Basal Ganglia and Cerebellum Flashcards
What part of the cerebellum does the floccus belong to?
The flocculonodular lobe
Where is the straight sinus located?
Within the tentorium cerebelli
What attaches the cerebellum to the brainstem?
3 peduncles = superior, middle and inferior
Where are the deep cerebellar nuclei located?
In the deep grey matter
What are the three layers of the cerebellar cortex?
Molecular layer = outer
Purkinje cell layer = middle
Granule cell layer = inner
Where do afferent projections to the cerebellum arrive from?
Spinal cord = from somatic proprioceptors and pressure receptors
Cerebral cortex = relayed via the pons
Vestibular apparatus = via the vestibular nuclei
Where in the cerebellum do afferent projections arrive?
Via cerebellar peduncles and project mainly to the granule cell layer
What is the only output from the cerebellum?
Via axons of Purkinje cells which mainly synapse on neurons of the deep cerebellar nuclei
What do efferent projections from the cerebellum contribute to?
Co-ordinating the functions of all the motor tracts of the brainstem and spinal cord
What happens to most efferent axons of the deep cerebellar nuclei?
Cross the midline and synapse in the thalamus = thalamus in turn sends fibres to the motor cortex
Why do lesions of the cerebellum cause ipsilateral signs and symptoms?
The cerebellar hemispheres influence the ipsilateral side of the body (e.g right side influences right side of body)
What happens if there is a unilateral cerebellar hemispheric lesion?
Disturbance of limb co-ordination = can result in intention tremor and unsteady gait in the absence of weakness or sensory loss
What happens if there is a midline cerebellar hemispheric lesion?
Disturbance of postural control = patient will tend to fall over when standing/sitting despite preserved limb co-ordination
What symptoms occur with bilateral cerebellar dysfunction?
Slowed slurred speech (dysarthria)
Bilateral uncoordination of arms
Staggering wide based gait (cerebellar ataxia)
What does acute alcohol exposure cause?
Bilateral cerebellar hemisphere dysfunction and cerebellar ataxia
What are the functions of the basal ganglia?
Facilitate purposeful movement
Inhibit unwanted movements
Role in posture and muscle tone
What are basal ganglia?
Masses of grey matter located near the base of each cerebral hemisphere
How do basal ganglia enhance normal movement?
Enhance outflow of the thalamus = pyramidal neurons under voluntary control issue command to move
What kind of pathway is utilised by basal ganglia to enhance normal movement?
Direct pathway = endpoint of feedback loop which stimulates cortex to enhance the desired movement
How do basal ganglia work with motor cortex to suppress unwanted movement?
Indirect pathway = inhibits outflow of thalamus
What side of the body is affected by basal ganglia dysfunction?
The contralateral side to the lesion
What symptoms are uncommon with basal ganglia lesions?
Paralysis, sensory loss, loss of power and ataxia
What motor signs occur with basal ganglia lesions?
Changes in muscle tone and dyskinesias
What are dyskinesias?
Abnormal involuntary movements
What are some examples of dyskinesias?
Tremor = sinusoidal movements Chorea = rapid asymmetrical movements usually affecting distal limb musculature Myoclonus = muscle jerks
What is Parkinson’s disease?
Degeneration of dopaminergic neurons of substantia nigra = akinesia, rigidity, resting tremor
What is Huntington’s disease?
Autosomal dominant condition = progressive degeneration of basal ganglia and cerebral cortex
What are some signs of Huntington’s disease?
Chorea and progressive dementia
What are the three sections of the cerebellum?
Vestibulocerebellum, pontocerebellum and spinocerebellum
What are some features of the vestibulocerebellum?
Consists of the flocculonodular lobe
Co-ordinates antigravity extensor muscles
What are some features of the pontocerebellum?
Co-ordinates voluntary movement
Encompasses most of cerebellum
What are some features of the spinocerebellum?
Consists of the vermis
Relates to posture
