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Superior oblique muscles of eyeball receive:
(a) $3^{rd}$ cranial nerve
(b) $4^{th}$ cranial nerve
(c) $6^{th}$ cranial nerve
(d) None of the above

Answer Verified Verified
Hint: The motor (efferent) nerves that regulate the six eye muscles (three pairs of antagonistic muscles) are cranial nerves (CN) III, IV, and VI. It regulates the behavior of the superior oblique muscle, one of the external eye muscles. This muscle runs up to the top of the eye from the back of the eye socket.

Complete step by step answer:
Cranial nerves III, IV, and VI functions as a motor activity that influences the direction of the gaze, the location of the eyelids, and the size of the pupils. In psychiatric patients, irregular oculomotor behavior is often witnessed and can be very insightful. In addition to the advanced approaches used in specialty clinics and testing laboratories, assessment strategies involve casual examination and basic assessments that include no equipment. Pupil size, extraocular motions, nystagmus, lid retraction, lid lag, and ptosis are examined in this report. These tests provide valuable information about the higher cortical activity, extrapyramidal motor functioning, and toxic/pharmacological condition of the organism beyond screening for diseases and localizing lesions.
The trochlear nerve is a motor nerve (a somatic different nerve) that innervates only one muscle: the superior oblique muscle of the eye, which works through the pulley- like trochlea, also called the fourth cranial nerve or CN IV.
So, the answer is ‘(b) $4^{th}$ cranial nerve’.

Additional information: Among the cranial nerves, the trochlear nerve is unique in many respects:
- In terms of the number of axons it comprises, it is the smallest nerve.
- It has an intracranial length of the largest.
- It is the only cranial nerve that exits from the brainstem's dorsal (rear) aspect.
- It innervates a muscle, the oblique superior muscle, from its nucleus on the opposite side (contralateral). Before arising on the contralateral side of the brainstem, the trochlear nerve deuces inside the brainstem.

Note: It is the longest and thinnest of all cranial nerves, rendering it vulnerable to trauma. The axons move dorsolaterally and caudally around the periaqueductal grey after leaving the trochlear nucleus and decussate almost entirely in the anterior medullary velum.
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