Membrane potential

physiology

What is membrane potential

difference between the electrical potential of intra-cellular fluid + extracellular fluid

How is membrane potential created

1. Intracellular + extracellular fluid are separated by the membrane 

2. Positive and negative charges are balanced on each side → no membrane potential 

3. Through ion channels, ions can travel to the intra/extracellular fluid → imbalance of charges → potential 

4. Membrane potential created by the separation of positive + negative charges across the membrane → accumulate along plasma membrane 

5. Greater the separation of charges → larger the potential 

*unit: mV

What are the conditions for membrane potential

Ion concentration gradient  ( Na +/ K + )

Selectively permeable membrane  ( many ion channels )

Equation for membrane potential

Nernst equation  E= 61/z log x [ion] out / [ion] in  → equilibrium potential ( difference in electric potential needed to balance the concentration gradient of the ion )  z: ion valence

Why is resting membrane potential closer to equilibrium potential of K + than Na+

Membrane permeability of K+ ions is greater than that of Na + ions

How do cells make use of membrane potential

Specialised cells can make changes to membrane potentials transiently through being triggered/ spontaneously → action potential which act as electrical signals 

Process: stimulus ( change in voltage (? ) ) → voltage gated Na+ channels open → more positively charged Na+ ions rush into the intra-cellular fluid → membrane becomes more positively charged → stimulus stops → Na + ions leave → membrane becomes more negatively charged → back to resting membrane potential