Resting & Action Potentials
- The cell is surrounded by body fluids and contains charged atoms like sodium (Na+), potassium (K+), and chloride (Cl–).
- The semipermeable membrane permits entry of (K+) and (Cl–) but effectively blocks the entry of (Na+) ions.
- Now charges want balance in terms of charge and concentration inside and outside of the cell.
- Since sodium ion is positive and due to less concentration of sodium inside the cell, the outside is more positive compared to inside.
- So to balance charge concentration, more potassium ions move inside the cell. But due to this, potassium concentration inside the cell is more than outside.
- So neither charge nor concentration balance takes place.
- So an equilibrium is reached with a potential difference across the membrane, negative on the inside and positive on the outside.
- There is an ionic current due to the movement of sodium ions inside the cell that further reduces the barrier of the membrane to sodium ions.
- There is an avalanche effect where sodium ions move inside rapidly to equate concentration inside as well as outside the cell.
- The concentration of potassium ion inside is greater than outside the cell. Therefore, potassium ion move outside the cell.
- An equilibrium is reached with a potential difference across the membrane, negative on the outside and positive on the inside.
|Fig. Resting & Action Potentials|