N15- Anatomy of Basal Ganglia and Cerebellum, and Control of Movement Flashcards
how do the basal ganglia and cerebellum operate?
Operate using feedback loops via thalamus
What is the difference between the function of the cerebral cortex and basal ganglia and cerebellum?
- Cerebral cortex- what is to be done
- basal ganglia and cerebellum- how it is to be done(quality and organisation of movement)
What are the functions of the basal ganglia?
- to facilitate purposeful movement
- inhibit unwanted movements
- role in posture and muscle tone
What does basal ganglia do?
-Receive and process information from
cerebral cortex
-Feedback processed information to cortex
via the thalamus
Is the basal ganglia connected to the spinal cord?
No direct spinal cord connections.
Can only influence movement via cortex
What are the basal ganglia?
A number of masses of grey matter located near the base of each cerebral hemisphere
Name the 5 basal ganglia.
- Caudate nucleus
- putamen
- Globus pallidus
- Subthalamic nucleus
- Substantia nigra
What basal ganglia make up the striatum?
- Caudate nucleus
- putamen
What basal ganglia make up the lenticular nucleus?
- putamen
- Globus pallidus
What basal ganglia makes up the corpus striatum?
- Caudate nucleus
- putamen
- Globus pallidus
In a coronal brain slice, what is the location of the putamen, Globus pallidus , internal capsule and thalamus from lateral to medial?
Putamen> Globus Pallidus>internal capsule> thalamus
what does the substantial nigra look like in an axial section through the midbrain and why?
darkly stained substantia nigra (two black lines)
-black pigment as they make dopamine
what are the 2 pathways of the basal ganglia?
- Direct pathway
- indirect pathway
How Do the Basal Ganglia Work With the Motor Cortex to Enhance Normal Movement?
Direct Pathway: Enhances outflow of thalamus, enhancing the desired movement:
- Pyramidal neurones under voluntary control issue command to move
- Endpoint of feedback loop: stimulates cortex to enhance the desired movement
What action does dopamine neurone have in the direct and indirect pathways?
Dopamine stimulates putamen in the direct pathway but acts as inhibitory neurotransmitter in indirect pathway
How Do the Basal Ganglia Work With the Motor Cortex to Supress Unwanted Movement?
-inhibits outflow of thalamus
what do unilateral lesions of the basal affect?
the contralateral side of the body
What do lesions of the basal ganglia not cause?
paralysis, sensory loss, loss of power, or ataxia
what do lesions of the basal ganglia cause?
1) Changes in muscle tone
2) Dyskinesias (abnormal, involuntary movements) including:
- tremor (sinusoidal movements),
- chorea (rapid, asymmetrical movements usually affecting distal limb musculature)
- myoclonus (muscle jerks)
What pathology cause Parkinson’s disease?
degeneration of dopaminergic neurons of the substantia nigra
Name features of Parkinson’s disease.
- Resting tremor
- Rigidity - increased resistance to passive movement
- Paucity of movement
- Difficulty in initiating movement, small shuffling steps, no arm-swing
- Depression
- Impaired cognitive function
What is the pathology of Huntington’s disease?
progressive degeneration of the basal ganglia and cerebral cortex
what are the signs of Huntington’s disease?
chorea and progressive dementia
where does the sub thalamic nucleus sit?
Below the thalamus
what is the second (unconscious) motor control centre?
cerebellum
The cerebellums connections are related to what?
function
where does the cerebellum sit in relation to the cerebral hemispheres?
posterior and inferior
what are the gyrus named in the cerebellum?
folia
what are the 3 lobes of the cerebellum?
- Anterior lobe
- Posterior lobe
- Flocculonodular lobe
what is superior to the cerebellum?
Tentorium Cerebelli
How is the cerebellum attached to the brainstem?
3 stalks termed Peduncles
Name the 3 peduncles.
Middle,
superior
inferior
what do the peduncles carry?
different tracts and information into cerebellum
where does the vermis sit if the cerebellum is flattened out?
down the middle
what is the small region of grey matter in the core of white matter in the cerebellum?
deep cerebellar nuclei
what does the pontocerebellum consist of?
cerebellar hemispheres
what is the main function of the pontocerebellum?
fine muscle coordination (mainly limbs)
where does the pontocerebellum receive input from?
Pontine nuclei, which in turn receive fibres from the cerebral cortex
where does the pontocerebellum project to?
Thalamic area (VL) (that in turn projects to the motor cortex)
what is pontocerebellum related to?
the cerebellum listening to the cortex
what is the spinocerebellum related to?
the cerebellum listening to the spinal cord
where does the spinocerebellum exist?
lateral margins of the spinal cord
what does the spinocerebellum consist off?
the vermis
what is the main function of the spinocerebellum?
posture and muscle tone
where does the spinocerebellum receive its main input from?
Spinocerebellar tracts carrying proprioception, touch and pressure information
where does the spinocerebellum project to?
Via DCN to the Thalamus and brainstem to influence corticospinal, rubrospinal, reticulospinal and vestibulospinal output
what is the vestibulocerebellum related to?
the cerebellum listening to the vestibular system
what does the vestibulocerebellum consist of?
Flocculonodular lobe
what is the vestibulocerebellums main function?
maintaining balance
where does the vestibulocerebellum receive input from?
vestibular nuclei
where does the vestibulocerebellum project to?
Vestibular nuclei and from there influences the spinal cord via vestibulospinal tracts
what do cerebellar hemispheres influence?
ipsilateral side of the body
what is caused by lesions in the cerebellar hemispheres?
lead to ipsilateral signs and symptoms (contrast with lesions of motor or sensory cortex)
what does a unilateral 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 a midline lesion cause?
Disturbance of postural control. Patient will tend to fall over when standing or sitting despite preserved limb coordination
what does bilateral cerebellar dysfunction result in?
slowed, slurred speech (dysarthria), bilateral incoordination of the arms and a staggering, wide based gait (cerebellar ataxia)
what does acute alcohol exposure result in?
bilateral cerebellar hemisphere dysfunction and presents with cerebellar ataxia
Summarise the roles of the cerebellum.
-Regulates quality of movement
-Plans, coordinates fine skilled movement
Store learned motor progammes. Activity precedes movement
-The spinal cerebellum monitors movement via spinal input and compares cortical intentions with the results.
-Integrates balance information and coordinates muscle activation
responsible for equilibration
