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Action potential PowerPoint Presentation

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Description : Check out this medical presentation on Neurology, which is titled "Action potential", to know about the Action Potential, brief, rapid, large, propogatory changes in membrane potentials produced by application of adequate stimulus to an excitable tissue.

Tags : Neurology, Action potential

Published on : Aug 23, 2021 | Views : 1884 | Downloads : 3

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Slide 1-

Action potential Action potentials are brief, rapid, large, propogatory changes in membrane potentials produced by application of adequate stimulus to an excitable tissue. Action potential = “impulse” Changes during AP – Depolarization followed by repolarization of membrane
Slide 2-

stimulator Recording electrode CRO -80 -60 -40 -20 0 +20 +40 Time ( msecs. ) Depolarization 1 msec Repolarization Membrane potential (mV) Recording of AP in nerve fiber - monophasic
Slide 3-

8 - after hyperpolarization 1 -70 1 2 3 Firing level 4 5 6 7 0 - Stimulus artifact 1 2 - Latent period - Local potentials 3 4 - Rapid depolarization 5 6 - Rapid repolarization - After depolarization 7 - Overshoot +30 8 Time in msec
Slide 4-

Events during A.P. – Stimulus artifact – due to leakage of electric current from stimulating electrode to recording electrode Latent period – It is isoelectric period. Indicates the time taken by the impulse to travel from stim. electrode due to the recording electrode. Duration varies with the distance between two electrodes.
Slide 5-

Local potential – slow depolarization produced due to opening of Na+ channels Firing level ( threshold potential ) – membrane potential at which rapid depolarization begins – which corresponds to 15 mV of depolarization from RMP.(-55mV )
Slide 6-

4)Rapid depolarization – due opening of fast voltage gated Na+ channels which causes entry of Na+ Overshoot – due to EqNa+ is + 60mV. Rapid repolarization – due to closure of voltage gated Na+ channels and opening of slow voltage gated K+ channels which increases K+ exit & stops Na+ entry.
Slide 7-

Afterpotentials – 7) Afterdepolarization – reduced rate of repolarization due to accumulation of K+ on the outer side of membrane. 8) Afterhyperpolarization – due to incomplete closure of K+ channel causing excess efflux of K+. Membrane potential comes to resting level by Na+-K+ pump.
Slide 8-

At firing level – rapid opening of activation gates of voltage gated Na-channels. Ionic basis of A.P.- I. Local potentials – partial opening of Na+ channels influx of Na+ along the electrochemical gradient causing slow depolarization II. Rapid depolarization – influx of Na+ causes depolarization which further increases opening of Na channels (positive feedback mechanism)
Slide 9-

IV.Rapid repolarization –increase in K+ efflux along electrochemical gradient. Peak at +30mV – Na+ entry stops because of closure (of inactivation gates of ) Na+ channels and opening of voltage gated K+ - channels III.Overshoot – membrane potential becomes +ve because Eq Na+ is + 60mV
Slide 10-

Vb )After hyperpolarization – K-channels remain open for longer period causing excess efflux of K+ resulting in hyperpolarization Va ) After depolarization –slow repolarization due to reduced rate of efflux of K+ caused by accumulation of +ve charge on outer side, RMP is reached V. After potential - VI. Hyperpolarization is corrected by Na+-K+ pump
Slide 11-

With each AP very small difference in conc. of Na+ & K+ in ICF & ECF. Types of AP – Spike potential- in nerve and skeletal muscle Plateau potential – in cardiac muscle Slow potential – in smooth muscle
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Role of Ca++ in A.P. – Ca++ is a membrane stabilizing factor . ↓Ca++ conc. → early opening of voltage gated Na+ channels → ↑excitability