**Question:** Downward and lateral gaze is action of

A. **Oculomotor Nerve (CN III)**
B. **Abducent Nerve (CN VI)**
C. **Vestibulocerebellopontine tract**
D. **Oculomotor Nerve (CN III)**

**Correct Answer:** D. **Oculomotor Nerve (CN III)**

**Core Concept:** The oculomotor nerve (CN III) plays a crucial role in controlling the movements of the extraocular muscles responsible for eye movements.

**Why the Correct Answer is Right:** The oculomotor nerve, innervated by the brainstem, is responsible for the control of eye movements, including the downward and lateral gaze. The oculomotor nerve controls the actions of the rectus muscles, which are responsible for the movements of the eyes. The rectus muscles include the superior rectus, inferior rectus, medial rectus, and lateral rectus muscles. Among these, the superior rectus, inferior rectus, and lateral rectus muscles are involved in downward and lateral gaze.

**Why Each Wrong Option is Incorrect:**

A. Oculomotor nerve (CN III) is responsible for vertical gaze (upward and downward gaze), not lateral gaze.
B. The abducens nerve (CN VI) controls the lateral rectus muscle, which is responsible for lateral gaze. However, it is not responsible for downward gaze.
C. The vestibulocochlear nerve (CN VIII) and vestibulocerebellopontine tract are involved in balance, hearing, and vestibular functions, not eye movements.
D. Oculomotor nerve (CN III) is responsible for both downward and lateral gaze, making it the correct answer.

**Clinical Pearl:** The oculomotor nerve (CN III) is responsible for not only upward and downward gaze but also lateral gaze. A thorough understanding of the oculomotor nerve and its actions is essential for interpreting eye movement disorders, as abnormalities in eye movements can indicate neurological pathologies like stroke, multiple sclerosis, or brain tumors.