Describe the ionic changes which leads to the the action potentials

Describe the ionic changes which leads to the the action potentials
1. In the non conducting tissues
2. In the auto rhythmic cells


Answer

1.

The cardiac action potential has 5 phases numbred from 0 to 5

  1. Phase 0- rapid depolarization phase
  2. Phase 1- initial repolarization
  3. Phase 2- plateau phase
  4. Phase 3- final Repolarization
  5. Phase 4- resting membrane potential



Phase 0 -initial rapid depolarization and overshoot
due to opening of fast voltage- gated Na+2 Channels and influx of Na+ into the cell

Phase 1- initial repolarization
Due to closure of Na+ channels and opening of one K+ channels

Phase 2- plateau phase
Due to a slower and prolonged opening of voltage-gated Ca2+ channels

Phase 3 - Final repolarization
Is due to closure of the Ca2+ channels and a slow, delayed increase of K+ efflux through various types of K+ channels





2.
The pacemaker potential has three phases
  1. Phase 0 (Depolarization phase of action potential)
  2. Phase 3 (Repolarization phase)
  3. Phase 4 (Prepotential, pacemaker potential)
Phase 4  (Prepotential, pacemaker potential )
Above ionic changes form first part of pre potential

Phase 0 (Depolarization phase)

This phase occurs due to opening of long lasting Ca+2 channels (L-type Ca++channels) and influx of Ca+2 into the cell


Phase 3 (Repolarization phase)
This is due to opening of K+ channels and efflux of K+

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