Basal Ganglia Flashcards
structures of basal ganglia
- striatum
- globus pallidus (interna/externa)
- subthalamic nucleus
- substantia nigra
all paired, subcortical structures
striatum - structures, input, blood supply
- Caudate nucleus, putamen
- receive input from cortex
- branches from ACA and MCA (medial/lateral striate arteries)
globus pallidus - output, blood supply
- main output to thalamus
- branches of ICA and MCA (anterior choroidal a, lateral striate aa.)
subthalamic nucleus - blood supply, which pathway is it part of?
- key component of INDIRECT pathway
- branches of PCA and PCOM
substantia nigra - structures, regulator of what?, blood supply
- pars compacta (DA), pars reticula (output to thalamus)
- key inhibitor/activator of striatal activity
- blood supply: branches of PCA and PCOM
common area of hemorrhage?
basal ganglia
-very susceptible vessels
functions of extrapyramidal motor system
- facilitates voluntary movement (initiates movement– gas)
- attenuates involuntary movements (prevents unwanted movements – brake)
neurotransmitters involved with basal ganglia
- glutamate (excitatory)
- GABA (inhibitory)
- dopamine (excitatory or inhibitory)
direct pathway of basal ganglia
NET ACTIVATION of cortex
- stepping on the gas
- facilitates movements
striatum (-) –> GPi (-) –> thalamus (+) –> cortex
effect of dopamine on direct pathway of basal ganglia
STRONGER NET ACTIVATION of cortex
-substantia nigra activates striatum, leading to further activation
indirect pathway of basal ganglia
- NET INHIBITION of cortex
- hitting the brakes
striatum (-) –> GPe (-) –> STN (+) –> GPi (-) –> thalamus (+) –> cortex
effect of dopamine on indirect pathway of basal ganglia
NET ACTIVATION of cortex
- lifts breaks
- substantia nigra inhibits the striatum, thus inhibiting the inhibition
synthesis of dopamine
tyrosine –[tyrosine hydroxylase]–> L-Dopa –> dopamine –> norepinephrine
four cardinal features of hypokinetic disorders
“Parkinsonism”
1) BRADYKINESIA (required)
2) resting tremor
3) rigidity
4) postural instability
symptoms of hyperkinetic disorders
- tremors (rhythmic, oscillatory)
- hemiballismus (violent, flailing)
- myoclonus (rapid, jerk like)
- chorea (random, purposeless)
- dystonia (abnormal co-contraction of muscles)
- tics (stereotypic movements, supressible)
epidemiology of Parkinson’s disease (incidence, onset)
- 1-3% of population above age 60%
- onset: 55-60 years
- most idiopathic
Parkinson’s disease is a result of a loss of which cells?
Parkinson’s is a result of a loss of DOPAMINE cells in the SUBSTANTIA NIGRA
Parkinson’s affects which basal ganglia pathway?
DIRECT PATHWAY
- less dopamine is available to activate the direct pathway
- leads to a NET DEACTIVATION of the cortex
features of Parkinson’s disease
2+ symptoms:
- bradykinesia (required)
- resting tremor
- rigidity
- postural instability (late finding)
Asymmetry of symptoms
Functional neuroimaging
Lewy body
characteristic histologic symptom of Parkinson’s
- intracytoplasmic collections
- in the cortex, substantia nigra, olfactory bulbs (widespread)
SPECT (DaTscan)
- tracer absorbed into striatum
- shows uptake of dopamine
- lack of tracer = lack of dopamine transport = lack of dopamine
Tx for Parkinsons
- dopaminergic medications
- –carbidopa/levodopa
- –dopamine agonists
- –prolong dopamine via MAO/COMT inhibitors
- surgery
- –lesioning treatment (GP)
- –deep brain stimulation (GP or STN)
lesioning treatment
- for Parkinson’s
- outdated
- lesion the globus palatus to alleviate inhibition of thalamus
deep brain stimulation
- Tx for Parkinson’s
- implant stimulator to inhibit target
- ADJUSTABLE
