Motor Disorders

Question 1

Are Basal Ganglia in the CNS or PNS?

Answer 1

CNS (A group of structures, not a ganglion which are in PNS)

Question 2

What are the 2 parts of the Lentiform Nucleus

Answer 2

• Globus Pallidus (medially)
• Putamen (laterally)

(The two are not functionally related, only anatomically)

Question 3

What are the 2 parts of the Globus Pallidus

Answer 3

Internal and external segment

Globus Pallidus Interna/ Externa

Question 5

Describe broadly the function of the 2 parts of the Lentiform Nucleus

Answer 5

• Striatum receives input from Cortex and Substantia Nigra pars compacta (SNc)
• Globus Pallidus sends output to Cortex via thalamus

Question 6

Describe the Substantia Nigra

Answer 6

• Part of Midbrain
• Contains dopaminergic neurons
• 2 components: pars compacta and pars reticulata

(Source of Dopamine)

Question 7

What pathway connects the Striatum to the Substantia Nigra?

Answer 7

Nigrostriatal pathway

Question 8

The Basal Ganglia is spread throughout the forebrain and is divided into 3 types of nuclei.

Name these 3 types and state their functions

Answer 8

• Input nuclei: Receive information
• Intrinsic nuclei: Info relayed to these for processing
• Output nuclei: Info passed to these

Question 9

List the Input Nuclei of the Basal Ganglia

Answer 9

Caudate nucleus + Putamen (Striatum)

Question 10

List the Intrinisc Nuclei of the Basal Ganglia

Answer 10

• Globus Pallidus Externa
• Subthalamic nucleus
• SNc (Substantia Nigra pars compacta)

Question 11

List the Output Nuclei of the Basal Ganglia

Answer 11

• Globus Pallidus Interna

- SNr (Substantia Nigra pars reticulata)

Question 12

The Basla Ganglia communicate with the Motor cortex via the Thalamus.

Thus, how are Thalamic and Cortical activity linked?

Answer 12

An increase in one causes an increase in other

Question 13

What are the 3 structural components of the cerebellum?

Which body parts are they associated with?

Answer 13

• 2 lateral hemispheres-> Ipsilateral/ distal body

- A midline Vermis-> Midline/ Trunk

Question 14

Describe the connection of the Cerebellum with the Brainstem

Answer 14

• Superior peduncle connects to Midbrain
• Middle peduncle (largest) connects to Pons
• Inferior peduncle connects to Medulla

Question 15

The Cerebellum sits above the 4th ventricle.

What can Cerebellar lesions cause?

Answer 15

Hydrocephalus

Question 16

Briefly describe the functions of the Basal Ganglia and Cerebellum

Answer 16

Basal Ganglia;
- Determines the most appropriate set of movements

Cerebellum;
- Determines the appropriate sequence of movements

Question 17

How does the Basal Ganglia carry out its function?

Answer 17

• Direct pathway reinforces/ facilitates appropriate movements (excitatory to motor cortex)
• Indirect pathway inhibits inappropriate movements (inhibitory to motor cortex)

Question 18

Between what structures are the Direct and Indirect Pathways?

Answer 18

Direct: Putamen to GPi (Globus Pallidus Interna)

Indirect: Putamen to GPe to Subthalamic nucleus)

Question 19

Describe the Direct Pathway

Answer 19

Putamen inhibits GPi, which inhibits Thalamus

Thus, net excitation of Thalamus

Question 20

Describe the Indirect Pathway

Answer 20

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

Question 21

Basal Ganglia have a dopaminergic input from the Substantia Nigra.

Describe how Dopamine facilitates movement by exiting the motor cortex

Answer 21

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

Question 22

What causes Parkinson’s?

List 8 symptoms

Answer 22

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

Question 23

Briefly compare Parkinson’s, Huntington’s Chorea and Hemiballismus in terms of movement

Answer 23

Parkinson’s- Decreased movement

Huntington’s Chorea- Increased movement
Hemiballismus- Increased movement

Question 24

Huntington’s Chorea is Autosomal Dominant, with early onset around 30-50yrs

Describe the cause

Answer 24

Loss/ reduced activity of Indirect Pathway, leading to Hyperkinetic features

Question 25

List 4 symptoms of Huntington’s Chorea

Answer 25

• 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

Question 26

Describe the cause of Hemiballismus How does it present?

Answer 26

- Damage to STN, possibly by sub-cortical stroke/ lacunar Infarct - Unilateral, explosive/ ballistic movements

Question 27

Do Basal Ganglia lesions present Ipsilaterally or Contralaterally? Explain why

Answer 27

Contralaterally - BG regulate Ipsilateral Motor Cortex - Corticospinal fibres from Motor Cortex decussate - Thus contralateral signs (Rare for SNc to be affected unilaterally)

Question 28

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?

Answer 28

Contralateral motor cortex Ipsilateral, as the Corticospinal fibres decussate (ending up on the same side)

Question 29

Cerebellar lesions can present with Vomiting/ Vertigo/ Difficulty walking etc. List 6 symptoms

Answer 29

“DANISH” - Dysdiadochokinesia/ Dysdiadochokinesis - Ataxia - Nystagmus (Fast phase towards side of lesion) - Intention tremor (Worsens as target is approached) - Slurred speech (Due to dysarthria) - Hypotonia

Question 30

What is Dysdiadochokinesia/ Dysdiadochokinesis? Why do we get Ataxia in Cerebellar disease?

Answer 30

Difficulty with rapidly alternating movements (Rapid pronation-supination-pronation....) Loss of unconsciousness proprioception from lower limbs

Question 31

What are 2 parts of the Striatum?

Answer 31

Caudate + Putamen (Functionally but not anatomically related) (Caudate nucleus is C-shaped)

Question 32

List and describe the pathways involved in the Basal Ganglia determining the most appropriate movements

Answer 32

1. Corticostriatal pathway: From Motor cortex to Striatum 2. Pallidothalamocortical pathway: From GP to Thalmus to Motor Cortex 3. Nigrostriatal pathway: From Substantia Nigra to Striatum 4. Corticospinal pathway: From Motor Cortex to contralateral LMN nucleus

Question 33

List and describe the pathways involved in the Cerebellum determining the most appropriate movements

Answer 33

1. Corticopontocerebellar pathway: From M+S Cortices to Pons (synapse with Ipsilateral pontine nuclei) to contralateral Cerebellum 2. Cerebello-thalamo-cortical pathway: From Cerebellum to contralateral Thalamus to Motor Cortex 3. Spinocerebellar tract: From spinal cord to Ipsilateral Cerebellum 4. Corticospinal pathway: From Motor Cortex to Contralateral LMN nucleus