GMED3008: Synapses and Neurotransmitters

Vocabulary flashcards covering the structure, function, and biochemistry of synapses and neurotransmitters.

Synapse

A specialized junction where information is transferred from one neuron to another or to a muscle or gland cell.

Electrical Synapse

A gap junction that allows direct passage of action potentials between cells for rapid, synchronous communication.

Chemical Synapse

A synapse that uses neurotransmitters to relay signals across a synaptic cleft from presynaptic to postsynaptic cells.

Gap Junction

Intercellular channel forming an electrical synapse, permitting ion flow and direct action-potential spread.

Functional Syncytium

A group of cells connected by electrical synapses that contract or fire in unison, e.g., heart muscle.

Axodendritic Synapse

Chemical synapse between an axon terminal and a dendrite.

Axosomatic Synapse

Chemical synapse between an axon terminal and a neuronal cell body.

Axoaxonic Synapse

Chemical synapse between two axon terminals.

Presynaptic Axon Terminal

The end of a neuron containing voltage-gated Ca2+ channels and synaptic vesicles.

Synaptic Vesicle

Membrane-bound sac in presynaptic terminals that stores neurotransmitter molecules.

Synaptic Cleft

The narrow gap between pre- and postsynaptic membranes across which neurotransmitters diffuse.

Postsynaptic Membrane

Region of the receiving cell containing ligand-gated receptors for neurotransmitters.

Excitatory Postsynaptic Potential (EPSP)

Local depolarization of the postsynaptic membrane that brings the neuron closer to threshold.

Inhibitory Postsynaptic Potential (IPSP)

Local hyperpolarization of the postsynaptic membrane that moves the neuron further from threshold.

Ionotropic Receptor

Ligand-gated ion channel where neurotransmitter binding directly opens the channel.

Metabotropic Receptor

G-protein-coupled receptor that indirectly opens an ion channel via second-messenger signaling.

Spatial Summation

Addition of postsynaptic potentials generated at different locations on the neuron at the same time.

Temporal Summation

Addition of postsynaptic potentials generated at the same site in rapid succession.

EPSP-IPSP Cancellation

Net effect at the axon hillock when excitatory and inhibitory inputs are integrated.

Acetylcholine (ACh)

Neurotransmitter that is excitatory at neuromuscular junctions and inhibitory at some parasympathetic synapses; broken down by acetylcholinesterase.

Acetylcholinesterase

Enzyme that degrades acetylcholine into acetate and choline in the synaptic cleft.

Gamma-Aminobutyric Acid (GABA)

Principal inhibitory amino-acid neurotransmitter in the brain; acts via Cl- channel ionotropic receptors.

Glutamate

Most abundant excitatory neurotransmitter in the CNS; acts through cation channel ionotropic receptors.

Glycine

Inhibitory amino-acid neurotransmitter in the spinal cord; opens Cl- channel ionotropic receptors.

Norepinephrine

Biogenic amine acting via metabotropic receptors; involved in arousal, dreaming, and mood regulation.

Dopamine

Biogenic amine that modulates skeletal muscle tone and movement; acts through metabotropic receptors.

Serotonin (5-HT)

Biogenic amine affecting perception, thermoregulation, mood, appetite, and sleep; uses metabotropic receptors.

Nitric Oxide (NO)

Gaseous neurotransmitter involved in memory, learning, and vasodilation; quickly inactivated by reaction with O2 and H2O.

Endorphins

Inhibitory neuropeptides in the CNS that reduce pain perception via metabotropic receptors.

Substance P (Tachykinin)

Excitatory neuropeptide involved in pain transmission and regulation of respiratory and cardiovascular functions.

Somatostatin

Inhibitory neuropeptide that suppresses growth hormone release; present in CNS and pancreas.

Neurotransmitter Removal

Clearance of transmitters by enzymatic degradation, re-uptake by transporters, or uptake by glial cells.

Voltage-Gated Calcium Channel

Presynaptic membrane channel that opens on depolarization, allowing Ca2+ influx and neurotransmitter release.

Exocytosis (at Synapse)

Fusion of synaptic vesicles with the presynaptic membrane to release neurotransmitter into the cleft.

Threshold Potential

Membrane voltage at the axon hillock that triggers opening of voltage-gated Na+ channels and an action potential.