Intracellular Amplifier

Contributing Author: Dr. Steve Andre (Muscle Physiologist)

All living cells maintain a difference in electrical charge between the solutions that are inside and outside the cell membranes. The voltage difference across the cell membrane is usually at a steady level known as the resting membrane potential. The resting membrane potentialis produced by the differential distribution of ions on either side of the membrane. In muscle fibers, the potassium concentration inside the cell is over 50 times greater than the ion’s concentration in the extra­cellular fluid. On the other hand, the concentration of sodium is 10 times greater outside the membrane than inside. The concentration gradient of potassium is greater and in the opposite direction to the sodium concentration gradient. The ion concentrations are governed by three factors:

• Sodium-potassium pump
• Relative rates of diffusion of these ions down concentration gradients
• Attraction...more