The number of thick myofilaments (myosin) surrounding
Single thin myofilament (actin) are

Options

A. 3
B. 6
C. 2
D. 4

Answer

To solve the question regarding the number of thick myofilaments (myosin) surrounding a single thin myofilament (actin), we can follow these steps:

### Step-by-Step Solution:

1. **Understand Myofilaments**:
- Myofilaments are the contractile proteins found in muscle cells. There are three types: thick myofilaments (myosin), thin myofilaments (actin), and elastic myofilaments (titin).

2. **Identify the Components**:
- Thick myofilaments are primarily composed of myosin protein.
- Thin myofilaments are primarily composed of actin protein.
- Elastic myofilaments (not directly relevant to this question) are made of titin protein.

3. **Arrangement of Myofilaments**:
- In muscle fibers, thick and thin myofilaments are arranged in an overlapping pattern.
- Each thick myofilament (myosin) is surrounded by six thin myofilaments (actin).

4. **Focus on the Thin Myofilament**:
- When considering a single thin myofilament (actin), it is surrounded by thick myofilaments (myosin) on either side.

5. **Count the Surrounding Thick Myofilaments**:
- For each thin myofilament, there are three thick myofilaments that surround it. This is because the arrangement allows for optimal overlap and interaction between the actin and myosin for muscle contraction.

6. **Final Answer**:
- Therefore, the number of thick myofilaments (myosin) surrounding a single thin myofilament (actin) is **3**.