Basal Ganglia Flashcards
cerebellar ataxia
lack of coordination of muscle movements
forced tremor
too many movements during movement
What can basal ganglia lesion lead to?
- parkinson’s disease
- huntington’s disease
What kind of tremor results from lesion to cerebellum? basal ganglia?
- cerebellum lesion = forced tremor
- basal ganglia lesion = rest/fine tremor
Parkinson’s disease involves:
a) too much movement
b) not enough movement
b) not enough movement
Huntington’s disease involves:
a) too much movement
b) not enough movement
a) too much movement
What are some symptoms of Parkinson’s disease?
- fine tremor (at rest)
- pill rolling tremor
- changes in mm tone
- poverty of movement (bradykinesia)
What are some symptoms of Huntington’s disease?
involuntary flinging and flailing movements (chorea)
TRUE or FALSE: the basal ganglia is a collection of subcortical ganglia.
FALSE: subcortical nuclei
Where does input to the basal ganglia come from?
cerebral cortex
Where does output from the basal ganglia go?
prefrontal, premotor, and primary motor cortices (via thalamus)
What are the principal nuclei of the basal ganglia? Which ones are input and output?
- striatum (caudate + putamen) - INPUT
- globus pallidus (internal + external) - OUTPUT
- substantia nigra - OUTPUT
- subthalamic nucleus
major neurotransmitter released from the basal ganglia?
GABA (inhibitory)
which neurotransmitter doe the neurons in the SNc (pars compacta) contain?
dopamine
Which neurotransmitter do the intrastriatal neurons contain?
acetylcholine
Which projection is the only excitatory intrinsic connection of the basal ganglia?
subthalamopallidal projection
What is the input nuclei of the basal ganglia?
SNc
What are the output nuclei of the basal ganglia?
GPi and SNr
which pathway is involved in increasing movement in the basal ganglia? Explain.
- activation of direct pathway DISINHIBITS thalamus
- increased thalamocortical activity
- increased movement
Which pathway is involved in decreasing movement via the basal ganglia? Explain.
- activation of indirect pathway INHIBITS thalamus
- inhibits thalamocortical neurons
- decreased cortical activity
- decreased movement
How does the normal brain initiate movement? Use the nuclei of the basal ganglia to explain. (hint: consider neurotransmitters involved)
- dopamine activates direct pathway: DA inhibits GPi from firing –> DISINHIBITION of thalamus –> increased thalamocortical activity -> increased movement
- dopamine inhibits the indirect pathway: DA inhibits striatal inhibition of GPe –> GPe inhibits GPi from firing –> DISINHIBITION of thalamus
How does the normal brain stop movement? Use the nuclei of the basal ganglia to explain. (hint: consider neurotransmitters involved)
- no dopamine released –> activation of indirect pathway –> striatum inhibits GPe from inhibiting GPi –> GPi further inhibits thalamus –> decreased cortical activity –> decreased movement
What is the cause of PD? How are the direct and indirect pathways affected in Parkinson’s disease? How is the thalamus affected? How are the neurotransmitters affected? How is movement affected?
- cause: loss of SNc cells –> low DA (deficiency)
- diminish excitatory effect on direct pathway
- enhance inhibitory effect on indirect pathway
- inhibition of thalamus
- decreased movement (hypokinesia)
What is the cause of HD? How are the direct and indirect pathways affected in Huntington’s disease? How is the thalamus affected? How are the neurotransmitters affected? How is movement affected?
- cause: striatal neurons of the indirect path (GABA) are lost
- no striatal inhibition –> GPe free to inhibit GPi
- disinhibition of thalamus
- increased movement (hyperkinesia)
Which principal nucleus in the basal ganglia is mainly affected by Huntington’s disease?
caudate nucleus
(hint: degeneration of striatal neurons in Huntington’s)
Which principal nucleus in the basal ganglia is mainly affected by Parkinson’s disease?
SNc
(hint: deficiency in DA)
What is the cause of hemiballismus? How are the direct and indirect pathways affected in hemiballismus? How is the thalamus affected? How is movement affected?
- cause: subthalamic nucleus blocked –> decreased excitatory action to GPi
- disinhibition of thalamus
- increased movement (hyperkinesia)
What are the 3 neurotransmitter systems used by the circuitry of the BG to facilitate movement?
- nigrostriatal dopaminergic system
- intrastriatal cholinergic system
- striatopallidal GABAergic system
do lesions of the BG produce contralateral or ipsilateral effects?
contralateral
