Excitable Tissues Overview

The ability of a membrane to preferentially allow certain molecules to pass through, depending on their solubility (water or lipid soluble).

The difference in the concentration of a substance between two sides of a membrane. Higher concentration to lower concentration.

The difference in electrical charge between two sides of a membrane. Opposite charges attract.

The difference in electrical charge across a cell membrane at rest or during stimulation/activation, in mV.

The membrane potential of a neuron when it is not sending signals.

The membrane potential at which the net movement of an ion across the membrane is zero (forces balance).

The movement of ions against a concentration gradient, requiring energy.

A protein that actively transports sodium ions out of the cell and potassium ions into a cell, maintaining concentration gradients.

The naturally occurring electrical potential difference across a cell membrane when the cell is not stimulated. It's the voltage difference between the inside and outside of the cell.

The membrane potential at which the net movement of a particular ion across the membrane is zero; the electrical gradient exactly balances the concentration gradient.

An equation used to calculate the equilibrium potential for a single ion, given the ion's concentration inside and outside the cell.

A crucial active transport protein that maintains the RMP by moving sodium ions out of the cell and potassium ions into the cell against their concentration gradients.

A rapid, transient change in membrane potential caused by the opening and closing of ion channels, which is an electrical impulse allowing signals via nerves, etc.

The minimum stimulus needed to trigger an action potential.

A method of measuring the RMP or action potential by inserting an electrode inside the cell.

The ability of a membrane to allow various substances, including ions, to pass through it.

A momentary reversal in electrical potential across a cell membrane, triggered by a stimulus. It occurs in excitable membranes like neurons and muscles.

The process where the inside of a cell membrane becomes less negative, often visualized as an uptrend in electrical potential (e.g., from -70mV to +35mV).

Returning to the polarized resting state, involving restoration of the negative charge inside the cell membrane and positive outside (e.g., from +35mV to -70mV).

The critical level of stimulus required to trigger an action potential. It's the point where positive feedback mechanisms take over.

Action potentials occur completely or not at all; there's no halfway. The strength of the stimulus determines whether or not an action potential occurs and its overall magnitude.

The measurement of electrical changes in a cell. Extra cellular records the transition; intra cellular records a single reading

Recording electrical activity outside the cell, providing an overall view

Recording electrical activity inside the cell, providing precise insights.

The electrical voltage difference across a cell membrane when the cell is not transmitting an impulse.

A rapid, temporary change in membrane potential that propagates along the neuron.

The initial phase of an AP, characterized by a rapid increase in membrane potential as sodium enters the cell.

The phase of AP during which the membrane potential returns to its resting state after reaching peak potential.

A phase after repolarization where membrane potential is more negative than resting potential.

Changes in membrane potential after an action potential that return to resting potential.

Proteins in the cell membrane controlling ion movement.

The process of an AP traveling along a nerve axon.

A nerve impulse that travels along the axon in the normal direction, away from the cell body.

A nerve impulse traveling in the opposite direction, towards the cell body, less common than orthodromic.

Local current flow that transmits signals along unmyelinated nerve fibers.

Action potentials travel along the entire axon in waves.

In unmyelinated neurons, the impulse propagates from the soma (starting point) as waves to ends in the form of a wave of action potential.

A rapid, sequential depolarization of the neuron's membrane, allowing the propagation of an electrochemical signal.

Moving away from the soma. (direction of signal travels)

Moving towards the soma (cell body)

Stimuli that are not strong enough to trigger an action potential.

The minimum stimulus needed to produce an action potential.

Stimuli stronger than the threshold stimulus, still producing an action potential.

A period of increased excitability, where a weaker stimulus than normal can trigger an action potential.

A period of decreased excitability after the supernormal period and before returning to baseline.

An action potential triggered by multiple stimuli (rather than a single stimulus).

Fast Na+ channels availability and proximity of Em (membrane potential) to the threshold potential.

Period where excitability of the axon returns to normal, and the threshold current inreases again.