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Neuro Objectives 22
1.
Cranial nerves:
 III: Rostral midbrain
o Efferents to ocular muscles
 IV: Caudal midbrain
o Efferents to superior oblique
 V: Midpons
o Afferents for face and anterior 2/3 of tongue (touch)
o Efferents to muscles of mastication
 VI: Caudal pons
o Efferents to lateral rectus
 VII: Caudal pons
o Afferents for anterior 2/3 of tongue (taste)
o Efferents to most facial muscles
 VIII: Pontomedullary junction
o Afferents to the organ of Corti, semicircular canals, saccule, and
utricle
 IX: Rostral medulla
o Afferents from posterior 1/3 of tongue (both taste and touch)
o Efferents to the parotid gland
 X: Rostral medulla
o Efferents to visceral organs of abdomen
o Efferents to skeletal muscle of pharynx, larynx, esophagus
 XI: Cervical cord
o Efferents to trapezius and sternocleidomastoid
 XII: Middle medulla
o Efferents to tongue muscles
2.
Midbrain/pons:
a.
Midbrain: Aqueduct, inferior colliculus, no pontine fibers, cerebral
peduncle
b.
Pons: 4th ventricle, no inferior colliculus, pontine fibers, no cerebral
peduncle
Pons/medulla:
a.
Pons: middle cerebellar peduncle, no olivary nucleus, no pyramids,
pontine fibers
b.
Medulla: no peduncle, interior olivary nucleus, pyramids, no cerebral
peduncle
Superior/inferior colliculi:
a.
Superior colliculi: rostral medulla, not demarcated well, clear cerebral
peduncle, red nucleus
b.
Inferior colliculi: caudal medulla, clearly demarcated, pontine fibers in
cerebral peduncle, decussation of cerebral peduncles
Cerebral peduncle: ventral lobes in the midbrain
Basal pons: ventral lobe with transverse pontine fibers
Middle cerebellar peduncle: connects pons to the cerebellum in the caudal pons
Pyramid: ventral lobe in the medulla that will turn into the basal pons
Olive: the protrusion resulting from the inferior olivary nucleus in the rostral
medulla
3.
Superior colliculus: Dorsal to periaqueductal gray in rostral midbrain
Periaqueductal gray: Clear staining tissue surrounding aqueduct in the midbrain
Red nucleus: Ventromedial in the rostral midbrain where the superior cerebellar
peduncles end
Substantia nigra: White staining tissue dorsal to the cerebral peduncles in the
midbrain
4th ventricle: Cavity running from the rostral medulla to the rostral pons
Cerebral aqueduct: Cavity running through the midbrain
Reticular formation: Middle area running coronally through brainstem
surrounding tracts
Inferior olivary nucleus: Dorsolateral to pyramids in the rostral medulla
4.
Rostral midbrain: No superior cerebellar peduncles (red nucleus), superior
colliculus
Caudal midbrain: Decussation of superior cerebellar peduncles, inferior
colliculus
Rostral pons: Pontine fibers, no middle cerebellar peduncle
Caudal pons: Pontine fibers, middle cerebellar peduncle
Rostral medulla: Inferior olivary nucleus, prominent inferior cerebellar peduncle
Caudal medulla: Nucleus gracilis/cuneatus, ventromedial medial lemniscus
5.
Blood supply:
Anterior
Posterior
Midbrain
Vertebral a.
Anterior spinal a.
Posterior spinal a. (caudal)
PICA (rostral)
Pons
Basilar a.
AICA (caudal)
Superior cerebellar a. (rostral)
Medulla
Basilar a.
Superior cerebellar a.
Posterior cerebral a.
Superior cerebellar a.
(caudal)
Posterior communicating a.
(rostral)
6.
Medial lemniscus (Contralateral touch/position): medial in caudal medulla →
medial to inferior olivary nucleus in the rostral medulla → dorsolateral in the
basal pons → ventromedial to the spinothalamic tract in the midbrain
Spinothalamic tract (Contralateral pain/temperature): lateral in caudal medulla
→ dorsal to inferior olivary nucleus in rostral medulla → lateral in basal pons →
dorsolateral to the medial lemniscus in the midbrain
Nuclei gracilis (Ipsilateral proprioception from legs): ventromedial in the caudal
medulla
Nuclei cuneatus (Ipsilateral proprioception from arms): ventrolateral in the
caudal medulla
Inferior cerebellar peduncle (Afferent input to the cerebellum): dorsolateral in
the medulla
Middle cerebellar peduncle (Pontine nuclei → contralateral cortex): connects
caudal pons to the cerebellum
Superior cerebellar peduncle (Efferent output of the cerebellum): dentate
nucleus in the cerebellum at the medullary level → dorsolateral to 4th ventricle in
the pons → ventromedial to the aqueduct in the midbrain
Cerebral peduncle (Corticospinal, corticopontine, corticobulbar tracts):
ventrolateral lobes in the midbrain
7.
Medial longitudinal fasciculus: medial throughout brainstem, ventral to the
ventricular system
Oculomotor nuclei: rostral midbrain, medial, multiple nuclei ventral to
periaqueductal gray
Trochlear nuclei: caudal midbrain, medial, dorsal to MLF, only cranial nerve
that leaves both dorsally and crosses the midline after the nucleus
Abducens nuclei: caudal pons, lateral to MLF
Hypoglossal nuclei: rostral medulla, medial, dorsal to MLF
8.
Abducens nuclei fibers:
a.
fibers → abducens nerve → lateral rectus to move eye laterally
b.
interneurons crossing midline → MLF → synapse on oculomotor nuclei
→ medial rectus to move contralateral eye medially
MLF role in eye movements: MLF coordinates the two eyes by providing a
pathway for input to the contralateral eye