Lecture 8 - Motor Disorders Flashcards
What is the basal ganglia?
Nuclei that are deep in the cerebral hemispheres responsible for motor control
What structures make up the Lentiform nucleus?
Putamen + Globus pallidus
What is the name of the white matter structure that surrounds the lentiform nucleus?
Internal capsule
What are the 3 main parts of the internal capsule surrounding the lentiform nucleus?
Ascending limb
Genu
Descending limb
What structures make up the striatum?
Caudate + Putamen
What are the main structures of the basal ganglia?
Caudate nucleus
Striatum (Caudate nucleus + Putamen)
Lentiform nucleus (Putamen + Globus pallidus)
Internal capsule
Thalamus
Lateral ventricles
How are the 2 structures positioned in relation to each other in the Lentiform nucleus?
Putamen = more superficial
Globus pallidus = deeper
Where are dopaminergic neurones located in the midbrain?
Substantia nigra
What part of the basal ganglia receives dopamine from the substantia nigra in the midbrain?
Putamen + Caudate (Striatum)
Do labels of brain (1)
Do labels of the basal ganglia (2)
What structure separates the cerebellum from the occipital lobe?
Tentorium cerebelli
What structures connect the cerebellum to the brainstem?
Cerebellar peduncles (white matter)
What key structure does the cerebellum form the roof of?
4th ventricle
What is the layout of the cerebellum?
2 lobes with a central structure called the vermis
What’s the structure separating the 2 lobes of the cerebellum called?
Vermis
What is the function of the prefrontal cortex, basal ganglia and cerebellum in movement?
Prefrontal cortex = decides rough plan of movement
Basal ganglia = receives rough plan from prefrontal cortex and analyses determining what needs to be stimulated (decides set of movement)
Cerebellum = decides the sequence the actions should be done in
Label cerebellum (3)
Generally, how does the basal ganglia decide the correct movements that need to be done?
Direct pathway facilitates correct movements
Indirect pathway Inhibits Inappropriate movements (III, Indirect Inhibits Innapropriate)
What is the function of basal ganglia in movement?
Decides most appropriate movements
What is the function of the cerebellum in movement?
Decides the appropriate sequence that movements should be in
What side of the body does the left cerebral hemisphere supply?
Right side of body
What side of the body does the left cerebellum supply?
Why?
Left side of body since its the right cerebral hemisphere that decussates supplying the left cerebellum
What is disinhibition?
Essentially inhibiting the inhibiting mechanism leading to increase activity
What is the main excitatory neurotransmitter?
What is the main inhibitory neurotransmitter?
Glutamate
GABA
What produces dopamine to supply the Putamen?
Substantial nigra pars compacta
What are the 2 pathways by which the Putamen can control movement?
Direct pathway
Indirect pathway
How does dopamine affect the direct pathway?
How does dopamine affect the indirect pathway?
Direct pathway = dopamine stimulates it which up-regulates appropriate movements
Indirect pathway = dopamine stimulates this pathway which inhibits inappropriate movements (Indirect Inhibits Inappropriate)
Image 4:
Talk about how the direct pathway works for stimulating movement:
Dopamine produced by substantia nigra inhibits the Globus Pallidus (internal) via the direct pathway. This means the thalamus isn’t inhibited so thalamus stimulates the cortex
Image 4:
Talk about how the indirect pathway works to inhibit movement:
Dopamine made in substantia nigra goes to Putamen
This stimulates the indirect pathway inhibiting the Globus Pallidus (external) so the subthalamic nucleus is not inhibited
STN stimulates the GLobus Pallidus (internal) which then inhibits the thalamus preventing it signalling to the motor cortex
What part of the brain is damaged in Parkinson’s disease?
Substantia nigra (dopaminergic neurones degenerate) so less dopamine reaches Putamen
What part of the pathway is damaged in Parkinson’s disease? (4)
How does this affect the pathway?
The substantia nigra (SNc)
Less dopamine to Putamen so GPi not inhibited so it inhibits the thalamus
How does Parkinson’s present?
How does this relate to the pathway?
Hypokinetic disorder
Brady Kinesia (slow movement since not receiving dopaminergic stimulus to start so slow initiation + termination of movement)
Rigidity (lead pipe rigidity)
Tremor
Psychiatric features
Why do Parkinson’s patients shuffle and struggle to initiate and stop their movement?
They produce a lot less dopamine so struggle to initiate movement
Image 4
What part of the pathway is damaged in hemiballismus?
Subthalamic nucleus (STN)
How does Hemiballismus present?
Explosive (ballistic) movement on the 1 side. Of the body
Using image 4:
Why does hemiballismus produce the symptoms it does?
Explosive movement since
STN damaged
If STN damaged, can’t stimulate GPi so cant inhibit the thalamus so get sporadic movemtn
What is Huntington’s chorea?
Autosomal dominant progressive disorder
What part of the pathway does Huntingtons Chorea damage? (4)
Inhibitory neurones to the GPe lost
Means GPe not inhibited so STN gets inhibited so GPi is not stimulated to inhiiibt the thalamus
So get overactivty of thalamus
How does Huntington’s chorea present?
Choreiform movemtns like fidgety
Dystonia (involuntary muscle contractions)
In coordination
Psychiatric features
What part of the body does the vermis of the cerebellum coordinate?
What do the hemispheres coordinate?
Vermis = trunk
Hemispheres = limbs
Where is the lesion if the patient can’t sit up but can coordinate limbs?
Vermis of cerebellum
How do cerebellar lesions present?
Vomiting
Vertigo
Difficulty walking
What is the pneumonic to remeber how cerebellar lesions present?
DANISH
How do cerebellar lesions present using the pneumonic?
Dysdiadochokinesia
Ataxia
Nystagmus
Intention tremor
Slurred speech
Hypotonia
How do you test for dysdiadochokinesia?
When patient holds out palm, then keeps flipping other hand on palm
What is nystagmus?
Flicker of eyes (faster towards the cerebellar lesion)
What is an intention tremor?
Pateint struggles to coordinate the closer they get to goal
When going to touch finger in distance coordination worse closer gets to finger
What causes slurred speech with a cerebellar lesion?
Cant coordinate laryngeal muscles
What are pendullar reflexes??
(Cerebellar lesions)
Hits patella and keeps swinging back and forth, reflex doesn’t terminate
