In the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

, the inferior salivatory nucleus is a cluster of neuron

Neuron

A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

s controlling the 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...

 input to the parotid gland

Parotid gland

The paired parotid glands are the largest of the salivary glands. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.-Location:The parotid glands...

. It is one of the components of the glossopharyngeal nerve

Glossopharyngeal nerve

The glossopharyngeal nerve is the ninth of twelve pairs of cranial nerves . It exits the brainstem out from the sides of the upper medulla, just rostral to the vagus nerve...

 (cranial nerve IX).

Location

Its precise location in humans has not yet been identified, but in other mammals it is located in the medulla

Medulla oblongata

The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...

 within the general visceral efferent cell column, superior to the nucleus ambiguus

Nucleus ambiguus

The nucleus ambiguus is a region of histologically disparate cells located just dorsal to the inferior olivary nucleus in the lateral portion of the upper medulla...

 and inferior to the superior salivatory nucleus.

Pathway

While still in the medulla, fibers of the inferior salivatory nucleus join with fibers of the gustatory nucleus

Gustatory nucleus

The gustatory nucleus is a component of the solitary nucleus. It is associated with the sense of taste.GABA is the primary inhibitory neurotransmitter.-See also:Inferior salivatory nucleus...

, nucleus ambiguus

Nucleus ambiguus

The nucleus ambiguus is a region of histologically disparate cells located just dorsal to the inferior olivary nucleus in the lateral portion of the upper medulla...

, and spinal nucleus of the trigeminal nerve

Trigeminal nerve

The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...

, and exit the medulla as the mixed glossopharyngeal nerve

Glossopharyngeal nerve

The glossopharyngeal nerve is the ninth of twelve pairs of cranial nerves . It exits the brainstem out from the sides of the upper medulla, just rostral to the vagus nerve...

 (cranial nerve IX). It sends fibers through the glossopharyngeal nerve's tympanic nerve

Tympanic nerve

The tympanic nerve is a branch of the glossopharyngeal nerve found near the ear.-Path:It arises from the petrous ganglion, and ascends to the tympanic cavity through a small canal, the fossula petrosa/tympanic canaliculus, on the under surface of the petrous portion of the temporal bone on the...

 and into the tympanic plexus

Tympanic plexus

In the tympanic cavity, the tympanic nerve divides into branches which form the tympanic plexus. This plexus is located on the surface of the promontory.This tympanic plexus gives off:* the lesser petrosal nerve...

. Exiting the plexus within the lesser petrosal nerve

Lesser petrosal nerve

The lesser petrosal nerve consists of parasympathetic fibres. It leaves the tympanic plexus to synapse in the otic ganglion, and eventually provide parasympathetic innervation to the parotid gland....

, these preganglionic fibers synapse with cells in the otic ganglion

Otic ganglion

The otic ganglion is a small, oval shaped, flattened parasympathetic ganglion of a reddish-gray color, located immediately below the foramen ovale in the infratemporal fossa. It gives innervation to the parotid gland for salivation....

, which send postganglionic fibers into the mandibular division

Mandibular nerve

The mandibular nerve is the largest of the three branches of the trigeminal nerve.-Roots:It is made up of two roots:* a large sensory root proceeding from the inferior angle of the trigeminal ganglion....

 of the trigeminal nerve

Trigeminal nerve

The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...

, then into the auriculotemporal nerve

Auriculotemporal nerve

The auriculotemporal nerve is a branch of the mandibular nerve that runs with the superficial temporal artery and vein, and provides sensory innervation to various regions on the side of the head.-Origin:...

, finally reaching their target, the parotid gland

Parotid gland

The paired parotid glands are the largest of the salivary glands. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.-Location:The parotid glands...

.

Function

Parasympathetic input from fibers of the inferior salivatory nucleus stimulates the parotid gland to vasodilate

Vasodilation

Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...

 and secrete saliva

Saliva

Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

.

External links

• http://sprojects.mmi.mcgill.ca/cns/histo/systems/cranialnerves/main.htm