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Question 1

Excitation-contraction coupling - sarcoplasmic reticulum

Answer 1

• Sarcoplasmic reticulum (separate body, separated by own membranes): Organelle structure inside these cells = basically a store of calcium that’s holding calcium in reserve and when it gets triggered by this calcium-induced calcium release = triggers the release of calcium from the store = large increase in the concentration of calcium in the intracellular fluid.

Question 2

flow of muscle contraction

Answer 2

action potential in myocardial contractile fibre –> entry of Ca2+ from extracellular fluid + release of Ca2+ from sarcoplasmic reticulum –> increased intracellular Ca2+ –> increase cross-beidge cycling b/w thick and thin filaments within sarcomere –> myocardial contraction
- NOTE: the greater the intracellular [Ca2+], the greater the force of the contraction