6- motor disorders Flashcards
what is the source of dopamine in the midbrain
substantia nigra pars compacta, SNc
what is the role of the striatum and what makes up the striatum
- receives input from Sac and cortex
- caudate nucleus and putamen
what forms the lentiform nucleus
putamen and globus palladus
what is the role of the direct pathways
reinforces appropriate movements (excitatory)
what is the role of the indirect pathways
edits out inappropriate movements (inhibitory)
what is the action of dopamine in the basal ganglia
excites the direct pathway via D1 and inhibits the indirect via D2.
which cortex does each basal ganglia regulate
the ipsilateral cortex
what happens if the SNc is affected unilaterally
contralateral signs due to desiccation of corticospinal tract
what causes Parkinson’s disease
degeneration of domapinergic neurones in SNc, lost dopamine driven facilitation of movement via indirect and direct pathways.
what causes bradykinesia in parkinsons
slow movements due to loss of cortical excitation
what causes hypophonia in parkinsons
bradykinesia of larynx and tongue
what causes decreases facial movement and micrographic in parkinsons
bradykinesia of face and hands
what is Huntington’s chorea
autosomal dominant disorder, causes loss of inhibitory projections from striatum to globus pallidus external. causes increased activation- hyperkinetic.
symptoms huntingtons
chorea, dystonia, loss of coordination, cognitive decline and behavioural disturbances
chorea
dance like movements due to increased motor activation
dystonia
uncomfortable contractions of agonists and antagonists simultaneously causing odd postures.
what is hemiballismus
damage to subthalamic nucleus or subcortical stroke causes unilateral explosive movements
describe anatomy of cerebellum
midline vermis and two lateral hemispheres.
how does the cerebellum communicate to the CNS
via the cerebellar peduncles
what does the superior, middle and inferior cerebellar peduncles connect to
midbrain, pons, medulla§
Role of cerebellum
decides on the most appropriate sequence of movements.
describe the direct pathway , and explain how it is excitatory.
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.
explain the indirect pathway and explain how it is inhibitory
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).
explain the indirect pathway and explain how it is inhibitory
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).
where is the lesion Huntington’s, parkinsons and hemiballismus
huntingtons- indirect pathway
parkinsons- substantia nigra pars compacta
hemiballismus- subthalamic nucleus
are basal ganglia/ cerebellar damage ipsilateral or contralateral
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
