Neurology II – Neurophysiology Vocabulary

Vocabulary flashcards summarizing the key terms and definitions from the Neurology II lecture on neurophysiology.

Neurophysiology

The study of how the nervous system functions, especially the electrical and chemical processes within neurons.

Membrane potential

The voltage difference between the inside and outside of a cell membrane created by unequal ion distribution.

Resting potential

The membrane potential of an undisturbed neuron, typically about –70 mV.

Local potential

A small, graded change in membrane potential produced when a stimulus opens chemically gated channels; strongest at the stimulus site.

Action potential

An all-or-none electrical impulse generated once threshold is reached that propagates along the axon.

Synaptic activity

The process of transferring a signal from one neuron to another across a synapse.

Sodium ion (Na⁺)

Ion concentrated outside the neuron; its influx depolarizes the membrane.

Potassium ion (K⁺)

Ion concentrated inside the neuron; its efflux helps repolarize or hyperpolarize the membrane.

Chemically gated channel

Membrane channel that opens when a specific chemical (ligand) binds; common on cell bodies and dendrites.

Voltage-gated channel

Ion channel that opens in response to a change in membrane potential; abundant on axons and terminals.

Mechanically gated channel

Channel that opens when the membrane is physically deformed by pressure or stretch; found on some dendrites.

Depolarization

A shift in membrane potential toward less negative values (closer to 0 mV).

Hyperpolarization

A shift in membrane potential toward more negative values than resting potential.

Threshold voltage

Approximately –55 mV; the membrane potential at which an action potential is triggered.

Trigger zone

Region at the axon hillock/initial segment where action potentials are initiated.

Continuous propagation

Slow, step-by-step conduction of an action potential along an unmyelinated axon (~1 m/s).

Saltatory propagation

Fast conduction in myelinated axons where the action potential jumps from node to node (up to 180 m/s).

Unmyelinated axon

Nerve fiber lacking a myelin sheath; conducts impulses by continuous propagation.

Myelinated axon

Nerve fiber wrapped in myelin; conducts impulses rapidly through saltatory propagation.

Oligodendrocyte

Central nervous system glial cell that forms myelin sheaths around multiple axons.

Multiple sclerosis (MS)

Autoimmune disease that destroys oligodendrocytes and myelin, disrupting nerve signaling.

MS symptoms

Can include sensory loss, spasticity, motor coordination problems, bladder/intestinal issues, and psychological changes.

MS diagnostic steps

Assessment of neurological symptoms, blood tests, spinal tap for microglia/inhibitory proteins, MRI scans, and evoked potential testing.