functions of basal ganglia

Question 1

Where are basal nuclei found

Answer 1

Found towards the base of brain subcortical regions
Collection of neuronal cell bodies
Alongside the thalamus

Question 2

What does basal nuceli do

Answer 2

Initiation and control of voluntary movements
eye movement coordination
Habits
Emotional and motivational behavioral responses

Question 3

Names of basal nuceli

Answer 3

Caudate- largest, outside

Globus pallidus underneath

Question 4

MOTOR Cortex function

Answer 4

Executive control
Planning complex behaviors
Decision making

Question 5

Feedback loop of voluntary movement - basal nuclei and cortex

Answer 5

Basal nuceli

• info from cortex Projected to the ventral lateral nucleus (thalamus)
• Provides major input to supplementary motor area

Cortex
- info goes back to the cortex

LOOP

Question 6

Components of basal nuclei

can be seen in cross section of the brain stem

Answer 6

Cell bodies - darker
White matter= tracts

Caudate nucelus( tadpole) and putamen
^ striatum ( striped appearance - INPUT REGION)
Globus pallidus - internal and external segments
Subthalamic nucelus
Substantia nigra - pars compacta and pars retcula
Nucelus accumbens

Question 7

Globus pallidus

Answer 7

internal =

external = connect different input regions with output regions with subthalmaic

Question 8

Nucleus accumbens

Answer 8

motivation and reward

Question 9

Substantia nigra

Answer 9

pars compacta - back to stiatum
DOPAMINE containing neurones
This region is lost in parkinsons

Question 10

2 circuits of the basal nuclei

Answer 10

Direct pathway

Indirect pathway

Question 11

Direct pathway

Answer 11

Allows movement to occur
Activation leads to removal of inhibitory input to thalamus
Leads of excitation of motor cortex - facilitates wanted movements

Question 12

Indirect pathway

Answer 12

Inhibits unwanted movement
Activation enhances inhibitory input to thalamus
No excitation of cortex

Question 13

Describe the pathway of direct pathway

Answer 13

GABergic striatal neurones (d1) inhibit GABAergic output neurones in the internal globul pallidus ( GPi) that are tonically active

no info is being sent to thalamus
Thalamus can now fire neurones - not being inhibited
Causes DISinhibition
- increased thalamic output to cerebral cortex
facilitates wanted movements

Question 14

Output of the basal nuceli

Where does it go to

Answer 14

Main output of basal nuceli is INHIBITORY ( GABAergic)

Motor cortex sends excitory signals to teh straitum via the corticostriatal pathways

Question 15

Disinhibition

Answer 15

Increased thalamic output to facilitate/initate movement

Question 16

Indirect pathway - describe

Answer 16

GABAergic striatal neurones (d2) inhibit GABAERGIC output neurones in the EXTERNAL globus pallidus that are tonically active

Reduced inhibition of subthalamus

Increased inhibition of thalamus = reducing excitation of the cortex

INHIBITS unwanted movements

Question 17

Nigrostrial pathway

Answer 17

Largest dopamingergic pathway in the brain
Orginates in substantia nigra pars compacta

Enhances activation of D1 neurones
Supresses activation of D2 neurones

Question 18

Disorders of basal nuclei

Answer 18

Parkinsons diseases

Huntingtons

Question 19

Parkinson disease

Answer 19

Loss of susbtantia nigra pars compacta dopamine neurones ( nigrostriatal )
Excessive inhibition of GPe= increased inhibition of hte thalamus

Bradykinesia - slowness of movement
RIgidity
Resting tremors of hand and jaw
Cognitive defects

Question 20

Huntingtons

Answer 20

Autosomal dominant progressive neurodegenerative disease
Loss of striatal neurones in the indirect pathway
Decreased inhibition of the thalamus and subsequent loss of cortical neurones

Failure to suppress unwanted movements
- dementia, spontaneous jerky movements, death, changes in mood and personality, hyperkinesia

Question 21

Additional parallel systems other than the motor loop - basal nuceli

Answer 21

Oculomotor loop

Prefrontal and orbitofrontal loops

Limbic loop

Question 22

Oculomotor loop

Answer 22

Control of gaze, saccadic (fast) eye movements

Question 23

Prefrontal and orbitofrontal loops

Answer 23

Cognition and exectutive motor planning

Question 24

Limbic loop

Answer 24

Emotional expression, visceral functions, autonomic nervous system dysfunction

Question 25

At rest

Answer 25

Striatum at rest
Globus pallidus tonically active
Inhibiting the thalamus
No excitation of cortex

Question 26

Excitation

Answer 26

Straitum excited
Globus pallidus transiently inhibited
Thalamus disinhibited so other inputs can excite
Excitation of cortex