Table of Contents
What does the Pretectal nucleus do?
Function. As part of the subcortical visual system, neurons within the pretectal nuclei respond to varying intensities of illuminance and are primarily involved in mediating non-conscious behavioral responses to acute changes in light.
What is Edinger-Westphal?
The Edinger-Westphal nucleus is a small parasympathetic motor nucleus in the midbrain and one of the two nuclei for the oculomotor nerve. It is one of the cranial nerve nuclei.
Is Edinger-Westphal parasympathetic?
The Edinger-Westphal nucleus contains a group of parasympathetic preganglionic cells that innervate the ciliary muscle and the pupillary constrictor.
Is Pretectal nucleus involved in accommodation reflex?
[4] This action occurs because the midbrain center for near reflex is more ventral than the pretectal nucleus, which controls the light reflex.
What is the Olivary Pretectal nucleus?
The olivary pretectal nucleus is a primary visual centre sensitive to luminance changes. It is involved in the pupillary light reflex, the consensual pupillary light reflex and related reflexes, such as the lid closure reflex whereby pupillary constriction takes place.
On which formation the nuclei of the oculomotor nerve are projected?
General somatic efferent (motor) nuclei The oculomotor nucleus: This nucleus is located in the upper part of the midbrain at the level of the superior colliculus. The oculomotor nuclei (left and right sides) form a single complex that lies in the central grey matter, ventral to the cerebral aqueduct (of Sylvius).
What muscles does oculomotor control?
The oculomotor nerve controls several muscles:
- Levator palpebrae superioris – raises the upper eyelid.
- Superior rectus muscle – rotates the eyeball backward, “looking up”
- Medial rectus muscle – adducts the eye, “looking towards your nose”
- Inferior rectus muscle – rotates the eyeball forwards, “looking down”
What controls accommodation in the eye?
The accommodation reflex Accommodation and convergence of the eyes is mediated by increased tone of the medial rectus muscle and pupil constriction (contraction of the pupillae constrictor muscle), which occur together when a person views a close object.
Is pretectal nucleus the Edinger Westphal?
The primary input to the Edinger–Westphal nuclei is from the pretectal olivary nuclei, which receive direct crossed retinal input. Early physiologic and anatomic evidence supported direct ipsilateral and contralateral projections from the pretectal olivary nuclei to the Edinger–Westphal nucleus.
What is light near dissociation?
Description. Light-near dissociation (LND) is a pupillary sign that occurs when the pupillary light reaction is impaired while the near reaction (accommodative response) remains intact. LND can occur unilaterally or bilaterally.
What Innervates the Edinger-Westphal nucleus?
The Edinger-Westphal nucleus contains a group of parasympathetic preganglionic cells that innervate the ciliary muscle and the pupillary constrictor. The axons of these cholinergic preganglionic neurons synapse with ganglion cells in the ciliary ganglion.
How many oculomotor nucleus are there?
two nuclei
There are two nuclei for the oculomotor nerve: The oculomotor nucleus originates at the level of the superior colliculus. The muscles it controls are the striated muscle in levator palpebrae superioris and other extraocular muscles except for the superior oblique muscle and the lateral rectus muscle.
How do you test oculomotor nerve?
Step One: Open the right eyelid and shine the light into the right eye. Look only into the right eye to assess for a response. A normal response is a brisk constriction of the right pupil. If the pupil gets larger or has a sluggish response, it is considered abnormal.
How do I test my eye accommodation?
Testing for the accommodation reflex follows nicely on from eye movements. Ask the patient to keep focusing on the tip of your index finger and slowly move it towards them, aiming for the tip of their nose. You need to be watching their pupils to make sure you see them constrict as your finger gets closer.
What is the oculomotor nucleus?
The oculomotor nucleus is found at the level of the superior colliculus. It contains the somatic efferent fibers that control the medial rectus, inferior rectus, superior rectus, inferior oblique, and the striated muscle in the levator palpebrae superioris. The oculomotor nucleus is split up into multiple subnuclei.
What muscles does the oculomotor nerve innervate?
The oculomotor nerve innervates all the extraocular muscles except the superior oblique (trochlear nerve) and lateral rectus (abducens nerve). The extraocular muscles are the inferior oblique and the superior, medial, and inferior rectus muscles.
What is the motor pool of the superior rectus?
After unilateral interruption of the oculomotor nerve, chromatolysis is evident in the ipsilateral oculomotor nucleus and also in the caudal two thirds of the contralateral oculomotor nucleus. These cells in the caudal two thirds of the contralateral nucleus are defined as the “motor pool” of the superior rectus muscle.
Which subnucleus of the oculomotor nucleus is responsible for parasympathetic innervation?
The subnucleus of the oculomotor nucleus that is responsible for parasympathetic innervation to the eye is the Edinger–Westphal nucleus. Its fibers travel with the oculomotor nerve as the long ciliary nerves.