Neurophysiology of Nerve Impulses

Flashcards with vocabulary terms and definitions related to the neurophysiology of nerve impulses.

Electrical Potential

Difference in concentration of charged particles between different parts of the cell

Electrical Current

Flow of charged particles from one point to another within the cell

Neurons (nerve cells)

Specialized cells that conduct messages in the form of electrical impulses throughout the body

Transmembrane Potential

The unequal charge across the plasma membrane, due to differences in the permeability of the membrane to various ions

Resting Potential

The transmembrane potential in an undisturbed cell (average -70 mV)

Membrane Channels

Control movement of ions across the plasma membrane

Leak Channels (passive)

Non-gated channels that are always open and important in establishing resting membrane potential

Gated Channels (active)

Channels that open and close in response to specific stimuli

Chemically Gated (ligand-gated) Channels

Gated channels that open/close when they bind specific chemicals (i.e. neurotransmitters)

Voltage-Gated Channels

Gated channels that open and close in response to changes in membrane potential

Mechanically Gated Channels

Gated channels that open and close in response to physical deformation of receptors (i.e. touch, pressure, vibration)

Depolarization

Shift from the resting membrane potential toward a more positive potential

Graded Potentials

A short-lived localized change in the resting membrane potential

Action Potential

A brief reversal of the membrane potential that affects the entire excitable membrane

Threshold

The minimum voltage to stimulate an action potential (average is about -55mV in many neurons)

Repolarization

The process that occurs when the stimulus is removed and the transmembrane potential begins to return to normal resting levels. is the re-establishment of the restingmembrane potential after depolarization. During this phase, potassium channels open, allowing K+ ions to flow out of the cell. This movement of potassium ions helps to restore the negative internal charge of the neuron, thus completing the action potential cycle.

Hyperpolarization

K+ continues to exit the cell until all of the voltage-gated K+ channels close

Refractory Period

The time period from which an action potential begins until the normal resting potential has stabilized

Absolute Refractory Period

As long as the voltage-gated Na+ channels are open, no stimulus will trigger an action potential

Relative Refractory Period

As long as the voltage-gated K+ channels are open, only an especially strong stimulus will trigger new action potential

Myelinated Internode

Area of the axon wrapped in myelin

Nodes of Ranvier

Small gaps between the myelinated internodes

White Matter

Consists of regions of CNS with many myelinated nerves

Gray Matter

Consists of unmyelinated areas of CNS (short axons)

Continuous Propagation

The action potential moves along the axon membrane in segments

Saltatory Propagation

The impulse jumps from node to node along the axon