Basal Ganglia

Question 1

What is the basal ganglia?

Answer 1

A series of interconnected subcortical nuclei that forms a series of segregated parallel loops with the cerebral cortex

Question 2

What are the individual loops of the basal ganglia associated with?

Answer 2

different cortical areas
-they process signal separately for skeletal motor, oculomotor, associative and limbic systems

Question 3

What are the key features of the basal ganglia?

Answer 3

-striatum
-Globus Pallidus
-Substantia nigra
-subthalamic nucleus

Question 4

What does the striatum consist of?

Answer 4

Putamen
Caudate

Question 5

What is the function of the striatum?

Answer 5

input to the basal ganglia from the cortex connections, are monosynaptic and excitatory

Question 6

What are the parts of the globus pallidus?

Answer 6

The external (outer) globus pallidus (GPe) next to the putamen
Internal division of the global pallidus (GPi)

Question 7

What are the parts of the Substantia nigra?

Answer 7

Pars compacta (SNc)- supplies dopaminergic input to the caudate and putamen
Pars reticulata (SNr) is structually and functionally like the GPi

Question 8

What projects to the basal ganglia?

Answer 8

cortex (except primary visual and auditory cortex)

Question 9

Where do the monosynaptic excitatory projections from the cortex go to in the basal ganglia?

Answer 9

striatum

Question 10

What are the basal ganglia associated functions?

Answer 10

-movement regulation
-skill learning
-habit information
-reward system
-selection of appropriate behaviours
-self-initiation of behaviours

Question 11

What is the neuronal circuit within the basal ganglia?

Answer 11

-big cortical output neurons send collaterals to the basal ganglia
-Medium spiny neurons project out the striatum to the GP or SNr>thal>ctx

Question 12

What are the synapses on neurons in the striatum called?

Answer 12

Medium Spiny Neurons

Question 13

How much of the cells in the striatum are made up by the medium spiny neurons?

Answer 13

95%

Question 14

What are the two types of medium spiny neurons?

Answer 14

D1 and D2

Question 15

What differentiates between the two types of medium spiny neurons?

Answer 15

the type of dopamine receptor they express

Question 16

What route is the loop that has a direct pathway?

Answer 16

runs directly through the basal ganglia

Question 17

What route is the loop that has an indirect pathways?

Answer 17

detoure via the subthalamic nucleus

Question 18

Where does the direct pathway originate from

Answer 18

The D1 medium spiny neurons in the striatum putamen

Question 19

What is the shortest pathways through the basal ganglia?

Answer 19

cortex> striatum> GPi> thalamus > cortex

Question 20

What does the activation of the direct pathway increase?

Answer 20

Cortical activity by releasing the thalamus from inhibition ‘dis-inhibition’

Question 21

Is the direct pathway pro-movement (go) or anti-movement (stop)?

Answer 21

Pro-movement (go)

Question 22

When does dis-inhibition occur?

Answer 22

when tonic inhibition is ‘released by an inhibitory input

Question 23

Where does dis-inhibition occur?

Answer 23

In the direct pathway when GPi is inhibited by input from the striatum

Question 24

What is the route of the indirect pathway?

Answer 24

Cortex>striatum>GPe>STN>GPi>tha>cortex

Question 25

What decreases as a result of this pathway?

Answer 25

cortical activity due to the inhibition of the thalamus

Question 26

What medium spiny neurons are excited by dopamine?

Answer 26

D1

Question 27

What does dopamine act to do?

Answer 27

increase movement via the direct pathway - increase a positive

Question 28

What medium spiny neurons are inhibited by dopamine?

Answer 28

D2

Question 29

What is the role of the substantia nigra compacta?

Answer 29

provide massive dopaminergic input into the medium spiny neurons in the striatum

Question 30

Why are medium spiny neurons spiny?

Answer 30

they have many dendritic spines

Question 31

Where does the excitatory input from the cortex terminate?

Answer 31

on the heads of dendritic spines

Question 32

Where do the dopaminergic projections from the substantia nigra synapse?

Answer 32

on the shafts of dendritic spines

Question 33

What disease shows the influences of dopamine as there is a loss of the cells that produce it?

Answer 33

Parkinson Disease

Question 34

What is akinesia?

Answer 34

a lack of movement

Question 35

What is Bradykinesia?

Answer 35

a slowness of movement

Question 36

What is the pathway shifted towards in a hypokinetic disorder?

Answer 36

indirect pathway

Question 37

What is the pathway shifted towards in a hyperkinetic disorder?

Answer 37

direct pathway

Question 38

What can disease of the basal ganglia lead too?

Answer 38

Parkinson and Huntington disease

Question 39

What is motor behaviour determined by?

Answer 39

the balance between direct and indirect pathways

Question 40

In a hypokinetic disease what pathways is insufficient and what pathway is in excess?

Answer 40

Insufficient- direct pathway output Excess- indirect pathway output

Question 41

In a hyperkinetic disease what pathway is insufficient and what pathway is in excess?

Answer 41

insufficient- indirect pathway excess- direct pathway

Question 42

What are examples of hyperkinetic diseases?

Answer 42

huntington's dystonia hemiballismus

Question 43

What are examples of hypokinetic diseases?

Answer 43

Parkinsons parkinsonism

Question 44

What is the 2nd most common neurodegenerative disorder, that is more common in the elderly?

Answer 44

Parkinson's disease

Question 45

What are the causes of Parkinson's disease?

Answer 45

-Idiopathic- most have no known cause -Genetic (5-15%) -Vascular Parkinson's disease- damage of the dopaminergic pathways following a stroke -Other neurogenerative diseases -Neuroleptic drugs

Question 46

What are the symptoms of Parkinson's disease?

Answer 46

cardinal symptoms: tremor rigidity bradykinesia postural instability and gait disorder other symptoms: dysarthria mask face micrographic (small hand writing)

Question 47

What is MPTP?

Answer 47

a drug that once in the body kills the DA cells in the substantia nigra

Question 48

What is MPTP converted to in the cells of the brain?

Answer 48

MPP and a highly reactive free radical

Question 49

What happens to MPP in the brain?

Answer 49

it is taken up by dopaminergic cells where it binds with the neuromelanin

Question 50

What happens when individuals take MPTP?

Answer 50

Dyskinesia, erratic, writhing movements of the face, arms , legs or trunk

Question 51

What hyperkinetic disorders are thought to be the product of an overactive direct pathway?

Answer 51

Hungtington's Dystonia Tardive Dyskinesia DOPA Hemiballismus Tourettes

Question 52

What is Huntington's disease?

Answer 52

inherited, genetic disease with the onset gradually between 30-50

Question 53

What are the symptoms of huntington's disease?

Answer 53

-jerky, random, uncontrollable, dance-like movements -changes to behaviour or personality: ->disinhibition -> compulsive behaviour ->worsening of addictions cognitive:

Question 54

Where does the initial damage occur that causes hungtinton's?

Answer 54

striatum- degeneration by enlargement of ventricles

Question 55

What occurs in the early stages of Huntington's disease?

Answer 55

DA levels are increased but expression of DA receptors is reduced producing hyperkinetic abnormal dance like movements

Question 56

What occurs in the later stages of Huntington's disease?

Answer 56

DA levels are significantly decreased and there is a decreased excitatory thalamic transmission to the cortex -hypokinetic symptoms develop that resemble parkinson's disease

Question 57

What is a hemiballismus-subthalamic nucleus stroke?

Answer 57

a stroke that damages the subthalamic nucleus and block the indirect pathway

Question 58

How is parkinson's disease treated?

Answer 58

lesioning the STN dramatically decreases symptoms

Question 59

What are the side effects of surgery and treatments for parkinson's disease?

Answer 59

-impulse control disorder -hypersexuality -impulsive + compulsive shopping -pathological gambling -compulsive hobbyism

Question 60

What does too much direct pathway lead to?

Answer 60

'release on the brakes'

Question 61

What does too much indirect pathway lead to?

Answer 61

apathy