Chapter contents
Overview
Origin & central course
Intracranial course
Final innervation
Coordination of muscles
Lower motor neuron lesion
Upper motor neuron lesion
MLF syndrome
| Cranial Nerve VI - Abducens Nerve | Page 5 of 8 |
Coordination of lateral rectus and medial rectus muscles
The exact control of eye movements requires input from integration centers in the brain that coordinate the output from the occulomotor, trochlear, and abducens nuclei which control the six extraocular muscles.
For eye movements in the horizontal plane, the lateral rectus muscle of one eye and the medial rectus muscle of the other eye must work precisely together.
The actions of these muscles is coordinated by the lateral gaze center located in the pontine reticular formation.
Inputs from higher centers of the brain synapse in the lateral gaze center, which then sends simultaneous signals to the ipsilateral abducens nucleus and to the contralateral occulomotor nucleus via the medial longitudinal fasciculus.
The abducens nucleus sends signals via CN VI to the lateral rectus muscle of the ipsilateral orbit to command that eye to be abducted. Simultaneously, the occulomotor nucleus generates a command via CN III to contract the medial rectus muscle of the contralateral orbit resulting in adduction of that eye.
The end result is that both eyes precisely fixate on or track the same object:
Figure 6-5. Coordination of lateral rectus and medial rectus muscles.
