Resting membrane potential

What factors determine the resting membrane potential?

1. The concentration of charged ions present 2. The relative permeability of the membrane to those ions 3. Presence of any ionic pumps that maintain a concentration gradient

What is the purpose of the Nernst equation?

It provides a formula that relates the numerical values of the concentration gradients to the electrical gradients that balance them. It is used to calculate the potential difference that any individual ion would produce if the membrane was fully permeable to it.

Schematic diagram of the main ions contributing to resting membrane potential

Note that the Na+/K+ pump actively pumps out 3 Na for every 2 K+ moved in and maintains the negative resting membrane potential

What is the Gibbs-Donnan effect?

The differential separation of charged ions across a semipermiable membrane i.e the charged particles fail to evenly distribute across the two sides of a semipermiable membrane

Describe Gibbs-Donnan equilibrium

The movement of solute across a semipermiable membrane depends on the chemical gradient and electrical gradient Movement occurs down the concentration gradient until a significant opposing electrical potential has developed. This prevents further movement of molecules and and gibbs donnan elquilibrium has been reached This electrochemical equilibrium and the potential difference across the cell is the equilibrium potential or membrane potential and can calculated using the Nernst equation

What is the Nernst equation?

The nernst equation can be used to calculate the resting membrane potential.What is the Nernst equation? E = 61.5 log { [ions inside] / [ions outside] }

What happens to the resting membrane potential if extracellular potasiumm rises ?

The resting membrane potential decreases i.e it is less negative. This makes sense as there is now more positive charge on the outside of the membrane so the difference between the intra and extracellular K+ is less. So when plugged into the Nernst equation the log of [C]outside / [C] inside the upper number is bigger so the over all result will be less negative Less negative Depolarises

What is the resting membrane potential?

The resting membrane potential is the potential difference across the cell membrane when no stimulation is occuring. The resting membrane potential is -60 to -90 mV with the cells being negatively charged on the inside

What is an action potential ?

The spontaneous depolarisation of an excitable tissue in response to a stimulus

When cl- Na+ and K+ are individually used what resting membrane potential is calculted?

cl- -70mV Na+ + 60mV K+ -90mV