PHYSIOLOGY
MUSCLE CONTRACTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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An increase in intracellular Ca2+ level
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A decrease in intracellular Ca2+ level
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An increase in adenosine triphosphate (ATP) level
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A decrease in ATPlevel
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Detailed explanation-1: -Rigor mortis sets in due to the depletion of ATP which is essential for the breaking of actin-myosin cross-bridges that happens during the relaxation of muscles. As the dead person has stopped breathing, oxygen required for aerobic respiration is not available resulting in the depletion of ATP.
Detailed explanation-2: -When ATP binds to troponin, it prevents cross-bridges from forming between actin and myosin filaments, resulting in irreversible muscle rigidity. ATP provides the energy for the actin-myosin cross-bridge to detach, which prevents the muscle from relaxing, resulting in rigor mortis.
Detailed explanation-3: -After death, when respiration ceases, the intracellular pH decreases due to the production of lactic and pyruvic acid. The anaerobic glycolysis of glycogen in the muscles causes glycogen depletion and thus reduced ATP concentrations.