| 脳: 中脳 |
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脳の矢状断。水色が中脳。
脳内での中脳の位置。赤で示す領域が中脳。左図は側面から、右図は正面から見たとき。
上丘を通過する水平断面における中脳の模式図。
|
| 名称 |
| 日本語 |
中脳 |
| 英語 |
midbrain |
| ラテン語 |
mesencephalon |
| 略号 |
MBr, MB |
| 関連構造 |
| 上位構造 |
脳幹 |
| 構成要素 |
被蓋、上丘、下丘、黒質、赤核、大脳脚 |
| 画像 |
| アナトモグラフィー |
三次元CG |
| Digital Anatomist |
内側
下方
下方
冠状断
大脳鎌
小脳テント
矢状断 |
| 関連情報 |
| Brede Database |
階層関係、座標情報 |
| NeuroNames |
関連情報一覧 |
| NIF |
総合検索 |
| MeSH |
Mesencephalon |
| グレイの解剖学 |
書籍中の説明（英語） |
| テンプレートを表示 |
中脳（ちゅうのう、英: midbrain, mesencephalon）は、脳の一部。狭義の脳幹（下位脳幹）のうち、もっとも上の部分であって、さらに上には第三脳室、下には橋、両外側には間脳がある。なめらかな動きを可能にする錐体外路性運動系の重要な中継所を含むほか、対光反射、視聴覚の中継所、眼球運動反射、姿勢反射（立ち直り反射）、γ運動ニューロン活動抑制、歩行リズムの中枢をも含む。
目次
- 1 解剖
- 2 機能
- 3 画像
- 4 参考文献
- 5 外部リンク
解剖
中脳の前面は大脳脚と呼ばれる一対の隆起である。大脳脚は橋の底部に続き、錐体路をなす線維が入っている。大脳脚の付け根に当たる部分は黒質と呼ばれるメラニンの多い層になっている。後面には四丘体と呼ばれる2対の隆起があり、それらのうち上の1対は上丘、下の1対は下丘と呼ばれる。上丘の中には数層の浅灰白層、下丘の中には下丘核と呼ばれる灰白質が入っている。四丘体のある部分を中脳蓋と呼ぶ。中脳蓋のすぐ前、中脳の内部のほぼ正中には中脳水道(シルビウス孔)と呼ばれる穴が開いている。中脳水道は神経管の内腔に由来し、上の第三脳室と下の第四脳室をつなぎ、脳脊髄液の通り道になっている。中脳水道の周りは中脳水道周囲灰白質（中心灰白質）に囲まれている。中脳水道周囲灰白質のすぐ前に、動眼神経核とエディンガー・ウェストファル核（動眼神経副核）がある。中脳蓋と黒質の間にある部分を被蓋と呼ぶ。なお、上で述べた意味での大脳脚（crus cerebri）と被蓋を合わせて大脳脚（pedunculus cerebri）と呼ぶことがある。被蓋には外側に内側毛帯があるほか、内側の下部には上小脳交叉（ウェルネキンク）、上部には赤核と呼ばれる鉄の多い核がある。橋との境目あたりには滑車神経核がある。
機能
上丘
上丘は、鳥類などでは視覚に重要な役割を果たしているが、ヒトでは視覚反射の中継所でしかない。視覚と関係するので視蓋とも呼ばれる。目に光が入ったときに瞳孔を収縮させる対光反射、見ている物が近づいたときにレンズを厚くしてピントを合わせる調節反射、それと同時に視線を内側に寄せる輻輳反射に関わる。
下丘
下丘は聴覚の重要な中継所である。耳から入った音の信号は蝸牛神経を通って蝸牛神経核で中継され、交叉した後外側毛帯となって下丘に入る。下丘から出た線維は下丘腕を通って内側膝状体へ送られ、中継された後聴放線を作って大脳皮質に送られる。
- 大脳脚、黒質、赤核の機能については運動系を参照。
- 滑車神経については独立した項を参照。
画像
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中脳の位置を様々な方向から見た動画。中脳を赤で、それ以外の部位を半透明にして示してある。（出典：Anatomography）
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下丘の高さでの中脳の断面。図の上が背側。Crusta：大脳脚、Subst. Nigra：黒質、Inferior colliculi：下丘、Central Grey matter：中心灰白質、Cerebral aqueduct：中脳水道、Nucleus of oculomotor nerve：動眼神経核、Medial lemniscus：内側毛帯
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脊椎動物胎仔の脳の主要構造を示す図。これらの領域は前脳（Procencephalon）、中脳（Mecencephalon）、および菱脳（Rhombencephalon）へと分化する。
参考文献
- Werner Kahle、長島聖司・岩堀修明訳『分冊 解剖学アトラスIII 第5版』（文光堂、ISBN 4-8306-0026-8）
外部リンク
|
ウィキメディア・コモンズには、中脳に関連するカテゴリがあります。 |
- 中脳 - 慶應医学部解剖学教室 船戸和弥
- 下丘 - 脳科学辞典
| Midbrain |
|
Inferior view midbrain (2), above (3)
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Human brainstem midbrain (B)
Forebrain (A) Hindbrain (C)
Spinal cord (D) |
| Details |
| Latin |
mesencephalon |
| Identifiers |
| Gray's |
p.800 |
| MeSH |
A08.186.211.132.659 |
| NeuroNames |
hier-445 |
| NeuroLex ID |
Midbrain |
| TA |
A14.1.03.005 |
| FMA |
61993 |
| Anatomical terms of neuroanatomy |
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
- 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 Clinical significance
- 4 See also
- 5 References
Structure
The midbrain comprises the tectum (or corpora quadrigemina), tegmentum, the cerebral aqueduct (or ventricular mesocoelia or "iter"), 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.). The midbrain is located below the cerebral cortex, and above the hindbrain placing it near the center of the brain.[3]
Specifically, the midbrain consists of:
- tectum
- inferior colliculi
- superior colliculi
- cerebral peduncle
- midbrain tegmentum
- crus cerebri
- substantia nigra
Corpora quadrigemina
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 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
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 (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. 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.[4]
Anatomical features of cross-sections through the midbrain
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.[5]
- 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.[6]
- 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
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 Aqueduct of Sylvius or cerebral aqueduct. Partial or total obstruction of the cerebral aqueduct during development can lead to congenital hydrocephalus.[9]
Function
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 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.
Clinical significance
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This section requires expansion. (February 2014) |
See also
|
Wikimedia Commons has media related to Mesencephalon. |
|
Look up midbrain in Wiktionary, the free dictionary. |
- list of regions in the human brain
References
- ^ Mosby's Medical, Nursing & Allied Health Dictionary, Fourth Edition, Mosby-Year Book 1994, p. 981
- ^ Breedlove, Watson, & Rosenzweig. Biological Psychology, 6th Edition, 2010, pp. 45-46
- ^ http://www.morris.umn.edu/~ratliffj/images/brain_slides/slide_5.htm
- ^ Haines, Duane E. Neuroanatomy : an atlas of structures, sections, and systems (8th ed. ed.). Philadelphia: Wolters Kluwer/ Lippincott Williams & Wilkins Health. p. 42. ISBN 978-1-60547-653-7.
- ^ Martin. Neuroanatomy Text and Atlas, Second edition. 1996, pp. 522-525.
- ^ Martin. Neuroanatomy Text and Atlas, Second edition. 1996, pp. 522-525.
- ^ Martin. Neuroanatomy Text and Atlas, Second edition. 1996, pp. 522-525.
- ^ Martin. Neuroanatomy Text and Atlas, Second Edition, 1996, pp. 35-36.
- ^ "Hydrocephalus Fact Sheet". National Institute of Neurological Disorders and Stroke. February 2008. Retrieved 2011-03-23.
- ^ 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.
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Nervous system
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|
| Central nervous system |
- Meninges
- Spinal cord
- Brain
- Rhombencephalon
- Midbrain
- Prosencephalon
|
|
| Peripheral nervous system |
| Somatic |
- Sensory nerve
- Motor nerve
- Cranial nerve
- Spinal nerve
|
|
| Autonomic |
- Sympathetic
- Parasympathetic
- Enteric
|
|
|
|
Index of the central nervous system
|
|
| Description |
- Anatomy
- meninges
- cortex
- association fibers
- commissural fibers
- lateral ventricles
- basal ganglia
- diencephalon
- mesencephalon
- pons
- cerebellum
- medulla
- spinal cord
- Physiology
- Development
|
|
| Disease |
- Cerebral palsy
- Meningitis
- Demyelinating diseases
- Seizures and epilepsy
- Headache
- Stroke
- Sleep
- Congenital
- Injury
- Neoplasms and cancer
- Other
- Symptoms and signs
- head and neck
- eponymous
- lesions
- Tests
|
|
| Treatment |
- Procedures
- Drugs
- general anesthetics
- analgesics
- addiction
- epilepsy
- cholinergics
- migraine
- Parkinson's
- vertigo
- other
|
|
Index of the peripheral nervous system
|
|
| Description |
- Anatomy
- Nerves
- cranial
- trigeminal
- cervical
- brachial
- lumbosacral plexus
- somatosensory
- spinal
- autonomic
- Physiology
- reflexes
- proteins
- neurotransmitters
- transporters
- Development
|
|
| Disease |
- Autonomic
- Congenital
- Injury
- Neoplasms and cancer
- Other
- Symptoms and signs
|
|
| Treatment |
- Procedures
- Local anesthetics
|
|
|
|
Anatomy of the midbrain
|
|
Tectum
(Dorsal) |
| Surface |
- Corpora quadrigemina:
- Inferior colliculus
- Superior colliculus
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| Grey matter |
|
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| White: Sensory/ascending |
- Spinotectal tract
- Central tegmental tract
|
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| White: Motor/descending |
|
|
|
Peduncle
(Ventral) |
| Tegmentum |
| White: Sensory/ascending |
- Lemnisci
- 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
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|
| Grey: other |
- Periaqueductal gray
- Raphe nuclei
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- Ventral tegmental area
- Pedunculopontine nucleus
- Red nucleus
|
|
- Rostral interstitial nucleus of medial longitudinal fasciculus
|
|
|
| Ventricular system |
|
|
|
| Base |
| White: Motor/descending |
- Cerebral crus: Corticospinal tract
- Corticobulbar tract
- Corticopontine tract/Frontopontine fibers/Temporopontine fibers
|
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| Grey: Substantia nigra |
- Pars compacta
- Pars reticulata
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|
| Surface |
- Superior cerebellar peduncle
- Interpeduncular fossa
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|
|
|
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Index of the central nervous system
|
|
| Description |
- Anatomy
- meninges
- cortex
- association fibers
- commissural fibers
- lateral ventricles
- basal ganglia
- diencephalon
- mesencephalon
- pons
- cerebellum
- medulla
- spinal cord
- Physiology
- Development
|
|
| Disease |
- Cerebral palsy
- Meningitis
- Demyelinating diseases
- Seizures and epilepsy
- Headache
- Stroke
- Sleep
- Congenital
- Injury
- Neoplasms and cancer
- Other
- Symptoms and signs
- head and neck
- eponymous
- lesions
- Tests
|
|
| Treatment |
- Procedures
- Drugs
- general anesthetics
- analgesics
- addiction
- epilepsy
- cholinergics
- migraine
- Parkinson's
- vertigo
- other
|
|
|
