Edinger-Westphal nucleus
The Edinger-Westphal nucleus is the accessory parasympathetic
Parasympathetic nervous system
The parasympathetic nervous system is one of the two main divisions of the autonomic nervous system . The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously...

 cranial nerve nucleus
Cranial nerve nucleus
A cranial nerve nucleus is a collection of neurons in the brain stem that is associated with one or more cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei. Lesions occurring at these nuclei can lead to effects resembling those seen by...

 of the oculomotor nerve
Oculomotor nerve
The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...

 (cranial nerve III), supplying the constricting muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s of the iris
Iris (anatomy)
The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina. "Eye color" is the color of the iris, which can be green, blue, or brown. In some cases it can be hazel , grey, violet, or even pink...

. Alternatively, the Edinger-Westphal nucleus is a term often used to refer to the adjacent population of non-preganglionic neurons that do not project to the ciliary ganglion
Ciliary ganglion
The ciliary ganglion is a parasympathetic ganglion located in the posterior orbit. It measures 1–2 millimeters in diameter and contains approximately 2,500 neurons. Preganglionic axons from the Edinger-Westphal nucleus travel along the oculomotor nerve and form synapses with these cells...

, but rather project to the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

, dorsal raphe nucleus, and lateral septal nuclei
Septal nuclei
The septal area are structures that lie below the rostrum of corpus callosum in front of lamina terminalis , composed of medium-size neurons grouped into medial, lateral, and posterior groups...


Unlike the classical preganglionic Edinger-Westphal neurons that contain choline acetyltransferase
Choline acetyltransferase
Choline acetyltransferase is an enzyme that is synthesized within the body of a neuron. It is then transferred to the nerve terminal via axoplasmic flow. The role of choline acetyltransferase is to join Acetyl-CoA to choline, resulting in the formation of the neurotransmitter acetylcholine...

, neurons of the non-preganglionic Edinger-Westphal nucleus contain various neuropeptides, such as Urocortin
Urocortin is a protein that in humans is encoded by the UCN gene.Urocortin is a potent anorexigenic peptide of 40 amino acids that induces fed-like motor activity when administered centrally or peripherally in fasted animals. Urocortin belongs to the corticotropin-releasing factor family that...

 and cocaine- and amphetamine-regulated transcript
Cocaine- and amphetamine-regulated transcript
Cocaine and amphetamine regulated transcript also known as CART is a 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 endogenous psychostimulant.- Function :CART is a neuropeptide that also...


Previously, it had been proposed to rename this group of non-preganglionic, neuropeptide-containing neurons to perioculomotor subgriseal neuronal stream, abbreviated pIIISG.

However, more recently, a final nomenclature has been determined. Preganglionic oculomotor neurons within the Edinger-Westphal nucleus shall be referred to as the EWpg, and the neuropeptide-containing neurons shall be known as the centrally-projecting Edinger Westphal nucleus, or EWcp.


The paired nuclei are posterior to the main motor nucleus (oculomotor 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...

) and anterolateral to the cerebral aqueduct
Cerebral aqueduct
The mesencephalic duct, also known as the aqueductus mesencephali, aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid , is within the mesencephalon and connects the third ventricle in the diencephalon to the fourth ventricle in the mesencephalon, which is between the pons...

 in the rostral midbrain at the level of the superior colliculus
Superior colliculus
The optic tectum or simply tectum is a paired structure that forms a major component of the vertebrate midbrain. In mammals this structure is more commonly called the superior colliculus , but, even in mammals, the adjective tectal is commonly used. The tectum is a layered structure, with a...


It is the most rostral of the parasympathetic nuclei in the brain stem
Brain stem
In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...



The Edinger-Westphal nucleus supplies preganglionic parasympathetic fibers to the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

, constricting
Constriction is a method used by various snake species to kill their prey. Although some species of venomous and mildly-venomous snakes do use constriction to subdue their prey, most snakes which use constriction lack venom. The snake initially strikes at its prey and holds on, pulling the prey...

 the pupil
The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In...

, accommodating
Accommodation reflex
The accommodation reflex is a reflex action of the eye, in response to focusing on a near object, then looking at distant object , comprising coordinated changes in vergence, lens shape and pupil size...

 the lens
Lens (anatomy)
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...

, and convergence of the eyes.

It has also been implicated in the mirroring
Mirror neuron
A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron "mirrors" the behaviour of the other, as though the observer were itself acting. Such neurons have been directly observed in primate and other...

 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.


The nucleus is named for both Ludwig Edinger
Ludwig Edinger
Ludwig Edinger was an influential German anatomist and neurologist and co-founder of the University of Frankfurt. In 1914 he was also appointed the first German professor of neurology....

, from Frankfurt
Frankfurt am Main , commonly known simply as Frankfurt, is the largest city in the German state of Hesse and the fifth-largest city in Germany, with a 2010 population of 688,249. The urban area had an estimated population of 2,300,000 in 2010...

, who demonstrated it in the fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 in 1885, and for Karl Friedrich Otto Westphal, from Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...

, who demonstrated it in the adult
An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age....

in 1887.

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