Basal Ganglia Part 2

Question 1

Step 1 or first order neurons? Last step for direct and indirect

Answer 1

*same for both direct and indirect
1st step =Cortex to Striatum
last step= thalamus to cortex

Question 2

Direct and indirect pathwat starting striatum?

Answer 2

direct= striatum to GPi to thalamus to motor cortex
indirect= striatum to GPe to subthalmic nuclei (STN) to GPi to thalamus to cortex

Question 3

IMPORTANT:at rest the globus pallidus internus is? excitation of BG pathway does what?

Answer 3

tonically inhibiting the thalamic motor nuclei

*excitation of BG pathway relieves the inhibition, allowing for excitation of the thalamic nuclei and motor cortex

Question 4

When does the thalamus activate the cortex?

Answer 4

all the time!

Question 5

If the thalamus is continually activating the cortex, why are we not moving all the time/

Answer 5

the PGi is tonically inhibiting the thalamic motor nuclei (uses a ‘break’ system)

Question 6

What does disinhibition mean?

Answer 6

a temporary loss of inhibition; relieving inhibition.

Ex: Stop stopping= go

Question 7

GP is tonically inhibiting the?

Answer 7

thalamus and motor activity

Question 8

the two pathways (direct and indirect), act to modify the balance of ____ and ____ on the GPi to achieve the desired movement

Answer 8

inhibition and disinhibition

Question 9

What pathway is dominating when at rest?

Answer 9

indirect

Question 10

What are Hypokinetic disorders? Example?

Answer 10

too much INDIRECT output, not enough direct output

Ex: Parkinson’s disease

Question 11

What are Hyperkinetic disorders? Exampele?

Answer 11

Too much direct input, insufficient indirect output

Ex: Huntington’s disease = korea= extra movement

Question 12

Loss of dopaminergic neurons of the Substania nigra (SN) chanvges what?

Answer 12

the balance between direct and indirect pathways

Question 13

Parkinson’s disease pathpphysiology

Answer 13

is a hypokinetic disorder (too much indirect, not enough direct)

• *loss of dopaminergic neurons of the substantia nigra; idiopathic
• encephalitis lethargica, head trauma, or carbon monoxide or manganese toxins

Question 14

presentation of patients with parkinsons?

Answer 14

1) akinesis, bradykinesis, hypokinesis= less movemtn or slower movement than normal
2) rigidity = tight muscles
3) resting tremor = never still
4) parkinsonian gait= start off by being stooped over and leaning forward, have difficulty initiating movement and start with slow and small steps; cannot turn properly (turn on a block)

Question 15

because the substania niagra work primarily to facilitate the direct pathway, a loss of SN neurons allows?

Answer 15

allows the indirect pathway to dominate

**therefore indirect pathway dominates = parkinson’s

Question 16

What is the treatment for Parkinson’s disease?

Answer 16

restore dopamine using L-DOPA; a dopamin supplement to help promote the dopaminergic neurons that Parinson’s patients have left
*can’t truly fix

Question 17

Huntington’s Disease pthophysiology

Answer 17

is a hyperkinetic disorder (too much direct, not enough indirect)

• *death of spiny neurons in the striatum, loss of cerebral cortical neurons
• autosomal dominant disorder (CAG repeat on chromosome 4), onset is 25-40 yrd
• other causes: rheumatic chorea, drug induced and lupus

Question 18

presentation of patients with Huntington’s?

Answer 18

1) chorea= dancing= involuntary movements while at rest
2) athetosis= abnormal muscle contractions cause involuntary writhing movements
3) ballismus= type of chorea (unintentional movement)
4) Dystonia= state of abnormal muscle tone resulting in muscular spasm and abnormal posture

Question 19

Treatment for Huntington’s?

Answer 19

symptomatic; no real cure

*dopamine blockers to cut down direct input (try to block input to SN)