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What nerve controls the pupil dilation?

What nerve controls the pupil dilation?

Oculomotor nerve (III) is responsible for the control of the pupil (constriction) via parasympathetic fibres (this is opposed by dilator tone controlled by sympathetic pathways).

What is 3rd nerve palsy?

A complete third nerve palsy causes a completely closed eyelid and deviation of the eye outward and downward. The eye cannot move inward or up, and the pupil is typically enlarged and does not react normally to light.

What happens when the oculomotor nerve is damaged?

Damage to any of these nerves or the muscle or muscles they innervate causes dysconjugate gaze, which results in characteristic patterns of diplopia (double vision). In addition, with oculomotor nerve damage, patients also lose their pupillary constriction to light as well as the elevation of their eyelid.

What muscle dilates the pupil?

iris dilator muscle
The iris dilator muscle has fibers arranged radially from the sphincter to the ciliary border, receives sympathetic innervation, and functions to cause dilation of the pupil (mydriasis).

What causes pupil dilation?

Muscles in the colored part of your eye, called the iris, control your pupil size. Your pupils get bigger or smaller, depending on the amount of light around you. In low light, your pupils open up, or dilate, to let in more light. When it’s bright, they get smaller, or constrict, to let in less light.

Which extraocular muscles are innervated by CN III?

The CN III innervates the levator palpebrae superioris, the superior rectus muscle, the inferior rectus muscle, the medial rectus muscle, the inferior oblique muscle, the sphincter pupillae, and the ciliary muscle.

How should nurse assess cranial nerves III IV and VI?

Cranial Nerve III, IV, and VI – Oculomotor, Trochlear, Abducens

  1. Test eye movement by using a penlight. Stand 1 foot in front of the patient and ask them to follow the direction of the penlight with only their eyes.
  2. Test bilateral pupils to ensure they are equally round and reactive to light and accommodation .

What muscles dilate and constrict the pupils?

a) When the iris sphincter muscle (green) contracts, it tightens the inner side of the iris, thus causing the pupil to constrict. b) When the iris dilator muscle (yellow) contracts, it pulls the inner side of the iris outward, thus causing the pupil to dilate.

What does the median nerve supply?

The median nerve is the branch of the brachial plexus that supplies most of the superficial and deep flexors in the forearm, thenar and lumbrical muscles. It also gives sensation to certain areas of the skin of the hand.

What is the nerve supply of skeletal muscle?

Describe the nerve supply of skeletal muscle. Skeletal muscle is supplied by somatic nerves. The nerve to a skeletal muscle is a mixed nerve containing 60% motor and 40% sensory fibers.

Where does the median nerve enter the arm?

After receiving inputs from both the lateral and medial cords of the brachial plexus, the median nerve enters the arm from the axilla at the inferior margin of the teres major muscle.