EXCITATION-CONTRACTION COUPLING

• • Excitation-Contraction Coupling:
  • Dependent on calcium-induced calcium release (CICR).
• • Excitation-Contraction Coupling:
  • SA and AV nodes (slow response action potentials) are connected to the atrium and ventricles, triggering the activation of fast response action potentials in the heart muscle.
• 1. Action potential spreads from the sarcolemma into the T-tubules
  2. Opening of L-Type channels: During plateau phase of action potential, calcium ions will increase influx through L-Type channels (dihydropyridine and then ryanodine receptor) *lock and key = opens
• 3. Increase of efflux of calcium ions from sarcoplasmic reticulum (Intracellular of cell increases calcium = inside sarcolemma)
• 4. Calcium binds to troponin C

  1. Tropomyosin moves out of the way
  2. Allows attachment of myosin and actin filaments thus allowing contraction
• 5. Relaxation

  1. Calcium is re-accumulated by the sarcoplasmic reticulum by an active calcium ATPase pump (Serca).

  • Absence of action potential
• SERCA is a primary active transport
• Excitation-Contraction Coupling:

  Dependent on calcium-induced calcium release (CICR).
• An action potential, initiated by the pacemaker cells in the sinoatrial (SA) and atrioventricular (AV) nodes, is conducted to contractile cardiomyocytes through gap junctions.
• Excitation-Contraction Coupling:

  Calcium plays a prominent role in this process.
• Excitation-Contraction Coupling:

  This occurs through gap junctions, with intercalated discs being essential for transferring action potentials and ions to stimulate contraction.