Hirsch - Basal Ganglia

Question 1

Gross Anatomy of the Basal Ganglia

(draw and label)

Answer 1

striatum: caudate and putamen

Globus pallidus (palladium): pars externa and pars interna

substania nigra: pars compacta and pars reticulata

VA/VL complex of thalamus

Subthalamic nuclei

Question 2

striatum

• know location

Answer 2

caudate and putamen

Question 3

globus pallidus (palladium)

• know location

Answer 3

pars externa and pars interna

Question 4

substania nigra

• know location

Answer 4

pars compacta and pars reticulata

Question 5

structure of caudate, putamen, and pallidum

Answer 5

caudate is a round/circle outside

larger portion right inside is putamen

inner core there is a pallidum

Question 6

medium spiny neurons have —– targets

Answer 6

medium spiny neurons have 3 targets

Question 7

medium spiny neuron body locates in –(2)– and targets —(3)—

Answer 7

caudate - > internal globus pallidus

caudate -> substantia nigra pars retinulata

putamen -> internal globus pallidus

putamen -> external globus pallidus

Question 8

dopaminergic neurons excite —- inhibit—–

Answer 8

dopaminergic neurons excite medium spiny cells and inhibit others

Question 9

medium spiny neurons receive —-

Answer 9

medium spiny neurons receive many excitatory cortical inputs

each input contribute little

Question 10

medium spiny neurons are silent unless…

Answer 10

medium spiny neurons are silent unless excited

= gabergic

Question 11

globus pallidus or substantia nigra pars retinulata

Answer 11

targets for medium spiny neurons

active unless inhibited

gabergic

medium spiny neurons wrap it aroundth

Question 12

there is topographic representation of the body in the putamen

Answer 12

mapped with respect to the body and function

receive info from multimodal association cortices & frontal eye fields

receive info from somatosensory, visual, premotor, and motor cortices

discharge in anticipation of body movements

Question 13

diverse function of basal ganglia

Answer 13

non motor loop: 1. executive/prefrontal loop 2. limbic loop (OCD related) 3. oculomotor loop

motor loop: upper motor neurons initiate and help coordinate voluntary movement 1. direct pathway (accelerate movement, huntingtons) 2. indirect pathway (brakes movement, parkinsons)

Question 14

direct pathway

Answer 14

accelerate movement

dis-inhibit thalamus (upper motor neurons)

know what happens when switched on

link:

1. cortex (glutamate excites)
2. putamen (gaba inhibits)
3. globus pallidus internal (gaba inhibits)
4. VA/VL thalamus (glutamate excites)

Question 15

direct pathway switch on

Answer 15

postive feedback

1. cortex (glutamate excites)
2. putamen (gaba inhibits)
3. globus pallidus internal (gaba inhibits)
4. VA/VL thalamus (glutamate excites)

* Know the diagram

Question 16

indirect pathway

Answer 16

brakes movement

link:

1. cortex (glutamate, excite)
2. putamen (gaba, inhibit)
3. globus pallidus external (gaba, inhibit)
4. sub thalamus nucleous (glutamate, excite)
5. globus pallidus internal (gaba inhibit)
6. VA/VL thalamus (glutamate excite)

know the diagram when it is on

Question 17

direct and indirect pathways are regulated by…

Answer 17

dopamine

excites direct pathway (D1 receptor) ==> ultimately excites movement

inhibits the indirect pathway (D2 receptor) ==> ultimately excites movement

** Net excitatory effect

Question 18

dopamine synthesized in …

Answer 18

substantia nigra pars compacta

* medium spiny cells project to

1. globus pallidus internal excited by dopamine via D1 receptor
2. globus pallidus external inhibited by D2 receptor

Question 19

Basal Ganglia

Answer 19

caudate

putamen

globus pallidus

Question 20

Basal Ganglia (caudate, putamen, globus pallidus) : projection neurons are …

Answer 20

GABAergic (inhibitory)

cells in striatum (caudate, putamen) are usually silent

cells in globus pallidus are usually active

Question 21

cortex, thalamus, subthalamic nucleus: projection neurons are …

Answer 21

glutamatergic (excitatory)

Question 22

substantia nigra, pars compacta: projection neurons are…

Answer 22

dopaminergic

can excite (D1 direct pathway) or inhibit (D2 indirect pathway) the medium spiny neurons

Question 23

Hyperkinesia - increased movements

• loss of subthalamic nucleus

Answer 23

hemiballismus

huntington’s disease

Question 24

hypokinesia - loss of substantia nigra pars compacta

Answer 24

parkinson’s disease

drug induced (neuroleptics, MPTP)

Question 25

Parkinson's disease

Answer 25

brady kinesia (hypokinesia) rigidity pill rolling tremor \* remove dopamine that excites direct pathway and inhibits indirect pathway direct pathway will decrease indirect pathway will increase

Question 26

Hemiballimus; lesion in indirect pathway (subthalamic nucleus)

Answer 26

activity in globus pallidus internal is reduced ---\> ultimately excites cortex

Question 27

Huntington's disease

Answer 27

loss of striatal neurons chromosome 4 mutation (huntingtin) involuntary movement (chorea) difficulty think through problems depressed irritable mood severe movement disorder akinesia (can hear and understand but not speak)

Question 28

huntington's disease is loss of

Answer 28

loss of putamen which decrease inhibitation of globus pallidus external ultimately increase in cortex activity

Question 29

therapies for parkinson's

Answer 29

L-Dopa Thalamotomy and Pallidotomy Deep brain stimulation of subthalamic nucleus Implantation of fetal dopaminergic neurons optically gated ion channels in damaged regions \* no cure; surgical procedure sometimes works