Midbrain
The midbrain ( mesencephalon gr ) is a part of the brainstem and is located between the bridge ( pons) and diencephalon ( diencephalon ). The midbrain controls most of the eye muscles and is an important part of the extrapyramidal system. Excitations of the sensory nerves are routed through the diencephalon ( diencephalon ) to the cerebrum ( telencephalon ) or switched to motor nerve cells.
The midbrain can be divided into three layers. In the fore-located base of the midbrain are the cerebral legs ( crura cerebri), in the dorsal midbrain follows the hood ( midbrain tegmentum ). Together they are called as cerebral peduncles ( " cerebrum stems "). This is followed by the midbrain roof ( tectum of midbrain or lamina tecti ). Between tegmentum and tectum is the aqueduct of the midbrain ( mesencephalic aqueduct ).
Cerebrum leg
The cerebrum legs ( crura cerebri, cerebral peduncle singular ) are the front part of the midbrain, with crura cerebri and cerebral peduncles are used by some authors as a synonym.
The crura cerebri are limited by shallow furrows sideways ( lateral) and towards the middle ( medial). In front lies between the cerebrum legs a pit ( interpeduncular fossa ). In this area, push some structures of the diencephalon ( mammillary body, pituitary stalk ) between the cerebrum leg. Caudal limits the cerebrum leg to the pons.
The cerebrum legs included, inter alia, the long tracts of the internal capsule. These nerve fiber strands can be further broken from outside to inside in the temporopontinus tract, corticospinal tract, optic tract and the optic tract corticonuclear frontopontinus. On the medial gutter enters the III. Cranial nerve ( oculomotor nerve ) to the brain surface.
Midbrain hood
The midbrain hood ( midbrain tegmentum ) is the largest portion of the midbrain. It contains the nucleus ruber, as an important switching core for the extrapyramidal system, the nucleus nervi oculomotorii, the nucleus nervi trochlear, the nucleus nervi accessory oculomotorii ( Edinger - Westphal nucleus) and the mesencephalic trigeminal nucleus. On the border of the cerebrum leg is the substantia nigra, which functionally is an important core area of motor skills. Other structures of the Tegmentums are the tegmental tract centralis of the dorsal longitudinal fasciculus and the medial and reticular parts of the formation. The ventral tegmental area is part of the mesolimbic system.
Midbrain roof
The midbrain roof ( tectum of midbrain ) is the dorsal part of the midbrain. It consists of a thin plate, which is called the quadrigeminal plate ( or lamina quadrigeminal tecti ). The two mouth upward lying hill ( rostral colliculus ) are referred to in humans as well as the upper hill ( superior colliculus ). For this analogy, the two mouth- distant hills ( caudal colliculus ) in humans as a lower hill ( inferior colliculi ) are referred to. In the animal anatomy is called instead of front and back hills due to the non upright posture. The superior colliculus are important for the optical reflections, the inferior colliculi are switching station of the auditory pathway. Mouth Windwärts ( rostral ) of the quadrigeminal plate is the pretectal area.
In birds, only the front hills are trained and very strongly developed. Here lies the primary visual center of the birds, it is also called the optic tectum.
This structure is in the brain, a central system for processing visual stimuli.
Nuclei and pathways in the midbrain
The following important core areas are located in the midbrain:
- Nucleus nervi oculomotorii
- Nucleus nervi trochlear
- Nucleus accessory nerve oculomotorii ( Edinger - Westphal nucleus)
- Mesencephalic nucleus of trigeminal
- Red nucleus
- Substantia nigra
- Reticular formation
Important pathways of the midbrain are:
- Corticospinal tract
- Spinothalamic tract
- Tegmental tract centralis
- Lemniscus medialis and lateralis
- Medial longitudinal fasciculus and the dorsal
- Fibrae corticopontinae
- Fibrae corticonucleares
- Fibrae temporopontinae
- Neurobiology
- Mesencephalon