Action potential

Nervous system-Action potential

1. Human Anatomy and Physiology-II Nervous system (Action potential) Mr N.JEGAN Associate Professor K.M.COLLEGE OF PHARMACY. MADURAI.

2. Action potential All cells for example muscle cells , neuron cells( nerve cells ) and cardiac cells posses electrical excitability, the ability to response to a stimulus and convert it into an action potential.

3. Nerve impulse A signal transmitted along a nerve fibre . It consists of a wave of electrical depolarization that reverses the potential difference across the nerve cell membranes.

4. Action potential-Definition An electrical signal that propagates along the surface of the membrane of a neuron (nerve cell ) due to the movement of ions ( sodium & potassium) between interstitial fluid and the inside of a neuron through specific ion channels in its plasma membrane.

5. MEMBRANE POTENTIAL An electrical potential difference across the membrane It is like voltage stored in battery In living cells the flow of ions rather than electrons constitutes the electrical current/ signal. The main path for current to flow across the membrane are through ion channels.

6. ION CHANNELS Ion channels open and close due to presence of gates When ion channels are opened, they allow specific ions to move across the plasma membrane , down their electrochemical gradient. As ions move , they create a flow of electrical current that can charge the membrane potential.

7. GENERATION OF ACTION POTENTIAL The principal ions involved are: 1.sodium (Na+) the main extracellular cation 2.potassium (K+) the main intracellular cation .

8. Action Potential-Phase It occur in four phase 1.Resting potential 2.Depolarizing Phase 3. Repolarizing phase 4. Repolarizing continue

9. Resting potential 1.All voltage gated Na + and K + channel closed 2.Small buildup of negative charge along the inside the surface of membrane and equal amount of positive charge along the outside the membrane.

10. Depolarizing Phase 1.When membrane potential reach axon, Na + Channel 2. Na + ion enter in to neuron through this channel 3. buildup of positive charge along the inside the surface of membrane

11. Repolarizing phase 1. Na + Channel inactivation close the channel. 2. K + channel open 3. Some K + ion leave the neuron 4. Negative charge begin to buildup of along the inside the surface of membrane.

12. Repolarizing phase continue 1. K + outflow continue , more K + ion leave the neuron. 2. More negative charge buildup of along the inside the surface of membrane. 3.Na + channel inactivation gate open 4.Return to resting stage when K + gates close.

13. GENERATION OF ACTION POTENTIAL ALONG AXON

14. Refractory period   It refers to the amount of time it takes for an excitable membrane to be ready to respond to a second stimulus once it returns to a resting state.

15. Thank you