Neurotransmitter

• A chemical messenger released by neurons to communicate with other cells.

Catecholamine

• A type of neurotransmitter made from the amino acid tyrosine. Includes dopamine, norepinephrine, and epinephrine — all important for attention, arousal, and emotion.

Monoamine

• A group of neurotransmitters (like serotonin and dopamine) that affect mood, emotion, and cognition. They have a single amine group in their chemical structure.

Ligand

• Any molecule that binds to a receptor. Neurotransmitters are ligands that activate receptors on neurons.

Receptor

• A protein on a cell’s surface or inside it that responds to specific signals (like neurotransmitters or hormones).

Ion Channel

• A pore in the cell membrane that allows ions (charged particles) to pass in or out, helping generate electrical signals in neurons.

G Protein-Coupled Receptor (GPCR)

• A type of receptor that, when activated by a neurotransmitter, starts a chain reaction inside the cell using G proteins.

Second Messenger

• A molecule inside the cell that passes along the signal from a receptor to other parts of the cell.