Question

multiple choice question
excitation - contraction coupling involves an increase in the concentration of ______ ions in the sarcoplasm.
o sodium
o calcium
o potassium
o hydrogen
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Explanation:

Excitation - contraction coupling in muscle cells is triggered by an increase in calcium ion concentration in the sarcoplasm. Calcium ions bind to troponin, causing a conformational change that exposes binding sites on actin for myosin, leading to muscle contraction.

Answer:

calcium