In striped muscles,cross bridges rapidly dissociative when

Options

A. ADP and inorganic phosphate seperates from mysosin head
B. ATP attaches to the myosin head
C. Calcium binds to tropomyosin
D. Troponin tropomyosin complex masks the active binding sites for myosin on the actin filaments

Answer

To solve the question regarding the dissociation of cross bridges in striped muscles, let's break down the process step by step.

### Step-by-Step Solution:

1. **Understanding Cross Bridges**:
- Cross bridges are formed between the myosin heads and actin filaments during muscle contraction. This interaction is crucial for muscle movement.

2. **Formation of Cross Bridges**:
- Initially, the myosin head, which is attached to ADP and inorganic phosphate (Pi), binds to the actin filament, forming a cross bridge.

3. **Power Stroke**:
- When the myosin head pivots, it pulls the actin filament towards the center of the sarcomere, resulting in muscle contraction. During this power stroke, ADP and Pi are released from the myosin head.

4. **Role of ATP**:
- After the power stroke, for the myosin head to detach from the actin filament, ATP must bind to the myosin head. This binding causes a conformational change in the myosin head.

5. **Dissociation of Cross Bridges**:
- The binding of ATP to the myosin head leads to the rapid dissociation of the cross bridge from the actin filament. This is the key step in muscle relaxation and allows the cycle to repeat.

6. **Conclusion**:
- Therefore, the correct answer to the question is that cross bridges in striped muscles rapidly dissociate when ATP attaches to the myosin head.

### Final Answer:
Cross bridges rapidly dissociate when ATP attaches to the myosin head.