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Flashcards in Brainstem; Midbrain Deck (39):
1

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

2

unilat lesion of the trochlear n

diplopia when looking down
ipsilat loss of motor control of superior oblique mm

3

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

4

locus ceruleus

main source of epinephrine

5

lateral lemniscus

fibers from cochlear and sup olivary nuclei
contains aud info from both ears
terminats; inf colliculus

6

tectospinal tract

origin; sup colliculus
term; high cervical spinal cord
function; reflex of turning head in resp to stimuli

7

inf colliculus

relay for aud info
lateral lemniscus ends here
origin of brachium fibers ->medial geniculate nucleus (MGN)

8

raphe nucleus

ventral part of periaqueductal gray
main source of serotonin

9

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

10

unilateral lesion of SCP

ipsilateral ataxia
hypotonia
dysmetria

11

cerebral peduncle contains fibers of

corticospinal (middle third)
corticobulbar (more medial)
corticopontine

12

unilat lesion of cerebral peduncle

contralat motor deficit in body
contralat drooping of the corner of the mouth

13

location of the trochlear nucleus

midbrain
dorsal to MLF

14

where do the fibers of the trochlear nuc decussate?

superior medullary velum

15

trochlear n. innervates

contralat superior oblique mm

16

unilat lesion of the trochlear nuc

diplopia when looking down
contralat loss of motor control of sup oblique mm

17

input of sup colliculus

retina and visual cortices via brachium of sup colliculus
somatosensory and aud inputs

18

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

19

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

20

brachium of sup colliculus

passes dorsally to medial geniculate nucleus
carries info from retina & vis corticis to sup colliculus

21

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

22

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

23

fasciculus retroflexus (habenulointerpeduncular tract) in midbrain

medial to red nuclueus
connects habenula to interpeduncular nuc

24

ventral tegmental area (VTA)

rich in dopaminergic neurons that project to nucleus accumbens (mesolimbic pathway) & to prefrontal cortex (mesocortical pathway)

25

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

26

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

27

unilat lesion of oculomotor nuc

ophthalmoplegia
lateral strabismus
ptosis

28

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)

29

unilat lesion of Edinger-Westphal nuc

dilated pupil, loss of lens accomodation to near vision

30

unilat lesion of oculomotor nerve

ophthalmoplegia
lateral or external strabismus
ptosis
dilated pupil
loss of lens accomodation
loss of pupillary light reflex (efferent)

31

oculomotor nerve emerges from

ventrally, from interpeduncular fossa

32

pars compacta

component of the substantia nigra
contains melanin-pigmented dopaminergic neurons -> striatum
degeneration of these neurons is major pathology in Parkinson's disease

33

pars reticulata

component of substantia nigra
mostly GABAergic neurons projecting to ventral anterior (VA) nuc of the thalamus, sup colliculus, and pedunculopontine nuc

34

pretectal area of the tegmentum of midbrain

recieves input from both eyes
invovled in pupillary light reflex

35

posterior commissure

connects pretectal areas

36

accessory oculomotor nuclei

present in pretectal area of midbrain
several small nuclei along sides of periaqueductal gray
imp for generation of vertical eye mvmt

37

lesion of the accessory oculomotor nuclei

deficits in vertical gaze

38

lateral geniculate nucleus

thalamic relay for visual info from retina
via optic nerve -> LGN - optic radiation-> primary visual cortex (brodmann area 17)

39

pineal gland

melatonin production
reg circadian rhythms
melotonin prod stim by darkness and inhibited by light
melotonin also has an antigonadotropic action