Basal Ganglia - Anatomy And Function

Question 1

What is the basal ganglia comprised of?

Answer 1

Caudate nucleus

Lentiform:
-Putamen 
Globus pallidus (internus & externus)
Substantia nigra
Subthalamic nucleus

Question 2

What is the striatum?

Answer 2

Caudate nucleus and putamen

Question 3

What is the lentiform nucleus?

Answer 3

Putamen and globus pallidus

Question 4

What does dopamine do?

Answer 4

DO has a stimulatory effect via the D1 receptor

DO activates striatum(caudate and putamen)

Question 5

What can damage to the basal ganglia cause?

Answer 5

Parkinson’s Disease

Hemiballismus

Question 6

What is the function of the basal ganglia?

Answer 6

motor
- limbic
- executive function
Gates proper initiation of movement 
interface with cortex

Question 7

Direct Pathway [4]

Answer 7

(promotes action)
1. Cortex excites the striatum, using GLU

2. Excited striatum is able to send inhibitory signals to the GPi, via GABA
3. Inhibitory signals to the GPi suppresses its activity
   - Prevents inhibitory signals being sent to the thalamus. [disinhibition of thalamus]
4. Thalamus is able to be excited and sends excitatory signals to the cortex.

Question 8

Indirect Pathway [6]

Answer 8

(inhibits action)

1. Cortex sends excitatory signals to striatum, via GLU
2. Excited striatum sends signals to GPe (decreases activity of GPe)
3. Decreased activity of the GPe allows excitation of the STN
4. Excited STN sends excitatory signals to GPi
   (increased activity)
5. Excited GPi sends inhibitory signals to thalamus (acitivity decreased)
6. Thalamus unable to send excitatory signals to cortex

Question 9

Hyperdirect pathway of movement

Answer 9

Stops movement very quickly by bypassing striatum

1. Cortex excites STN
2. Excited STN excited GPi
3. Active GPi sends inhibitory signals to thalamus
4. Thalamus unable to send excitatory signals to cortex

Question 10

Substantia Nigra

Answer 10

Releases DA

projects to striatum

Question 11

Medium spiny neurons

Answer 11

Motor striatal cells with DA receptors

2 groups
1) contains dopamine-1 receptors [D1] which stimulates excitation = direct pathway

2)contains dopamine-2 receptors [D2] which has inhibitory signals = indirect pathway

Question 12

Striatum interneurons

Answer 12

Modulates DA release using ACh

1) Acting on MSN with D1
- inhibits direct pathways
- inhibits effects of DA
- inhibits striatal cells in direct loop

2)Acting on MSN with D2
=increase excitation
=stimulates indirect pathway
=prevents movement