The Edinger–Westphal nucleus (accessory oculomotor nucleus, or visceral oculomotor nucleus) is one of two nuclei of the

oculomotor nerve The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of ...

. It is located in the

midbrain The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek ''mesos'', " ...

. It contributes the autonomic parasympathetic (i.e. visceral) component to the oculomotor nerve, providing innervation to the

iris sphincter muscle The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris. It encircles the pupil of the iris, appropriate to its function as a constrictor ...

and

ciliary muscle The ciliary muscle is an intrinsic muscle of the eye formed as a ring of smooth muscleSchachar, Ronald A. (2012). "Anatomy and Physiology." (Chapter 4) . in the eye's middle layer, uvea ( vascular layer). It controls accommodation for viewing ...

to mediate the

pupillary light reflex The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retinal ganglion cells of the retina in the back of the eye, there ...

and accommodation, respectively. It is composed of

parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...

pre-ganglionic cell bodies that synapse in the

ciliary ganglion The ciliary ganglion is a bundle of nerve parasympathetic ganglion located just behind the eye in the posterior orbit. It is 1–2 mm in diameter and in humans contains approximately 2,500 neurons. The ganglion contains postganglionic parasympath ...

. The term "Edinger–Westphal nucleus" also referred to what is now known as the centrally-projecting Edinger–Westphal nucleus, intermingled population of non-preganglionic neurons that do not project to the

but to various regions throughout the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...

Anatomy

Centrally-projecting Edinger–Westphal nucleus

Alternatively, the term Edinger–Westphal nucleus is often used to refer to the adjacent population of non-preganglionic neurons that do not project to the

, but rather project to the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

dorsal raphe nucleus The dorsal raphe nucleus is located on the midline of the brainstem and is one of the raphe nuclei. It has rostral and caudal subdivisions. * The rostral aspect of the ''dorsal'' raphe is further divided into interfascicular, ventral, ventrolatera ...

, lateral

septal nuclei The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum. The septal nuclei are loca ...

lateral hypothalamic area The lateral hypothalamus (LH), also called the lateral hypothalamic area (LHA), contains the primary orexinergic nucleus within the hypothalamus that widely projects throughout the nervous system; this system of neurons mediates an array of cogni ...

and the

central nucleus of the amygdala The central nucleus of the amygdala (CeA or aCeN) is a nucleus within the amygdala. It "serves as the major output nucleus of the amygdala and participates in receiving and processing pain information." CeA "connects with brainstem areas that con ...

, among other regions. Unlike the classical preganglionic neurons that contain choline acetyltransferase, neurons of the Centrally-projecting Edinger–Westphal nucleus contain various

neuropeptide Neuropeptides are chemical messengers made up of small chains of amino acids that are synthesized and released by neurons. Neuropeptides typically bind to G protein-coupled receptors (GPCRs) to modulate neural activity and other tissues like the ...

such as

urocortin Urocortin is a protein that in humans is encoded by the ''UCN'' gene. Urocortin belongs to the corticotropin-releasing factor (CRF) family of proteins which includes CRF, urotensin I, sauvagine, urocortin II and urocortin III. Urocortin is invol ...

and

cocaine- and amphetamine-regulated transcript Cocaine- and amphetamine-regulated transcript, also known as CART, is a neuropeptide protein that in humans is encoded by the ''CARTPT'' gene. CART appears to have roles in reward, feeding, and stress, and it has the functional properties of an ...

. Previously, it had been proposed to rename this group of non-preganglionic, neuropeptide-containing neurons to perioculomotor subgriseal neuronal stream, abbreviated ''pIII_SG''. However, more recently, a final nomenclature has been determined. Preganglionic oculomotor neurons within the Edinger–Westphal nucleus are to be referred to as the ''EWpg'', and the neuropeptide-containing neurons shall be known as the centrally-projecting Edinger Westphal nucleus, or ''EWcp''.

Anatomical relations

The paired nuclei are posterior to the main motor nucleus (

oculomotor nucleus The fibers of the oculomotor nerve arise from a nucleus in the midbrain, which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle. From ...

) and anterolateral to the

cerebral aqueduct The cerebral aqueduct (aqueductus mesencephali, mesencephalic duct, sylvian aqueduct or aqueduct of Sylvius) is a conduit for cerebrospinal fluid (CSF) that connects the third ventricle to the fourth ventricle of the ventricular system of the brai ...

in the rostral

at the level of the

superior colliculus In neuroanatomy, the superior colliculus () is a structure lying on the roof of the mammalian midbrain. In non-mammalian vertebrates, the homologous structure is known as the optic tectum, or optic lobe. The adjective form ''tectal'' is commonly ...

. It is the most rostral of the parasympathetic nuclei in the

brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

Function

The Edinger–Westphal nucleus supplies

preganglionic In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers. All preganglionic fibers, whether they are in the sympathetic division or in the parasympathetic division, are cholinergic (that is, these f ...

parasympathetic fibers to the eye, constricting the

pupil The pupil is a black hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black ...

, accommodating the

lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

, and convergence of the eyes.

Neurophysiology

Pupillary light reflex

The EWN receives feedback from the

locus coeruleus The locus coeruleus () (LC), also spelled locus caeruleus or locus ceruleus, is a nucleus in the pons of the brainstem involved with physiological responses to stress and panic. It is a part of the reticular activating system. The locus coerule ...

about illumination of the retina in order for the EWN to adjust the size of the pupil in response to varying ambiental brightness.

Accommodation

Research

It has also been implicated in the mirroring of pupil size in sad facial expressions. When seeing a sad face, participants' pupils dilated or constricted to mirror the face they saw, which predicted both how sad they perceived the face to be, as well as activity within this region.

Eponym

The nucleus is named for both Ludwig Edinger, from

Frankfurt Frankfurt, officially Frankfurt am Main (; Hessian: , "Frank ford on the Main"), is the most populous city in the German state of Hesse. Its 791,000 inhabitants as of 2022 make it the fifth-most populous city in Germany. Located on its na ...

, who demonstrated it in the

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal deve ...

in 1885, and for

Karl Friedrich Otto Westphal Karl Friedrich Otto Westphal (23 March 1833, in Berlin – 27 January 1890, in Kreuzlingen) was a German psychiatrist from Berlin. He was the son of Otto Carl Friedrich Westphal (1800–1879) and Karoline Friederike Heine and the father of Alexa ...

, from

Berlin Berlin ( , ) is the capital and largest city of Germany by both area and population. Its 3.7 million inhabitants make it the European Union's most populous city, according to population within city limits. One of Germany's sixteen constitue ...

, who demonstrated it in the

adult An adult is a human or other animal that has reached full growth. In human context, the term ''adult'' has meanings associated with social and legal concepts. In contrast to a " minor", a legal adult is a person who has attained the age of major ...

in 1887.

Additional images

File:Gray696.png, The cranial nerve nuclei schematically represented; dorsal view. Motor nuclei in red; sensory in blue. File:Gray697.png, Nuclei of origin of cranial motor nerves schematically represented; lateral view. File:Gray698.png, Primary terminal nuclei of the afferent (sensory) cranial nerves schematically represented; lateral view.

References

External links

Diagram at Columbia
* * * {{DEFAULTSORT:Edinger-Westphal nucleus Cranial nerve nuclei Oculomotor nerve Midbrain