Motor Control 2 Flashcards

1
Q

What is the cerebellum responsible for?

A

The co-ordination of voluntary movements

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2
Q

Define co-ordination

A

Control of the timing of sequences of contractions in different muscles to make a movement smooth and reliable

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3
Q

What makes up the outer part of the cerebellum?

A

A highy convoluted grey matter cerebellar cortex

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4
Q

What makes up the layer beneath the cerebellar cortex of grey matter?

A

White matter containing axons going to and from the cortex?

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5
Q

Where are the deep cerebellar nuclei?

A

Deep within the white matter of the cerebellum

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6
Q

What are the three functional areas of the cerebellum?

A

Archicerebellum (Vestibulocerebellum)

Paleocerebellum

Neocerebellum

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7
Q

What is the function of the archicerebellum?

A

Concerned with posture and balance, with major input form the vestibular system

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8
Q

What is the paleocerebellum?

A

More important in 4 legged animals, has control of gait in humans

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9
Q

What is the function of the neocerebellum?

A

Makes up 90% of cerebellum, responsible for unconscious co-ordianation of voluntary movements

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10
Q

Where does input to the cerebellum reach first?

A

All of it goes to the cortex/cerebellar hemisphere

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11
Q

Where does output come from in the cerebellum?

A

The dentate nucleus

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12
Q

Where does output from the dentate nucleus in the cerebellum go?

A

It is relayed but eh thalamus to the MC

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13
Q

How can information reach the cerebellar cortex?

A

In two ways. Firstly, a direct route via the pons of the brainstem
Or, an indirect route which traverses several brain areas and finally makes connections in the inferior olive nucleus in the brainstem

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14
Q

What is the name of the fibres running from the pons to the cerebellar cortex? (direct route)

A

Mossy fibres

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15
Q

What is the name of the fibres running from the inferior olive to the cerebellar cortex? (indirect route)

A

Climbing fibres

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16
Q

Do CS tract neuron collaterals pass to the cerebellum?

A

Yes, passing copies of signals being sent to the motoneurons

17
Q

What is the major electrical input to the cerebellum with regard to movement?

A

The readiness potential

18
Q

How can motor learning take place in the cerebellum?

A

Via the circuits that are contained within it - developing preferential pathways

19
Q

What is the function of the circuits within the cerebellum?

A

To enable the precise timing of movements to be calculates

20
Q

Does the cerebellum carry a motor homunculus?

A

Yes

21
Q

What fibres form the output from the cerebellum?

A

Purkinje cells

22
Q

What is the effect of mossy fibres on the purkinje cells? Where do the mossy fibres come from?

A

They act on around 1000 cells per mossy fibre, slightly raising the level of excitation but not enough to fire APs. They are responsible for the readiness potential

23
Q

What is the effect of climbing fibres on the pukinje cells? Where do they come from?

A

The make powerful excitatory contact with the cells on a 1:1 basis. They do cause APs to fire, inhibiting the dentate nucleus. This creates the binary like signal that will be mentioned further

24
Q

What is the principle of motor learning with respect to climbing fibres?

A

The learning process is about finding the right climbing fibre over time

25
Q

What occurs as a result of mossy and climbing fibre action to the purkinje cells?

A

Synaptic strengthening - this means that eventually only mossy fibre input is needed to cause APs to discharge from the purkinje cells
Movement becomes automatic and the climbing fibres are no longer needed for that specific movement. The synaptic strengthening is permanent, and involves increased calcium permeability and protein synthesis

The mossy fibre activity creates a binary type pattern of excitation signal, constant but with a small gap between each purkinje fibre excitation. The strengthened purkinje fibres will discharge an AP in temporal pattern. The inhibitory action of the nucleus of these APs punches gaps of inhibition into the stream of mossy excitations. This forms a temporal code which can be passed to the MC to produce a smooth and reliable movement

26
Q

What is ataxia?

A

Global deficit - incoordination. Specific effects depend on the area of the cerebellum damaged

27
Q

Describe decomposition of movement that can occur in patients with cerebellar damage?

A

Instead of movement signals being formed smoothly via the combination of mossy and climbing fibres in a healthy individual, they decompose into simpler units e.g. joint by joint

28
Q

What effect does decomposition of movement have on speech?

A

Dysarthria or staccato speech - no aphasia but mechanical aspects of speech are slow, impaired and syllable by syllable

29
Q

What is asynergia?

A

Lack of cooperation between agonists and antagonists, may contract together

30
Q

What is dysmetria?

A

‘Past-pointing’. goal directed movements lack accuracy, point past, short or to the side of the target

31
Q

What is an intentional tremor?

A

Occurs during movement and particularly towards the end, NOT at rest

32
Q

What is dysdiachokinesia?

A

An inability to make rapidly alternating opposite movements

33
Q

Describe posture, gait and balance deficits? Information from what system is of particular relevance?

A

Patients adopt a wide stance with a tendency to fall over (drunken sailor’s gait). Associated with the vestibular system