An action potential is a rapid change in the electrical potential of a nerve or muscle cell membrane in response to stimulation. It allows electrical impulses to travel across the cell membrane. There are six stages of an action potential: 1) Resting stage with a large negative potential, 2) Depolarization from sodium ion influx, 3) Repolarization by potassium ion efflux, 4) A spike potential from the sharp depolarization and repolarization waves, 5) A negative after potential where the potential does not fully return to resting, and 6) Sometimes hyperpolarization where the potential becomes more negative than resting due to excess potassium permeability.

1. Action Potential
Md. Hamidul KowsarMd. Hamidul Kowsar
Dept. of PharmacyDept. of Pharmacy
Presentation
on

2. Action Potential
A rapid change in the electrical potential on the surface of a cell
(e.g. a nerve cell or muscle cell) in response to stimulation, and
then leads to the transmission of an electrical impulse (nerve
impulse ) that travels across the cell membrane.
Stages of action potential :
1. Resting stage
2. Depolarization stage
3. Repolarization stage
4. Spike potential
5. Negative after potential
6. Hyperpolarization

3.  Resting stage
Action Potential
The membrane is said to be ‘polarized’
during this stage because of the very
large negative membrane potential that is
present.
 Depolarization stage
When the negativity of the membrane
potential rises rapidly in positive direction
due to influx (enter) of sodium ions.
Repolarization stage
The negativity of the membrane
potential re-establishes towards the
normal negative resting membrane
potential due to efflux of potassium ions.

4. Action Potential
 Spike potential
The sharp rise of the depolarization
wave and the rapid fall of repolarization
wave is called spike potential.
 Negative after potential
At the termination of spike potential, the
membrane potential sometimes fails to
reach the normal resting stage.
 Hyperpolarization
Sometimes the negativity of membrane
potential become more than its normal
level. It is due to excess permeability of
membrane to the K at the end of spik
potential.

5. Action Potential

6. Thanks to all

7. Thanks to all