Membrane Transport and Action Potential Review

This set of flashcards covers key concepts related to membrane transport mechanisms, action potentials, and neurophysiology, including definitions and processes.

Simple Diffusion

The process by which nonpolar, small, and hydrophobic molecules pass through the membrane without the need for channels or carriers.

Ion Channel

A protein structure that allows charged ions to cross the cell membrane, characterized by selective permeability and gating mechanisms.

Facilitated Diffusion

A transport process that requires carrier proteins to move specific molecules across the membrane, faster than passive diffusion.

Active Transport

The movement of molecules against their concentration gradient, requiring metabolic energy, typically in the form of ATP.

Resting Membrane Potential (Em)

The voltage difference across a cell membrane when the cell is not actively transmitting signals, typically around -70 mV for neurons.

Equilibrium Potential (Ei)

The membrane potential at which there is no net movement of a specific ion across the membrane, assuming complete permeability to that ion.

Threshold Membrane Potential

The critical level of depolarization that must be reached to trigger an action potential, commonly around -55 mV.

Absolute Refractory Period

The time after an action potential during which a second action potential cannot be initiated, regardless of stimulus strength.

Relative Refractory Period

The period following an action potential when a stronger-than-normal stimulus is necessary to elicit a second action potential.

Signal Propagation

The process by which an action potential travels along the axon, leading to stimulation of adjacent membrane sections.

Myelin Sheath

Insulating layer around axons, produced by Schwann cells, that speeds up electrical signal conduction.

Synapse

The junction between two neurons where information is transferred from one neuron to another using neurotransmitters.

Chemical Synapse

A synapse at which a neurotransmitter is released from the presynaptic neuron to bind to receptors on the postsynaptic neuron.

Agonist

A substance that enhances or mimics the action of a neurotransmitter by binding to its receptor.

Antagonist

A substance that inhibits or blocks the action of a neurotransmitter by preventing it from binding to its receptor.

Conductance (gi)

A measure of how easily ions can flow through a membrane, affecting the overall membrane potential (Em).

Resistivity

A material property that quantifies how strongly it opposes the flow of electric current.

Permittivity

A measure of how much a material can permit electric fields to be established within it, influencing capacitance.

Focal Length

The distance from the lens to the image where light rays converge, critical for sharp vision.