Cerebral aqueduct

Fig. 4.6(b) GnRH +ve neurones (relative density) in the brain dot = mammalian, circle = avian, forms. Parasagittal view of distribution in Musk Shrew (Suncus murinus) — from bulb to median eminence (ME), optic X (OC), cerebral aqueduct (Aq), and preoptic area (POA) (from Schwanzel-Fukuda and Pfaff, 1994). 

The midbrain (mesencephalon) is the top of the brain stem. The dorsal midbrain is the tectum, which is involved in eye movements and reflexive reactions to sensory stimuli. The mesencephalic reticular formation projects upward to the forebrain and is involved in arousal and attention. The periaqueductal gray area surrounds the cerebral aqueduct, and integrates analgesic, defensive/aggressive, sexual, and autonomic responses. The red nucleus and substantia nigra are important structures in motor function. 

Detach the cerebellum and other neural tissue from the unsectioned portion of the head and examine the midbrain, cerebellum, medulla oblongata, cerebral aqueduct, and fourth ventricle. 

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