PHYSIOLOGY
MUSCLE CONTRACTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Simple diffusion
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Facilitated diffusion
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Endocytosis
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Active transport
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Detailed explanation-1: -Stimulation of the muscle fibre, causes a wave of depolarisation to pass down the t-tubule, and the SR to release calcium ions into the sarcoplasm. Calcium is pumped back up into the SR to lower calcium ion concentration in the sarcoplasm, to relax the muscle (turn off contraction).
Detailed explanation-2: -As a key regulator of cellular calcium homeostasis, the Sarcoendoplasmic Reticulum Calcium ATPase (SERCA) pump acts to transport calcium ions from the cytosol back to the sarcoplasmic reticulum (SR) following muscle contraction.
Detailed explanation-3: -Unlike release, calcium reuptake into the SR is constitutively active and requires coupling of the energy of ATP hydrolysis to calcium transport. This is accomplished by Ca2+-ATPase, which generates a thousandfold concentration gradient of calcium across the SR in resting muscle.
Detailed explanation-4: -Calcium pumps are a family of ion transporters found in the cell membrane of all animal cells. They are responsible for the active transport of calcium out of the cell for the maintenance of the steep Ca2+ electrochemical gradient across the cell membrane.