Brainstem; Midbrain Flashcards
midbrain-pons junction level characterized by
1 - decussation of trochlear n. w/in sup medullary velum
2 - narrow cerebral aqueduct (replaces 4thv)
3 - decussation of the superior cerebellar peduncle
unilat lesion of the trochlear n
diplopia when looking down
ipsilat loss of motor control of superior oblique mm
periaqueductal gray, stimulation of it
analgesic effect
act of serotonergic and adrenergic descending pathways that act spinal enkephalin interneurons which block trans of pain info in local spinal dorsal horn circuits
locus ceruleus
main source of epinephrine
lateral lemniscus
fibers from cochlear and sup olivary nuclei
contains aud info from both ears
terminats; inf colliculus
tectospinal tract
origin; sup colliculus
term; high cervical spinal cord
function; reflex of turning head in resp to stimuli
inf colliculus
relay for aud info
lateral lemniscus ends here
origin of brachium fibers ->medial geniculate nucleus (MGN)
raphe nucleus
ventral part of periaqueductal gray
main source of serotonin
superior cerebellar peduncle (SCP) decussates in midbrain, SCP consists mainly of
cerebellar efferent fibers fr deep cerebellar nuclei that project to contralateral red nucleus and ventral lateral nucleus of thalamus
unilateral lesion of SCP
ipsilateral ataxia
hypotonia
dysmetria
cerebral peduncle contains fibers of
corticospinal (middle third)
corticobulbar (more medial)
corticopontine
unilat lesion of cerebral peduncle
contralat motor deficit in body
contralat drooping of the corner of the mouth
location of the trochlear nucleus
midbrain
dorsal to MLF
where do the fibers of the trochlear nuc decussate?
superior medullary velum
trochlear n. innervates
contralat superior oblique mm
unilat lesion of the trochlear nuc
diplopia when looking down
contralat loss of motor control of sup oblique mm
input of sup colliculus
retina and visual cortices via brachium of sup colliculus
somatosensory and aud inputs
output of the sup colliculus
to the pulvinar
controls reflex mvmt of orientation of the head via the tectospinal tract
involved in generation of saccadic eye mvmts via cntions w frontal eye field & pontine reticular formation
medial geniculate nuclues
belongs to the diencephalon
thalamic relay for aud info
recieved inf from inf colliculus via brachium of inf colliculus and relays it to primary auditory cortex (Brodmann areas 41&42) via acoustic radiation
brachium of sup colliculus
passes dorsally to medial geniculate nucleus
carries info from retina & vis corticis to sup colliculus
superior cerebellar peduncle (in midbrain)
lateral to red nucleus
many fibers synapse w/in the red nucleus
rest go up to ventrolateral (VL) nuc of thalamus
rubrospinal tract (in midbrain)
medial and ventral to red nucleus
origin; red nuc
term; C and upper T levels of SC
fun: facilitates distal flexor MN of Upper limbs
fasciculus retroflexus (habenulointerpeduncular tract) in midbrain
medial to red nuclueus
connects habenula to interpeduncular nuc
ventral tegmental area (VTA)
rich in dopaminergic neurons that project to nucleus accumbens (mesolimbic pathway) & to prefrontal cortex (mesocortical pathway)
red nucleus
motor coordination upper limb flexors
inputs: contralat deep cerebellar nuclei (via SCpeduncle)
ipsilat motor cortex
outputs; via central tegmental tract to inf olive for motor neuron
substantia nigra
belongs to basal ganglia
motor control
1 - pars compacta - melanin-pigmented dopaminergic neurons projection to striatum (parkinsons)
2 - pars reticulata - mostly GABAergic neurons -> to VA of thalamus, sup colliculus, & pedunculopontine nuc
unilat lesion of oculomotor nuc
ophthalmoplegia
lateral strabismus
ptosis
Edinger-westphal nucleus
pre-g parasymp fibers -> ciliary ganglia - short ciliary br of V3 -> constrictor mm and ciliary mm (constric of pupil and accomodation of lens)
unilat lesion of Edinger-Westphal nuc
dilated pupil, loss of lens accomodation to near vision
unilat lesion of oculomotor nerve
ophthalmoplegia lateral or external strabismus ptosis dilated pupil loss of lens accomodation loss of pupillary light reflex (efferent)
oculomotor nerve emerges from
ventrally, from interpeduncular fossa
pars compacta
component of the substantia nigra
contains melanin-pigmented dopaminergic neurons -> striatum
degeneration of these neurons is major pathology in Parkinson’s disease
pars reticulata
component of substantia nigra
mostly GABAergic neurons projecting to ventral anterior (VA) nuc of the thalamus, sup colliculus, and pedunculopontine nuc
pretectal area of the tegmentum of midbrain
recieves input from both eyes
invovled in pupillary light reflex
posterior commissure
connects pretectal areas
accessory oculomotor nuclei
present in pretectal area of midbrain
several small nuclei along sides of periaqueductal gray
imp for generation of vertical eye mvmt
lesion of the accessory oculomotor nuclei
deficits in vertical gaze
lateral geniculate nucleus
thalamic relay for visual info from retina
via optic nerve -> LGN - optic radiation-> primary visual cortex (brodmann area 17)
pineal gland
melatonin production
reg circadian rhythms
melotonin prod stim by darkness and inhibited by light
melotonin also has an antigonadotropic action
