Source of `Ca^(+ +)` for muscle contraction is both sarcoplasmic ( endoplascmic ) reticulum as well as extracellular fluid in case of
a. Skeletal muscles
b. Smooth muscles
C. Cariac muscles

Options

A. A only
B. b and c only
C. a and c only
D. b only

Answer

To determine the source of calcium ions (Ca²⁺) for muscle contraction in skeletal, smooth, and cardiac muscles, we can analyze each type of muscle tissue based on their physiological characteristics.

### Step-by-Step Solution:

1. **Understanding Muscle Types**:
- **Skeletal Muscles**: These muscles are under voluntary control and have a well-developed sarcoplasmic reticulum (SR) which stores calcium ions.
- **Smooth Muscles**: These muscles are involuntary and have a less developed SR. They primarily rely on extracellular fluid (ECF) for calcium.
- **Cardiac Muscles**: These muscles are also involuntary and have a moderate SR. They derive calcium from both the SR and ECF.

2. **Calcium Source in Skeletal Muscles**:
- In skeletal muscles, the sarcoplasmic reticulum is the main source of calcium ions. When a muscle fiber is stimulated, calcium is released from the SR, which triggers contraction.

3. **Calcium Source in Smooth Muscles**:
- Smooth muscles have a lower concentration of sarcoplasmic reticulum. They mainly obtain calcium from the extracellular fluid, which enters the muscle cells through calcium channels during contraction.

4. **Calcium Source in Cardiac Muscles**:
- Cardiac muscles utilize both the sarcoplasmic reticulum and extracellular fluid for calcium. The ECF plays a significant role in calcium influx, which is crucial for cardiac muscle contraction.

5. **Conclusion**:
- The question asks for the muscle type that derives calcium from both the sarcoplasmic reticulum and extracellular fluid. Based on the analysis:
- **Skeletal muscles** primarily use the SR.
- **Smooth muscles** primarily use ECF.
- **Cardiac muscles** use both sources.
- Therefore, the correct answer is **C. Cardiac muscles**.

### Final Answer:
The source of Ca²⁺ for muscle contraction is both the sarcoplasmic reticulum and extracellular fluid in the case of **C. Cardiac muscles**.