The Trochlear Nerve and The Abducent Nerve
The Trochlear Nerve is the fourth of the Twelve Cranial Nerves, whereas the Abducent Nerve is the sixth. They both consist of afferent and efferent motoric fibers. The word Afferent means toward the centre, as in from a peripheral area of a limb to the central nervous system. The word Efferent is the opposite of Afferent, meaning away from the centre and toward the periphery; when the stimulus is carried from the brain to a peripheral area.
The pathway for the efferent fibers of the Trochlear Nerve is the following (from the initiation in the brain to the termination in the periphery):
- The Nucleus of the Trochlear Nerve can be found in the Inferior Colliculus of the Encephalic Tract (Brainstem).
- It is the only Nucleus which provides fibers to the nerve bundle known as the Trochlear Nerve.
- It exits the skull through the Superior Orbital Fissure.
- It innervates a singular eye muscle: the Superior Oblique Eye Muscle.
- This nerve motorically governs the abduction, depression and internal rotation of the eye.
The pathway for the efferent fibers of the Abducent Nerve is the following (from the initiation in the brain to the termination in the periphery):
- The Nucleus of the Abducent Nerve can be found in the Facial Colliculus of the Brainstem.
- It exits the skull via the Superior Orbital Fissure.
- It innervates the Lateral Rectus muscle of the eye.
- This nerve governs the muscle responsible for retracting the eye within the orbit.
The pathway for the afferent fibers of both nerves is the following (from the stimulatory cells in the periphery to the final synapse in the brain): exactly the opposite of the efferent pathway, respectively.