L44 Movement Disorders Basal Ganglia Flashcards
what does the BG receive info about motor commands from?
prefrontal cortex
premotor cortex
primary motor cortex
does the BG have any direct synaptic connections with motor neurons?
NO - through the thalamus, the BG participates in the initiation and control of voluntary movement
what is the role of the BG?
initiation an control of voluntary movement through the thalamus
what are the 4 nuclei of the BG?
straitum - caudate n. + putamen
globus pallidus - GPm, GPl
subthalamic n.
substantia nigra - pars reticulata and pars compacta
are the motor neurons in the BG excitatory or inhibitory?
inhibitory
what type of receptors are D1 receptors in the striatum?
excitatory
what type of receptors are D2 receptors in the striatum?
inhibitory
what is the effect of the direct pathway on movement?
facilitate movement
what is the effect of the indirect pathway on movement?
inhibits movement
describe Parkinson’s disease
bilateral degeneration of dopaminergic cells in SN
what type of disorder of Parkinson’s disease?
HYPOkinetic
what are the sx/sx of Parkinson’s disease?
bilateral... akinesia bradykinesia resting tremors muscular rigidity .. see notes on video lecture
describe Huntington’s Chorea?
bilateral degeneration/loss of strial GABA neurons that EXPRESS D2 receptors
what type of disorder is Hungtinton’s Chorea?
HYPERkinetic
what are the sx/sx of Huntington’s Chorea
irregular bilateral movements
dyskinesia
involuntary movement of head, arms, legs
marked change in mental status
describe hemiballismus
lesion of the subthalamic n. usually from stroke
what type of disorder is hemiballismus?
HYPERkinetic
what are the sx/sx of Hemiballismus?
irregular movements of the limbs and trunk on contralateral side
involuntary flinging arms and writhing movements of the leg ON ONE SIDE
what is parkinsonism?
describes symptoms involving any combo of resting tremors, muscular rigidity, bradykinesia, impaired postural reflex
what are the 4 things that can look like parkinson’s disease (perhaps differential dx)?
drug induced vascular repetitive head trauma postencephalitic neoplastic
describe drug induced parkinsonism?
- antipsychotic drugs (DA receptor blockers)
- depletors of DA stores (reserpine - old BP med)
- toxic contaminants (MPTP) - homemade drugs toxin…
describe vascular parkinsonism
strokes affecting the BG (nigrostriatal path)
affects lower body and gait
describe reptitive head truma
boxing-like injury associated with dementia because of damage to the midbrain
describe postencephalitic parkinsonism
virally induced degenerations of substantia nigra
describe Sydenham’s chorea
linked to childhood rheumatic fever
transient, but preg women are susceptible for recurrence
describe drug induced chorea
caused by L-dopa, anticonvulsants or antipsychoics as a result of enhancing dopaminergic transmission within the BG
what are drug therapies for parkinson’s disease?
L-dopa dopamine agonist drugs that enhance dopamine release MAO inhibitors COMT inhibitors anticholinergic drugs
what does L-dopa do?
increases rate of dopamine synthesis in the still functional SNc
given orally with cabidopa to prevent dopamine synthesis outside of CNS
effectiveness decreases over time as SNc neurons die out
what do dopamine receptor agonists do?
D2 agonist - bromocriptine
D1 and D2 agonist - pergolide
bypass degenerating nigrostriatal neurons and acts directly on postsynaptic receptors
what are drugs that enhance dopamine release?
anti-viral drug
amantadine - good effect on akinesia and rigidity, but PSYCHO
may promote release of dopamine or block ACh receptors
what do MAO inhibitors do?
selegiline - block dopamine breakdown
may delay the need for other therapies
what do COMT inhibitors do?
inhibit dopamine breakdown– increase dopamine effects
may be given in addition to L-dopa and carbidopa
what makes up the lentiform nucleus?
putamen and globus pallidus
what makes up the striatum?
caudate n. + putamen
what provides vital modulation to the direct and indirect pathways?
substantia nigra — dopamine producing cells projects into the striatum to release DA
what is the function of DA in the direct and indirect pathways?
regulates BG function – thus, indirectly regulating cortical control of movement
ALWAYS cortical excitation = increased movement!
what type of feedback is seen in direct BG loop
positive - cortical input increases cortical activity
what type of feedback in seen in indirect BG loop?
negative - cortical input supresses cortical activity
describe neoplastic parkinsonism
tumors can disturb the nigrostriatal system
describe athetosis
striatal or thalamic injury can yield continuous writhing
what do anticholinergic drugs do?
muscarinic antagonists - suppress ACh mediated excitation of striatal neurons
ACh makes parkinsonism WORSE!
what sites are ablated (burned) in surgical ablation?
subthalamus
medial globus pallidus
both of them are way overactive = hyperkinesis
what sites are involved in deep brain stimulation
thalamus
golbus pallidus
subthalamus
what happens when you increase DA transmission (maybe from L-dopa drug)?
PSYCHOSIS
what is therapeutically given for brain degeneration?
block D2 receptors
