Neurophysiology Glossary

A rapid, all-or-none reversal of membrane polarity that propagates along excitable cell membranes, generated by the sequential activation of voltage-gated sodium and potassium channels.

A sensory neuron that carries information from peripheral receptors toward the central nervous system.

The region of the neuron cell body where the axon originates, containing the highest density of voltage-gated sodium channels and serving as the integration zone where the decision to fire an action potential is made.

The use of calcium ions (Ca2+) as intracellular messengers to trigger processes such as neurotransmitter release, muscle contraction, gene expression, and synaptic plasticity.

A shift in the membrane potential toward a less negative (more positive) value, typically caused by the influx of positively charged ions such as sodium or calcium.

A motor neuron that carries signals from the central nervous system to effector organs such as muscles and glands.

A non-invasive technique that records the electrical activity of the brain through electrodes placed on the scalp, measuring the summed postsynaptic potentials of large cortical neuron populations.

A small depolarization of the postsynaptic membrane caused by the opening of cation channels in response to neurotransmitter binding, bringing the cell closer to the threshold for firing.

Gamma-aminobutyric acid, the principal inhibitory neurotransmitter in the adult mammalian central nervous system, acting primarily through GABA-A (ionotropic) and GABA-B (metabotropic) receptors.

The principal excitatory neurotransmitter in the central nervous system, acting on AMPA, NMDA, and kainate ionotropic receptors as well as metabotropic glutamate receptors.

A local change in membrane potential whose amplitude is proportional to stimulus strength, decreasing with distance from the point of origin. Includes EPSPs, IPSPs, and receptor potentials.

A set of nonlinear differential equations developed in 1952 that quantitatively describe how ionic currents through voltage-gated sodium and potassium channels produce the action potential.

A shift in the membrane potential toward a more negative value than the resting potential, typically caused by potassium efflux or chloride influx, making the neuron less likely to fire.

A hyperpolarization of the postsynaptic membrane that moves the potential further from threshold, reducing the likelihood of action potential generation.

A transmembrane protein that forms a selective pore allowing specific ions to pass through the cell membrane. Can be voltage-gated, ligand-gated, or mechanically gated.

A persistent increase in synaptic strength lasting hours to weeks, induced by high-frequency stimulation. Widely studied at hippocampal synapses as a model for learning and memory.

A lipid-rich insulating layer surrounding axons, formed by oligodendrocytes in the CNS and Schwann cells in the PNS, that enables rapid saltatory conduction.

The chemical synapse between a motor neuron axon terminal and a skeletal muscle fiber, where acetylcholine is released to initiate muscle contraction.

A chemical substance released from the presynaptic terminal of a neuron that transmits signals across the synaptic cleft to activate receptors on the postsynaptic cell.

Gaps in the myelin sheath along a myelinated axon where voltage-gated ion channels are concentrated, allowing regeneration of the action potential during saltatory conduction.

An electrophysiology technique that uses a glass micropipette to record ionic currents through individual ion channels or across entire cell membranes with very high resolution.

A graded change in the membrane potential of a sensory receptor cell in response to a stimulus, which is proportional to stimulus intensity and can trigger action potentials in the associated sensory neuron.

The period following an action potential during which the membrane is less responsive or unresponsive to further stimulation, ensuring unidirectional propagation and limiting firing frequency.

An active transport pump that uses ATP to move 3 Na+ ions out and 2 K+ ions into the cell per cycle, maintaining the ionic concentration gradients essential for the resting membrane potential and action potential generation.

The specialized junction between two neurons or between a neuron and an effector cell where signal transmission occurs, either chemically via neurotransmitters or electrically via gap junctions.