USMLE Step 1 Neuroanatomy Review 26 14 Midbrain (4_5)

USMLE Step 1 Neuroanatomy Review 26 14 Midbrain (4_5)

 

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Play USMLE Audio MP3 26 14 Midbrain (4_5) Below

Begin 26 14 Midbrain (4_5) Transcription

Now we’re going to take a look at the inferior colliculus level of the midbrain. Please refer to figure 9.3.

Student doctor, where in the midbrain is the auditory reflex center located?

  • The auditory reflex center is located in the inferior colliculus.

The left and right inferior colliculi are connected by fibers just as the superior colliculi are. Student doctor, what is the commissure called that interconnects the inferior colliculi?

  • This is the brachium of the inferior colliculus.

What is the function of the brachium of the inferior colliculus?

  • The brachium of the inferior colliculus is involved in the projection of fibers to the medial geniculate body.
  • The abbreviation of the medial geniculate body is of course MGB.

Now student doctor, where in the midbrain is the nucleus of the trochlear nerve located?

  • The nucleus of the trochlear nerve is located in the periaqueductal grey near the midline.

Student doctor, what nuclei in the central grey region contain the cell bodies of noreprinephrine-containing neurons in the brain?

  • This is the locus coeruleus.

Now what is the name of the fasciculus located near the midline and dorsal to the decussation of the superior cerebellar peduncle?

  • This is the medial longitudinal fasciculus.

And this has what abbreviation?

  • The MLF.

What kind of fibers are contained within the medial longitudinal fasciculus?

  • These are vestibular fibers.

And these vestibular fibers of the medial longitudinal fasciculus are involved in what function?

  • In the coordination of eye movement.

What segment of the central tegmental tract that is containing what two types of fibers is also located at the level of inferior colliculus in the midbrain?

  • The central tegmental tract containing the rubroolivary and reticulothalamic fibers.

Now whereabouts is the central tegmental tract located at the level of the superior colliculus?

  • At the level of superior colliculus, the central tegmental tract is located centrally in the tegmentum.

And where is it located at the level of the inferior colliculus?

  • At the level of the inferior colliculus the central tegmental tract is lateral to the MLF, or medial longitudinal fasciculus.

Now moving out laterally in the tegmentum. Two tracts lie laterally to the central tegmental tract. Student doctor, what are these two tracts lateral to the central tegmental tracts?

  • These are the spinal lemniscus and the medial lemniscus.

Now student doctor, what is the conspicuous decussation in the central tegmentum at the level of inferior colliculus?

  • This is the decussation of the superior cerebellar peduncle.

Student doctor, what three tracts are located at the base of both the rostral and caudal midbrain?

  • The corticopontine, the corticospinal, and the combination of the corticopontine and the corticobulbar.

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