What is the midbrain?

The midbrain, or mesencephalon, is a small region of the brain located between the forebrain and hindbrain. It contains the tectum and tegmentum. The tectum, the midbrain's rear portion, includes the superior and inferior colliculi. The superior colliculus helps track objects in the visual field using input from the retina and visual cortex. The inferior colliculus receives auditory fibers and sends them to the thalamus. The tegmentum, located in front of the tectum, contains fiber tracts, the red nucleus, the periaqueductal gray, and the substantia nigra. The red nucleus helps coordinate sensorimotor information. The periaqueductal gray suppresses pain. The substantia nigra influences movement and motor coordination. The midbrain also contains the reticular formation which is responsible for arousal and alertness.

Where is the midbrain located in the brain?

The midbrain, a relatively small region of the brain , is located within the brainstem between the forebrain and the hindbrain. Also referred to as the mesencephalon, the midbrain connects the cerebrum with the spinal cord. The midbrain consists of the tectum and tegmentum. The tectum is the rear portion of the midbrain, and the tegmentum is in front of the tectum. The midbrain also contains the substantia nigra, the crus cerebri, and a portion of the reticular formation.

What are the main parts of the midbrain?

The midbrain, a small region of the brainstem , has two main parts: the tectum and tegmentum.

What are some functions of the midbrain?

The midbrain, a small region of the brainstem , has roles in motor movement, especially eye movement, and in visual and auditory processing. The tectum, located in the rear, includes the superior colliculus, which handles visual reflexes like tracking objects, and the inferior colliculus, which processes auditory information. The tegmentum, in front of the tectum, contains the red nucleus for sensorimotor coordination, the periaqueductal gray for pain suppression due to endorphin concentration, and the substantia nigra, which has a role in mediating movement and motor coordination. The midbrain also contains the reticular formation, which is involved in alertness, and cranial nerves that stimulate muscles controlling eye movement, lens shape, and pupil diameter.

How does the midbrain help with movement and vision?

The midbrain, a small region of the brainstem, has two main parts called the tectum and tegmentum. The tectum is in the rear and helps with visual reflexes, especially tracking objects. It gets input from the retina and visual cortex through the superior colliculus. The tegmentum, located in front of the tectum, includes the red nucleus, which helps coordinate sensorimotor information, and the substantia nigra, which uses dopamine to mediate movement and motor coordination. The midbrain also contains cranial nerves that stimulate muscles that control eye movement, lens shape, and pupil diameter.

What problems can happen if the midbrain is damaged?

Midbrain damage can disrupt motor movement, especially eye movement, and affect auditory and visual processing. Because the midbrain contains the reticular formation , which is responsible for arousal and alertness, damage to the midbrain can also affect these functions. The symptoms of neurological disease help doctors determine the location of lesions. Damage to the brainstem, where the midbrain is located, is life-threatening because it houses control centers for consciousness, respiration, and blood pressure.

midbrain

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Diagram of a human brain showing a median sagittal section, highlighting the fourth ventricle and cerebellum in the hindbrain, with labeled anatomical structures including the pons, medulla oblongata, and central canal of the spinal cord.

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Also called:: mesencephalon

Related Topics:: crus cerebri; roof plate; mesencephalic tegmentum; Edinger-Westphal nucleus; oculomotor nucleus

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Structures of the human brain Sagittal section of the human brain, showing structures of the cerebellum, brainstem, and cerebral ventricles.

midbrain

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Also known as: mesencephalon

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What is the midbrain?
The midbrain, or mesencephalon, is a small region of the brain located between the forebrain and hindbrain. It contains the tectum and tegmentum.

The tectum, the midbrain's rear portion, includes the superior and inferior colliculi. The superior colliculus helps track objects in the visual field using input from the retina and visual cortex. The inferior colliculus receives auditory fibers and sends them to the thalamus.

The tegmentum, located in front of the tectum, contains fiber tracts, the red nucleus, the periaqueductal gray, and the substantia nigra. The red nucleus helps coordinate sensorimotor information. The periaqueductal gray suppresses pain. The substantia nigra influences movement and motor coordination. The midbrain also contains the reticular formation which is responsible for arousal and alertness.
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1. human nervous system: Midbrain
2. midbrain
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Where is the midbrain located in the brain?
The midbrain, a relatively small region of the brain, is located within the brainstem between the forebrain and the hindbrain. Also referred to as the mesencephalon, the midbrain connects the cerebrum with the spinal cord.

The midbrain consists of the tectum and tegmentum. The tectum is the rear portion of the midbrain, and the tegmentum is in front of the tectum. The midbrain also contains the substantia nigra, the crus cerebri, and a portion of the reticular formation.
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1. human nervous system: Midbrain
2. midbrain
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What are the main parts of the midbrain?
The midbrain, a small region of the brainstem, has two main parts: the tectum and tegmentum.
- Tectum The tectum is the midbrain's rear portion, made of the superior and inferior colliculi. The superior colliculus gets input from the retina and visual cortex and helps track objects. The inferior colliculus gets auditory fibers and connects to the thalamus.
- Tegmentum The tegmentum is in front of the tectum and contains fiber tracts and the red nucleus, the periaqueductal gray, and the substantia nigra. The red nucleus helps coordinate sensorimotor information. The periaqueductal gray helps suppress pain. The substantia nigra has two parts (pars reticulata and pars compacta) and impacts movement and motor coordination.
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1. human nervous system: Midbrain
2. midbrain
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What are some functions of the midbrain?
The midbrain, a small region of the brainstem, has roles in motor movement, especially eye movement, and in visual and auditory processing. The tectum, located in the rear, includes the superior colliculus, which handles visual reflexes like tracking objects, and the inferior colliculus, which processes auditory information. The tegmentum, in front of the tectum, contains the red nucleus for sensorimotor coordination, the periaqueductal gray for pain suppression due to endorphin concentration, and the substantia nigra, which has a role in mediating movement and motor coordination. The midbrain also contains the reticular formation, which is involved in alertness, and cranial nerves that stimulate muscles controlling eye movement, lens shape, and pupil diameter.
1 Britannica Source
1. midbrain
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How does the midbrain help with movement and vision?
The midbrain, a small region of the brainstem, has two main parts called the tectum and tegmentum. The tectum is in the rear and helps with visual reflexes, especially tracking objects. It gets input from the retina and visual cortex through the superior colliculus. The tegmentum, located in front of the tectum, includes the red nucleus, which helps coordinate sensorimotor information, and the substantia nigra, which uses dopamine to mediate movement and motor coordination. The midbrain also contains cranial nerves that stimulate muscles that control eye movement, lens shape, and pupil diameter.
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Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What problems can happen if the midbrain is damaged?
Midbrain damage can disrupt motor movement, especially eye movement, and affect auditory and visual processing. Because the midbrain contains the reticular formation, which is responsible for arousal and alertness, damage to the midbrain can also affect these functions.

The symptoms of neurological disease help doctors determine the location of lesions. Damage to the brainstem, where the midbrain is located, is life-threatening because it houses control centers for consciousness, respiration, and blood pressure.
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1. nervous system disease: Brainstem
2. midbrain
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midbrain, region of the developing vertebrate brain that is composed of the tectum and tegmentum. 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.

The tectum (from Latin for “roof”) makes up the rear portion of the midbrain and is formed by two paired rounded swellings, the superior and inferior colliculi. The superior colliculus receives input from the retina and the visual cortex and participates in a variety of visual reflexes, particularly the tracking of objects in the visual field. The inferior colliculus receives both crossed and uncrossed auditory fibres and projects upon the medial geniculate body, the auditory relay nucleus of the thalamus.

The tegmentum is located in front of the tectum. It consists of fibre tracts and three regions distinguished by their colour—the red nucleus, the periaqueductal gray, and the substantia nigra. The red nucleus is a large structure located centrally within the tegmentum that is involved in the coordination of sensorimotor information. Crossed fibres of the superior cerebellar peduncle (the major output system of the cerebellum) surround and partially terminate in the red nucleus. Most crossed ascending fibres of that bundle project to thalamic nuclei, which have access to the primary motor cortex. A smaller number of fibres synapse on large cells in caudal regions of the red nucleus; those give rise to the crossed fibres of the rubrospinal tract, which runs to the spinal cord and is influenced by the motor cortex.

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The substantia nigra is a large pigmented cluster of neurons that consists of two parts, the pars reticulata and the pars compacta. Cells of the pars compacta contain the dark pigment melanin; these cells synthesize dopamine and project to either the caudate nucleus or the putamen, both of which are structures of the basal ganglia and are involved in mediating movement and motor coordination. These two structures, in addition to the globus pallidus, form the striatum. By inhibiting the action of neurons in the caudate nucleus and the putamen, the dopaminergic cells of the pars compacta influence the neuronal output of the neurotransmitter GABA (gamma-aminobutyric acid). The neurons in turn project to the cells of the pars reticulata, which, by projecting fibres to the thalamus, are part of the output system of the corpus striatum.

The periaqueductal gray region of the tegmentum is made up of gray matter (neural tissue with relatively few axons covered in myelin) and surrounds the cerebral aqueduct, a short canal that runs between the third and fourth ventricles of the brain. The periaqueductal gray appears to function primarily in pain suppression, a result of its naturally high concentrations of endorphins.

Also within the midbrain are the crus cerebri, tracts made up of neurons that connect the cerebral hemispheres to the cerebellum. The midbrain also contains a portion of the reticular formation, a neural network that is involved in arousal and alertness. Cranial nerves in the midbrain that stimulate the muscles controlling eye movement, lens shape, and pupil diameter form the nuclear complex of the oculomotor nerve and the trochlear nucleus.

The midbrain is affected by certain developmental disorders, including cobblestone lissencephaly (type II lissencephaly), in which neurons fail to migrate between the 12th and the 24th week of gestation, resulting in a lack of formation of grooves and folds in the brain surface.

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The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Michele Metych.

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