Organization of the Brainstem Flashcards
Tegmentum
The area between these ventral structures and the floor of the ventricular system
The only places where there’s much neural tissue dorsal to the ventricular system are the ________ and the ______ medulla.
Midbrain, caudal
The _________ tract is always in the most ventral part of the brainstem.
corticospinal tract
The spinothalamic tract is always located ______ in the tegmenjtum.
laterally
The __________ (the continuation of the posterior column system) starts out medially and then moves progressively closer to the spinothalamic tract (rotating nearly 180 in the process), until the two wind up adjacent to each other in the midbrain.
medial lemniscus
Caudal Medulla
No fourth ventricle.
Posterior columns (FG and FC) end by synapsing in the posterior column uncle (NG and NC).
The posterior column nuclei contain the second-order neurons for the major touch/position pathway, and their axons cross the midline to form the medial lemniscus. The pyramid on each side contains the corticospinal tract. The spinothalamic tract is in its typical segmental location.
Rostral medulla
The fourth ventricle opens up.
The inferior olivary nucleus, a large nucleus related to the cerebellum, accounts for the bulge called the olive on the lateral surface of the rostral medulla; its output cross the midline and form most of the inferior cerebellar peduncle. The medial longitudinal fasiculus (MLF) can be seen at this and all subsequent levels of the brainstem.
Inferior olivary nucleus
A large nucleus related to the cerebellum. Can be seen in the rostral medulla.
Medial longitudinal fascicles (MLF)
A small tract important in eye and head movements, can be seen at rostral medulla and all subsequent levels of the brainstem.
Caudal Pons
The fourth ventricle continues.
The most obvious feature is the basal pons, contains scattered clumps of gray matter called pontine nuclei.
The medial lemniscus slumps down and begins to creep over toward the spinothalamic tract.
Rostral pons
The fourth ventricle narrows as it funnels down into the aqueduct of the midbrain.
The basal pons is still obvious.
The superior cerebellar peduncle leaves the cerebellum and enters the brainstem on its way to the contralateral thalamus.
Inferior colliculus
Above the aqueduct on each side, a major component of the auditory pathway.
Corticobulbar tract
The cranial nerve equivalent of the corticospinal tract
Caudal midbrain
The fourth ventricle is all gone, replaced by the aqueduct (which is surrounded by periaqueductal gray (PAG). Above the aqueduct on each side is an inferior colliculus.
The medial lemniscus is adjacent tho the spinal tract.
The superior cerebellar peduncles decussate= crosses.
Rostral midbrain
The aqueduct continues, on its way into the third ventricle. Above the aqueduct on each side is a superior colliculus. The superior cerebellar peduncles have crossed and now barrel right through or around the red nucleus (mostly without synapsing) on their way to the thalamus. The cerebral peduncle still contains corticopontine, corticospinal, and corticobulbar fibers. The spinothalamic tract and medial lemniscus are now a continuous band of fibers getting ready to terminate in the thalamus.
