Basal Pt 2 Flashcards
What is Huntington’s chorea? Where is the lesion? Is it inheritable?
involuntary jerky movements of face, tongue & limbs due to lesion of striatum & cortex
underactivity of indirect path facilitates direct path
loss of striatal GABA neurons that project to GP
Autosomal dominant, chromosome 4
What is athetosis?
writhing movement of limbs
loss of striatal GABA neurons seen in chorea
What is hemiballismus?
flailing of limbs
lesion of subtahalmus (virus) reduces inhibitory control over thalamus & cortical output
Parkinson’s disease is a deficiency of what?
dopamine!
What does Parkinson’s result in? It is degeneration of what? What is the tx, what can excess cause?
rests tremor, rigidity, inability to switch strategies, bradykinesia
degeneration of pigemented dopaminergic neurons in SNc
Tx= enhance DA levels or Rx that acts as DA antagonist
excess can cause schizophrenic-like symptoms
In Parkinson’s reduced DA projects to what two things and what does it cause in each?
dorsal striatum (caudate & putamen): involuntary movements ventral striatum (nucleus accumbens): bradykinesia, cognitive dysfunctions
Where do basal ganglia also project to outside of the GP-thalamus-cortex loops?
onto motor control centers in reticular formation (pedunculopontine nucleus)
GPi/substantia nigra reticulata–> ? –> ?
Is this pathways largely activating or inhibiting?
reticular formation–> flexor/extensor muscles
largely inhibiting
Extrapyramidal basal ganglia projections are affected by what? What do you get loss of and what does this cause?
PD= extrapyramidal disorder
loss of DA regulation= GPi/SNr has less dampening effect on reticular formation
With PD (parkinson’s) the reticulospinal tract is _______ which manifests inappropriate levels of _____ such as _____ muscle tremor & tension
less regulated; tonic activity; increased
What is the net effect of Parkinson’s and decreased DA levels on indirect and direct pathways actions of the GPi neurons?
dysregulation of indirect & direct pathway actions on GPi neurons= altered thalamo-cortical activity & behavior= tremor, bradykinesia, rigidity
PD pts have less ____ & rely more on ____ cues from _____ cortices for action initiating actions
DA; external; sensory
Post mortem studies show what?
greatest degeneration of DA projection system affects putamen area
In some cases where does DA degeneration begin and where does it progress to?
begins w/part of caudate in executive loop & extends to motivational loop
What are motor dysfunctions in PD initially? What can this initially be overridden by?
faulty executive decisions w/diminished ability to produce internally cued actions
can be overridden by visual loop (kinesia paradoxa) in early stages
Drug addiction is reinforced via what system?
mesolimbic DA system?
What four drugs transiently enhance DA levels in accumbens? And how do they do this?
amphetamine, cocaine, heroine & nicotine
either inhibit DA uptake or enhance its release
What do opioids do?
facilitate DA release by inhibiting GABA inhibition of DA neurons in VT
Nicotine stimulates what cells via what receptors?
VT DA cells via nicotinic cholinergic receptors
Cocaine & amphetamine inhibit what?
DA uptake at synapses in n. accumbens
DA release underlies what?
incentive learning & long term memories that contribute to craving
Addiction is associated w/an imbalance b/w what two areas acting on the n. accumbens?
PFC & VTA
Chronic drug & alcohol abuse is associated w/what?
hypofrontality: decrease in ability of vmPFC/OFC to inhibit accumbens which leads to behavioral disinhibition
enhanced activity of DA neurons in VTA= sensitization of responses to drugs & drug-related environmental stimuli
What is the spiraling effect?
drug intake spreads to other CS loops & impacts them
What are the loops impacted by the spiraling effect?
VTA DA neurons project to accumbens whose inhibitory neurons project onto substantia nigra these then innervate the dorsal striatum of executive & motor loops
addictive drugs active this loop to develop drug seeking habits (once dorsal striatum is recruited)
