[A] : In vertebrates, motor fibres to striped muscle, parasympathetic fibres to smooth muscle. and preganglionic sympathetic fibres are cholinergic.
[R]: Cholinergic designates the type of nerve fibre that releases acetylcholine from its ending when stimulated by a nerve impulse.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion (A):**
- The assertion states that in vertebrates, motor fibers to striped muscles, parasympathetic fibers to smooth muscles, and preganglionic sympathetic fibers are cholinergic.
- Motor fibers are responsible for transmitting signals from the central nervous system to muscles, particularly skeletal (striped) muscles, which are under voluntary control.
- Parasympathetic fibers are part of the autonomic nervous system and control smooth muscles, which are involuntary and found in organs like the gastrointestinal tract.
- Preganglionic sympathetic fibers also belong to the autonomic nervous system and are involved in the fight-or-flight response.

2. **Understanding Cholinergic Fibers:**
- Cholinergic fibers are those that release acetylcholine (ACh) as a neurotransmitter when stimulated.
- This means that all the mentioned fibers (motor to striped muscles, parasympathetic to smooth muscles, and preganglionic sympathetic fibers) release acetylcholine, confirming the assertion.

3. **Understanding the Reason (R):**
- The reason states that cholinergic designates the type of nerve fiber that releases acetylcholine from its ending when stimulated by a nerve impulse.
- This is a correct definition of cholinergic fibers, as they are characterized by the release of acetylcholine at synapses.

4. **Evaluating the Relationship between A and R:**
- Both the assertion (A) and the reason (R) are true statements.
- Furthermore, the reason (R) correctly explains why the assertion (A) is true, as it provides the definition of cholinergic fibers, which is essential to understanding the assertion.

5. **Conclusion:**
- Since both A and R are true, and R is the correct explanation of A, we conclude that the correct answer is that both statements are true and R is the correct explanation of A.

**Final Answer:**
Both A and R are true, and R is the correct explanation of A.

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