Basal ganglia and cerebellum

Question 1

As well as modulating motor control, what function are basal ganglia and cerebellum thought to be linked to?

Answer 1

Learning

Question 2

Where are the basal ganglia located?

Answer 2

In the white matter in the middle of the brain

Question 3

What structures does the basal ganglia consist of?

Answer 3

Striatum, globus pallidus, substantia nigra and subthalamic nucleus

Question 4

What does the striatum consist of

Answer 4

Caudate and putamen

Question 5

What are the two segments of the globus pallidus

Answer 5

External (GPext) or lateral segment

Internal (GPint) or medial segment

Question 6

What are the two parts of the substantia nigra?

Answer 6

Consists of the pars compacta (SNc) and pars reticula (SNr)

Question 7

What is the function of the basal ganglia?

Answer 7

Planning and programming movement
Elaborating associated movements (swinging arms when walking)
Smoothness of complex action
Involved in moderating and coordinating movements

Question 8

Describe the start of the circuit of basal ganglia

Answer 8

They start in the cerebral cortex (primary motor, premotor, supplementary, somatosensory and parietal) and these neurones go to the striatum (caudate and putamen)

Question 9

What are the two pathways of the circuits after the striatum?

Answer 9

The direct pathway and indirect pathway

Question 10

What is the direct pathway?

Answer 10

Putamen -> Globus pallidus internal segment and substantia nigra

Question 11

What is the indirect pathway?

Answer 11

Putamen -> Globus pallidus external segment -> Subthalamic nucleus -> Globus pallidus internal segment

Question 12

What effect does the direct pathway have on the motor cortex?

Answer 12

Excitatory

Question 13

What effect does the indirect pathway have on the motor cortex?

Answer 13

Inhibitory

Question 14

What modulates the functions of the pathways?

Answer 14

Nigro-striatal pathway

Question 15

Where do these projections go once they exit the basal ganglia?

Answer 15

Thalamus then they go back to the cortex to the supplementary motor area and primary motor area

Question 16

How are the basal ganglia also involved in cognitive function?

Answer 16

There are cortical loops that go through the basal ganglia and connects the basal ganglia with the prefrontal association cortex and limbic cortex. They’re involved in selecting and enabling various cognitive, executive and emotional programmes that are stored in these cortical areas

Question 17

What causes Parkinson’s disease?

Answer 17

Neuronal degeneration of the Substantia Nigra Pars Compacta, it is caused by the progressive depletion of dopamine neurones

Question 18

When do clinical signs appear in Parkinson’s?

Answer 18

When about 80% of the dopamine cells in the substantia nigra have died

Question 19

When there is loss of nigra-striatal dopaminergic neurones in the caudate and putamen which leads to a loss of connection between the striatum and substantia nigra pars compact, what happens?

Answer 19

Excitation of the motor cortex is reduced

Question 20

What are the signs of parkinson’s disease?

Answer 20

Akinesia, parkinsonian gait and stooped posture

Question 21

What is akinesia?

Answer 21

When it is difficult to initiate movements because they’ve lost the feedback between the basal ganglia and cortex

Question 22

What is Huntington’s disease and what causes it?

Answer 22

It is a neurodegenerative disorder that is caused by an abnormality on chromosome 4, it is autosomal dominant.

Question 23

What does the abnormality on chromosome 4 cause?

Answer 23

Degeneration of GABAnergic neurones in the striatum which means that excitatory effect of the direct pathway is no longer controlled by inhibitory pathway

Question 24

What are the main sign’s of Huntington’s?

Answer 24

Choreic movements- Rapid, jerking, involuntary movements

Question 25

Which parts of the body are affected first in Huntington's?

Answer 25

Hands and face

Question 26

What are the three horizontal lobes of the cerebellum?

Answer 26

Anterior, posterior and flocculonodular

Question 27

What are the three coronal zones of the cerebellum?

Answer 27

Vermis- in the middle Intermediate hemisphere Lateral hemisphere

Question 28

What are the three layers in the cerebellar cortex, starting with the most internal?

Answer 28

Granule cells Purkinje cells Molecular layer

Question 29

What does the molecular layer contain?

Answer 29

Axons of the granule cells and dendrites of the Purkinje cells

Question 30

What are the three deep nuclei in the cerebellum?

Answer 30

Fastigial Interposed Dentate

Question 31

What is the fastigial nucleus involved in?

Answer 31

Control of balance and is connected with vestibular nuclei

Question 32

What are the interposed and dentate nuclei involved in?

Answer 32

Both are involved in voluntary movement and are connected to the thalamus and red nucleus

Question 33

What are the three sources of input to the cerebellum?

Answer 33

Mossy fibres- that bring information from the cerebral cortex and pons Mossy fibres from the spinocerebellar tract Climbing fibres from the inferior olive

Question 34

What is the function of the vestibulocerebellum (flocculonodular lobe)?

Answer 34

Involvement with balance, posture and regulation of gait | Also involved in coordination of head movements with eye movements

Question 35

What is the function of the spinocerebellum?

Answer 35

Coordination of speech, adjustment of muscle tone and coordination of limb movement

Question 36

What is the function of the cerebrocerebellum?

Answer 36

Coordination of skilled movements, cognitive function, attention, processing of language and emotional control

Question 37

Overall, what are the 4 main functions of the cerebellum?

Answer 37

Balance and posture, coordination of voluntary movement, cognitive functions and motor learning

Question 38

What occurs in vestibulocerebellar syndrome?

Answer 38

Patients tend to lose their balance with gait ataxia and a tendency to fall

Question 39

What is spinocerebellar syndrome highly associated with as a cause?

Answer 39

Chronic alcoholism

Question 40

What occurs in spinocerebellar syndrome?

Answer 40

It mainly affects the legs and causes an abnormal gait or a wide stance

Question 41

What occurs in cerebrocerebellar syndrome?

Answer 41

It mainly affects the arms and affects coordinated movements, speech becomes very slow and hesitant

Question 42

What are the 5 main signs of cerebellar disorders?

Answer 42

``` Ataxia Dysmetria Intention tremor Dysdiadochokinesia Scanning speech- staccato ```

Question 43

What is dysmetria?

Answer 43

Inappropriate force and distance on target directed movements

Question 44

What is an intention tremor?

Answer 44

Increasingly oscillatory trajectory of a limb in a target directed movement

Question 45

What the balls is dysdiadochokinesia?

Answer 45

Inability to perform rapidly alternating movements

Question 46

How is intention tremor assessed clinically?

Answer 46

Nose-finger tracking