6- motor disorders

Question 1

what is the source of dopamine in the midbrain

Answer 1

substantia nigra pars compacta, SNc

Question 2

what is the role of the striatum and what makes up the striatum

Answer 2

• receives input from Sac and cortex

- caudate nucleus and putamen

Question 3

what forms the lentiform nucleus

Answer 3

putamen and globus palladus

Question 4

what is the role of the direct pathways

Answer 4

reinforces appropriate movements (excitatory)

Question 5

what is the role of the indirect pathways

Answer 5

edits out inappropriate movements (inhibitory)

Question 6

what is the action of dopamine in the basal ganglia

Answer 6

excites the direct pathway via D1 and inhibits the indirect via D2.

Question 7

which cortex does each basal ganglia regulate

Answer 7

the ipsilateral cortex

Question 8

what happens if the SNc is affected unilaterally

Answer 8

contralateral signs due to desiccation of corticospinal tract

Question 9

what causes Parkinson’s disease

Answer 9

degeneration of domapinergic neurones in SNc, lost dopamine driven facilitation of movement via indirect and direct pathways.

Question 10

what causes bradykinesia in parkinsons

Answer 10

slow movements due to loss of cortical excitation

Question 11

what causes hypophonia in parkinsons

Answer 11

bradykinesia of larynx and tongue

Question 12

what causes decreases facial movement and micrographic in parkinsons

Answer 12

bradykinesia of face and hands

Question 13

what is Huntington’s chorea

Answer 13

autosomal dominant disorder, causes loss of inhibitory projections from striatum to globus pallidus external. causes increased activation- hyperkinetic.

Question 14

symptoms huntingtons

Answer 14

chorea, dystonia, loss of coordination, cognitive decline and behavioural disturbances

Question 15

chorea

Answer 15

dance like movements due to increased motor activation

Question 16

dystonia

Answer 16

uncomfortable contractions of agonists and antagonists simultaneously causing odd postures.

Question 17

what is hemiballismus

Answer 17

damage to subthalamic nucleus or subcortical stroke causes unilateral explosive movements

Question 18

describe anatomy of cerebellum

Answer 18

midline vermis and two lateral hemispheres.

Question 19

how does the cerebellum communicate to the CNS

Answer 19

via the cerebellar peduncles

Question 20

what does the superior, middle and inferior cerebellar peduncles connect to

Answer 20

midbrain, pons, medulla§

Question 21

Role of cerebellum

Answer 21

decides on the most appropriate sequence of movements.

Question 22

describe the direct pathway , and explain how it is excitatory.

Answer 22

SNc gives dopamine to the putamen.
putamen sends inhibitory fibres to the GPi. this inhibits globus pallidus. as the globus pallidus inhibits the thalamus, the overall effect is excitation.

Question 23

explain the indirect pathway and explain how it is inhibitory

Answer 23

SNc gives dopamine to the putamen.
putamen sends inhibitory neurones to the GPe. the GPe is normally inhibitory on the STN, and so this activates the STN (inhibition of inhibition). this stimulates the GPi. As the GPi is normally inhibitory to the thalamus, this inhibits the thalamus (negative x positive).

Question 24

explain the indirect pathway and explain how it is inhibitory

Answer 24

SNc gives dopamine to the putamen.
putamen sends inhibitory neurones to the GPe. the GPe is normally inhibitory on the STN, and so this activates the STN (inhibition of inhibition). this stimulates the GPi. As the GPi is normally inhibitory to the thalamus, this inhibits the thalamus (negative x positive).

Question 25

where is the lesion Huntington’s, parkinsons and hemiballismus

Answer 25

huntingtons- indirect pathway
parkinsons- substantia nigra pars compacta
hemiballismus- subthalamic nucleus

Question 26

are basal ganglia/ cerebellar damage ipsilateral or contralateral

Answer 26

basal ganglia- contralateral as only one decussation in pathway by the corticospinal pathway

cereballar- ipsilateral as both the corticospinal pathway and the corticopontocereballar pathway decussate