Fns Lecture 24 Mesencephalon

Front 1

inferior colliculus

Back 1

major midbrain auditory relay nucleus
encapsulated by fibers of lateral lemniscus
tonotopic representation of cochlea
receive inputs from cochlear nuclei via lateral lemniscus
outputs to MGB of thalamus via IC brachium
functions to relay auditory impulses to higher levels, crucial for sound localization

Front 2

periaqueductal gray

Back 2

surrounds cerebral aqueduct
sends fibers bilaterally to inhibitory interneurons in dorsal horn
inhibit release of substance P from pain fibers
inhibit activation of lamina 1 and 2 associated with pain transmission
stimulation produced profound analgesia

Front 3

trochlear nucleus

Back 3

egg in MLFs nest.
GSE - innervates contralateral superior oblique

Front 4

decussation of superior cerebellar peduncle

Back 4

crossing fibers en route to thalamus fill tegmentum

Front 5

superior colliculus

Back 5

three layers
superficial - inputs from optic tract, primary visual cortex
outputs to thalamus via SC brachium
functions to alert visual areas of cerebrum to visual stimuli, aids in conscious localization of moving targets

Front 6

intermediate and deep layers

Back 6

visual, auditory, somatosensory inputs
function in orientation of head toward visual auditory and somatosensory stimuli, production of voluntary and reflexive saccades

Front 7

oculomotor complex

Back 7

between MLF fibers
GSE nuclei - cholinergic neurons, innervate all extraocular muscles except LR6 and SO4
GVE nuclei- edinger westphal nuclei- parasympathetic preganglionic fibers to ciliary ganglion, whose post G fibers innervate ciliary muscle and constrictor pupillae muscle of iris

Front 8

red nucleus

Back 8

encapsulated by superior cerebellar peduncle
inputs from motor areas of cerebral cortex and cerebellum
outputs via crossed RST
functions to excite upper limb flexor motorneurons

Front 9

substantia nigra

Back 9

dorsal pars compacta - dopamine
ventral pars reticulata - GABA secretion
PARKINSONS DISEASE ASSOCIATED WITH DEGENERATION OF PARS COMPACTA

Front 10

Pretectal nucleus

Back 10

mediates pupillary light reflex

Front 11

posterior commissure

Back 11

contains crossing fibers that are part of the pupillary light reflex of the contralateral eye

Front 12

pupillary light reflex PLR

Back 12

light shone in one eye causes both pupils to constrict (direct and indirect)
right retina>right pretectal olivary nucleus>R, L EWnucleus>LR ciliary ganglia>LR sphincter pupillae nerves

Front 13

lesion of left optic nerve

Back 13

light in left eye
no direct or indirect PLR
light in right eye
see direct and indirect PLR

Front 14

lesion of left oculomotor nerve

Back 14

light in left eye
only see indirect PLR
light in right eye
only see direct PLR

Front 15

oculomotor nerve palsy

Back 15

ipsilateral LMN paralysis
complete ptosis of eye lid - lose levator palpebrae superioris muscle
eye deviated laterally and downward - unopposed action of LR and SO muscles
pupil fully dilated, lose PLR due to GVE interruption

Front 16

Ventral syndrome
superior alternating hemiplegia

Back 16

damage oculomotor root, corticospinal, corticobulbar fibers
see ipsilateral paralysis of oculomotor nerve
contralateral hemiplegia of corticospinal tract
contralateral paralysis of lower facial muscles due to corticobulbar damage

Front 17

tegmental syndrome
benedikts

Back 17

damage to
rednucleus, SCP - intention tremor and ataxia in contralateral limbs
ML and STT - contralateral loss of 2pt tactile, pain and thermal
oculomotor nerve - ipsilateral oculomotor nerve palsy

Front 18

collicular syndrome
parinauds

Back 18

paralysis of vertical upward or downward gaze, direction of which depending on midbrain lesion