CICR Process

• sarcoplasmic reticulum in skeletal muscle:

  • arrival of an action potential in the t-tubule causes the terminal cisternae of the sarcoplasmic reticulum to release calcium ions (Ca2+) into muscle cells cytoplasm
  • this calcium ion binds to troponin, causing cross bridge formation and the production of a contraction
  • this sequence of events also happen in cardiac muscle, but its a little different -> large functional significance
• cardiac sarcoplasmic reticulum - calcium induced calcium release (CICR):

  1. arrival of an action potential at the sarcolemma, depolarising the sarcolemma
  2. opening of voltage gated calcium ion channels in the sarcolemma
  3. influx of a small amount of calcium ions from the extracellular fluid
  4. causing sarcoplasmic reticulum to release larger amounts of calcium ions, amplifying its effect
  5. binds with troponin
  6. contraction
• sarcoplasmic reticulum:

  • the sarcoplasmic reticulum in cardiac cells is not as well developed, compared to muscle cells, which is why the calcium induced calcium release is an addition system within cardiac cells to allow release of enough calcium to meet contractile needs
  • CICR can also be manipulated to meet the needs of the body