What cranial nerve causes pupillary reflex?

The oculomotor nerve is responsible for the efferent limb of the pupillary reflex; it drives the iris muscles that constrict the pupil.

What nerves are involved in pupil reflexes?

The pupillary light reflex pathway involves the optic nerve and the oculomotor nerve and nuclei. Parasympathetic Innervation of the Eye.

Which cranial nerve dilates the pupil?

Oculomotor Nerve
Motor nerve- Oculomotor Nerve-Controls most eye muscles. Works closely with Cranial Nerves 4 & 6. Controls eye movement, pupil dilation, and pupillary constriction. It also controls the muscles that elevate the upper eyelids.

What part of the brain is responsible for pupillary reflex?

The hypothalamus is the control center for many homeostatic mechanisms. It regulates both autonomic function and endocrine function. The roles it plays in the pupillary reflexes demonstrates the importance of this control center.

Why do pupils constrict in light response?

Light detected by the retina of your eye is converted to nerve impulses that travel down the optic nerve. Some of these nerve impulses go from the optic nerve to the muscles that control the size of the pupil. More light creates more impulses, causing the muscles to close the pupil.

How many cranial nerves are strictly motor nerves?

four cranial nerves
There are four cranial nerves with primarily motor function.

What does abducens nerve do?

Cranial nerve six (CN VI), also known as the abducens nerve, is one of the nerves responsible for the extraocular motor functions of the eye, along with the oculomotor nerve (CN III) and the trochlear nerve (CN IV).

Why is the pupillary reflex an autonomic reflex?

Pupillary Reflex Pathways. The pupil is under competing autonomic control in response to light levels hitting the retina. The sympathetic system will dilate the pupil when the retina is not receiving enough light, and the parasympathetic system will constrict the pupil when too much light hits the retina.

How to conduct a cranial nerve examination?

• Ask patient to turn head to one side and push against examiners hand or ask to flex head against resistance, palpate and evaluate strength of sternocleidomastoid muscle. • Evaluate both right and left side, compare for symmetry. CRANIAL NERVES 39 40.

Which cranial nerve is responsible for pupillary constriction?

– Pupil dilation and loss of reactivity to light (inability of the pupil to constrict to light) – Inability to follow and object in direction of CN III (the quickest test is to observe upward gaze which is all CN III; the eye on the affected side does – Inability to open the eyelid.

Which two nerves are involved in the pupillary reaction?

Introduction to Pupillary Responses. There are a handful of pupillary abnormalities that every clinician should know.

What is direct and consensual pupillary reflex?

Direct and consensual pupillary light reflexes test for appropriate neurological pathway connections and functioning of both cranial nerve II and III. Light entering the eye is processed through the pupillary light reflex, and signals directed to the iris sphincter muscle to adjust the amount of light that reaches the retina.