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Midbrain
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Midbrain
Inferior view midbrain (2), above (3)
Human brainstem Midbrain (B)
Thalamus (A) Pons (C)
Medulla oblongata (D)
Details
Identifiers
Latin
mesencephalon
MeSH
A08.186.211.132.659
NeuroNames
hier-445
NeuroLex ID
Midbrain
TA
A14.1.03.005
FMA
61993
Anatomical terms of neuroanatomy
[edit on Wikidata]
The midbrain or mesencephalon (from the Greek mesos, middle, and enkephalos, brain[1]) is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.[2]
Contents
[hide]
1 Structure
1.1 Corpora quadrigemina
1.2 Cerebral peduncle
1.3 Anatomical features of cross-sections through the midbrain
1.4 Development
2 Function
3 See also
4 References
Structure[edit]
The midbrain comprises the tectum, tegmentum, the cerebral aqueduct, and the cerebral peduncles, as well as several nuclei and fasciculi. Caudally the midbrain adjoins the metencephalon (afterbrain) (pons and cerebellum); while rostrally it adjoins the diencephalon (thalamus, hypothalamus, etc.)[3]
Specifically, the midbrain consists of:
tectum
inferior colliculi
superior colliculi
cerebral peduncle
midbrain tegmentum
crus cerebri
substantia nigra
Brain Anatomy - Mid-fore-hindbrain.
Corpora quadrigemina[edit]
Main article: Corpora quadrigemina
The corpora quadrigemina ("quadruplet bodies") are four solid lobes on the dorsal side of the cerebral aqueduct, where the superior posterior pair are called the superior colliculi and the inferior posterior pair are called the inferior colliculi. The homologous structures are called optic lobes in some lower vertebrates (fishes and amphibians) where they integrate sensory information from the eyes and certain auditory reflexes.[4][5]
The four solid lobes help to decussate several fibres of the optic nerve. However, some fibers also show ipsilateral arrangement (i.e., they run parallel on the same side without decussating.)
The superior colliculus is involved with saccadic eye movements; while the inferior is a synapsing point for sound information. The trochlear nerve comes out of the posterior surface of the midbrain, below the inferior colliculus.
Cerebral peduncle[edit]
Main article: cerebral peduncles
The cerebral peduncles are paired structures, present on the ventral side of the cerebral aqueduct, and they further carry tegmentum on the dorsal side and cresta or pes on the ventral side, and both of them accommodate the corticospinal tract fibres, from the internal capsule (i.e., ascending + descending tracts = longitudinal tract.) the middle part of cerebral peduncles carry substantia nigra[citation needed] (literally "Black Matter"), which is a type of basal nucleus. It is the only part of the brain that carries melanin pigment.
Between the peduncles is the interpeduncular fossa, which is a cistern filled with cerebrospinal fluid.[citation needed] The oculomotor nerve comes out between the peduncles, and the trochlear nerve is visible wrapping around the outside of the peduncles. The oculomotor is responsible for pupil constriction (parasympathetic) and certain eye movements.[6]
Anatomical features of cross-sections through the midbrain[edit]
Cross-section of the midbrain at the level of the superior colliculus.
Cross-section of the midbrain at the level of the inferior colliculus.
The midbrain is usually sectioned at the level of the superior and inferior colliculi.
Mesencephalon of human embryo
A horizontal (transverse) cross-section at the level of the superior colliculus shows the red nucleus, the nuclei of the oculomotor nerve (and associated Edinger-Westphal nucleus), the cerebral peduncles or crus cerebri, and the substantia nigra.[7]
A horizontal (transverse) cross-section at the level of the inferior colliculus still shows the substantia nigra. Also apparent are the trochlear nerve nucleus, and the decussation of the superior cerebellar peduncles.[7]
Both sections will show the cerebral aqueduct, which connects the third and fourth ventricle and the periaqueductal gray.[7]
One mnemonic for remembering the structures of the midbrain involves visualizing the mesencephalic cross-section as an upside down bear face. The two red nuclei are the eyes of the bear and the cerebral crura are the ears. The tectum is the chin and the cerebral peduncles are the face and ears.
Development[edit]
During embryonic development, the midbrain arises from the second vesicle, also known as the mesencephalon, of the neural tube. Unlike the other two vesicles, the forebrain and hindbrain, the midbrain remains undivided for the remainder of neural development. It does not split into other brain areas. while the forebrain, for example, divides into the telencephalon and the diencephalon.[8]
Throughout embryonic development, the cells within the midbrain continually multiply and compress the still-forming cerebral aqueduct. Partial or total obstruction of the cerebral aqueduct during development can lead to congenital hydrocephalus.[9]
Function[edit]
The mesencephalon is considered part of the brainstem. Its substantia nigra is closely associated with motor system pathways of the basal ganglia. The human mesencephalon is archipallian in origin, meaning that its general architecture is shared with the most ancient of vertebrates. Dopamine produced in the substantia nigra and ventral tegmental area plays a role in excitation, motivation and habituation of species from humans to the most elementary animals such as insects. Laboratory house mice from lines that have been selectively bred for high voluntary wheel running have enlarged midbrains.[10] The midbrain helps to relay information for vision and hearing.
See also[edit]
Wikimedia Commons has media related to Mesencephalon.
Look up midbrain in Wiktionary, the free dictionary.
list of regions in the human brain
References[edit]
Jump up ^ Mosby's Medical, Nursing & Allied Health Dictionary,≈ Fourth Edition, Mosby-Year Book 1994, p. 981
Jump up ^ Breedlove, Watson, & Rosenzweig. Biological Psychology, 6th Edition, 2010, pp. 45-46
Jump up ^ http://www.morris.umn.edu/~ratliffj/images/brain_slides/slide_5.htm
Jump up ^ Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
Jump up ^ Ferrier, David (1886). "Functions of the optic lobes or corpora quadrigemina". doi:10.1037/12789-005.
Jump up ^ Haines, Duane E. Neuroanatomy : an atlas of structures, sections, and systems (8th ed.). Philadelphia: Wolters Kluwer/ Lippincott Williams & Wilkins Health. p. 42. ISBN 978-1-60547-653-7.
^ Jump up to: a b c Martin. Neuroanatomy Text and Atlas, Second edition. 1996, pp. 522-525.
Jump up ^ Martin. Neuroanatomy Text and Atlas, Second Edition, 1996, pp. 35-36.
Jump up ^ "Hydrocephalus Fact Sheet". National Institute of Neurological Disorders and Stroke. February 2008. Retrieved 2011-03-23.
Jump up ^ Kolb, E. M., E. L. Rezende, L. Holness, A. Radtke, S. K. Lee, A. Obenaus, and Garland T, Jr. 2013. Mice selectively bred for high voluntary wheel running have larger midbrains: support for the mosaic model of brain evolution. Journal of Experimental Biology 216:515-523.
[show]
v
t
e
Nervous system
Central nervous system
Meninges
Spinal cord
Brain
Rhombencephalon
Medulla
Pons
Cerebellum
Midbrain
Forebrain
Diencephalon
Retina
Optic nerve
Cerebrum
Limbic system
Peripheral nervous system
Somatic
Sensory nerve
Motor nerve
Cranial nerve
Spinal nerve
Autonomic
Sympathetic
Parasympathetic
Enteric
[show]
v
t
e
Anatomy of the midbrain
Tectum
(Dorsal)
Surface
Corpora quadrigemina:
Inferior colliculus
Brachium
Superior colliculus
Brachium
Grey matter
Pretectal area
White: Sensory/ascending
Spinotectal tract
Central tegmental tract
White: Motor/descending
Tectospinal tract
Peduncle
(Ventral)
Tegmentum
White: Sensory/ascending
Lemnisci
Medial
Lateral
Ascending MLF
Vestibulo-oculomotor fibers
Spinothalamic tract
Anterior trigeminothalamic tract
Dentatothalamic tract
White: Motor/descending
Rubrospinal tract
Rubro-olivary tract
Descending MLF
Grey: cranial nuclei
GSA
Mesencephalic- GSE
Oculomotor nucleus, Trochlear nucleus- GVE
Edinger–Westphal nucleus
Grey: other
Periaqueductal gray
Raphe nuclei
dorsal
Ventral tegmental area
Rostromedial tegmental nucleus
Pedunculopontine nucleus
Red nucleus
Rostral interstitial nucleus of medial longitudinal fasciculus
Parabrachial area
Interpeduncular nucleus
Midbrain reticular formation
Ventricular system
Cerebral aqueduct
Base
White: Motor/descending
Cerebral crus: Corticospinal tract
Corticobulbar tract
Corticopontine tract/Frontopontine fibers/Temporopontine fibers
Grey: Substantia nigra
Pars compacta
Pars reticulata
Surface
Superior cerebellar peduncle
Decussation
Interpeduncular fossa
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