MID BRAIN ::
It forms the connecting link for the fore brain and the hind brain it extends from the pons to the lower surface of the cerebrum it is a short and narrow segment that provides conduction pathaways to and from the higher and lower centres it consists of the crus cerebri tectum tegmentum substantia nigra and the red nucleus
Crus-cerebri are two white rope like bundles of nerve fibres arising from cerebral cortex Tectum comprises of four rounded elevations called colliculi These are concerned with righting reflexes triggered by auditory and visual impulses
Tegmentum : It consists of nuclei of III, IV, and V cranial nerves and fibres from the thalamus cortex and spinal cord This part is also concerned with sub-conscious motor functions
Substantia nigra is the lamina of grey - matter with black pigments The cells of this region have connections with corpus- striatum and these fibres (nigro-striatal tract ) play an important role in controlling muscle tone and rigidity Damage to this portion or deficiency of neurotransmitter (dopamine) in this region causes Parkinson s disease
fig Mid Brain
Red nucleus: It is a large ovoid mass of grey matter lying dorsal to substantia nigra it receives and conveys impulses through the spinal - cord hypothalamus cerebral cortex and brain -stem (medulla oblongata pons and cerebellum )
In short mid brain besides being the connecting link between the fore brain and hind brain is an important center for various righting and postural reflexes These reflexes are being directed through visual and auditory impulses
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