Which ions are involved in muscle contraction ?

Options

A. `Ca^(++),Mg^(++)`
B. `Ca^(++),Na^(+)`
C. `Na^(+),K^(+)`
D. `Mg^(++),K^(+)`

Answer

**Step-by-Step Solution:**

1. **Understanding Muscle Contraction**: Muscle contraction involves the interaction between two types of filaments: thick filaments (myosin) and thin filaments (actin). For contraction to occur, the active sites on actin must be exposed.

2. **Role of Calcium Ions**: In a resting muscle, the active sites on actin are masked by a protein called troponin. When the concentration of calcium ions (Ca²⁺) increases, calcium binds to troponin, causing a conformational change that removes the masking of the active sites on actin.

3. **Binding of Myosin**: Once the active sites on actin are exposed, myosin heads can bind to these sites. This binding is crucial for the contraction process to occur.

4. **Role of Magnesium Ions**: While calcium ions are essential for muscle contraction, magnesium ions (Mg²⁺) play a role in muscle relaxation. Calcium blockers, which can be represented by magnesium, help in the relaxation of the muscle after contraction.

5. **Conclusion**: The primary ions involved in muscle contraction are calcium and magnesium. Calcium is responsible for initiating contraction, while magnesium aids in relaxation.

**Final Answer**: The ions involved in muscle contraction are calcium (Ca²⁺) and magnesium (Mg²⁺).

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