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Nervous System > Motor Control > Flashcards

Motor Control Flashcards

1
Q

What is direct control of muscles via?

A

Alpha motor neurons in the spinal cord

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2
Q

What control spinal reflexes?

A

Brainstem nuclei

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3
Q

What four systems control movement?

A

Descending control pathways
Basal ganglia
Cerebellum and local spinal cord
Brain stem circuits

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4
Q

What innervate muscles to initiate reflex and voluntary movements?

A

Lower motor neurons at cranial and spinal levels

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5
Q

What happens to lesions at lower motor neurons at cranial and spinal levels?

A

Flaccid paralysis and muscle atrophy

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6
Q

What regulates alpha motor neuron activity?

A

Upper motor neurons in brainstem or cortex synapse with multiple lower circuit neurons

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7
Q

What neurons are the proximal shoulder muscles mapped to?

A

Medial motor neurons

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8
Q

What happens if there is damage to sensory inputs?

A

Paralysis as if the motorneurons themselves had been damaged

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9
Q

What nerve does the biceps jerk test?

A

C6

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10
Q

What nerve is the triceps jerk reflex?

A

C7

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11
Q

What nerve is the patellar tendon reflex?

A

L4

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12
Q

What nerve is the achilles tendon reflex?

A

S1

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13
Q

What do flexor or withdraw reflexes use?

A

Information from pain receptors in skin muscles and joints

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14
Q

What do flexor or withdrawal reflexes do?

A

Withdraw part of the body war from painful stimuli and in towards the body

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15
Q

What can increased sensory action potentials from pain receptors cause?

A

Increased activity in the flexor muscles of the affected part via a number of excitatory interneurons
Antagonistic extensors are inhibited

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16
Q

What does excess load cause?

A

GTO reflex to be activated

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17
Q

How can stretch reflexes be overridden?

A

Strong descending inhibition hyper polarises alpha motor neurons and the stretch reflex can’t be evoked

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18
Q

What does activity of gamma motor neurons depend on?

A

Descending pathways - high activity causes muscle to become extremely resistant to stretch and is spastic

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19
Q

What pathways control voluntary movements of distal muscles?

A

Lateral pathways

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20
Q

What do ventromedial pathways control?

A

Posture and locomotion

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21
Q

Where does 2/3rds of the cortocospinal tract originate?

A

Areas 4 and 6 of frontal motor cortex

22
Q

Where does the corticospinal tract decussate?

A

Medulla

23
Q

Where do the CST axons synapse?

A

Ventral horn motor neurons and interneurons to control muscles

24
Q

Where does the RST start?

A

Red nucleus of midbrain

25
Q

What happens if there are lesions in the CST and RST?

A

Fine movements of arms and hands lost

Can’t move shoulders, elbows, wrists, fingers independently

26
Q

What happens if there is a lesion in the CST alone?

A

Same deficits but after a few months functions reappear as they have been taken over by RST

27
Q

Where do the ventromedial pathways originate?

A

Brainstem

28
Q

What do area 6 neurons drive?

A

Complex movements on either side of the body

29
Q

What is the function of the pre motor area of area 6?

A

Connects reticulospinal neurons innervating proximal motor units

30
Q

What is the function of the supplementary motor area of area 6?

A

Innervates distal motor units directly

31
Q

What does microstimulation in a specific area of the primary motor cortex elicit?

A

Coordinated movements of hand and mouth or movements that bring hands into central space to inspect/manipulate objects

32
Q

What ares generate the mental image of body in space?

A

Areas 5 and 7

33
Q

What happens when these areas are damaged?

A

Humans with damage have bizarre body images, may neglect or ignore one side of their body

34
Q

Where are decisions taken about what actions/movements to take and their likely outcome?

A

Prefrontal and parietal cortex

35
Q

What does cortical damage cause?

A

Immediate flaccidity of contralateral muscles - lift limb and release it drops passively

36
Q

What is initial hypotonia?

A

Spinal circuits deprived of cortical input when they regain function, the spare connections strengthen and new connections sprout

37
Q

What is Babinski’s sign?

A

When the lateral side of dorsal foot is touched, plantar flexion should occur
However in babies and those with cortical damage you see extension

38
Q

What is spasticity?

A

Increased muscle tone, hyperactive stretch reflex, clonus oscillatory contract muscles in response to stretch

39
Q

What are the features of upper motor neurone syndrome?

A 
Injury site determines symptoms
Initital hypotonia
Babinski's sign
Spasticity 
Loss of fine finger movements
40
Q

Where does subcortical input to area 6 come from?

A

Ventral lateral nucleus in dorsal thalamus

41
Q

What is the subcortical input called?

A

VLo, arises from basal ganglia

42
Q

What are the major components of basal ganglia?

A

Corpus striatum - caudate and putamen nucleus

43
Q

What receive excitatory cortical inputs on dendrites?

A

Medium spiny neurons in putamen and caudate

44
Q

What does the putamen fire before?

A

Limb/trunk movements

45
Q

What does the caudate fire before?

A

Eye movements

46
Q

Is the cortex to putamen inhibitory or excitatory?

A

Excitatory

47
Q

Is putamen to globus pallidus inhibitory or excitatory?

A

Inhibitory

48
Q

Is globus pallidus to Vlo neurons inhibitory or excitatory?

A

Inhibitory

49
Q

Is VLo to SMA inhibitory or excitatory?

A

Excitatory

50
Q

What is the effect of cortical excitation?

A

Excites putamen which inhibits the globus pallidus whichh release cells in VLo from inhibition so boosts SMA activity

51
Q

What do lesions to the cerebellum cause?

A

Uncoordinated inaccurate movements (Ataxia)

52
Q

What does the cortico-ponto-cerebellar projection connect?

A

Cortex, pontine nucleus and cerebellum

Nervous System (16 decks)

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