What is the midbrain and where is it located?

The midbrain is the shortest part of the brainstem, connecting the pons below to the diencephalon and cerebrum above. It surrounds the cerebral aqueduct, which links the third and fourth ventricles.

What are the main external features of the midbrain?

Externally, the midbrain has a ventral aspect with two crura cerebri and the interpeduncular fossa, where the oculomotor nerve emerges, and a dorsal aspect with four colliculi for reflexes and the trochlear nerve emerging below the inferior colliculi.

How is the internal structure of the midbrain organized?

Internally, the midbrain is divided by the cerebral aqueduct into the tectum, which contains the colliculi, and the cerebral peduncles, which include the tegmentum, substantia nigra, and crus cerebri.

What are the key functions of the superior and inferior colliculi?

The superior colliculi mediate visual reflexes, and the inferior colliculi are involved in auditory reflexes, connecting to geniculate bodies for sensory processing.

Which cranial nerves are associated with the midbrain?

The midbrain is associated with the oculomotor nerve (III), which emerges ventrally, and the trochlear nerve (IV), which emerges dorsally below the inferior colliculi.

What is the arterial supply to the midbrain?

The midbrain receives blood from branches of the basilar artery, direct basilar branches, and branches from the posterior communicating and anterior choroidal arteries.

What is the role of the medial longitudinal fasciculus (MLF) in the midbrain?

The MLF is a myelinated tract that interconnects nuclei of cranial nerves III, IV, VI, VIII, and XI, coordinating head and eye movements in response to vestibular stimuli.

Midbrain – Colliculi, Crura & Substantia Nigra

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