Foundations of Body Functions: Action Potentials

Electrical changes in a neuron's resting membrane potential (RMP) caused by stimulation.

Action potential has two main phases: depolarization (loss in polarization) and repolarization (return to polarization).

Loss of the neuron's polarized state; the inside of the membrane becomes more positive.

Return of the neuron to its polarized state; the inside of the membrane becomes more negative.

Changes in ion concentrations (specifically Na+ and K+) across the neuron's membrane drive the action potential.

Action potential recording showing two phases, representing depolarization and repolarization.

Action potential recording showing a single phase, usually representing only depolarization.

Neve fibers covered with a myelin sheath, allowing faster action potential propagation.

Nerve fibers without myelin sheath; action potential propagates more slowly.

A rapid change in membrane potential across a neuron or muscle cell membrane, involving depolarization and repolarization.

The process of the cell's membrane potential becoming less negative (more positive) as Na+ rushes in.

The process where the membrane potential returns to its resting potential as K+ leaves the cell.

The electrical potential difference across the membrane when a neuron is at rest, typically around -70 mV.

The critical voltage level (-55 mV) required to trigger an action potential; If the stimulus exceeds the RMP, it can trigger the Threshold Potential

Channels whose opening or closing depends on the membrane potential.

Graded passive depolarizations that decay over a short distance, causing a slight change in the membrane potential (initial response to stimulus).

A protein that actively transports Na+ out of and K+ into the cell, maintaining the resting membrane potential after the action potential.

Slow, local reduction in membrane potential, caused by a stimulus. A preliminary phase that can trigger an action potential.

Rapid increase in membrane potential due to the opening of voltage-gated sodium channels. It occurs after the threshold potential is reached.

The time between nerve stimulation and the start of the action potential.

Represents the time taken for the nerve impulse to travel from the stimulation point to the recording point.

Affected by the distance between stimulating and recording electrodes, and the nerve fiber conduction velocity.

Used to calculate nerve fiber conduction velocity.

A large, short wave in the nerve action potential; approximately 105 mV, lasting 0.5-1 msec in thick myelinated nerve fibers.

Represents depolarization due to sodium influx. Consists of slow depolarization to threshold and rapid depolarization to overshoot (+35 mV).

Represents repolarization, primarily due to potassium efflux, causing the rapid voltage change.

Using microelectrodes to record inside nerve fibers and a reference electrode outside the stimulated area.

Action potentials have distinct phases; latent period, spike potential, and after potentials.

Small waves following action potentials with longer durations, categorized as negative and positive.

A short-duration (4 msec) after-potential where the membrane is partially depolarized, caused by slow potassium efflux.

A longer-duration (40 msec) after-potential where the membrane is hyperpolarized due to continuous potassium efflux.

Action potentials begin at the axon hillock (initial segment) and travel down the axon to the terminal.

The transmission of the action potential signal along an axon to communicate between nervous system locations.

Action potential propagation in unmyelinated axons, where depolarization happens sequentially along the nerve.

Action potential propagation in myelinated axons, where the signal jumps between Nodes of Ranvier.

Myelinated axons transmit signals much faster (up to 120 m/s) compared to unmyelinated (0.5-2.0 m/s).

Gaps in the myelin sheath of a nerve fiber where action potential regeneration occurs.

Movement of electrical current between adjacent areas of different electrical potentials in a cell or tissue.

The rate at which an action potential travels down a nerve fiber, influenced by myelination.

Increased myelin thickness increases membrane resistance, allowing for faster 'jumps' (saltatory conduction) between nodes of Ranvier, thus speeding up signal transmission.

The rapid transmission of an action potential along a myelinated axon, "jumping" between the nodes of Ranvier.

Loss of myelin in multiple sclerosis slows down action potential conduction due to decreased membrane resistance.

The phase of an action potential where the cell's membrane potential becomes less negative, leading to an electrical signal.

The phase of an action potential where the cell's membrane potential returns to its resting negative value.

Specialized channels in the nerve cell membrane that open and close in response to changes in membrane voltage, allowing the flow of sodium (Na+) and potassium (K+) ions.

The relatively slow propagation of an action potential along unmyelinated axons.

Gaps in the myelin sheath along the axon where the action potential is regenerated.