Identify the incorrect combination from the following

Options

A. Sarcomere - Part of myofibril between two Dobie's lines
B. Motor unit - Set of skeletal muscle fibres and innervated by the afferent neuron
C. Triad system- T tubule and two on cisternae either side
D. Motor endplate - The depression of sarcolemma opposite the synaptic end bulbs

Answer

**Step-by-Step Solution:**

1. **Understand the Question**: The question asks to identify the incorrect combination from a list of statements related to muscle structure and function.

2. **Analyze Each Option**:
- **Option 1**: The statement claims that a sarcomere is a part of a microfibre between two "dobby's lines".
- **Correction**: The correct terminology is that a sarcomere is the region between two Z lines, not "dobby's lines". This statement is incorrect.

- **Option 2**: The statement about motor units being a set of skeletal muscle fibers innervated by afferent neurons.
- **Evaluation**: This statement is true. Motor units consist of motor neurons and the muscle fibers they control.

- **Option 3**: The statement regarding the triad system, which includes T-tubules and two terminal cisternae on either side.
- **Evaluation**: This statement is also true. The triad structure is essential for muscle contraction.

- **Option 4**: The statement about the motor end plate being a depression of the sarcolemma opposite the synaptic end bulbs.
- **Evaluation**: This statement is true. The motor end plate is indeed a specialized region of the sarcolemma.

3. **Identify the Incorrect Statement**: After analyzing all options, it is clear that the first statement about the sarcomere is incorrect. Sarcomeres are defined by the Z lines, not "dobby's lines".

4. **Conclusion**: The incorrect combination is the first option regarding the definition of a sarcomere.

**Final Answer**: The incorrect combination is the first option regarding the sarcomere.

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