Structures

Question 1

What structures are in both the superior and inferior peduncle?

Answer 1

Cerebral peduncle
-basilar midbrain
- substantia nigra
Cerebral aqueduct and PAG

Question 2

Basilar midbrain

Answer 2

• both the superior and inferior peduncle

- descending corticospinal, corticobulbar, and corticopontine fibers

Question 3

The basilar midbrain portion of the cerebral peduncle is called

Answer 3

crus cerebri

Question 4

Substantia nigra

• _____ nucleus associated with ______
• ________ portion of the cerebral peduncle
• loss of these neurons results in _______

Answer 4

• both the superior and inferior peduncle
• dorsal portion of the cerebral peduncle
• extrapyramidal nucleus associated with basal nuclei
• parkinsons

Question 5

Cerebral aqueduct (of silvius) connects ____ and _____

Answer 5

• both the superior and inferior peduncle

- 3rd and 4th ventricles

Question 6

Key structures of superior midbrain includes:

Answer 6

• superior colliculus
• CN III nuclei
• Red nucleus

Question 7

Superior colliculus

Answer 7

• superior midbrain

- coordination of eye and head movements

Question 8

CN III nuclei

Answer 8

• superior midbrain
• oculomotor nerve nucleus: GSE
• edinger-westphal nucleus: GVE preganglionic parasympathetic, pupillary constriction

Question 9

Red nucleus

• type of nucleus?
• input from?
• contributes axons to?

Answer 9

• superior midbrain
• extrapyramidal motor nucleus
• receives input from the superior cerebellar peduncle
• contributes axons to the rubrospinal tract and inferior olivary nucleus

Question 10

What structures make up the inferior midbrain?

Answer 10

• inferior colliculus
• decussation of the superior cerebellar peduncle
• CN IV nucleus

Question 11

Inferior colliculus

Answer 11

• inferior midbrain

- auditory pathway reflexes and part of the conscious auditory pathway

Question 12

Decussation of the superior cerebellar peduncle (inferior midbrain)

Answer 12

• inferior midbrain
• efferent fibers from the deep cerebellar nuclei (dentate) cross the midline to synapse in the red nucleus and the VL nucleus of the thalamus

Question 13

CN IV nucleus

Answer 13

• inferior midbrain
• trochlear nucleus contributing GSE axons to the superior oblique muscle
• only CN to exit dorsally from brainstem

Question 14

Structures included in the Superior pons

Answer 14

• decussation of the superior cerebellar peduncle
• closure of the IVth ventricle
• superior cerebellar peduncle

Question 15

Decussation of the superior cerebellar peduncle (superior pons)

Answer 15

• Superior pons
• this fiber tract contains efferent axons from the deep cerebellar nuclei (dentate nucleus, mainly) bound for the contralateral red nucleu and the VL of the thalamus
• also contains the axons of the ventral spinocerebellar tract that are “re-crossing” the midline in this decussation

Question 16

Closure of the IVth ventricle

Answer 16

• Superior pons

- becoming the cerebral aqueduct

Question 17

Superior cerebellar peduncle

Answer 17

• Superior pons
• efferents of the cerebellum
• ipsilateral at this point, beginning its decussation

Question 18

Structures of the middle pons

Answer 18

• middle cerebellar peduncle

- CN V (3 of 4 nuclei)

Question 19

Middle cerebellar peduncle

Answer 19

• middle pons
• consists of descending pyramidal motor tracts (CST, CBT)
• transverse fibers of the pontocerebellar tract (crossing midline)
• deep pontine nuclei (receiving the corticopontine fibers)

Question 20

CN V nuclei in middle pons

Answer 20

• middle pons
• chief sensory : where GSA’s for touch and conscious proprioception synapse
• spinal tract and nucleus of V: extend caudally from here to C4; where the pain, temperature, and light touch GSA and GVA axons travel and synapse
• motor nucleus: where the SVE neurons arise and project axons to the muscles of mastication
• mesencephalic nucleus of V: SUPERIOR PONS TO SUPERIOR MIDBRAIN; GSA’s for unconscious proprioception from the face synapse

Question 21

Structures of the inferior pons

Answer 21

• caudal end of the basilar pons
• CN VI
• CN VII

Question 22

Caudal end of the basilar pons

Answer 22

• inferior pons

- caudal from here the corticospinal and corticobulbar tracts will be seen as the pyramids

Question 23

CN VI

Answer 23

• inferior pons

- the abducens nucleus for GSE’s to the lateral rectus muscle

Question 24

CN VII

Answer 24

• inferior pons
• facial nerve motor nucleus
• represents the SVE nucleus for muscles of facial expression
• (note facial colliculus)

Question 25

Structures of the open medulla

Answer 25

- pyramids - inferior cerebellar peduncle - inferior olivary nucleus - CN VIII nuclei

Question 26

Pyramids

Answer 26

- open medulla - as the transition from the basilar pons to the basilar medulla occurs, the corticospinal and the last fibers of the corticobulbar tracts takes up their namesake tract, the pyramids - ventral most pyramidal shaped protrusions from the medulla - will end as the decussation of the pyramids in the caudal-most closed medulla

Question 27

inferior cerebellar peduncle

Answer 27

- open medulla | - appear as the lateral "ears" of the tegmentum and represent the various spinal and olivary input to the cerebellum

Question 28

Inferior olivary nucleus

Answer 28

- open medulla - very convoluted nucleus of the ventrolateral tegmentum of the open (and most rostral of closed) medulla - contributes to the "climbing fibers" to the contralateral cerebellum via the inferior cerebellar peduncle

Question 29

structures of the closed medulla

Answer 29

- the obex - the "necklace of cranial nerve nuclei" - CN IX, X, XI (cranial portion), and XII - the decussation of the medial lemniscus - the decussation of the pyramids

Question 30

The obex

Answer 30

- closed medulla | - this is caudal end/beginning of the fourth ventricle

Question 31

the necklace of cranial nerve nuclei

Answer 31

- closed medulla - rostral to the decussation of the medial lemniscus - sulcus limitans "folds" and the basilar nuclei are pushed dorsally, displacing the sensory (dorsal horn) nuclei laterally - results in the consistent arrangement of these nuclei from medial to lateral: GSE, SVE, GVE, GVA, GSA, and SSA

Question 32

CN IX, X, XI (cranial portion) and XII

Answer 32

- closed medulla - all nuclei associated with these CN - dorsal motor nucleus of X, nucleus ambiguus, hypoglossal nucleus.....etc

Question 33

Decussation of the Medial Lemniscus

Answer 33

- closed medulla - dorsal to central somatotopism is C, T, L, S - fasciculi gracilis and cuneatus synapse in their nuclei - the 2nd order afferents next cross the midline as the internal arcuate fibers and ascend to the medial lemniscus

Question 34

Decussation of the pyramids

Answer 34

- closed medulla - "final act" rostral to caudal in the brainstem - lateral corticospinal tract will cross the midline and move dorsally to take up its more dorsolateral tegmental area of the cord white matter - anterior corticospinal tract continues ipsilaterally until the level of input where it innervates the GSEs to the axial muscles bilaterally