Resting Membrane Potential

equilibrium potential (Eion)

the electrical potential difference that exactly balances the ionic concentration gradient.

There is no net movement of ions when separated by a phospholipid membrane.

What occurs when equilibrium potential is reached?

K+ channels in the phospholipid bilayer.

What are the channels are involved in reaching equilibrium potential?

the voltage (electrostatic force) that will exactly counteract the ion's diffusional force (concentration gradient)

How does the Eion counteract with the diffusional force?

membrane potential (Vm)

voltage across the neuronal membrane at any movement

Miniscule changes in ionic concentrations

What can cause large changes in Vm?

At the inside and outside membrane surfaces

How are electrical charges balanced in a cell?

Driving force

What determines the rate of movement of ions?

Using the Nernst Equation if concentration is known

How can equilibrium potential (Eion) be calculated?

Vm-Eion

driving force equation

inside negatively charged relative to the outside

- negative membrane potential =-Vm

What roles does K+ (potassium) do to equilibrium potential?

inside positively charged relative to the outside

- positive membrane potential =+Vm

What roles does K+ (potassium) do to equilibrium potential?

Nernst Equation

calculates exact value of the equilibrium potential for each ion in mV

-charge of the ion

-temperature

-ratio of the ion concentration outside (o) vs. inside (i) the cell

What does the nernst equation take into consideration?

K+

Which ion is more concentrated inside the cell?

Na+ and Ca2+

Which ions are more concentrated outside the cell?

The equilibrium potential of the ion to which the membrane is most permeable

What drives the membrane potential?

Theoretical values

What are individual ion equilibrium potentials?

Membrane potential (Vm)

What is the actual potential across a membrane called?

When the membrane is permeable ONLY to that ion

When is the membrane potential the same as an equilibrium potential for an ion?

K+ > Cl- > Na+ > Ca2+

Order of permeability

if relative ion permeability is known, actual resting membrane potential can be calculated by Goldman Equation

When to use Goldman Equation?