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Brain: Inferior olivary nucleus
Microcircuitry of the cerebellum. Excitatory synapses are denoted by (+) and inhibitory synapses by (-). MF: Mossy fiber. DCN: Deep cerebellar nuclei. IO: Inferior olive. CF: Climbing fiber. GC: Granule cell. PF: Parallel fiber. PC: Purkinje cell. GgC: Golgi cell. SC: Stellate cell. BC: Basket cell.
Transverse section of medulla oblongata below the middle of the olive. (Inferior olivary nucleus labeled at center right.)
Gray's	subject #187 781
Part of	Olivary body
NeuroNames	hier-696
MeSH	Olivary+Nucleus

The inferior olivary nucleus is the largest nucleus situated in the olivary body, part of the medulla oblongata.

It consists of a gray folded lamina arranged in the form of an incomplete capsule, opening medially by an aperture called the hilum.

Emerging from the hilum are numerous fibers which collectively constitute the peduncle of the olive. The axons, also known as olivocerebellar fibers, leave the olivary nucleus, exit through the hilum, and decussate with those from the opposite olive in the raphé.

Then, as internal arcuate fibers they pass partly through and partly around the opposite olive and enter the inferior peduncle to be distributed to the cerebellar hemisphere of the opposite side from which they arise.

The fibers are smaller than the internal arcuate fibers connected with the median lemniscus.

Fibers passing in the opposite direction from the cerebellum to the olivary nucleus are often described but their existence is doubtful.

Much uncertainty also exists in 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.

Section of the medulla oblongata at about the middle of the olive.

Diagram showing the course of the arcuate fibers.

Sagittal section through right cerebellar hemisphere. The right olive has also been cut sagitally.

• Neuroanatomy at UW Bs97/TEXT/P6/overview.htm

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.

v • d • e Brain: rhombencephalon (hindbrain)
Myelencephalon/medulla	Arcuate nucleus of medulla, Solitary nucleus, Hypoglossal nucleus, Nucleus ambiguus, Olivary body, Inferior olivary nucleus, Cuneate nucleus, Accessory cuneate nucleus, Gracile nucleus, Inferior salivatory nucleus, Raphe nuclei (Obscurus, Magnus, Pallidus), Area postrema, Posterior nucleus of vagus nerve, Reticular formation (Gigantocellular nucleus, Parvocellular reticular nucleus, Ventral reticular nucleus, Lateral reticular nucleus, Paramedian reticular nucleus), Pyramid (Decussation)
Metencephalon/cerebellum	Vermis, Flocculus, Arbor vitae
Metencephalon/pons	Pontine tegmentum, Superior salivary nucleus, Trapezoid body, Pontine nuclei (Superior olivary nucleus, Trigeminal nerve nuclei, Abducens nucleus, Facial motor nucleus, Cochlear nuclei, Vestibular nuclei), Locus ceruleus, Paramedian pontine reticular formation, Median raphe nucleus - Reticular formation (Caudal pontine reticular nucleus, Oral pontine reticular nucleus, Tegmental pontine reticular nucleus)
Fourth ventricle	Obex, Median aperture