The Midbrain

i. Midbrain is located between diencephalon(consists of epithalamus, thalamus & hypothalamus) and the pons varolli.
ii. It contains the cerebral aqueduct or iter that connects the third and fourth ventricles.

iii. The corpora quadrigemina are four rounded elevations on the dorsal surface of the mid brain. The two superior colliculi are involved in visual reflexes and the two inferior colliculi are relay centres for auditory reflexes that operate when it is necessary to move the head to hear sounds more distinctly.
iv. The mid brain also contains on its inferior surface two thick fibrous tracks called cerebral peduncles or crura cerebri.

V. The tracts of ascending and descending nerve fibres from RAS (Renin Angiotensin system) connect the cerebrum and mid brain.

vi. Near the centre of the mid brain is a mass of grey matter scattered within the white matter. It is called the red nucleus. It plays an important role in controlling posture and muscle tone, modifying some motor activities and motor coordination.

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