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Video Summary:
The action potential in cardiac muscle has 5 phases. Phase 0 or initial depolarization is due to the opening of fast sodium channels and rapid Na influx. Phase1 or initial depolarization is due to the closure of fast sodium channels and efflux of a small quantity of potassium through open potassium channels. Phase 2 or plateau is due to the opening of slow or L type of calcium channels leading to Ca influx and closure of potassium channels which prevents the K efflux. Calcium channels stay open for quite some time so we get a long plateau. Then Phase 3 or final repolarization is due to the closure of Ltype calcium channels that prevent further Ca entry and opening of slow K channels leading to K efflux. Phase 4 is resting membrane potential till the next action potential. To restore the ionic balance, NaK ATPase pump moves Na out and K in, and NaCa exchanger and Ca pump moves the Ca out.

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Chapters
00:00 Intro
00:35 Ions Involved in Action Potential
01:01 Phase 0: Upstroke
01:49 Phase 1: Initial Repolarization
02:09 Phase 2: Planeau
03:21 Phase 3: Final Repolarization
03:44 Phase 4: Resting Membrane Potential
03:56 Restoration of Ionic Balance
04:51 Summary

Dr Vipul Navadiya

DISCLAIMER: This video is for education purposes only. Although every effort is made to ensure the accuracy of the material, viewers should refer to the appropriate regulatory body/authorized websites, guidelines, and other suitable sources of information as deemed relevant and applicable. In view of the possibility of human error or changes in medical science, any person or organization involved in the preparation of this work accepts no responsibility for any errors or omissions, or results obtained from the use of information in this video.