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Midbrain - Anatomy & Physiology (view source)
Revision as of 16:42, 6 August 2011
, 16:42, 6 August 2011→Midbrain Structure & Function
The midbrain arises from the [[CNS_Development_-_Anatomy_%26_Physiology#Development_of_the_Brain|mesencephalon]]. One of the key roles of this area of the brain during development is the maintainence of a patent cerebral aqueduct to facilitate the appropriate development of higher brains structures including the cerebral hemispheres.
The midbrain arises from the [[CNS_Development_-_Anatomy_%26_Physiology#Development_of_the_Brain|mesencephalon]]. One of the key roles of this area of the brain during development is the maintainence of a patent cerebral aqueduct to facilitate the appropriate development of higher brains structures including the cerebral hemispheres.
==Midbrain Structure & Function==
==Midbrain Structure & Function==
The midbrain has a stratified structure comprising various layers including the tectum, tegmentum and cerebral peduncle. These structures are found in a dorsoventral sequence. The tectum lies dorsally to the cerebral aqueduct and it has four major rounded surface swellings; colliculi (see below).
The midbrain has a stratified structure comprising various layers including the tectum, tegmentum and cerebral peduncle. These structures are found in a dorsoventral sequence. The tectum lies dorsally to the cerebral aqueduct and it has four major rounded surface swellings; colliculi (see below). The tegmentum is the core of the midbrain and a large proportion of it is made up by the [[Sensory_Pathways_-_Anatomy_%26_Physiology#Ascending_Reticular_Formation_.28Spinoreticular_Tract.29|reticular formation]].
===Oculomotor Nerves===
===Cranial Nerve Nuclei===
The oculomotor nerves [[Cranial_Nerves_-_Anatomy_%26_Physiology|(Cranial Nerve III)]] have their superficial nuclei within the midbrain.
The major cranial nerve nuclei within the midbrain are the mesencephalic nuclei of the [[Cranial_Nerves_-_Anatomy_%26_Physiology|trigeminal nerves (V)]], the trochlear nuclei (IV), the principle and parasympathetic oculomotor nuclei [[Cranial_Nerves_-_Anatomy_%26_Physiology|(Cranial Nerve III)]], the 'red nuclei' (so named due to it's pronounced vascularity) and the periaqueductal gray nuclei. The periaqueductal gray nuclei is a core of gray nervous tissue located adjacent to the cerebral aqueduct. The oculomotor nerve emerges from the mid brain rostral to the pons.
===Cerebral Aqueduct===
===Cerebral Aqueduct===
Within the lumen of the midbrain lies the cerebral aqueduct which acts as a simple passage between the spinal cord and the third and fourth ventricles.
Within the lumen of the midbrain lies the cerebral aqueduct which acts as a simple passage between the spinal cord and the third and fourth ventricles.
====Rostral Colliculi====
====Rostral Colliculi====
The rostral colliculi are placed closer together in comparison to the caudal. The rostral colliculi are also joined to the thalamus, but by the 'lateral geniculate bodies' rather than the medial. The rostral colliculi help to integrate the visual pathways and also are involved in somatic reflexes that are caused by visual cues. The rostral colliculi have also been suggested to be involved in spatial integration.
The rostral colliculi are placed closer together in comparison to the caudal. The rostral colliculi are also joined to the thalamus, but by the 'lateral geniculate bodies' rather than the medial. The rostral colliculi help to integrate the visual pathways and also are involved in somatic reflexes that are caused by visual cues. The rostral colliculi have also been suggested to be involved in spatial integration.
===''Substantia nigra''===
The ''substantia nigra'' is a prominent area of the mid brain and is identifiable on cross sections by it's darker pigmentation. This pigmentation is due to the gradual accumulation of pigmentation of neurons and is associated with basal nuclei within the tissue. The ''substantia nigra'' nuclei are involved in the control of voluntary movement.
===Crura cerebri===
These are visible on the ventral surface of the mid brain and comprise of fibre tracts that are in passage between the telencephalon and the brain stem. The oculomotor nerves (see above) also emerge in this region of the mid brain, directly rostral to the pons.
==Structure and Function==
==Structure and Function==