Ncert Exercises & Solutions

34. Calcium ion concentration in blood affects muscle contraction. Does it lead to tetany in certain cases? How will you correlate fluctuation in blood calcium with tetany?

For the muscle fibre to contract. the binding site on thin filaments must be uncovered. This occurs when Ca²⁺ bind to another set of regulatory proteins, called troponin complex which control the position of tropomyosin on the thin filament.

The calcium binding rearranges the tropomyosin troponin complex, exposing the myosin-binding sites on the thin filament. When Ca²⁺ is present in the cytosol, the thin and thick filament slide part each other resulting in muscle contraction.
Similarly, when the Ca²⁺ concentration falls, the binding sites get covered and contraction stops.

In case of tetany there occur low calcium levels in bodyfluid due to diminished function of parathyroid gland. This giand is mainly involved in the secretion of parathyroid hormone which is associated in regulating calcium levels in blood. Tetany results in periodic painful muscular spasm (wild contraction) and tremors.

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