Cerebellum and Basal Ganglia Flashcards
Where is the cerebellum located?
Posterior and inferior to the cerebral hemispheres
Below the tentorium cerebelli
What are the lobes of the cerebellum?
Anterior
Posterior
Flocculonodular
What fissure separates the anterior and posterior lobes of the cerebellum?
Primary fissure
What fissure separates the posterior and flocculonodular lobes of the cerebellum?
Posterolateral fissure
What attaches the cerebellum to the brainstem?
Peduncles (superior, middle, inferior)
What is the name of gyri in the cerebellum?
Folia
Where are the cerebellar nuclei and what is there function?
Deep grey matter
Send information to the brainstem and thalamus which can influence areas of the motor cortex or the descending tracts to modify movements
What are the 3 layers of the cerebellar cortex?
Molecular (outer)
Purkinje (middle)
Granule (inner)
Where do afferent projections to the cerebellum mainly project to?
Granule cell layer
What structure do the purkinje cells communicate with?
Deep cerebellar nuclei
The only output of the cerebellum is via axons of ____ cells
Purkinje
What are the functional divisions of the cerebellum?
Pontocerebellum (conscious movement)
Spinocerebellum (automatic function e.g. posture)
Vestibulocerebellum (equilibrium balance and posture) (flocculonodular lobe)
Vermis (posture, limb movement and eye movement)
Cerebellar hemispheres influence ipsilateral/contralateral side of the body
Ipsilateral
What does a unilateral cerebellar hemispheric lesion cause?
Disturbance of coordination in limbs
Can result in intention tremor and unsteady gait (in the absence of weakness or sensory loss)
What does bilateral cerebellar hemispheric dysfunction cause?
Results in slowed, slurred speech (dysarthria), bilateral incoordination of the arms and staggering wide based gait (cerebellar ataxia)
Acute alcohol exposure typically results in bilateral cerebellar hemisphere dysfunction and presents with cerebellar ataxia
What does a midline cerebellar lesion cause?
Disturbances to postural control
Patients will tend to fall over when standing or sitting despite preserved limb coordination
What are the basal ganglia and where are they located?
Masses of grey matter located near the base of each cerebral hemisphere
Name the parts of the basal ganglia
Caudate nucleus Putamen Globus pallidus Subthalamic nucleus Substantia nigra
Name the basal ganglia that make up the striatum
Caudate nucleus
Putamen
Name the basal ganglia that make up the corpus striatum
Caudate nucleus
Putamen
Globus pallidus
Name the basal ganglia that make up the lenitucular nucelus
Putamen
Globus pallidus
Which basal ganglia has a black strip and why is it black?
Substantia nigra
Produces dopamine and a black biproduct
What does the internal capsule separate?
Separates the caudate nucleus and the thalamus from the putamen and the globus pallidus
What are the functions of the basal ganglia? (3)
To facilitate purposeful movement
Inhibit unwanted movements
Role in posture and muscle tone
What is an inhibitory neuron?
A neuron that releases neurotransmitter that inhibits the next neuron
What are the main input nuceli of the basal ganglia?
Caudate nucleus
Putamen
What are the main output nuceli of the basal ganglia?
Globus pallidus
Substantia nigra
________ has inhibitory neurons which inhibit the thalamus to prevent unwanted movements
Globus pallidus
What does the direct pathway do?
Enhances the outflow of the thalamus, enhancing the desired movement
(silencing of neurons in the globus pallidus so the thalamus is no longer inhibited and movement can occur)
What does the indirect pathway do?
Inhibits the outflow of the thalamus
Involves the subthalamic nucleus which leads to suppression of unwanted movements by inhibiting the thalamus
Unilateral lesions of the basal ganglia affect the contralateral/ipsilateral side of the body
Contralateral
What symptoms do lesions of the basal ganglia cause?
Changes in muscle tone
Dyskinesias (abnormal, involuntary movements): tremor, chorea, myoclonus
What 2 disorders are associated with the basal ganglia?
Parkinson’s disease
Huntington’s disease
