Which one of the following is the third cranial nerve?

Appeared in: AIIMS Raipur NO - 2019 (Shift-1)

Explanation

The Oculomotor nerve is designated as the third cranial nerve (CN III).
It is a motor nerve that controls most of the muscles responsible for eye movement (superior, inferior, and medial rectus, and inferior oblique).
It also has a parasympathetic function, controlling the sphincter pupillae muscle for pupil constriction and the ciliary muscle for accommodation.
Additionally, it innervates the levator palpebrae superioris muscle, which lifts the upper eyelid.

Option B: The Optic nerve is the second cranial nerve (CN II), not the third.
Option C: The Abducens nerve is the sixth cranial nerve (CN VI), not the third.
Option D: The Trochlear nerve is the fourth cranial nerve (CN IV), not the third.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Identification of Cranial Nerves as background academic context rather than a clinical decision trigger.
Assessing the 12 cranial nerves is a fundamental part of a neurological examination for nurses to detect abnormalities in the brain and nervous system.
A common bedside test for Oculomotor nerve (CN III) function is checking the pupillary light reflex (PERRLA: Pupils Equal, Round, Reactive to Light and Accommodation). A sluggish or non-reactive pupil can indicate increased intracranial pressure or nerve compression, requiring urgent medical attention.
What if? If a patient presents with a 'down and out' gaze and a drooping eyelid (ptosis), the nurse should suspect a CN III palsy, not a CN VI palsy, which would cause an inability to look outward.

How to Approach the Question

This is a factual recall question from anatomy.
The first step is to read the question carefully and identify the key term: 'third cranial nerve'.
Recall the list of the 12 cranial nerves and their corresponding numbers. Using a mnemonic can be very helpful for memorization.
A common mnemonic is: 'Oh Oh Oh To Touch And Feel Very Good Velvet, Such A Heaven'.
Match the third word ('Oh' for Oculomotor) to the options provided.
Evaluate each option based on your knowledge. The Optic nerve is II, Abducens is VI, and Trochlear is IV.

Concept Tested & Keywords

Qv1x13qtbL5EzFdXO2YI-i

E6 Anatomy Applied Ashalatha 4e pp. 425-427, 426-428

Practise the full AIIMS Raipur NO - 2019 (Shift-1)

Attempt every question from this paper in a timed mock, then review the full solution for each one.