Electrical Properties of The Cell Membrane and Ion Channels

Flashcards on Electrical Properties of Cell Membranes and Ion Channels.

Membrane Composition

Fat and proteins that compose the cell membrane.

Membrane Capacitance

The membrane's capacity to store electrical charge.

Resistance of the membrane

The extent to which the membrane impedes or reduces electrical current.

Capacitor

A device that stores electrical charge. It stores negative charges just inside the membrane, and positive charges just outside the membrane, creating an electric potential (voltage) across the membrane.

Membrane Capacitance (Cm)

The ability of the mebrane to separate charges.

Resistor (Rm)

Electrical components that represents the ion channels (protein paths letting ions through) in a resting cell membrane model.

Capacitor (Cm)

Electrical component that represents the lipid bilayer, storing electric charge, in a resting cell membrane model.

Nernst Equation

The equilibrium potential (voltage) for one specific ion, dependent on the amount of that ion is inside vs. outside the cell.

Electromotive force (EMF)

The measure of the driving force behind each ion type (like Na⁺ , K⁺, Cl⁻) across the membrane, which is equal to its equilibrium potential

Ion Currents in the Resting Membrane

At rest, there is a passive sodium current (INa), caused by diffusion (Na⁺ wants to enter the cell and an active sodium pump current (I*Na), pushing Na⁺ out of the cell, using energy (ATP).

Kirchhoff’s Voltage Law (KVL)

In an equivalent electrical circuit of a neuron, the sum of all voltages (like EMFs and voltage drops across resistors) must equal zero.

Kirchhoff’s Current Law (KCL)

In an equivalent electrical circuit of a neuron, at any junction (node) in the circuit, the total current coming in equals the total current going out.

Sodium Equilibrium Potential (ENa)

The equilibrium potential for sodium, which is +60 mV.

Potassium Equilibrium Potential (EK)

The equilibrium potential for potassium, which is –94 mV.

Chloride Equilibrium Potential (ECl)

The equilibrium potential for chloride, which is –80 mV.

Electrochemical Driving Force (EDF)

The force that pushes ions across the membrane and depends on the equilibrium potential (Ei) and membrane potential (Em).

Ohm’s Law

V=I⋅R. Voltage (difference in electrical potential) I = Current (flow of ions) R = Resistance (how much the membrane resists ion flow)

Ion Permeability (Conductance)

The ability of an ion to pass through the membrane.

Net current for ions

INa = gNa (EM - ENa); IK = gK (EM-EK); Ic₁ = gc (EM - ECI)

Voltage Clamp Technique

Method used to study how ions move through a cell membrane by keeping the membrane potential (voltage) constant while measuring the current.

Patch clamp

Developed by Erwin Neher and Bert Sakmann, this technique isolates a small patch of the membrane to observed tiny electrical currents caused by ion channels when acetylcholine (a neurotransmitter) was applied.

Ion Channel Diseases (Channelopathies)

Diseases that results from changes (mutations) in the structure or function of ion channels.