Exam Three - Basal Ganglia Flashcards
The ______ and ______ control postural reflexes and hand eye movements
brainstem and cerebellum
the _____ and _____ control voluntary movement
cerebral cortex and basal ganglia
3 levels of control of voluntary movement
1 - planning movement
2 - initiating movement
3 - executing movement
what is involved in the planning movement phase
basal nuclei
cortical association areas
cerebellum
what is involved in executing movement
cerebellum
movement
the basal ganglia sends output to
cerebral cortex and brian stem
T or F: all output from the cerebellum is inhibitory
T
the basal ganglia is involved in (3)
1 - voluntary movement
2 - procedural learning associated with habits
3 - eye movements
embryologically the basal ganglia arises from the ?
telencephalon
what makes up the basal ganglia (4)
1 - striatum
2 - globus pallidus
3 - subthalamic nucleus
4 - substantia nigra
caudate and putamen role
initiation and control of gross movement
circuits of the basal ganglia
loops that involves the cortex, the basal ganglia, and thalamus
the striatum normally works on this
GPi (inhibits it)
this is involved in cognitive and proprioceptive control of movement
motor thalamus
what is involved in the indirectly pathway
striatum
GPe
STN
GPi
Thalamus
What does the GPe act on and what does it do
inhibits the STN
what does the STN act on and what does it do
it excites the GPi
what is the only excitatory pathway within the intrinsic basal ganglia
STN-GPi
What happens in the indirect pathway
the striatum inhibits GPe which no longer inhibits STN. STN can now excite GPi which inhibits the thalamus so the thalamus is not sending motor info to the cortex. inhibition of unwanted movement
focused selection
supression of competing motor programs
the direct pathway is via
caudate/putamen
what is affected in parkinsons
substantia nigra
locus coeruleus
parkinsons is characterized by
abnormal movements
speed difficulties
cognitive changes
hypokinetic disordered alter the balance of _______ signals in the direct and indirect pathways
inhibitory
describe the direct pathway in parkinsons
substantia nigra -> D1 -> caudate/putamen -> globus pallidus internal -> VA/VL of thalamus - > frontal cortex
describe the indirect pathway in parkinsons
substantia nigra -> D2 -> caudate -> globus pallidus external -> subthalamic nucleus -> globus pallidus interal -> VA/VL of thalamus -> frontal cortex
in the direct pathway what is degenerated in parkinsons? indirect?
D1
D2
If D1 and D2 are degenerated what happens?
D1 can’t excite the direct pathway which leads to a diminished inhibition of the GPi segment so it inhibits the VA/VL more which leads to a decreased excitation of the frontal cortex
D2 can’t inhibit the indirect pathway so there is increased inhibition of the caudate/putamen on the GPe so it can’t inhibit the subthalamic nucleus which has an increased excitation on the GPi so it inhibits the VA/VL more and leads to decreased excitation of the frontal cortex
What are the 7 main symptoms of parkinsons
tremor
slowed movement
rigid muscle
impaired posture and balance
loss of automatic movements
speed changes
writing changes
what is huntington’s disease
progressive neurological disorder leading to neuron death and degeneration of the caudate and putamen
huntington’s disease direct pathway
the striatum dies so the GPi is less inhibited so it inhibits the thalamus more and there is decreased movement
huntington’s indirect pathway
the striatum dies so it can’t inhibit GPe so it inhibits the STN more. The STN is turn can’t excite GPi which will no longer inhibit the thalamus thus leading to increased movement
chorea
sudden, rapid, jerky, purposeless movement involving limbs, trunk, or face
dystonia
a condition of abnormal muscle tone that causes impairment of voluntary muscle movement
what is the etiology of HD
an autosomal dominant mutation in the gene huntingtin
CAG is repeated
what is the most common cause of hemiballism. Where is the lesion?
stroke, subthalamic nucleus
what causes chorea
pregnancy (gravidarum), huntingtons, infections, lupus, erythematosus, focal vascular lesions, PD, Levodopa
what is degenerated in huntinton’s (pathways?)
the connection between the caudate/putamen and globus pallidus
what is involved in initiating movement
motor cortex
the basal nuclei receives input from
cerebral cortex
what is the associated ventricle of the basal ganglia
lateral ventricles
putamen + caudate + nucleus accumbens =
striatum
role of nucleus accumbens
encodes motor programs that facilitate the aquisition of a given reward in the future
this connects to the glubus pallidus and receives afferents from substantia nigra and striatum. it also has a role in integration of somatic motor function
subthalamic nucleus
what are the 2 main motor pathways of the basal ganglia
direct
indirect
this prevents unwanted muscles contractions from competing with voluntary movement
indirect pathway
this facilitates the initiation and execution of voluntary movement
direct pathway
the direct pathway starts with
the striatum
the GPi normally does this
it inhibits the thalamus
the thalamus normally does this to the cortex
excites
in the direct pathway what happens?
the thalamus is disinhibited
striatum inhibits GPi so GPi doesn’t inhibit the thalamus anymore
what does the striatum do to the GPe
it inhibits it
direct pathway ________ the movement. Indirect pathway ________ the movement
starts, modulates
the indirect pathway is via
subthalamic
2 diseases associated with the basal ganglia
parkinsons
huntingtons
what causes parkinsons
loss of basal ganglia that release dopamine
T or F: Parkinsons is a hypokinetic disorder
T
In huntington’s which pathway is affected first
indirect
hemibalism
rare hyperkinetic movement disorder characterized by involuntary, violent, coarse and wide amplitude movements involving ipsilateral arm and leg
T or F: Huntingtons is primarily a hyperkinetic disorder
T
