Week 9 - Basal Ganglia

Question 1

What does the basal ganglia do and what will disorders of it lead to?

Answer 1

Primarily concerned with the control of movement

Disorders of the BG will result in abnormality of posture, motor control and muscle tone

Basal ganglia also influences a variety of wiser functions: executive behaviours, emotions and motor learning

Question 2

What is the location of the basal ganglia?

Answer 2

• Basal nuclei are located deep within each hemisphere
• Situated just below the lateral ventricle in each hemisphere
• Connections with other regions in the brain - thalamus, sub thalamic nuclei and substantia nigra of the midbrain

Question 3

What terms can the BG nuclei be divided by?

Answer 3

Striatum and pallidum

Question 4

What is the striatum?

Answer 4

Includes the caudate nucleus and the putamen structures

These strictures are separated by the internal capsule however their functions and anatomy are very similar

They are often considered/named as just the striatum

Question 5

What is the pallidium?

Answer 5

includes the globus pallidus

Consists of both the external and internal globus pallidus

Question 6

What are the putamen and the globus pallidus collectively caled?

Answer 6

Lentiform nucleus

Question 7

Definition of BG?

Answer 7

A collective term for a group of anatomically and functionally related subcortical nuclei.

These nuclei are found deep within the cerebral hemispheres

Question 8

What does the subthalamic nucleus do?

Answer 8

Connects to the globus pallidus and the substantia nigra

Question 9

What are the two parts of the substantia nigra called?

Answer 9

SN pars compacta
SN pars reticula

Question 10

What neurotransmitters are involved in the basal ganglia?

Answer 10

Dopamine → excitatory and inhibatory effect (comes from substantia nigra)
GABA → inhibitory
Glutamic acid → excitatory

Question 11

How do neurotransmitters relate to the BG?

Answer 11

Neurotransmitters involved in the connections from the motor cortex to the basal ganglia is excitatory and the output from the thalamus back to the motor cortex is excitatory also.

Question 12

What is the pedunculopontine nucleus?

Answer 12

→ Particular connection important when considering the overall effect that the basal ganglia has in influencing muscle tone and posture

→ Within pons - peduncopontine nucleus will connect w/the reticulospinal tract and the vestibulospinal tract, which has important control over our tone + posture

Question 13

What are the pathways within the basal ganglia?

Answer 13

Direct pathway

Indirect pathway

Question 14

Outline of the direct pathway?

Answer 14

Motor cortex → D1 receptors bind to dopamine → Striatum → Internal globus pallidus → thalamus → motor cortex

Question 15

Overall effects of direct pathway?

Answer 15

→ Provide greater excitatory output from the thalamus
→ This allows for movement to occur

Question 16

Outline of the indirect pathway?

Answer 16

Motor cortex → D2 receptors bind to dopamine → Striatum → External globus pallidus → subthalamic nucleus → internal globus pallidfus → thalamus

Question 17

Overall effects of indirect pathway?

Answer 17

→ Greater amount of innovation coming from the thalamus, and therefore less excitation from the thalamus to the cortex

→ Means movement is inhibited

Question 18

What is the overall role of the basal ganglia?

Answer 18

To provide a balance between a lot of movement and not enough movement.

Feedback loop

Balancing act is to control which pathway is more dominant, at which time to allow the perfect amount of movement to occur.