L10: Motor Control- The Cerebellum Flashcards
Where is the cerebellum located
Close to the brainstem
What is the cerebellum involved in
Control of motor tone
Sensorimotor coordination
Motor learning e.g playing an instrument
What are the 3 anatomical components of the cerebellum
Spino-cerebellum
Vestibulo-cerebellum
Cerebro-ponto-cerebellum
Which region is Spino-cerebellum located within the cerebellum
Medial region
Which region is the vestibulo cerebellum located within the cerebellum
Caudal region
Which region is the cerebro-cerebellum located
Lateral hemispheres
What input does the spino-cerebellum receive
Receive sensory input from spinal cord
What is the output of the spino-cerebellum from
Reticular formation
Red nucleus
What pathways does the spine-cerebellum involve
Medial and lateral descending pathways
From the reticular formation and red nucleus where does the info go
Motor cortex
From the motor cortex what is the output
Control over axial musculature (medial pathway)
And posture
What does the vestibulo-cerebellum receive input from
Vestibular nucleus (ventromedial pathway)
What is the output of the vestibulo-cerebellum to
Vestibular nucleus (ventromedial pathway)
What does the output of vestibulo-cerebellum control
Posture and balance and eye movement
What is the input of the cerebral-cerebellum from
Primary motor cortex
What is the output of the cerebro-cerebellum to
Primary motor cortex
Therefore what is the cerebral-cerebellum involved in
Intra cerebral motor loop
What is the parallel fibres in the cerebellum derived from
Granule cells
What are mossy fibres
Fibres that carry sensory into into cerebellum that interact with granule cells and then parallel cell fibres and then purkinje fibres
What is the the role of climbing fibres
Sensory input directly to purkinje fibres
Where does purkinje fibres send signal to
Deep cerebellar nuclei
What other cells in the cerebellum can directly interact with the deep cerebellar nucleus
Mossy fibres
Climbing fibres
What effect does climbing fibres have on the purkinje fibres
Excitatory influence
What effect does mossy fibres have on purkinje fibres
Indirect excitatory influence via parallel fibres of granule cells
What cell is the only output from the deep cerebellar nuclei
Purkinje fibres
What type of output does purkinje fibres have
Inhibitory output
If the mossy fibres and climbing fibres that give an excitatory input to the deep cerebellar nuclei, what does the inhibitory input from the purkinje fibres do
The inhibition from the purkinje fibres modulate the level of excitation
Overall what is the output of the cerebellum
Inhibitory
What does the deep cerebellar nuclei do
Compare the 2 inputs from the mossy and climbing cells and after processing an inhibitor signal is sent
Where does the deep cerebellar nuclei send the information to
Brain stem and thalamus
What is the comparison of the deep cerebellar nuclei of
Intended movement
Actual movement
Via mossy and climbing fibres
Summarise the 4 roles of the cerebellum
1) regulate posture by adjusting the descending motor pathways
2) acts as a compactor of actual movement and intended movement
3) acts as time to result in smooth muscle performance
4) involved in motor memory
What does the basal ganglia integrate
Sensory and moto info
What type of movement does the basal ganglia initiate
Voluntary movement
What is the basal ganglia composed of
Subcortical nuclie
Where does the sensory and motor info to the basal ganglia come from
Cortex
When the basal ganglia has intergrated the info where does it send info to
Pre-motor Cortex via thalamus
In normal resting situation what is the outflow of the basal ganglia
Inhibitory to the cortex
When the pre-frontal cortex is switched on i.e when the body wants to move (voluntary movement) what type of signal is sent to the basal ganglia from the cortex
Excitatory flow
What does the excitatory outflow from the pre-frontal cortex do to the basal ganglia
Switch it off
What does switching off basal ganglia do to the thalamus
Switch it on as it is no longer inhibited by the basal ganglia = disinhibition
What type of signal is sent to the supplementary motor cortex
Excitatory so it initiates a movement
What are the structures in the basal ganglia
Caudate nucleus, putamen, nucleus accumbens = striatum
Subthalamic nuclues
globus pallidus: internal and external
Substantia niagra: reticulata and pars compacta
Where does input from the cortex go to in the basal ganglia
Striatum
Where is output from the basal ganglia from
Globus pallidus: internal
Substantia nigra: reticulata
Where does the output of the internal segment of globus pallidus and reticulata of substantia nigra go to
Thalamus
What is the signal of output of the basal ganglia to the thalamus at rest
Inhibitory
What are the 2 pathways within the basal ganglia called
Direct pathway
Indirect pathway
What does the direct pathway involve
Signal from the striatum directly to the substantia nigra reticulata and globus pallidus internal
What is the indirect pathway
Signal from the striatum indirectly to the globus pallidus external a and subthalamic nucleus
When the cortex signal to the striatum what happens as a result of the direct pathway
1) Promoting movement as the stratium sends an inhibitory signal to the substantia nigra reticulata and globus pallidus internal to inhibit it
2) inhibitory signal is no longer sent to the thalamus so it becomes activated = disinhibition
What does the substantia nigra pas compact release
Dopamine
What receptors does dopamine act on
D1 receptors on the striatum
When dopamine binds to D1 receptors in the striatum, what happens to the striatum
Increases inhibition down the direct pathway to cause the activation of the thalamus and SNR and GPI are inhibited
What is the overall outcome of the indirect pathway in the basal ganglia
Suppress movement
How does the indirect pathway inhibit movement
1) the striatum sends an inhibitory signal to the globus pallidus external
2) globus pallidus external becomes inhibited and therefore can no longer inhibit the subthalamic nucleus which usually drives the SNR and GPI
3) subthalamic nucleus is also further excited by the cortex which sends an excitatory signal to the SNR/GPI that inhibits the thalamus
When dopamine is released by the substantia nigra pars compacta what receptors does the dopamine act on to become involved in the indirect pathway
D2 receptors
What affect does the binding of dopamine to D2 receptors have on the striatum
Striatum becomes inhibited
If the striatum becomes inhibited by dopamine what affect does this have on the globus pallidus external
1) GPE is no longer inhibited
2) GPE sends inhibitory signals to the subthalamic nucleus
3) subthlamic nuclues reduces in the excititory signal to SNR/GPI so outflow of SNRI/GPI is reduced
4) thalamus becomes activated
5) movement is initiated
Regardless of the pathway being direct or indirect what does dopamine do
Cause the initiation of movement
If there is an imbalance in direct and indirect pathway what does this result in
Motor dysfunction
What are the 2 broad categories of disorders
Hypokinetic
Hyperkinetic
What does hypokinetic disorders mean
Less movement disorders
Give an example of less movement disorders
Parkinson’s disease
What does hyperkinetic disorders mean
Too much movement disorders
Name examples of hyperkinetic disorders
Huntington’s disease
Hemiballism
Tardive dyskinesia
What are the 3 main symptoms of Parkinson’s disease
Tremor
Bradykinesia
Rigidity
What are the causes of Parkinson’s disease
Loss of nitro-strait also dopaminergic pathway
What is the treatment for Parkinson’s disease
L-dopa
Dopamine agonist
Drugs that prevent dopamine breakdown e.g monoamine oxidase b inhibitors
What are the 3 symptoms of Huntington’s disease
Excessive movement
Uncontrollable rapid motor patterns
Dementia or psychiatric disturbance
What is the cause of Huntington’s disease
Autosomal dominant disorder
What is the primary pathology of Huntington’s disease
1) Loss of striata output in indirect pathway
2) GPE is inhibited less and sends inhibitory signals to STN
3) STN decreases input to SNR and GPI
4) output to thalamus decreases
5) this causes involuntary movement
What are the 3 treatments for symptomatic relief for Huntington’s disease
Tetrabenazine
Chlorpromazine
Baclofen
What does tetrabenazine do
Decreases dopamine release by inhibiting VMAT
What is chlorpromazine
Dopamine antagonist
What is baclofen
GABA- b agonist which decreases spinal reflexes that are increased in Huntington’s disease
What is the symptom of hemiballismus
Violent flailing movement to limbs
What is the cause of hemiballismus
Damage to STN
What is the effect of tardive dyskinesia
Uncontrolled movement of face and trunk muscles
What is the cause of tardive dyskinesia
Long term exposure to antipsychotic drugs (dopamine receptor antagonist)
What dysfunction can occur if there is damage to the spinocerebellum
Ataxia (unsteady gait)
Dysmetria (inaccurate termination of movement) and intention tremor
Dysdiadochokinesia (inability to perform rapid alternating movements)- get patient to tap their foot quickly or flip hands
Hypotonia (decreased muscle tone)
What dysfunction can occur if there is damage to the vestibulo-cerebellum
Ataxia
Slow saccades (slow movement of the eye to left to right )
Nystagmus (vibration of the eye)
What dysfunction can occur if there is damage to the cerebro-cerebellum
Ataxia (unsteady gait)
Dysmetria(intention tremor)
Dysarthria (articular speech due to poor oropharngeal control)
