Neurophysiology: Nerve Impulses, Synapses, and Propagation

Vocabulary flashcards covering nerve impulses, membrane potentials, conduction, myelin-related topics, synapses, and postsynaptic potentials from the lecture notes.

Resting Membrane Potential (RMP)

Voltage difference across the neuron's membrane when the cell is at rest, established by ion gradients and selective permeability.

Differential Permeability

Membrane selectivity that makes the neuron more permeable to certain ions (e.g., K+) than others, helping set the resting potential.

Na+/K+ ATPase Pump

Energy-dependent transporter that pumps 3 Na+ out and 2 K+ in to maintain ionic gradients and the resting membrane potential.

Gated Na+ Channel

Ion channel that opens in response to stimuli to allow Na+ influx during depolarization.

Nongated (Leak) K+ Channel

Always-open potassium channel contributing to resting potential by allowing K+ efflux.

Extracellular Fluid

Fluid outside the neuron rich in Na+ and Cl− that influences ion gradients and signaling.

Local Potential

Graded, subthreshold change in membrane potential that can summate to trigger an action potential.

Depolarization

Change in membrane potential toward a more positive value due to Na+ influx.

Repolarization

Return toward the resting membrane potential after depolarization, mainly via K+ efflux.

Hyperpolarization

Membrane potential becoming more negative than the resting potential, often following IPSPs.

Threshold

Critical level of depolarization that must be reached to trigger an action potential.

Action Potential

All-or-none electrical impulse that travels along the axon, involving rapid depolarization and repolarization.

Absolute Refractory Period

Interval after an action potential during which no new action potential can be fired, regardless of stimulus strength.

Relative Refractory Period

Interval after an action potential when a stronger-than-normal stimulus can trigger another AP.

Continuous Conduction

Propagation of an action potential along unmyelinated axons through sequential channel openings.

Saltatory Conduction

Propagation of an action potential along myelinated axons by jumping between nodes of Ranvier.

Node of Ranvier

Gaps in the myelin sheath with high density of voltage-gated Na+ channels, where APs are regenerated.

Myelin Sheath

Insulating layer around axons (produced by Schwann cells in the PNS) that increases conduction velocity.

Schwann Cell

Glial cell in the peripheral nervous system that forms the myelin sheath around axons.

Internode

Myelinated segment of an axon between two nodes of Ranvier.

Multiple Sclerosis (MS)

Demyelinating disease that damages the myelin sheath, disrupting conduction; described as having 'no gates below the myelin'.

Conduction Velocity

Speed at which an action potential travels along an axon; affected by temperature, myelination, and diameter.

Electrical Synapse

Synapse where electrical current passes directly between cells via gap junctions.

Gap Junction

Tight connection between cells that allows direct electrical communication through channels.

Connexons

Protein channels that form gap junctions between adjacent cells.

Chemical Synapse

Synapse that uses neurotransmitter release to communicate across a synaptic cleft.

Presynaptic Terminal

End of the neuron that releases neurotransmitter into the synaptic cleft.

Synaptic Vesicle

Vesicles in the presynaptic terminal that store neurotransmitters for release.

Synaptic Cleft

The narrow gap between presynaptic and postsynaptic membranes where neurotransmitters diffuse.

Neurotransmitter

Chemical messenger released by the presynaptic neuron to bind receptors on the postsynaptic membrane.

Ligand-Gated Ion Channel

Postsynaptic receptor channel that opens when a neurotransmitter binds, allowing ion flow.

Postsynaptic Membrane

Membrane of the receiving neuron where neurotransmitter receptors are located.

Voltage-Gated Ca2+ Channel

Channel in the presynaptic terminal opened by depolarization to allow Ca2+ influx and trigger neurotransmitter release.

Ca2+ Trigger for Neurotransmitter Release

Calcium influx into the presynaptic terminal prompts vesicle fusion and neurotransmitter release.

EPSP (Excitatory Postsynaptic Potential)

Depolarizing postsynaptic potential that brings the membrane closer to threshold and increases AP likelihood.

IPSP (Inhibitory Postsynaptic Potential)

Hyperpolarizing postsynaptic potential that moves the membrane away from threshold and decreases AP likelihood.

Postsynaptic Potential (PSP)

Generic term for EPSP or IPSP, changes in postsynaptic membrane potential due to synaptic activity.