EDTA injected into muscles combines with `Ca^(2+)` and
(a) Stops contraction
(b) Causes contraction
(c) Slows down contraction
(d) None of the above 

Options

A. Stops contraction
B. Causes contraction
C. Slows down contraction
D. None of the above

Answer

To solve the question regarding the effect of EDTA injected into muscles, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Muscle Contraction**:
- Muscle contraction involves the interaction between two proteins: actin and myosin. For contraction to occur, myosin must bind to actin, which requires that the active sites on actin be exposed.

2. **Role of Calcium Ions**:
- In a resting muscle, the active sites on actin are masked. When calcium ions (Ca²⁺) are released into the muscle, they bind to the regulatory proteins on actin, leading to the unmasking of the active sites. This allows myosin to bind to actin, forming cross-bridges and initiating contraction.

3. **Effect of EDTA**:
- EDTA (Ethylenediaminetetraacetic acid) is a chelating agent that binds to calcium ions. When EDTA is injected into the muscles, it binds to the available Ca²⁺ ions.

4. **Consequences of EDTA Binding**:
- By binding to calcium, EDTA prevents calcium from interacting with the regulatory proteins on actin. This means that the active sites on actin remain masked and cannot bind to myosin effectively.

5. **Conclusion**:
- As a result, the contraction process is hindered. Since the active sites on actin are not exposed due to the absence of free calcium ions, the muscle contraction will slow down. Therefore, the correct answer is (c) Slows down contraction.

### Final Answer:
(c) Slows down contraction

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