Voltage Gated Ion Channels (VGICs) Lecture Notes

This set of vocabulary flashcards covers the fundamental principles of voltage-gated ion channels, membrane potential, and cellular excitability as presented in the lecture.

Excitable cells

Cells, such as neurons, that can be stimulated to generate electrical signals.

Voltage gated ion channels (VGICs)

Membrane-spanning proteins with a central pore that open or close in response to changes in membrane voltage.

Voltage

A measure of the overall difference in potential energy (stored energy) between the two sides of a membrane, caused by the unequal distribution of ions.

Voltage sensors

Components of VGICs that cause the channel to open only when the membrane voltage is within a specific range.

Inactivation

The process where most voltage-gated ion channels close or stop conducting after the pore has opened.

Current

In biological systems, the rate of movement of electric charge mediated by the movement of ions.

Resistance

The opposition to current flow, caused by the lipid bilayer preventing ions from moving across the membrane.

Electrochemical gradient

The combined driving force arising from the concentration gradient of an ion and the electrical driving force (e.g., positive charges attracted to the negative interior).

High voltage activated (HVA) calcium channels

Channels activated at $\sim -35\,mv$ and above that selectively conduct $Ca^{2+}$ ions.

Low voltage activated (LVA) calcium channels

Channels activated at or near the resting membrane potential ($\sim \text{RMP}$).

HCN channels

A specific type of ion channel family that is activated by hyperpolarisation from the resting membrane potential.

Inward current

The net intracellular accumulation of positive charge, resulting from either positive ions flowing in or negative ions flowing out of the cell.

Depolarisation

The result of an inward current, representing a net accumulation of positive charge inside the membrane.

Outward current

The net intracellular accumulation of negative charge, resulting from either negative ions flowing in or positive ions flowing out of the cell.

Hyperpolarisation

The result of an outward current, representing a net accumulation of negative charge inside the membrane.

Sodium channel density at Nodes of Ranvier

The heavy concentration of sodium channels at specific points on a neuron, measured at $1,000-5,000$ per $\mu\text{m}^2$.

Ohm's Law

The electrical principle represented by the formula $V = IR$, where $V$ is voltage, $I$ is current, and $R$ is resistance.

Voltage clamp

An experimental method where current is injected to hold voltage constant, used to measure isolated currents.

Current clamp

An experimental method used to record voltage changes, such as action potentials, across the membrane.