Anatomy and function of the basal ganglia

Question 1

Which anatomical structures constitute the basal ganglia?

Answer 1

Caudate nucleus
Putamen
External globus pallidus
Internal globus pallidus
Subthalamic nucleus
Substantia nigra

Question 2

What is the globus pallidus split into?

Answer 2

Pars Interna

Pars Externa

Question 3

What is the pallidum?

Answer 3

Globus pallidus internal and external

Question 4

What is the lentiform nucleus?

Answer 4

Putamen and globus pallidus

Question 5

What is the corpus striatum?

Answer 5

Caudate nucleus, putamen, pallidum

Question 6

What is the neostriatum?

Answer 6

Caudate and putamen

Question 7

Describe the cycle of how the basal ganglia interfaces with the cerebral cortex

Answer 7

Basal ganglia —> Thalamus —> Cerebral Cortex

Question 8

List the basal ganglia loops

Answer 8

Motor loop
Oculomotor loop
Prefrontal loop
Limbic loop

Question 9

What is the purpose of the motor loop?

Answer 9

To filter movement

Question 10

Which neurotransmitter is excitatory?

Answer 10

Glutamate

Question 11

Which neurotransmitter is inhibitory?

Answer 11

GABA

Question 12

Describe the direct pathway

Answer 12

Cortex (excitatory) —-> Striatum (inhibitory) —> Globus pallidus internal (inhibitory) —-> Thalamus (excitatory) —> Cortex

Question 13

What is the function of the direct pathway?

Answer 13

Promote movement

Question 14

Describe the inhibitory pathway

Answer 14

Cortex (excitatory) —> Striatum (inhibitory) —> Globus pallidus external (inhibitory) —> Subthalamic nucleus (excitatory) —> Globus pallidus internal (inhibitory) —> Thalamus (excitatory) —> Cortex

Question 15

What is the function of the indirect pathway?

Answer 15

Withhold movement

Question 16

Describe the hyperdirect pathway

Answer 16

Cortex (excitatory) —> Subthalamic nucleus (excitatory) —> Globus pallidus internal (inhibitory) —> Thalamus (excitatory) —> Cortex

Question 17

What is the function of the hyperdirect pathway?

Answer 17

Pause movement

Question 18

The cortex to striatum pathway is always ….

Answer 18

Excitatory

Question 19

The striatum outputs are always …

Answer 19

Inhibitory

Question 20

The thalamus to cortex pathways are always …

Answer 20

Excitatory

Question 21

The inhibition of the thalamus does what to movement?

Answer 21

Prevents movement

Question 22

Reducing inhibition of the thalamus does what to movement?

Answer 22

Facilitates movement

Question 23

How does striatum ‘know’ if a motor plan is to be promoted (direct pathway) or prevented (indirect pathway)?

Answer 23

2 POPULATIONS OF STRIATUM CELLS

with specialised DOPAMINE receptors

Question 24

Where is dopamine released from?

Answer 24

Dopamine is released by the substantia nigra

Question 25

What receptors are found on the medium spiny neurons?

Answer 25

Dopamine receptors
D1 - Direct - DA ramps up, MSN excitation
D2 - Indirect - DA dampens down MSN excitation

Question 26

Release of dopamine tips the pathway towards what of movement?

Answer 26

Promotion

Question 27

Which neurotransmitter do interneurons use?

Answer 27

Acetylcholine

Question 28

What does acetylcholine do?

Answer 28

Opposes the effects of dopamine

Question 29

Release of acetylcholine tips the pathway towards what of movement?

Answer 29

Prevention

Question 30

Describe pathway balance

Answer 30

the ‘balance’ of activity between the 2 medium spiny neuron populations determines the likelihood of movement taking place through the direct & indirect pathways

this balance is regulated by dopamine & acetylcholine

and influenced by the cortical inputs to the striatum