BMS11004 WEEK 11 - THURSDAY

Question 1

give location of motor cortex

Answer 1

telencephalon

Question 2

location of basal ganglia, and its subcomponents

Answer 2

forebrain
cuadate, putamen, globus pallidus, subthalamic nucleus

Question 3

give location of lateral nucleus of thalamus

Answer 3

diencephalon

Question 4

give location for substantia nigra

Answer 4

midbrain

Question 5

give key components in initiation of movement

Answer 5

motor cortex (telencephalon)
basal ganglia (forebrain)
ventral lateral nucleus of thalamus (diencephalon)
substantia nigra (midbrain)

Question 6

what is motor loop

Answer 6

motor cortex connecting to basal ganglia, feedbacks to premotor area via ventrolateral complex of thalamus (VLo) = indirect and direct pathway

Question 7

what does VLo stand fo

Answer 7

ventrolateral complex of Thalamus

Question 8

detail direct pathway for basal ganglia and motor loop in movement initiation

Answer 8

doesnt initiate cortical input, globus pallidus inhibits VLo
inputs from cortex converge on striatum, which inhibits GPi activity and releases VLo to active area 6 which then initiates movement

Question 9

why is the direct pathway of basal ganglia for movement initiation set up as convergence of cortical input on striatum? what does this allow

Answer 9

integrating cortical input to trigger response allows rapidity of response, with “engine running” and inhibition of inhibition releasing “brake”

Question 10

give an overview of role of indirect pathway of basal ganglia for initiating movement

Answer 10

module direct pathway, involves substantia nigra which acts via striatum to maintain balance between inhibiting/activating VLo
and GP external segment

Question 11

detail indirect pathway for basal ganglia initiating movement

Answer 11

SN excitatory input stimulates VLo (by activating GPi inhibition via direct, and GPe inhibiting GPi in indirect which stops it inhibiting VLo)
GPe is inhibited by caudate putamen = VLo inhibitied
SN inhibition decreases GPe inhibition from caudate putamen
this allows GPi inhibition, so activates VLo
so SN balances VLo activation

Question 12

in the whole GPi, GPe, VLo pathway, where does substantia nigra get info from

Answer 12

decision-making, emotive centres involved in risk/reward judgements

Question 13

what does degeneration in GPi, GPe, VLo circuit cause

Answer 13

Parkinsons’/Huntington’s

Question 14

what does GPe inhibition from caudate putamen cause

Answer 14

VLo inhibition

Question 15

what does VLo activation from SN result from

Answer 15

direct= inhibit GPi
indirect= GPe inhibit GPi, which stops it inhibiting VLo

Question 16

when GPi is inhibited, what does this allo

Answer 16

activates VLo

Question 17

outline incidence of Pakinsons (family, sporadic)

Answer 17

10-15% genetic mutation
sporadic for 85-90%

Question 18

define hypokinesia

Answer 18

paucity/insufficiency of movement

Question 19

define bradykinesia

Answer 19

very slow movements

Question 20

define akinesia

Answer 20

no movement

Question 21

give symptoms of Parkinsons

Answer 21

hypok/brady/akinesia
ridigity, resting tremor (4-5Hz)
shuffling gait, bad balance, flexed posture
mask-like expression
mood disorder
lost smell sense

Question 22

where are dopaminergic neurons lost in Parkinsons

Answer 22

Substantia Nigra

Question 23

what is degeneration of dopaminergic neurons marked by?

Answer 23

presence of Lewy bodies- intracellular protein aggregate

Question 24

how long does L-DOPA work as a treatment

Answer 24

5 years

Question 25

how does L-DOPA work, and why not

Answer 25

boosts capacity of remaining dopaminergic neuron, but eventially not enough left

Question 26

give side effects of L-DOPA

Answer 26

increased motor response fluctuation and drug related dyskinesias (erratic movements)

Question 27

what does reduced dopaminergic input from substantia nigra to striatum cause for direct/indirect pathways (Parkinsons)

Answer 27

increased activity of indirect pathway
decreased activity of direct pathway

Question 28

Parkinsons- reduced dopamine input from substantia nigra to striatum causes less/more inhibition of GPi, and what does this cause?

Answer 28

less inhibition of GPi = increase inhibitory activites meaning less activity in VLo and less motor cortex activation (causing hypokinesis)

Question 29

what is a pallidotomy

Answer 29

removing GPi for parkinsons
this prevents VLo activity decreasing, causing less motor cortex activation

Question 30

how does DBS treat Parkinson

Answer 30

inhibit GPi hyperactivity

Question 31

what is commonness of huntingtons

Answer 31

3-7 per 100,000

Question 32

give symptoms for early Huntingtons

Answer 32

hyperkinesia (overactivity)
dyskinesia/chorea (involuntary jerking, twitches)= erratic, discoord movements

Question 33

give symptoms of late Huntingtons

Answer 33

akinesia, dystonia (muscle spasms)
dementia
personality disorder, psychosis

Question 34

what causes Huntingtons

Answer 34

autosomal dominant gene mutations

Question 35

in early huntingtons neuronal degeneration of indirect pathway, how does this cause hyperkinesis and chorea (including GPi, GPe and VLo)

Answer 35

initially in indirect pathway in striatum, reduced inputs to GPe so increased GPi inhibition, disinhibits VLo = inappropriate movement initiations

Question 36

in later huntingtons neuronal degeneration of direct pathway, how does this cause akinesis (including GPi, GPe and VLo)

Answer 36

in striatal direct pathway GPe degenerate so releases Gpi and overinhibits VLo

Question 37

compare occurance for PD, HD

Answer 37

PD idiopathic, sporadic, common and 10% inherited
HD rarely sporadic, rare, inherited

Question 38

compare gene mutations in PD, HD

Answer 38

PD multiple gene mutations with either low and common or high and rare penetrance
HD only HTT mutation

Question 39

explain how genetic mutations in HD, PD work

Answer 39

PD encodes proteins for protein degredation, mitochondiral function
HD, HTT protein unclear, perhaps in intracellular transport, protein aggregation

Question 40

explain how basal ganglia act as funnel

Answer 40

collects info from prefrontal and motor cortex, decides what info to act on

Question 41

connect cerebellum with motor learning

Answer 41

modulates upper motor neurons, no direct connections to spinal cord
needed for learning execution of planned, voluntary, multi-joint movements

Question 42

how does muscle memories form

Answer 42

strengthen existing neural pathways
cerebellum form loop with motor cortex using spinal cord, vestibular system
project back to motor cortex via thalamus and detects, corrects differences between intended/actual movements

Question 43

what does lesions to cerebellum cause

Answer 43

cerebellar ataxia- poorly integrated movement
dysynergia- lose ability to touch nose, coordinate multiple muscles and joints in sequence