7 - Basal Ganglia

Question 1

hypokinetic movement disorder?

Answer 1

too little movementq

Question 2

hyperkinetic movement disorder?

Answer 2

too much movement, and often abnormal involuntary movements

Question 3

what is the input region of the basal ganglia?

Answer 3

striatum

Question 4

what neurons are found within the striatum?

Answer 4

medium spiny neurones
interneurones

Question 5

what type of neurones are medium spiny neurones?

Answer 5

GABAergic
neuropeptides

inhibitory

Question 6

where do medium spiny neurones project to and from?

Answer 6

project from basal ganglia to other regions

Question 6

where do interneurons project?

Answer 6

w/i the basal ganglia

Question 7

what type of neurons are interneurons?

Answer 7

GABAergic
cholinergic

Question 8

what are the two pathways that input into the striatum?

Answer 8

• corticostriatal - main input
• nigrostriatal - fine tunes excitation

Question 9

what type of pathway is the corticostriatal pathway?

Answer 9

glutamatergic

Question 10

where does the corticostriatal pathway receive input from?

Answer 10

whole cerebral cortex

Question 11

what type of pathway is the nigrostriatal pathway?

Answer 11

dopaminergic

Question 12

where does the nigrostriatal pathway receive input from?

Answer 12

substansia nigra pars compacta

Question 13

when dopamine and glutamate interact, what do they do?

Answer 13

modulate synaptic strength

Question 14

which dopamine pathway is direct?

Answer 14

D1

Question 15

which dopamine pathway is indirect?

Answer 15

D2

Question 16

what neuropeptide is associated with the D2 pathway?

Answer 16

enkephalin

Question 17

what neuropeptide is associated with the D1 pathway?

Answer 17

dynorphin

Question 18

what is the basal ganglia responsible for?

Answer 18

fine tuning the initiation, control and termination of movements

Question 19

what are the different components of the basal ganglia?

6

Answer 19

• putamen
• caudate
• globus pallidus internus
• globus pallidus externus
• substantia nigra
• subthalmic nucleus

Question 20

the striatum refers specifically to what two components?

Answer 20

caudate and putamen

Question 21

what are hte two pathways involving dopamine in the basal ganglia?

Answer 21

indirect pathway
direct pathway

Question 23

how does the indirect pathway affect movement>

Answer 23

negative modulator of movement

Question 24

how does the direct pathway affect movement?

Answer 24

positive modulator of movement

Question 25

how does dopamine affect the direct and indirect pathways within the basal ganglia?

Answer 25

increased movements by activating direct pathways and inhibiting indirect pathway

Question 26

outline how the direct pathway initiates movement?

Answer 26

* motor cortex sends excitatory signals to the striatum via glutamate * striatum sends inhibitory signals to the GPi and SNr via GABA * stops their resting function which is to inhibit the thalamus * thalamus is now dis-inhibited * thalamus sends excitatory signals to motor cortex via glutamate * motor cortex allows movement to occur

Question 27

what role does dopamine play in the direct pathway w/i the basal ganglia?

Answer 27

* activates stiatum by interacting with D1 receptors (excitatory) * increases striatum's inhibitory effect * increases propensity towards movement

Question 28

outline how the indirect pathway regulatesmovement:

Answer 28

* motor cortex sends excitatory signals to the striatum via glutamate * striatum sends inhibitory signals to the GPe via GABA * GPe sends reduced GABA signals to subthalmic nucleus * subthalmic nucleus is dis-inhibited = sends more glutamate to GPi * excites GPi = sends more inhibitory signals to the thalamus via GABA * thalamus is inhibited = sends less excitatory signals to motor cortex * no impules is sent down spinal cord = decreased movement

Question 29

what role does dopamine play in the indirect pathway w/i the basal ganglia?

Answer 29

* binds to D2 receptors (inhibitory) * striatal neurons have reduced inhibition * supresses excitatory actions of subthalmic nucleus * GPi has less inhibition on the thalamus * increases motor cortec excitation

Question 30

what type of receptor are the D1 and D2 receptors?

Answer 30

G coupled protein receptors

Question 31

D1 and D2 are both G coupled receptors - what is their overall effect?

Answer 31

* activates the conversion of ATP to cAMP * causes phosphorylation/activation of intracellular substrates

Question 31

what are levels of dopamine during resting conditions?

Answer 31

low synaptic and extrasynaptic levels

Question 32

what are dopamine levels in active movement?

Answer 32

phasic dopamine release

Question 33

which dopamine receptors are preferential in resting conditions?

Answer 33

D2

Question 34

which dopamine receptors are preferential in active movement/learning?

Answer 34

D1

Question 35

how are the dopamine pathways different in parkinsons?

Answer 35

* relative overactivity of indirect pathways * relative underactivity of direct pathways

Question 36

what are 3 behavioural impairments in PD?

Answer 36

* cognitive disturbances - later dementia related to Lewy body pathology * impulse behaviour * depression, anxiety

Question 37

impulse behaviours in PD are linked to what?

Answer 37

severe dopaminergic deficit in ventral striatal areas

Question 38

depression and anxiety in PD are linked to what?

Answer 38

monoamine cell loss in brainstem

Question 39

what are 4 hyperkinetic movement disorders?

Answer 39

* chorea * dystonia * myoclonus * tic disorders

Question 40

what are three hallmarks of chorea?

Answer 40

* rapid, random irregular movements * flitting between various muscle groups and body parts * motor impersistence - can't maintain voluntary movements

Question 41

what is the pathophysiology of chorea?

Answer 41

* relative overactivity of direct pathways - excessive movement * underactivity of indirect pathways - no suppression of unwanted movements

Question 42

what is the pathophysiology of Huntington's disease?

Answer 42

* selective loss of D2 receptor-bearing indirect pathway neurones = involuntary movements * later loss of direct pathway neurones = hypokinetic movement disorders * loss of encephalin in indirect pathways

Question 43

what DNA sequence is altered in Huntington's disease?

Answer 43

expanded CAG repeats

Question 44

what are the two hallmarks of Tourette's syndrome?

Answer 44

* rapid, repetitive movements or vocalisations * comorbid neuropsychiatric illness - OCD or ADHD

Question 45

what is the pathophysiology of Tourette's?

Answer 45

* loss of cholinergic and GABAergic striatal interneuones = reduced basal ganglia inhibition * increased dopamine D2 receptor binding