![]() Retinal ganglion cell neurons ( first-order). ![]() Indirect pupillary reflex ( consensual pupillary reflex): constriction of the pupil in response to illumination of the contralateral eye.Direct pupillary reflex: constriction of the pupil in response to ipsilateral light stimulation.Definition: constriction of the pupils in response to light.Short ciliary nerves make the pupillary muscle fibers short (leading to miosis), while long ciliary nerves make the pupillary muscle fibers long. Indirectly by relaxation of the iris dilator muscle.Second-order neuron: ciliary ganglion → short ciliary nerves → pupillary sphincter.First-order neuron: fibers from Edinger-Westphal nucleus → oculomotor nerve fibers (located in the periphery of the oculomotor nerve) → ciliary ganglion.Contraction of the iris sphincter muscle (surrounds pupil).Definition: constriction of the pupil ( Indirectly by relaxation of the iris sphincter muscle.Third-order neuron: postganglionic sympathetic fibers form a plexus along the internal carotid artery → cavernous sinus → plexus forms long ciliary nerve and enter superior orbital fissure → dilator muscle of the iris ( pupillary dilation), superior tarsal muscle of the eyelid (upper eyelid retraction), sweat glands of the upper face.Second-order neuron: preganglionic sympathetic fibers (exit from the T 1 segment of the spinal cord) → rises to the upper cervical region along the cervical sympathetic trunk (passes near subclavian vessels and lung apex) → sympathetic trunk → superior cervical ganglion.First-order neuron: sympathetic hypothalamic fibers → lateral intermediate columns of the spinal cord → ciliospinal center of Budge ( C8–T2).Contraction of the iris dilator muscle (surrounds the peripheral part of iris).Definition: dilation of the pupil ( > 4 mm in daylight).Pupillary control is mediated by both parasympatheticand sympatheticinnervation. Accommodation: preganglionic parasympathetic fibers from Edinger-Westphal nucleus travel with the oculomotor nerve → ciliary muscle contraction → increased lens convexity.Convergence: contraction of both medial rectus muscles → eyes look inward.Miosis: contraction of iris sphincter muscle.Accommodation reflex: The synkinetic constriction of the pupil ( miosis), convergence of the eyes, and accommodation of lens convexity in response to a suddenly closer object.Occurs via the medial recti muscles bilaterally and is mediated by the oculomotor nerve ( CN III).Simultaneous inward movement of both eyes to maintain focus on close objects (e.g., eyes crossing when looking at one's own nose). ![]()
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