Basal Pt 2

Question 1

What is Huntington’s chorea? Where is the lesion? Is it inheritable?

Answer 1

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

Question 2

What is athetosis?

Answer 2

writhing movement of limbs

loss of striatal GABA neurons seen in chorea

Question 3

What is hemiballismus?

Answer 3

flailing of limbs

lesion of subtahalmus (virus) reduces inhibitory control over thalamus & cortical output

Question 4

Parkinson’s disease is a deficiency of what?

Answer 4

dopamine!

Question 5

What does Parkinson’s result in? It is degeneration of what? What is the tx, what can excess cause?

Answer 5

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

Question 6

In Parkinson’s reduced DA projects to what two things and what does it cause in each?

Answer 6

dorsal striatum (caudate & putamen): involuntary movements
ventral striatum (nucleus accumbens): bradykinesia, cognitive dysfunctions

Question 7

Where do basal ganglia also project to outside of the GP-thalamus-cortex loops?

Answer 7

onto motor control centers in reticular formation (pedunculopontine nucleus)

Question 8

GPi/substantia nigra reticulata–> ? –> ?

Is this pathways largely activating or inhibiting?

Answer 8

reticular formation–> flexor/extensor muscles

largely inhibiting

Question 9

Extrapyramidal basal ganglia projections are affected by what? What do you get loss of and what does this cause?

Answer 9

PD= extrapyramidal disorder

loss of DA regulation= GPi/SNr has less dampening effect on reticular formation

Question 10

With PD (parkinson’s) the reticulospinal tract is _______ which manifests inappropriate levels of _____ such as _____ muscle tremor & tension

Answer 10

less regulated; tonic activity; increased

Question 11

What is the net effect of Parkinson’s and decreased DA levels on indirect and direct pathways actions of the GPi neurons?

Answer 11

dysregulation of indirect & direct pathway actions on GPi neurons= altered thalamo-cortical activity & behavior= tremor, bradykinesia, rigidity

Question 12

PD pts have less ____ & rely more on ____ cues from _____ cortices for action initiating actions

Answer 12

DA; external; sensory

Question 13

Post mortem studies show what?

Answer 13

greatest degeneration of DA projection system affects putamen area

Question 14

In some cases where does DA degeneration begin and where does it progress to?

Answer 14

begins w/part of caudate in executive loop & extends to motivational loop

Question 15

What are motor dysfunctions in PD initially? What can this initially be overridden by?

Answer 15

faulty executive decisions w/diminished ability to produce internally cued actions
can be overridden by visual loop (kinesia paradoxa) in early stages

Question 16

Drug addiction is reinforced via what system?

Answer 16

mesolimbic DA system?

Question 17

What four drugs transiently enhance DA levels in accumbens? And how do they do this?

Answer 17

amphetamine, cocaine, heroine & nicotine

either inhibit DA uptake or enhance its release

Question 18

What do opioids do?

Answer 18

facilitate DA release by inhibiting GABA inhibition of DA neurons in VT

Question 19

Nicotine stimulates what cells via what receptors?

Answer 19

VT DA cells via nicotinic cholinergic receptors

Question 20

Cocaine & amphetamine inhibit what?

Answer 20

DA uptake at synapses in n. accumbens

Question 21

DA release underlies what?

Answer 21

incentive learning & long term memories that contribute to craving

Question 22

Addiction is associated w/an imbalance b/w what two areas acting on the n. accumbens?

Answer 22

PFC & VTA

Question 23

Chronic drug & alcohol abuse is associated w/what?

Answer 23

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

Question 24

What is the spiraling effect?

Answer 24

drug intake spreads to other CS loops & impacts them

Question 25

What are the loops impacted by the spiraling effect?

Answer 25

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)