Midbrain

Midbrain or mesencephalon is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.

Structure

The midbrain is located below the cerebral cortex, and above the hindbrain placing it near the center of the brain. It is a part of the brainstem and forms a central part of the brain.

Parts of the Midbrain

The midbrain is composed of several parts:

• Tectum: The dorsal part of the midbrain, responsible for auditory and visual responses.
• Tegmentum: A part of the midbrain involved in many unconscious homeostatic and reflexive pathways.
• Cerebral peduncle: This contains the large ascending (sensory) and descending (motor) nerve tracts that run to and from the cerebrum from the pons. Mainly it connects the forebrain and the hindbrain.
• Crus cerebri: A white matter tract of the cerebral peduncle which contains the motor tract fibers.
• Substantia nigra: Literally 'black substance', it is closely associated with motor planning, learning, emotion, and addiction.

Function

The midbrain serves important functions in motor movement, particularly movements of the eye, and in auditory and visual processing. It is located within the brainstem and between the two other developmental regions of the brain, the forebrain and the hindbrain; compared with those regions, the midbrain is relatively small.

Clinical significance

Damage to the midbrain can cause a variety of motor and sensory problems, including Parkinson's disease, schizophrenia, and problems with vision and hearing. In some cases, it can also lead to coma or death.

See also

• Brain
• Brainstem
• Forebrain
• Hindbrain

References

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  Midbrain of the Human Brainstem

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  Location of Midbrain in inferior view

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  Human brainstem thalamus posterior view

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  Gray's Anatomy illustration of the midbrain

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  Brain ventricle anatomy diagram

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  Oculomotor nerve nucleus

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  Midbrain - inferior colliculus

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  Brain Anatomy - Midbrain, Forebrain, Hindbrain

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  Human embryo at 8 weeks