VPB 121: Veterinary Physiology - II (2+1)

PRINCIPLES OF MEMBRANE POTENTIAL

Basic Physics 

• In the tissue the fluid outside (interstitial fluid) and inside (intracellular fluid) are electrolytic solutions, containing 150 to 160 mEq / litre of positive ions (cations) and the same concentration of negative ions (anions). 
• Generally a very small excess of negative ions accumulate immediately inside the cell membrane along it’s inner surface, and an equal number of positive ions accumulate immediately outside the membrane, the effect of which is the establishment of membrane potential between the inside and outside of the cell membrane. 
• Such a membrane whose inside is more negative than the outside is said to be a polarized membrane. The basic means by which membrane potentials develop are
  • Passive diffusion of ions i.e. diffusion along concentration gradient,
  • Active transport of ions against concentration gradient and creation of imbalance between negative and positive charges.