This incessant change in pupil size has no pathologic significance, 4 although it is described in diverse conditions ranging from encephalitis In the awake state, the pupil is rather constantly moving, a condition Brain stem diagram represents section through levelĪt a given moment, any or all of the aforementioned factors may variably That uniocular light stimulus evokes bilateral and symmetric pupillaryĬonstriction. Postganglionic fibers innervate the pupillary sphincter muscles. After synapsing in the ciliary ganglia (CG), the 3 Preganglionic parasympathetic fibers ( heavy dashed lines) leave ventral aspect of midbrain in the substance of the third cranial Neurons to both Edinger–Westphal parasympathetic motor nuclei (E–W), which comprise the dorsal aspect of the oculomotor The PTN is connected by crossed and uncrossed intercalated Geniculate nucleus (LGN) is bypassed by these pupillomotorįibers. Terminate in pretectal nuclear complex (PTN). Light in left eye ( dotted arrow) stimulates retina (RET), whose afferent axons ( fine dashed lines) ascend optic nerve (ON), decussate at chiasm (CHI), and Iris color, on the other hand, may affectĬonstriction amplitude and velocity but not pupillary size. Occipital cortex above the pretectal area and from the reticular formation Light adaptation, and supranuclear influences from the frontal and Retinal illumination, the near-effort reflex, the state of retinal 2 In addition, the size of the pupils is influenced by the intensity of Pupillary size directly by dilator muscle innervation or indirectlyīy central inhibition of the oculomotor parasympathetics (Edinger-Westphal Outflow to the pupillary sphincter and ciliary muscle and (6) theĮfferent sympathetic pathway from the hypothalamus In the oculomotor nuclear complex (5) the efferent parasympathetic Of the superior colliculus (4) pretectal area of the mesencephalonĪnd the interconnecting neurons to pupilloconstrictor motor cells Not the lateral geniculate body) (3) brachium These include: (1) retinal receptors (2) ganglionĬell axons in the optic nerve, optic chiasm, and optic tract (but Pupillary function depends on the integrity of the structures along theĬourse of the pupillomotor pathway ( Fig. Loewenfeld's scholarly text, The Pupil: Anatomy, Physiology and Clinical Applications, is recommended reading for encyclopedic information about the pupil. They may be sampled and evaluated by simple clinical procedures. That control pupil size and reactivity are highly complex, yet The retina, the special sensory apparatus that it serves. The pupil is a kinetic indicator of both ocular motor function and the Protecting them like the pupil* of His eye.
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