When we want to stare at an object, we fixate on that object. When tracking an object, we use smooth pursuit to keep our eyes focused on an object as it moves. This type of motion typically occurs when moving a gaze between objects. Saccades are rapid, jerky motions of the eye. Several movements assist with this process: saccades, smooth pursuit, fixation, accommodation, vestibulo-ocular reflex, and optokinetic reflex. The oculomotor nerve helps to adjust and coordinate eye position during movement. As the neurons in the ciliary ganglion differentiate, they extend axons to innervate the blood vessels of the choroid plexus as well as the striated muscles of the iris and ciliary body. These cells migrate ventrolaterally and rostrally toward the optic vesicle. Some cells may also originate from the ectodermal placode caudal to the eye. The parasympathetic nerve supply of the oculomotor nerves develops from the caudal midbrain and rostral hindbrain neural crest cells. Most research about the development of parasympathetic nerves and the ciliary ganglion has been on chickens. These muscles derive from the first preoptic myotome. They originate from the basal plate and innervates the superior rectus, inferior rectus, medial rectus, and inferior oblique muscles. Somatic nerves are homologous with ventral roots of spinal nerves. The tegmentum includes cranial nerves III and IV, Edinger-Westphal nuclei, oculomotor nuclei, trochlear nuclei, red nuclei, and reticular nuclei.Ĭranial nerve III has somatic and autonomic functions. Neuroblasts from the basal plates develop into the tegmentum. The midbrain develops from the mesencephalon. The oculomotor nerve and its associated cranial nerve nuclei exist within the midbrain.
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