Chapter contents Overview Somatic motor component Origin, central course Intracranial course Final innervation Visceral motor component Origin and course Final innervation

Cranial Nerve III - Oculomotor Nerve Page 8 of 16 Somatic motor component, vertical gaze 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 vertical plane, the superior rectus, inferior rectus, inferior oblique, and superior oblique muscles of the eyes must work precisely together. The actions of these muscles is coordinated by the vertical gaze center which is thought to be located in the periaqueductal grey matter of the midbrain at the level of the superior colliculus (its location has not yet been positively identified). The vertical gaze center projects to the oculomotor nuclei which control the superior rectus, inferior rectus and inferior oblique muscles as well as to the trochlear nuclei which control the superior oblique muscles. The center that controls torsional movements of the eye is probably close to, or the same as, the vertical gaze center since all muscles that elevate or depress the eyes also cause them to rotate about their anterior-posterior axis of motion. The lateral gaze center is discussed in the abducens nerve (CN VI) module. Figure 3-8. Vertical gaze center, CN III & CN IV.

Last revised: March 22, 1998