Neuro Objectives 22

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. Posterior spinal a. (caudal)

Anterior spinal a. 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