Cardiac Muscle, Dr. D. Penney

Ion Channels:

• Fast - initial rapid inward Na⁺ current.
  - secondary outward K⁺ movement repolarization

  Slow* - Ca⁺⁺ moves inward, responsible for maintained depolarization of the "plateau phase" (Phase 2)

* An increase in contraction frequency increases Ca⁺⁺ movement inward, giving the "staircase" phenomenon (Treppe, Bowditch) in cardiac muscle.

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