Motor Disorders Flashcards
Are Basal Ganglia in the CNS or PNS?
CNS (A group of structures, not a ganglion which are in PNS)
What are the 2 parts of the Lentiform Nucleus
- Globus Pallidus (medially)
- Putamen (laterally)
(The two are not functionally related, only anatomically)
What are the 2 parts of the Globus Pallidus
Internal and external segment
Globus Pallidus Interna/ Externa
Describe broadly the function of the 2 parts of the Lentiform Nucleus
- Striatum receives input from Cortex and Substantia Nigra pars compacta (SNc)
- Globus Pallidus sends output to Cortex via thalamus
Describe the Substantia Nigra
- Part of Midbrain
- Contains dopaminergic neurons
- 2 components: pars compacta and pars reticulata
(Source of Dopamine)
What pathway connects the Striatum to the Substantia Nigra?
Nigrostriatal pathway
The Basal Ganglia is spread throughout the forebrain and is divided into 3 types of nuclei.
Name these 3 types and state their functions
- Input nuclei: Receive information
- Intrinsic nuclei: Info relayed to these for processing
- Output nuclei: Info passed to these
List the Input Nuclei of the Basal Ganglia
Caudate nucleus + Putamen (Striatum)
List the Intrinisc Nuclei of the Basal Ganglia
- Globus Pallidus Externa
- Subthalamic nucleus
- SNc (Substantia Nigra pars compacta)
List the Output Nuclei of the Basal Ganglia
- Globus Pallidus Interna
- SNr (Substantia Nigra pars reticulata)
The Basla Ganglia communicate with the Motor cortex via the Thalamus.
Thus, how are Thalamic and Cortical activity linked?
An increase in one causes an increase in other
What are the 3 structural components of the cerebellum?
Which body parts are they associated with?
- 2 lateral hemispheres-> Ipsilateral/ distal body
- A midline Vermis-> Midline/ Trunk
Describe the connection of the Cerebellum with the Brainstem
- Superior peduncle connects to Midbrain
- Middle peduncle (largest) connects to Pons
- Inferior peduncle connects to Medulla
The Cerebellum sits above the 4th ventricle.
What can Cerebellar lesions cause?
Hydrocephalus
Briefly describe the functions of the Basal Ganglia and Cerebellum
Basal Ganglia;
- Determines the most appropriate set of movements
Cerebellum;
- Determines the appropriate sequence of movements
How does the Basal Ganglia carry out its function?
- Direct pathway reinforces/ facilitates appropriate movements (excitatory to motor cortex)
- Indirect pathway inhibits inappropriate movements (inhibitory to motor cortex)
Between what structures are the Direct and Indirect Pathways?
Direct: Putamen to GPi (Globus Pallidus Interna)
Indirect: Putamen to GPe to Subthalamic nucleus)
Describe the Direct Pathway
Putamen inhibits GPi, which inhibits Thalamus
Thus, net excitation of Thalamus
Describe the Indirect Pathway
Putamen inhibits GPe, which inhibits STN, which excites GPi, which inhibits Thalamus
(Subthalamic Nucleus net effect: Thalamus inhibition)
Thus, reduced/ absent inhibition of STN, resulting in Thalamus inhibition
Basal Ganglia have a dopaminergic input from the Substantia Nigra.
Describe how Dopamine facilitates movement by exiting the motor cortex
Excites direct pathway by;
- Stimulating excitatory D1 receptors on striatal neurones, which are in the pathway
Inhibits indirect pathway by;
- Activating inhibitory D2 receptors on striatal neurones, which are in the pathway
What causes Parkinson’s?
List 8 symptoms
Degeneration of dopaminergic neurones in SNc(->reduced cortical activity)
- Tremor (Possiblely due to dysfunction of indirect pathway)
- Rigidity (Possibly due to reduced coordination between agonists/ antagonists)
- Bradykinesia (Slow movements due to cortical activity loss)
- Hypophonia (Quiet speech, larynx + tongue bradykinesia)
- Micrographia (Hand bradykinesia)
- Decreased facial movement (Face bradykinesia)
- Dementia
- Depression
Briefly compare Parkinson’s, Huntington’s Chorea and Hemiballismus in terms of movement
Parkinson’s- Decreased movement
Huntington’s Chorea- Increased movement
Hemiballismus- Increased movement
Huntington’s Chorea is Autosomal Dominant, with early onset around 30-50yrs
Describe the cause
Loss/ reduced activity of Indirect Pathway, leading to Hyperkinetic features
List 4 symptoms of Huntington’s Chorea
- Chorea (dance like movements)
- Loss of coordination
- Cognitive decline + behavioural disturbances
- Dystonia (Odd postures due to over activity in + loss of coordination between agonists and antagonists
Describe the cause of Hemiballismus
How does it present?
- Damage to STN, possibly by sub-cortical stroke/ lacunar Infarct
- Unilateral, explosive/ ballistic movements
Do Basal Ganglia lesions present Ipsilaterally or Contralaterally?
Explain why
Contralaterally
- BG regulate Ipsilateral Motor Cortex
- Corticospinal fibres from Motor Cortex decussate
- Thus contralateral signs
(Rare for SNc to be affected unilaterally)
The Cerebellum uses sensory information from Proprioceptive neurones and sensory cortices to determine the most appropriate sequence of actions.
(Sensory input from Ipsilateral spinal cord and contralateral sensory cortices)
Where are its outputs to?
Thus, are signs of Cerebellar damage Ipsilateral or contralateral?
Contralateral motor cortex
Ipsilateral, as the Corticospinal fibres decussate (ending up on the same side)
Cerebellar lesions can present with Vomiting/ Vertigo/ Difficulty walking etc.
List 6 symptoms
“DANISH”
- Dysdiadochokinesia/ Dysdiadochokinesis
- Ataxia
- Nystagmus (Fast phase towards side of lesion)
- Intention tremor (Worsens as target is approached)
- Slurred speech (Due to dysarthria)
- Hypotonia
What is Dysdiadochokinesia/ Dysdiadochokinesis?
Why do we get Ataxia in Cerebellar disease?
Difficulty with rapidly alternating movements (Rapid pronation-supination-pronation….)
Loss of unconsciousness proprioception from lower limbs
What are 2 parts of the Striatum?
Caudate + Putamen (Functionally but not anatomically related)
(Caudate nucleus is C-shaped)
List and describe the pathways involved in the Basal Ganglia determining the most appropriate movements
- Corticostriatal pathway: From Motor cortex to Striatum
- Pallidothalamocortical pathway: From GP to Thalmus to Motor Cortex
- Nigrostriatal pathway: From Substantia Nigra to Striatum
- Corticospinal pathway: From Motor Cortex to contralateral LMN nucleus
List and describe the pathways involved in the Cerebellum determining the most appropriate movements
- Corticopontocerebellar pathway: From M+S Cortices to Pons (synapse with Ipsilateral pontine nuclei) to contralateral Cerebellum
- Cerebello-thalamo-cortical pathway: From Cerebellum to contralateral Thalamus to Motor Cortex
- Spinocerebellar tract: From spinal cord to Ipsilateral Cerebellum
- Corticospinal pathway: From Motor Cortex to Contralateral LMN nucleus
