It is functionally associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation.

Visualizing these cross-sections as an upside-down bear face helps remember its structures, with the peduncles forming ears, aqueducts mouth, and tectum chin.

[2] The position of the tectum is contrasted with the tegmentum, which refers to the region in front of the ventricular system, or floor of the midbrain.

The reticulospinal tract, which exerts some control over alertness, takes input from the tectum,[6] and travels both rostrally and caudally from it.

The tectospinal tract connects the superior colliculi to the cervical nerves of the neck, and co-ordinates head and eye movements.

The cerebral aqueduct is a narrow channel located between the tectum and the tegmentum, and is surrounded by the periaqueductal grey,[9] which has a role in analgesia, quiescence, and bonding.

The dorsal raphe nucleus (which releases serotonin in response to certain neural activity) is located at the ventral side of the periaqueductal grey, at the level of the inferior colliculus.

The main bulk of the tegmentum contains a complex synaptic network of neurons, primarily involved in homeostasis and reflex actions.

The spinothalamic tract – another ribbon-like region of fibres – are located at the lateral edge of the tegmentum; at the level of the inferior colliculus it is immediately dorsal to the medial lemiscus, but due to the rostral widening of the tegmentum, is lateral of the medial lemiscus at the level of the superior colliculus.

A prominent pair of round, reddish, regions – the red nuclei (which have a role in motor co-ordination) – are located in the rostral portion of the midbrain, somewhat medially, at the level of the superior colliculus.

Older texts refer to the crus cerebri as the cerebral peduncle; however, the latter term actually covers all fibres communicating with the cerebrum (usually via the diencephalon), and therefore would include much of the tegmentum as well.

The substantia nigra has extremely high production of melanin (hence the colour), dopamine, and noradrenalin; the loss of dopamine-producing neurons in this region contributes to the progression of Parkinson's disease.

The outward expansion compresses the still-forming cerebral aqueduct, which can result in partial or total obstruction, leading to congenital hydrocephalus.