Solitary nucleus
Encyclopedia
The solitary tract and nucleus are structures in the brainstem that carry and receive visceral sensation and taste
from the facial
(VII), glossopharyngeal
(IX) and vagus
(X) cranial nerves
.
). The solitary tract runs in the middle of the nucleus, creating a speck of white matter
(axons of the tract), surrounded by grey matter
(the nucleus). This stands out on a stained section, which is where the name solitary comes from.
The NTS is divided into a rostral gustatory nucleus
and caudal region of neurons. Sub regions of the NTS can be related to the distribution of inputs - particularly contacts from cranial primary afferent neurons (see below) related to cardiovascular, respiratory and gastrointestinal functions. There is some degree of localization within the caudal region so that many cardiovascular neurons sit near the midline of the nucleus, and many respiratory related neurons are located laterally within the nucleus.
(via IX) and aortic bodies
(via X) as well as stretch receptors from the aorta and carotid arteries called arterial baroreceptors. In addition, chemically and mechanically sensitive neurons with endings located in the heart, lungs, airways, gastrointestinal system, liver and other viscera send axons via cranial nerves (IX and X) chiefly that directly enter the brainstem to form synapses within the caudal two-thirds of the NTS. Neurons that synapse in this nucleus mediate the gag reflex, the carotid sinus reflex, the aortic reflex, the cough reflex, the baroreceptor and chemoreceptor reflexes, several respiratory reflexes and reflexes within the gastrointestinal system regulating motility and secretion. Information about the gut wall, as well as stretch of the lungs and dryness of mucous membrane
s, also synapse
s at the NTS. These first central neurons within the NTS can participate in autonomic reflexes that may be as simple as two central neurons with the second neuron being an efferent or motor neuron that projects back directly to the organ such as the heart forming some of the simplest reflex pathways in the brain.
and the central nucleus of the amygdala
, as well as to other nuclei in the brainstem (such as the parabrachial area and other visceral motor or respiratory networks).
Taste
Taste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....
from the facial
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
(VII), glossopharyngeal
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...
(IX) and vagus
Vagus nerve
The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...
(X) cranial nerves
Cranial nerves
Cranial nerves are nerves that emerge directly from the brain, in contrast to spinal nerves, which emerge from segments of the spinal cord. In humans, there are traditionally twelve pairs of cranial nerves...
.
Anatomy
The nucleus of the solitary tract, or NTS , is located along the length of the medulla oblongata (with a small portion in the lower ponsPons
The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
). The solitary tract runs in the middle of the nucleus, creating a speck of white matter
White matter
White matter is one of the two components of the central nervous system and consists mostly of myelinated axons. White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color is due to...
(axons of the tract), surrounded by grey matter
Grey matter
Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil , glial cells and capillaries. Grey matter contains neural cell bodies, in contrast to white matter, which does not and mostly contains myelinated axon tracts...
(the nucleus). This stands out on a stained section, which is where the name solitary comes from.
The NTS is divided into a rostral 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...
and caudal region of neurons. Sub regions of the NTS can be related to the distribution of inputs - particularly contacts from cranial primary afferent neurons (see below) related to cardiovascular, respiratory and gastrointestinal functions. There is some degree of localization within the caudal region so that many cardiovascular neurons sit near the midline of the nucleus, and many respiratory related neurons are located laterally within the nucleus.
Inputs to the NTS
In addition to afferent taste information from nerves VII, IX and X, the NTS also handles primary afferent signals from a variety of visceral regions and organs. These afferents include chemoreceptors in the carotidCarotid body
The carotid body is a small cluster of chemoreceptors and supporting cells located near the fork of the carotid artery ....
(via IX) and aortic bodies
Aortic body
In the human heart, the aortic body is one of several small clusters of chemoreceptors, baroreceptors, and supporting cells located along the aortic arch.-Function:...
(via X) as well as stretch receptors from the aorta and carotid arteries called arterial baroreceptors. In addition, chemically and mechanically sensitive neurons with endings located in the heart, lungs, airways, gastrointestinal system, liver and other viscera send axons via cranial nerves (IX and X) chiefly that directly enter the brainstem to form synapses within the caudal two-thirds of the NTS. Neurons that synapse in this nucleus mediate the gag reflex, the carotid sinus reflex, the aortic reflex, the cough reflex, the baroreceptor and chemoreceptor reflexes, several respiratory reflexes and reflexes within the gastrointestinal system regulating motility and secretion. Information about the gut wall, as well as stretch of the lungs and dryness of mucous membrane
Mucous membrane
The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...
s, also synapse
Synapse
In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...
s at the NTS. These first central neurons within the NTS can participate in autonomic reflexes that may be as simple as two central neurons with the second neuron being an efferent or motor neuron that projects back directly to the organ such as the heart forming some of the simplest reflex pathways in the brain.
Outputs from the NTS
Information goes from the NTS to a large number of other regions of the brain including the paraventricular nucleus of the hypothalamusHypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
and the central nucleus of the amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
, as well as to other nuclei in the brainstem (such as the parabrachial area and other visceral motor or respiratory networks).