Action Potential Study Guide Flashcards

Vocabulary flashcards focusing on key terminology, ion channel mechanics, action potential phases, refractory periods, and conduction types based on Nervous System Part 2 lecture notes.

Depolarization

A change in membrane potential where it becomes less negative than the resting potential.

Repolarization

A change in membrane potential where it moves back toward resting potential after depolarization.

Hyperpolarization

A change in membrane potential where it becomes more negative than the resting potential.

Graded potential

A membrane potential change that starts near the point of stimulation and decreases in strength as it spreads.

Subthreshold graded potential

A graded potential that is too weak by the time it reaches the trigger zone to trigger an action potential.

Suprathreshold graded potential

A graded potential strong enough to remain above threshold at the trigger zone, resulting in an action potential.

Action potential

A rapid, brief reversal of membrane potential with a total amplitude of about $100\,mV$ (roughly $-70\,mV$ to $+30\,mV$) lasting about $1\,ms$.

Leakage (nongated) channel

An ion channel that is always open and helps set the resting membrane potential.

Chemically gated channel

An ion channel that opens when the appropriate chemical or neurotransmitter binds.

Voltage-gated channel

An ion channel that opens in response to a change in membrane potential.

Mechanically gated channel

A gated ion channel type that opens in response to mechanical forces.

Voltage-gated Na+ channels

Channels that are closed at rest, open upon depolarization to let Na+ enter the cell, and are shortly afterward blocked by an inactivation gate.

Voltage-gated K+ channels

Channels that are closed at rest and open after a delay following depolarization, allowing K+ to leave the cell.

Threshold membrane potential

The minimum membrane potential that must be reached to fire an action potential.

Threshold stimulus

The minimum stimulus needed to achieve an action potential.

Absolute refractory period

A time period during which another action potential cannot be generated, regardless of the stimulus strength.

Relative refractory period

A time period during which another action potential can occur, but requires a larger-than-normal stimulus.

Continuous conduction

Conduction of an action potential along an unmyelinated membrane without the myelin-based jumping pattern.

Saltatory conduction

Conduction in a myelinated axon where action potentials appear to jump from one node of Ranvier to the next.

Nodes of Ranvier

Gaps along a myelinated axon that contain voltage-gated Na+ (Nav) channels where action potentials occur.

Multiple sclerosis (MS) connection

A condition where demyelination can reduce or block signal conduction because current leaks out of regions previously insulated between nodes.

Sodium-channel blockers

Substances such as tetrodotoxin and Novocaine that plug gated sodium channels, preventing action potentials from occurring.

Stimulus intensity coding

The representation of stimulus strength in the nervous system coded by action-potential frequency (impulses per second) rather than amplitude.