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Flashcards in Motor Control II Deck (38)
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1
Q

true or false:

commands to perform precise movements are encoded in the integrated activity of large populations of neurones in M1

A

true

2
Q

how is posture instability corrected?

A

A change in body position initiates rapid compensatory feedback messages from brainstem vestibular nuclei to spinal cord motor neurones

In addition before movements begin, brainstem reticular formation nuclei (controlled by the cortex) initiate feedforward anticipatory adjustments to stabilize postur

3
Q

what is initial hypotonia?

A

“spinal shock” - spinal circuits are deprived of cortical input

4
Q

what is the babinski sign?

A
  • adult, plantar flexion – baby or cortical damage – extension : both indicate incomplete upper control of spinal circuits
5
Q

what does increased muscle tone, hyperactive stretch reflex, clonus oscillatory contract/relax muscles in response to stretch cause?

A

removal of cortical suppressive (inhibitory) influences

6
Q

where does the Major subcortical input to area 6 come from?

A

ventral lateral nucleus in dorsal thalamus (Vlo)

7
Q

where does Input to VLo comes from

A

basal ganglia

8
Q

what are te Major components of basal ganglia

A

Corpus striatum (striped body) - includes two principal nuclei the caudate and the putamen

9
Q

where does Corpus striatum receives inputs from ?

A

all over cortex –

corticostriatal pathway - multiple parallel pathways with different functions

10
Q

medium spiny neurones in putamen and caudate receive excitatory (glutamatergic) cortical inputs on?

A

dentrites

11
Q

each cortical axon contacts ….. of spiny neurones so integrating the influence of …. of cortical cells

A

1000s

12
Q

are the axons inhibitory or excitatory?

A

inhibitory (GABAergic)

13
Q

where do the axons project to?

A

globus pallidus and to substantia nigra pars reticulata

14
Q

does the putamen fire before limb/trunk movements or after?

A

before

15
Q

does the caudate fire after eye movements or before?

A

before

16
Q

what type of pathway is cortex to putamen?

A

excitatory pathway

17
Q

what type of pathway is putamen to globus pallidus?

A

inhibitory

18
Q

what type of pathway is globus pallidus to VLo neurones?

A

inhibitory

19
Q

what type of pathway is VLo back to SMA?

A

excitatory

20
Q

functional consequence of cortical activation of putamen is

A

excitation

21
Q

what happens to globus pallidus at rest?

A

neurones are spontaneously active and inhibit VLo

22
Q

function of Cortical excitation

A

excites putamen which

inhibits the inhibitory Globus pallidus which therefore

releases cells in VLo from inhibition so

activity in VLo boosts SMA activity

This acts as a positive feedback loop focussing or funnelling activation of widespread cortical areas back onto cortical SMA

23
Q

what does the gating operation of the basal ganglia depend on?

A

a type of disinhibitory arrangement

24
Q

what does the direct pathway act as? and what is its function?

A

positive feedback loop, a “GO” signal to the SMA in cortex

it enhances the initiation of movements by the SMA

25
Q

what is the indirect pathway?

A

antagonizes the direct route

Striatum inhibits GPe (globus pallidus external) which then inhibits both GPi (GP internal) and STN (subthalamic nuclei)

Cortex excites STN; this excites Gpi; which inhibits thalamus

Direct pathway selects specific motor actions
Indirect pathway suppresses competing/inappropriate action

26
Q

what is the direct pathway via?

A

caudate/putamen

27
Q

what is the indirect pathway via?

A

subthalmic nucleus

28
Q

what is are examples of basal ganglia disorders?

A

parkinsons disease

huntington’s disease

29
Q

what is hypokinesia?

A

slowness, difficult to make voluntary movements, increased muscle tone (rigidity), tremors of hand and jaw.

30
Q

how is hypokinesia caused?

A

degeneration of neurones in substrantia nigra (SN) and their dopaminergic (excitatory) inputs to the striatum

31
Q

true or false:

dopamine can enhance cortical inputs through the “direct” pathway and suppress inputs through “indirect” pathway

A

true

32
Q

what does the depletion of dopamine cause?

A

closes down activation of the focussed motor activities that funnel through thalamus to SMA

33
Q

what is characteristic chorea?

A

spontaneous, uncontrolled, rapid flicks and major movements with no purpose

34
Q

what is the cause of characteristic chorea?

A

profound loss of caudate, putamen and globus pallidus

so loss of the ongoing inhibitory effects of the basal ganglia

35
Q

how much of the total CNS neurones come from the cerebellum?

A

50%

36
Q

what do lesions to the cerebellum cause?

A

produce uncoordinated inaccurate movements : ataxia : fail to touch nose with eyes shut : similar to alcohol which depresses cerebellar circuits

37
Q

what are parts of the cortico-ponto-cerebellar projection?

A

Layer 5, areas 4 & 6, somatosensory cortex

38
Q

what is the cortico-ponto-cerebellar projection

A

connects cortex, pontine nuclei and cerebellum - 20 mill axons, 20x more that CST

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