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A PICTURE REPRESENTATION OF THE PATHWAYS OF THE EYES

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A PICTURE REPRESENTATION OF THE PATHWAYS OF THE EYES

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DISCUSSION FOR CONSTRICTION AND DILATION

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DISCUSSION FOR CONSTRICTION AND DILATION

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1. In order to innervate the iris sphincter smooth muscle via M3 muscarinic receptors, the ciliary ganglion transmits parasympathetic postganglionic axons in the short ciliary nerve.

2. A direct and congruent pupillary response is created as a result of the bilateral E-W nuclei's innervation.

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Motor neuron (Sphincter muscles & Iris dilator muscles)

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Motor neuron (Sphincter muscles & Iris dilator muscles)

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Sphincter muscles

Responsible for the constriction of the pupil

Iris dilator muscles

Responsible for the dilation of the pupil

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1. Following that, the midbrain bilaterally transmits fibers to the efferent Edinger-Westphal nucleus of the oculomotor complex.

2. Efferent pupillary parasympathetic preganglionic fibers move via the oculomotor nerve to synapse in the ciliary ganglion.

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The retinal ganglionic cells in Jennie's eye are stimulated by a light stimulus.

Starting in the retinal ganglion cell layer, afferent pupillary fibers pass through the optic nerve, optic chiasm, and optic tract before entering the brachium of the superior colliculus and proceeding to the pretectal region of the midbrain.

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Ganglionic cells (retinal interneuron) are the final output neuron

They are the ones that collect the information from bipolar cells and amacrine cells

Edinger-Westphal nucleus supplies preganglionic parasympathetic fibers to the eye and it will be the cause for the constriction of the sphincter muscles and the dilation of the iris dilator muscles.

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Sensory neurons (Bipolar, Unipolar, and Multipolar neurons) 

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Sensory neurons (Bipolar, Unipolar, and Multipolar neurons) 

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Transmit signals from photoreceptors to Ganglion cells

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PROCESS OF EYE DILATION AND CONSTRICTION

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PROCESS OF EYE DILATION AND CONSTRICTION

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They are the ones that capture the stimulus coming from the penlight of the nurse.

The lights are then converted to electrical impulses

These electrical impulses are sent through the optic nerves

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The pupils typically dilate (become larger) in the dark (i.e., when light is removed). The iris sphincter relaxes and the iris dilator contracts as a result of this reaction. The sympathetic nervous system regulates the iris dilator.

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The pupil of the eye dilates usually from 3mm to 8mm when exposed to dark areas.

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A light stimulus is introduced to Jennie’s eye, which stimulates the retinal ganglionic cells.

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These behaviors explain why the pupil increases in size when it is subjected to dark environments and decreases in brighter ones (Ou, 2021).

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The Pupil of the Eye | How does the Pupil Dilate, Work and Function | Why is it Black

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Dilate to let in more light in reaction to external stimuli.

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Constriction to decrease the light entering the eye.

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Pupillary Light Reflex Pathway (Parasympathetic Innervation Pathway)

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Pupillary Light Reflex Pathway (Parasympathetic Innervation Pathway)

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The parasympathetic system constricts the pupil to protect itself when light intensity increases to an uncomfortable level by decreasing the amount of light entering the eye.

Pupillary constriction occurs via innervation of the iris sphincter muscle, which is controlled by the parasympathetic system

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The iris, which usually ranges from 2 - 8 millimeters in diameter depending on the amount of light in the environment, plays a vital role in our ability to see by controlling the amount of light that enters the pupil by using special muscles.

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Jennie went to Nurse Rose for her pupillary assessment, which usually takes place in a dark or dimly light room. Her pupils were initially 6 millimeters in size but constricted to 3 millimeters when they were exposed to Rose’s penlight. Jennie asked why this phenomenon occurred and Nurse Rose explained to her that her pupils dilate and constrict to control the amount of light that enters the eye.