Inferior olivary nucleus
Encyclopedia
The inferior olivary nucleus is the largest nucleus situated in the olivary body
, part of the medulla oblongata
.
, meaning that it is involved in control and coordination of movements, sensory processing and cognitive tasks likely by encoding the timing of sensory input independently of attention or awareness .
There is some evidence that it is stimulated by ghrelin
.
.
Olivocerebellar fibers are neurons that have their cell bodies in the inferior olivary nucleus. Their axons leave medially through the hilum, cross the midline, and ascend into the cerebellum via the inferior cerebellar peduncle
. Once they enter the cerebellum, they are referred to as the climbing fibers. Finally, they terminate by synapsing in the cerebellar cortex, including the cortex of the vermis
, paramedian lobule, and the cerebellar hemispheres
.
The fibers leaving the inferior olivary nucleus at the hilum may be referred to as the "peduncle" of the olive. They cross with those from the opposite olive in the raphe
. After the raphe, they may be referred to as the internal arcuate fibers
.
The fibers are smaller than the internal arcuate fibers connected with the medial lemniscus
.
Fibers passing in the opposite direction from the cerebellum
to the olivary nucleus are often described as the CTT, but their existence is doubtful.
Much uncertainty exists also with regard to the connections of the olive and the spinal cord
.
Important connections between the cerebrum
and the olive of the same side exist, but the exact pathway is unknown.
Many collaterals from the reticular formation and from the pyramids enter the inferior olivary nucleus.
Removal of one cerebellar hemisphere is followed by atrophy of the opposite olivary nucleus.
Olivary body
In anatomy, the olivary bodies or simply olives are a pair of prominent oval structures in the medulla oblongata, the lower portion of the brainstem...
, part of the medulla oblongata
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...
.
Function
It is closely associated with the cerebellumCerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
, meaning that it is involved in control and coordination of movements, sensory processing and cognitive tasks likely by encoding the timing of sensory input independently of attention or awareness .
There is some evidence that it is stimulated by ghrelin
Ghrelin
Ghrelin is a 28 amino acid peptide and hormone that is produced mainly by P/D1 cells lining the fundus of the human stomach and epsilon cells of the pancreas that stimulates hunger. Ghrelin levels increase before meals and decrease after meals. It is considered the counterpart of the hormone...
.
Anatomy
It consists of a gray folded lamina arranged in the form of an incomplete capsule, opening medially by an aperture called the hilumHilum (anatomy)
In human anatomy, the hilum is a depression or fissure where structures such as blood vessels and nerves enter an organ.-Examples of hila:* Hilum of kidney, admits the renal artery, vein, ureter, and nerves...
.
Olivocerebellar fibers are neurons that have their cell bodies in the inferior olivary nucleus. Their axons leave medially through the hilum, cross the midline, and ascend into the cerebellum via the inferior cerebellar peduncle
Inferior cerebellar peduncle
The upper part of the posterior district of the medulla oblongata is occupied by the inferior cerebellar peduncle , a thick rope-like strand situated between the lower part of the fourth ventricle and the roots of the glossopharyngeal and vagus nerves.Each cerebellar inferior peduncle connects the...
. Once they enter the cerebellum, they are referred to as the climbing fibers. Finally, they terminate by synapsing in the cerebellar cortex, including the cortex of the vermis
Cerebellar vermis
The cerebellar vermis is located in the medial, cortico-nuclear zone of the cerebellum, residing in the posterior fossa of the cranium. The primary fissure in the vermis curves ventrolaterally to the superior surface of the cerebellum, dividing it into anterior and posterior lobes....
, paramedian lobule, and the cerebellar hemispheres
Cerebellar hemisphere
The cerebellum consists of three parts, a median and two lateral, which are continuous with each other, and are substantially the same in structure. The median portion is constricted, and is called the vermis, from its annulated appearance which it owes to the transverse ridges and furrows upon it;...
.
The fibers leaving the inferior olivary nucleus at the hilum may be referred to as the "peduncle" of the olive. They cross with those from the opposite olive in the raphe
Raphe
Raphe has several different meanings in science. Pronounced .In botany and planktology it is commonly used when describing a seam or ridge on diatoms or seeds....
. After the raphe, they may be referred to as the internal arcuate fibers
Internal arcuate fibers
Internal arcuate fibers are the axons of second-order neurons contained within the gracile and cuneate nuclei of the medulla oblongata.These fibers cross from one side of the medulla to the other to form the medial lemniscus....
.
The fibers are smaller than the internal arcuate fibers connected with the medial lemniscus
Medial lemniscus
The medial lemniscus, also known as Reil's band or Reil's ribbon, is a pathway in the brainstem that carries sensory information from the gracile and cuneate nuclei to the thalamus.-Path:...
.
Fibers passing in the opposite direction from the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
to the olivary nucleus are often described as the CTT, but their existence is doubtful.
Much uncertainty exists also with regard to the connections of the olive and 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...
.
Important connections between the cerebrum
Telencephalon
The cerebrum or telencephalon, together with the diencephalon, constitutes the forebrain. The cerebrum is the most anterior region of the vertebrate central nervous system. Telencephalon refers to the embryonic structure, from which the mature cerebrum develops...
and the olive of the same side exist, but the exact pathway is unknown.
Many collaterals from the reticular formation and from the pyramids enter the inferior olivary nucleus.
Removal of one cerebellar hemisphere is followed by atrophy of the opposite olivary nucleus.