Deep Brain Structures 1 Flashcards
function of basal ganglia as a collective group
to refine movement
basal ganglia consist of:
- caudate
- putamen
- globus pallidus
- claustrum
- amygdala
caudate + putamen =
striatum
putamen + GP =
lenticular system
caudate
- lateral to lateral ventricles
- a circular nucleus
putamen
- fuses w/ head of caudate
- the outside portion
amygdala
- the end of the caudate
- related to emotion
internal capsule
- mass of fibers between the GP/putamen and the caudate
- represents the ascending and descending fibers to and from cortex
basal ganglia afferents are from:
4 regions
- cerebral cortex
- substantia nigra
- thalamus
- subthalamic nucleus
where do the basal ganglia relay the afferent input that it receives?
GP
cerebral cortex as basal ganglia afferent
- one of the largest projections
- excitatory to basal ganglia
substantia nigra as basal ganglia afferent
- projects mainly to caudate but also to putamen
- inhibitory via dopamine
- excitatory via Ach
clinical correlation of substantia nigra being excitatory and inhibitory
- Parkinson’s treament
- it’s a loss of dopa so you get extra Ach
- tx: anticholinergic
thalamus as basal ganglia afferent
- the thalamus is sensory relay for everything except smell
- excitatory to basal ganglia
subthalamic nucleus as basal ganglia afferent
-excitatory to basal ganglia
what is considered the receptive portion of the basal ganglia?
-caudate and putamen
where do the caudate and putamen project to after receiving afferents?
GP
basal ganglia output is from?
GP
modality of GP
-ALL inhibitory
basal ganglia efferents go to:
3 regions
- thalamus
- subthalamus
- red nucleus
basal ganglia efferent to thalamus
- encourages everything to fire
- goes on to cortex
basal ganglia efferents to subthalamus
also gets back to the cortex
basal ganglia efferents to red nucleus
-goes to the spinal cord
what happens if you lose inhibition to the red nucleus (i.e a lesion above the red nucleus but below the basal ganglia)
-you’ll see a release of function
-red nucleus can fire at well
= decorticate posturing
since all of the basal ganglia efferents are inhibitory, what is the neurotransmitter?
GABA
which of the basal ganglia project to the spinal cord?
NONE
since basal ganglia don’t project to the SC, how is movement modulated?
it does so in the cerebral cortex and brainstem nuclei like the red nucleus
GP effect on motor curcuits
- GP exerts a continuous inhibitory effect on motor thalamocortical curcuits
- acts as a “brake”
what is the outcome if the basal ganglia inhibitory feedback loop (i.e the brake) is removed?
tremor/shake
“if you remove the brake you get a shake”
tremor is aka
dyskinesias
athetosis
slow, worm like, writhing of extremities or neck
when is athetosis seen?
cerebral palsy
choreaform dyskinesia
-quick, jerky, involuntary, distal extremity, tongue, face
in general, dyskinesias are secondary to:
- release phenomenon
- i.e an inhibitor is gone so movement that it suppressed is now “released”
- disinhibition
what is less understood about dyskinesias?
- there are also inhibition manifestions
- like in PD: flat affect and shuffling gait or in tardive dyskinesia
tardive dyskinesia can be caused by:
- psych meds that inhibit DA action in striatum
- ex: Haldol and prolixen
basal ganglia issue in PD
dopa loss from the substantia nigra
basal ganglia issue in Huntington’s
GABA loss from caudate
Sydenham’s chorea
- self limiting
- seen in kids that were not treated for strep and develop rhuematic fever
- get small hemorrhaged and develop st. vitas dance tremor
hemiballism
- unilateral lesion of the subthalamic nucleus
- usually d/t stroke
- causes huge flailing contralateral tremor
if there are infarcts of small vessels, what is always the answer?
- DM
- HTN
- smoking
wilson’s disease
- familial disorder of copper metabolism
- lesions putamen and GP
- aka hepatolenticular degeneration
hallmark of wilson’s disease
- Kayser-Fleischer rings
- flapping tremor
internal capsule
- contains motor fibers going out and sensory fibers going back up
- has ant. and post limb
- comes from all over brain but 90% are from 3 areas
what are the 3 areas that make up 90% of the internal capsule?
- pre central gyrus
- post central gyrus
- premotor area
anterior limb of the internal capsule
all connections b/w the basal ganglia and the thalamus
posterior limb of internal capsule
- descending and ascending input
- FAL and fal areas (face arm leg)
FAL of internal capsule posterior limb
-location of motor fibers from pre central gyrus that give rise to the corticospinal tract
fal of internal capsule posterior limb
-location of sensory info that is traveling back up to the post central gyrus
striate arteries are branches of what artery?
middle cerebral a.
middle cerebral a. supplies:
the dorsolateral surface of the brain
outcome of stroke at the middle cerebral a.
- motor AND sensory loss
- contralateral muscle weakness and parasthesia
outcome of stroke at the striate arteries
-lose either motor or sensory but rarely both
what is a stroke to the striate arteries called?
lacunar infarct
brodemann’s areas
-numbers of areas in the brain that individually correspond to specific function
brodemann area 4
- pre central gyrus
- principal motor area
- contributes 1/3 of the corticospinal tract
brodemann area 6
-pre motor area
result of a lesion of area 6
loss of initiation of motor function
area 3 2 1
postcentral principal sensory area
anatomy of thalamus
- one of each side of brain
- related to 3rd ventricle
- has hypothalamic sulcus and hypothalamus beneath it
what is the structure called in some people who have a connected thalamus?
massa intermedia
foramen monroe
opening of 3rd ventricle leading to the lateral ventricles
