What component of the nervous system is involved in pupil constriction?
The parasympathetic nervous system is the main system responsible for pupil constriction in response to light. The integrated afferent input is transmitted along the axons of the retinal ganglion cells (RGC), which contribute to the optic nerve.
What are the components of pupillary light reflex?
The pupillary light reflex requires CN II, CN III, and central brain stem connections. Light shined in one eye stimulates retinal photoreceptors, and subsequently retinal ganglion cells, whose axons travel through the optic nerve, chiasm, and tract to terminate in the pretectum (pretectal nucleus).
What type of reflex is pupil constriction?
pupillary light reflex
The pupillary light reflex is an autonomic reflex that constricts the pupil in response to light, thereby adjusting the amount of light that reaches the retina. Pupillary constriction occurs via innervation of the iris sphincter muscle, which is controlled by the parasympathetic system.
Why do pupils constrict in bright light?
The pupil is the part of your eye that controls how much light gets in. In bright light, your pupils get smaller (constrict) to limit the amount of light that enters. In the dark, your pupils get bigger (dilate). That allows more light in, which improves night vision.
What are the five essential components of a reflex arc?
The reflex arc consists of 5 components:
- sensory receptor.
- sensory neuron.
- integration center.
- motor neuron.
- effector target.
What happens during the pupillary light reflex?
A greater intensity of light causes the pupil to constrict (miosis/myosis; thereby allowing less light in), whereas a lower intensity of light causes the pupil to dilate (mydriasis, expansion; thereby allowing more light in). Thus, the pupillary light reflex regulates the intensity of light entering the eye.
What is light reflex pathway?
The right direct reflex is intact. When light is shone into right eye, right pupil constricts. Direct reflex of the right pupil is unaffected, The right afferent limb, right CN II, and the right efferent limb, right CN III, are both intact. The left consensual reflex is lost.
What happens to pupil in bright light?
In dim light, your pupil expands to allow more light to enter your eye. In bright light, it contracts. More light creates more impulses, causing the muscles to close the pupil. Part of the optic nerve from one eye crosses over and couples to the muscles that control the pupil size of the other eye.
What is constriction of the pupil called?
The black circle in the center of your eye is your pupil. It changes size thousands of times a day. When you’re in dim light, it gets bigger to let more light in. When you’re in bright light, it shrinks to protect your eye and keep light out. When your pupil shrinks (constricts), it’s called miosis.
What is the pathophysiology of the pupillary light reflex?
NEUROANATOMY OF THE PUPILLARY LIGHT REFLEX. The physiological result of the neuroanatomical pathways as described above is that light shined in one eye will result in pupillary constriction in both the ipsilateral pupil ( direct pupillary light reflex) and the contralateral pupil ( consensual pupillary light reflex).
What is the difference between right direct and consensual pupillary reflexes?
Right direct pupillary reflex is the right pupil’s response to light entering the right eye, the ipsilateral eye. Right consensual pupillary reflex is the right pupil’s indirect response to light entering the left eye, the contralateral eye.
What muscle constricts the pupil in response to light?
The pupillary light reflex constricts the pupil in response to light, and pupillary constriction is achieved through the innervation of the iris sphincter muscle. Anatomy and Physiology
What is the afferent pathway for pupillary constriction and lens accommodation?
Afferent pathway for pupillary constriction, lens accommodation, and convergence: Afferent input from the retina is sent to the lateral geniculate nucleus via the optic tract. Fibers from the LGN then project to the visual cortex.
