Read the statements.
A. Preganglionic nerve fibres of III, VII, IX and X cranial nerves are a part of the parasympathetic nervous system
B. V, VII, IX and X cranial nerves are mixed nerves
C. Trochlear nerves are the largest cranial nerves
D. Abducens nerves are sensory in nature
which of the above statements are correct ?

Options

A. A and D
B. A and B
C. B and C
D. A and C

Answer

To determine which of the statements regarding cranial nerves are correct, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** Preganglionic nerve fibers of III, VII, IX, and X cranial nerves are a part of the parasympathetic nervous system.

- The III cranial nerve is the oculomotor nerve, which is involved in eye movement and parasympathetic functions such as pupil constriction.
- The VII cranial nerve is the facial nerve, which controls facial expressions and has parasympathetic functions related to salivary and lacrimal glands.
- The IX cranial nerve is the glossopharyngeal nerve, which has sensory and motor functions and also contributes to parasympathetic innervation of the parotid gland.
- The X cranial nerve is the vagus nerve, which is the longest cranial nerve and has extensive parasympathetic functions throughout the body.

**Conclusion:** Statement A is correct.

### Step 2: Analyze Statement B
**Statement B:** V, VII, IX, and X cranial nerves are mixed nerves.

- The V cranial nerve is the trigeminal nerve, which is responsible for sensation in the face and motor functions for mastication (chewing).
- The VII cranial nerve is the facial nerve, which is indeed a mixed nerve as it has both sensory (taste) and motor functions (facial expressions).
- The IX cranial nerve is the glossopharyngeal nerve, which is also a mixed nerve with sensory and motor functions.
- The X cranial nerve is the vagus nerve, which is a mixed nerve involved in various autonomic functions.

**Conclusion:** Statement B is correct.

### Step 3: Analyze Statement C
**Statement C:** Trochlear nerves are the largest cranial nerves.

- The trochlear nerve (IV cranial nerve) is responsible for innervating the superior oblique muscle of the eye.
- The largest cranial nerve is actually the trigeminal nerve (V cranial nerve), not the trochlear nerve.

**Conclusion:** Statement C is incorrect.

### Step 4: Analyze Statement D
**Statement D:** Abducens nerves are sensory in nature.

- The abducens nerve (VI cranial nerve) is primarily a motor nerve that controls the lateral rectus muscle of the eye, which is responsible for lateral eye movement.
- It does not have sensory functions.

**Conclusion:** Statement D is incorrect.

### Final Conclusion
The correct statements are A and B.

### Summary of Correct Statements
- **Correct Statements:** A and B
- **Incorrect Statements:** C and D