Ion Channels Flashcards

Flashcards related to Ion Channels

Myotonia Congenita

Channelopathy resulting from a mutation in the CLC1 chloride channel gene

Current

Net flow of charge, with the direction of current flow conventionally defined as the direction of positive charge flow

Conditions for Current Flow Across a Membrane

Requires ions, open channels, and a driving force (concentration gradient, voltage).

Hodgkin and Huxley's Contribution

A method to measure currents during an action potential, used in squid giant axons

Patch-clamp Method

A method allowing recording of current from single channels, detecting conformational changes of a single protein

Patch-clamp Recording Configurations

Cell-attached, Whole-cell, Inside-out, and Outside-out

Voltage Clamp

A technique where injected current is equal and opposite to the current flowing through the cell, maintaining a constant command voltage (Vc)

Ohm's Law in Ion Channels

I = gV, where I is current, g is conductance, and V is voltage

Equilibrium Potential (Eion)

The voltage at which the driving force due to the concentration gradient and the driving force due to voltage exactly balance one another

Nernst Equation

Eion = (RT/ZF) ln ([ion]out/[ion]in)

Driving Force

The difference between the membrane potential and the equilibrium potential

Reversal Potential (Eion)

The magnitude of current flow depending on ion concentration gradient, membrane potential and conductance

Macroscopic Current Equation

I = i . n . Po, where I is macroscopic current, i is single channel current, n is number of channels, and Po is the probability of open channel

Channel Gating

Transition of channels between open and closed states, regulated by voltage, ligand, temperature, light, or stretch

Rectification

Non ohmic IV relationship. Current passes in one direction better than it does in another.

K inward rectifier

Open at rest, little outward current, Voltage dependent block can be caused by intracellular cations

Nicotinic ACh receptor

Ligand gated channel (receptor); permeable to both Na+ and K+ in presence of ACh

Goldman-Hodgkin-Katz Equation for Reversal Potential

Vrev = (gNa . ENa+ ) + (gK . EK+ ) / (gNa + gK)