitter, a decarboxylated form of glutamate.

Biogenic amines

A group of neurotransmitters including norepinephrine, serotonin, acetylcholine, dopamine, and histamine.

Ionotropic receptors

Neurotransmitter-gated ion channels that allow fast signaling and can be excitatory or inhibitory.

Metabotropic receptors

Cell surface receptors that, upon activation, initiate a signaling cascade through intracellular second messengers rather than forming an ion channel.

Excitatory Postsynaptic Potential (EPSP)

Depolarization of the postsynaptic membrane, often resulting from Na+ influx through ionotropic receptors like AMPA.

Inhibitory Postsynaptic Potential (IPSP)

Hyperpolarization of the postsynaptic membrane, often resulting from Cl- influx through receptors such as GABAa.

NT release mechanism

Involves action potential propagation, vesicle docking due to Ca2+, and fusion allowing neurotransmitter release.

Receptor specificity

Receptors show high specificity for their neurotransmitters, with agonists mimicking and antagonists blocking their activity.