PHYSL 212 Lecture 4: Membrane Potentials (Terms)

Neurons

Nerve cells that are the basic building blocks of the human brain

Central Nervous System

Division of the nervous system containing the brain and spinal cord that is responsible for information processing in the body

Peripheral Nervous System

Division of the nervous system containing the cranial and spinal nerves that is responsible for connecting and carrying information throughout the body

Myelin Sheath

A fatty layer around motor and sensory neurons that provide insulation and physical support to the axon

Nodes of Ranvier

Gaps in the myelin sheath that regenerate electrical signals to faster transmit the signal

Membrane Potential

Relative membrane voltage based on a point of reference, typically compared to the extracellular voltage (V_i - V_o)

Nernst Equation

An equation that calculates a certain ion’s equilibrium potential with respect to the concentration gradient of said ion

Equilibrium Potential

The relative charge of a cell’s membrane when a specific ion’s concentration gradient is directly opposite to the electrical driving force of the ion, in which there is no net movement of the ion across the membrane

Resting Potential (Steady State)

The membrane potential of a neuron cell at rest, defined by the weighted combination of permeabilities of different ions through the membrane

Leak Channel

A membrane ion channel that is non gated and remains constantly open, giving ions different permeabilities through the membrane depending on the permeability of the channel

Hyperpolarization

The act of further polarizing the membrane past resting potential such that its membrane potential is more negative

Depolarization

The act of reversing the charge of the membrane away from resting potential such that its membrane potential is more positive

Repolarization

The act of reverting the charge of the membrane back to resting potential such that its membrane potential returns to rest

Ionic Current

The net charge moving out of a cell via movement of ions

Negative (Inward) Current

An ionic current formed via the movement of positive ions into the cell or negative ions out of the cell, overall making the outside of the cell more relatively negative

Positive (Outward) Current

An ionic current formed via the movement of negative ions into the cell or positive ions out of the cell, overall making the outside of the cell more relatively positive

Conductance

A measure of easiness of ion flow across a resistor

Resistance

Inverse of conductance, representing the obstacles to ion flow across a resistor

Voltage

The electrical driving force to move charges

Ohm’s Law

The relationship between conductance and voltage that gives rise to current, defined by I = G(V_m - V_rest)

Ion Channels

Membrane proteins that allow ion flow across a membrane, driven by the electrochemical force

Ligands

Physical substances that bind to membrane channels

Post-Translational Modifications (PTMs)

Modifications to a ion channel protein that cause it to change conformationally