Physiology - Basal Ganglia

Question 1

What is the striatum made of?

Answer 1

Caudate and putamen

Question 2

What is the function of the substantia nigra (compacta)

Answer 2

Provides dopamine for basal ganglia pathway

Question 3

NB: REVISE PATHWAY

Question 4

What does the indirect basal ganglia pathway do?

Answer 4

Inhibits the thalamus

Less info back to cortex

Question 5

What does the direct pathway of the basal ganglia do?

Answer 5

Stimulates thalamus

Go Pathway

Question 6

List the functions of the basal ganglia.

Answer 6

Motor Function
- Helps motor cortex select appropriate motor cortex neurons for voluntary movement - initiation, scaling, sequencing
- Abnormal functioning = Parkinson’s/Huntington’s Disease
Cognitive/Psychological Functions
- Helps prefrontal cortex organize thoughts
- Helps limbic system organize emotions
- Reward-mediated learning, attention
- Abnormal functioning - drug addiction, ADHD, psychosis , Parkinson’s disease, Huntington’s disease
Dopamine in Basal Ganglia = Learning and Attention - reinforcement of preceding actions that produced reward (drug addiction, ADHD)

Question 7

Describe the signs of Parkinson’s disease

Answer 7

· Signs: (Extrapyramidal)
- Resting tremor (pill rolling), 4-6 Hz
- Rigidity: lead-pipe (tone increases through range of motion), or with tremor “cogwheel”, not velocity dependent
- Akinesia, bradykinesia: lack of movement, slow movement, mask-like face, quiet speech, micrographia
- Posture and gait abnormalities: forward leaning posture, postural instability, retropulsion, shuffling gait, falls
- Dementia
- Depression
Autonomic dysfunction

Question 8

When is the onset of parkinson’s disease?

Answer 8

45 - 70 years

Question 9

What is the pathology behind PD?

Answer 9

· Death of dopamine neurons 
	- Idiopathic (80% of cases) - environmental factors, genetic predisposition
	- Genetic (single gene)
	- Specific toxin
Trauma

Question 10

Why does loss of DA cause movement problems?

Answer 10

· Generation of movement requires selection of motor cortex neurons
· Basal ganglia usually select these neurons
· DA is needed to allow some pathways in basal ganglia to be selected instead of others
· Lack of DA = all pathways are equal
· Co-activation of agonists and antagonists = rigidity
Difficulty getting main agonists active enough to trigger movement

Question 11

What is the treatment options for PD?

Answer 11

· Replace dopamine (L-dopa)
· Direct dopamine-receptor antagonists
· Surgical: stimulate basal ganglia nuclei (Deep Brain Stimulation)
Dopamine cell replacement - experimental

Question 12

What causes Huntington’s disease?

Answer 12

Progressive death of medium spiny neurons in caudate/putamen

Unbalanced activity of surviving neurons

Question 13

What is the inheritance of Huntington’s disease?

Answer 13

Autosomal dominant - repeated CAG triplets in Huntingtin gene

Question 14

List the symptoms/signs of Huntington’s Disease

Answer 14

Motor Cortex Deficit - chorea (excessive, spontaneous, irregular, random, brief, abrupt movements), eventual loss of voluntary movement
Other cortex - dementia, mania, irritability, agitation, paranoia

Question 15

What are the treatment options for Huntington’s disease?

Answer 15

There are none.

Question 16

Name the different subregions of the cerebellum and their functions:

Answer 16

Spinocerebellum: posture, balance, locomotion (clinic: trunk ataxia, broad-based gait)
Cerebrocerebellum: planning and feedback to control limbs (clinic: hypotonia, intention tremor, limb ataxia)
Vestibulocerebellum: posture, eye movement (clinic: falls, vertigo, disordered eye movement)

Question 17

Name the two fibres bringing input into the cerebellum.

Answer 17

Climbing fibre input (intended movement)

Mossy fibre input (actual movement)

Question 18

What is the function of the cerebellum in motor control?

Answer 18

Helps to plan movement
Online correction
Motor learning
Perhaps helpful in cognitive functions

Question 19

What disorders would affect the cerebellum?

Answer 19

Stroke, alcoholic cerebellar degeneration, tumours, genetic, infection

Question 20

What are the signs of cerebellar disorder?

Answer 20

DANISH 
- Dysmetria 
- Ataxia 
- Nystagmus 
- Intention tremor
- Slurred speech 
- Hypotonia 
\+ Titubation

Question 21

What are the treatments for cerebellar disorders?

Answer 21

Treat causes (e.g. vitamin deficiency)
Symptomatic treatment, physiotherapy

Question 22

What are the clinical signs of a damaged spinocerebellum?

Answer 22

Trunk ataxia, broad-based gait

Question 23

What are the clinical signs of a damaged cerebrocerebellum?

Answer 23

Hypotonia, intention tremor, limb ataxia

Question 24

What are the clinical signs of a damaged vestibulocerebellum?

Answer 24

Falls, vertigo, disordered eye movement

Question 25

What is dysdiaochokinesia?

Answer 25

Decreased rapid alternating movements (part of ataxia which is a clinical sign of a damaged cerebellum)