In the human brainstem, the solitary nucleus, also called nucleus of the solitary tract, nucleus solitarius, and nucleus tractus solitarii, (SN or NTS) is a series of purely sensory
nuclei (clusters of nerve cell bodies) forming a vertical column of
grey matter embedded in the
medulla oblongata
The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involun ...
. Through the center of the SN runs the
solitary tract, a white bundle of nerve fibers, including fibers from the
facial,
glossopharyngeal and
vagus nerves, that
innervate
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
the SN. The SN projects to, among other regions, the
reticular formation
The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of the reticular formation ...
,
parasympathetic preganglionic neurons,
hypothalamus and
thalamus, forming circuits that contribute to autonomic regulation. Cells along the length of the SN are arranged roughly in accordance with function; for instance, cells involved in taste are located in the rostral part, while those receiving information from cardio-respiratory and gastrointestinal processes are found in the caudal part.
Inputs
* Taste information from the
facial nerve via the
chorda tympani (anterior 2/3 of the tongue), glossopharyngeal nerve (posterior 1/3) and vagus nerve (small area on the epiglottis)
* Chemoreceptors and mechanoreceptors of the general visceral afferent pathway (GVA) in the
carotid body via glossopharyngeal nerve,
aortic bodies
The aortic bodies are one of several small clusters of peripheral chemoreceptors located along the aortic arch. They are important in measuring partial pressures of oxygen and carbon dioxide in the blood, and blood pH.
Structure
The aortic bodies ...
, and the
sinoatrial node, via the vagus nerve
* Chemically and mechanically sensitive neurons of the general visceral afferent pathway (GVA) with endings located in the heart, lungs, airways, gastrointestinal system, pharynx, and liver via the glossopharyngeal and vagus nerves. Organ specific regions of neuronal architecture are preserved in the solitary nucleus. Additional minor GVA input from the nasal cavity, soft palate and sinus cavities enters via the facial nerve.
Neurons that
innervate
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
the SN 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.
Neurons which transmit signals about the gut wall, the stretch of the
lungs, and the dryness of
mucous membranes also innervate the SN. The first central neurons within the SN can participate in simple autonomic reflexes.
Outputs
Information goes from the solitary nucleus to a large number of other regions of the brain including the
paraventricular nucleus of the
hypothalamus 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 ...
, as well as to other nuclei in the brainstem (such as the
parabrachial area
The parabrachial nuclei, also known as the parabrachial complex, are a group of nuclei in the dorsolateral pons that surrounds the superior cerebellar peduncle as it enters the brainstem from the cerebellum. They are named from the Latin term fo ...
, 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 ...
, the
dorsal raphe nucleus, and other visceral motor or respiratory networks). The signals projected from the SN to the parabrachial area originate in the oral cavity and gastrointestinal tract. The pathways for gastric and gustatory (taste) processes are believed to terminate in different subdivisions of the parabrachial area, but still interact in the SN. Some neuronal subpopulations in the SN, such as the
noradrenergic cell group A2 and the
aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...
-sensitive
HSD2 neurons
HSD2 neurons are a small group of neurons in the brainstem which are uniquely sensitive to the mineralocorticosteroid hormone aldosterone, through expression of HSD11B2. They are located within the caudal medulla oblongata, in the nucleus of ...
project as far ventral as the
bed nucleus of the stria terminalis.
Additional images
File:Gray694.png, Section of the medulla oblongata at about the middle of the olive.
File:Gray698.png, Primary terminal nuclei of the afferent (sensory) cranial nerves schematically represented; lateral view.
See also
*
Solitary tract
References
External links
*
{{Authority control
Cranial nerve nuclei
Medulla oblongata
Vagus nerve
Glossopharyngeal nerve
Facial nerve