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The Nervous System: Physiology > Motor Control 2 > Flashcards

Motor Control 2 Flashcards

1
Q

How are lots of neurones involved in deciding a direction

A

As Each one has a preferred direction and will fire greater for a movement in that direction than any other

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2
Q

Whats happens to the discharging neurones when you have a preferred direction

A

Neurones preferring that direction will fire more and others less resulting in a population vector.

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3
Q

What controls the overall movement direction

A

Population vector encoded by the integrated activity of all the neurones.

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4
Q

How does feedback occurs when you need to correct postural instability

A

Via vestibulo-spinal system
(brainstem vestibular nuclei to spinal cord motor neurones)

To correct postural instability

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5
Q

How do you stabilise posture before movement occurs

A

Reticular formation via Reticulospinal tracts make feedforward anticipatory adjustment to stabilise posture before you make a move

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6
Q

What is the symptoms of upper motor neurone syndrome/damage to descending motor pathway

A

Spinal shock - spinal cord deprived of cortical input

Babinskis sign

Spasticity

Loss of fine finger movements

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7
Q

The symptoms of an upper motor lesion depends on what

A

Injury site

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8
Q

What is the affect of cortical damage

A

Immediate flaccidity of contralateral muscle - have no drive

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9
Q

What occurs after spinal shock in upper motor lesion that leads to the return of reflexes

A

Days later spinal circuits regain function - spared connections strengthen and new connections sprout.

A consistent pattern of motor signs emerges

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10
Q

What is seen in spasticity

A

Increased muscle tone

hyperactive stretch reflex

Clonus oscillatory contract/relax muscles in reponse to stretch

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11
Q

Why does spasticity occur in upper motor lessons

A

Due to removal of cortical suppressive influences

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12
Q

What does Babinskis sign indicate

A

Incomplete upper control of spinal circuits

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13
Q

What is the overall pathway of the motor loop

A

Communication occurs from motor cortex to the basal ganglia then to ventral lateral nucleus in dorsal thalamus (VLo) then back to the supplementary areas in the cortex area 6

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14
Q

What part of the cortex targets the basal ganglia motor loop

A

Frontal (motor cortex4+6)
Prefrontal
Parietal (sensory cortex)

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15
Q

What is the overall function of the cortical activation of basal ganglia

A

Part of a motor loop with the function of a Positive Feedback Loop which focusses widespread cortical activation onto the Supplementary Motor Area

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16
Q

What two pathway does information from the motor cortex reach the spinal cord

A

Lateral pathway (red nucleus)

Ventromedial pathway
reticular nuclei and superior colliculus and vestibular nuclei

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17
Q

What is the major component of the basal ganglia

A

Corpus striatum

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18
Q

What is the corpus striatum

A

two principal nuclei the caudate and the putamen

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19
Q

What is the function of the corpus striatum

A

Input zone of the basal ganglia receiving input from all over the cortex in the motor loop

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20
Q

What is the pathway to the basal ganglias corpus striatum called

A

corticostriatal pathway - multiple parallel pathways with different functions

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21
Q

What type of neurones are in putamen and caudate

A

Medium spiny neurones- which have large dendritic trees in to intergrate signals

22
Q

Where do the medium spiny neurones of the putamen and caudate receive signals from

A

Somatosensory, premotor and motor cortical inputs

23
Q

What cortical inputs are received by the medium spiny neurones dendrites

A

excitatory glutamatergic

24
Q

What are the axons of the medium spiny neurones

A

Inhibitory - GABAergic

25
Q

Where do the axons of the medium spiny neurone in the putamen project

A

Globus pallidus

26
Q

Where do the axons of the medium spiny neurone in the caudate project

A

substantia nigra pars reticulata

27
Q

When does the putamen fire its axons

A

Before limb/trunk movements (predictive)

28
Q

When does the caudate fire its axons

A

Before eye movements

predictive

29
Q

What is the exact process of the motor loop: cortex - basal ganglia - cortex

A

Cortex excites putamen

Putamen inhibits Globus Pallidus

Globus Pallidus stops inhibiting thalamus VLo neurons

VLo neurons boost SMA activity

30
Q

What happens at rest of globes pallidus neurones

A

Spontaneously active and inhibit VLo

31
Q

What arrangement is present in the basal ganglia to gate the operation of the motor loop

A

A chain of neurones arranged in dis-inhibitory circuit

32
Q

What is the two pathways in the basal ganglia

A

Direct - promote movement in SMA

Indirect - suppressing competing actions to the one direct pathway

33
Q

How does the indirect pathway suppress the competing actions

A

The Putamen+caudate (striatum) inhibits the globes pallidus external which further inhibits GPi and Subthalamic Nuclei (STN)

34
Q

What occurs when cortex excites the STN

A

Excites GPi which inhibits the thalamus

35
Q

What is two basal ganglia disorders

A

Parkinsons

Huntingtons

36
Q

What is the cause of parkinson

A

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

37
Q

What is the symptoms of Parkinsons

A

Hypokinesia:

Slowness
Difficulty making voluntary movements
Increased Tone
Tremors of hand & jaw

38
Q

What is dopamine affect on cortical inputs

A

Enhance cortical inputs the direct pathway

Suppress inputs through indirect pathway

39
Q

What is the affect of depleted dopamine in motor control

A

Close down actions funnelled through the thalamus to the SMA

40
Q

What is the symptoms of huntingtons disease

A

Hyperkinesia

Dementia

Personality
Disorders

Characteristic chorea

41
Q

What is seen in characters chorea

A

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

42
Q

What is the cause of Huntington’s

A

A heredity disease cause by the profound loss of caudate, putamen and globes pallidus

43
Q

What is the affect of the profound loss of the basal ganglia in huntington’s disease

A

loss of the ongoing inhibitory effects of the basal ganglia

44
Q

How much of the brain volume and CNS neurones if the cerebellum made off

A

Cerebellum is 10% of brain volume and 50% of CNS neurones

45
Q

What can lesions of the cerebellum lead to

A

Uncoordinated inaccurate movements - ataxia

46
Q

What is another cause of ataxia with the cerebellum

A

Cerebellar depression by alcohol

47
Q

What information does the cerebellum send the cortex

A

Instructions on direction, timing and force of movements

48
Q

What is the cortico-ponto-cerebellar projection

A

Connects the cortex, pons and cerebellum

as the cerebellum connects to the cortex via the ventrolateral thalamus

49
Q

Where does the motor loop go after basal galena and VLo to achieve refinement

A

by a feedback loop through pons, cerebellum, thalamus and back to the cortex

50
Q

How does this cortico-ponto- cerebellar projection provide refinement of motor loop

A

It makes use of motor learning stored in the cerebellum, based on predictions, calculations and experience,

comparing what was intended to what happens then compensating.

The Nervous System: Physiology (15 decks)

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