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Neuro > The Motor System > Flashcards

The Motor System Flashcards

1
Q

What does motor control involve

A

Motor control involves a dynamically changing mix of conscious and unconscious regulation of muscle force, informed by continuous and complex sensory feedback, operating in a framework sculpted by evolutionary pressures

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2
Q

Examples of voluntary motor control

A

Running
Walking
Talking

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3
Q

Examples of goal directed motor control

A

Conscious
Controlled

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4
Q

Examples of involuntary motor control

A

Eye movement
Facial expressions
Postural muscles

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5
Q

How is motor control governed

A

By upper and lower neurons

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6
Q

Where are Lower motor neuron cell bodies found

A

In the brain stem or spinal cord

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7
Q

Where do lower motor neurons project to

A

Muscles

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8
Q

Where do upper motor neurons originate

A

In higher centres in the cerebral cortex

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9
Q

Where do upper motor neurons project to

A

They project to the lower motor neurons

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10
Q

Describe a basic descending control system

A

Association cortex
Motor cortex
Brainstem circuits
Spinal circuits
Motor unit
Effect

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11
Q

What is control of muscle force depend on

A

Individual muscle fibres act in an all or one manner and so the control of muscle force depends on the way in which lower motor neurons activate different types of muscle fibre

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12
Q

What are the 3 types of muscle

A

Skeletal
Smooth
Cardiac

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13
Q

What percentage of muscle makes up or body weight

A

40%

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14
Q

What is an example of antagonistic arrangement of muscles

A

Bicep/tricep/eye

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15
Q

What is an antagonistic arrangement of muscles

A

Combined co-ordinated actions

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16
Q

What is recruitment of muscle fibres

A

Fast/slow twitch

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17
Q

What is a fasciculi

A

A group of muscle fibres

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18
Q

What is a muscle fasciculus

A

Several muscle fibres which make up a muscle cell

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19
Q

What makes a muscle fibre

A

Several myofibrils

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20
Q

What do myofibrils contain

A

Actin and myosin myofilaments

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21
Q

What is a motor unit

A

A single alpha motor neuron + all the muscle fibres it innervates

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22
Q

If a motor neuron innervates a fewer number of fibres causes what

A

A greater movement resolution eg-finger tips

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23
Q

What does activation of the alpha motor neuron cause

A

The alpha motor neuron depolarises and causes contraction of all the muscle fibres in that unit going along with the all or none theory

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24
Q

How do we increase the power of the muscle

A

More motor units are activated

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25
Q

The number of muscle fibres innervated by a single motor neuron depends on

A

The functional requirements of that muscle
- level of control
- strength

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26
Q

What are lower motor neurons

A

They originate in the grey matter of the spinal. Cord or in the brain stem

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27
Q

What is includes in the unit of control of muscle force

A

The lower motor neuron and the muscle fibres it connects with

28
Q

What do all lower motor neurons innervate

A

They all innervate a single muscle

29
Q

What does the motor pool contain

A

Alpha and gamma motor neurons

30
Q

How are motor pools arranged

A

Motor pools are arranged in a rod like shape within the ventral horn of the spinal cord

31
Q

How are cell bodies in the ventral horn activated

A

They are activated by sensory information from the muscle and descending information from the brain

32
Q

How much tension is on the muscle is sensed by what

A

Golgi tendon organs sense tension

33
Q

What senses stretch of muscle fibres

A

Muscle spindles

34
Q

Where is the Golgi tendon organs found

A

They are found within the tendon where the muscle joins to the bone

35
Q

What is the function of the Golgi tendon organ

A

It sends ascending sensory information to the brain via the spinal cord about how much force there is in the muscle

36
Q

What is the Golgi tendon organ critical for

A

Pro-perception

37
Q

When a muscle is under extreme tension what does the Golgi tendon organ do

A

During extreme tension it is possible that the Golgi tendon organ can act to inhibit muscel fibres via the circuit in the spinal cord to prevent damage

38
Q

What are reflexes

A

Reflexes can be quite simple or quite complex
They can operate without engaging with the brain and are critical for the avoidance of injury and effective motor control

39
Q

What is the most simple reflex

A

Monosynaptic

40
Q

What is an example of a monosynaptic reflex

A

The patellar tendon reflex

41
Q

What are intrafusal fibres innervated by

A

They are innervated separately by gamma motor neurons

42
Q

What is needed for an efficient motor control system

A

An efficient motor control system needs to know how much each muscle is stretching which is provided by the muscle spindles

43
Q

Where are muscle sensory receptors found

A

In the muscle spindles

44
Q

What are coiled around the intrafusal fibres

A

Sensory fibres

45
Q

What does reciprocal innervation explain

A

Reciprocal innervation of antagonistic muscles explains why the contraction of one muscle induces the relaxation of the other

46
Q

What does reciprocal innervation allow

A

Execution of smooth movements

47
Q

Where do motor commands originate

A

In the motor cortex pyramidal cells in layers 5-6 of the grey matter

48
Q

What type of motor neurons are found in the motor pyramidal cells

A

Upper motor neurons

49
Q

Where do axons from the pyramidal cells project to

A

Directly or indirectly via the brainstem to the spinal cord

50
Q

In the spinal cord upper motor neurons synapse with what

A

Lower motor neurons

51
Q

What do axons of the upper motor neurons make

A

The pyramidal tracts

52
Q

What is the motor homunculus

A

The homunculus is a reasonable representation of what areas of the motor cortex control what in the body

53
Q

What do both dorsolateral tracts and ventromedial tracts both contain

A

They both contain a direct corticospinal route
They both contain an indirect route via brainstem nuclei

54
Q

What is the brain stem nuclei that the dorsolateral tract travel by

A

The red nucleus

55
Q

What are the brainstem nuclei that the ventromedial tracts travel through

A

They travel through the tectum, vestibular nuclei, reticular formation and cranial nuclei

56
Q

What do the dorsolateral tracts innervate

A

They innervate the contralateral side of one segment of the spinal cord

57
Q

What does the ventromedial tracts innervate

A

The ventromedial tracts diffuse there innervation which projects to both sides and multiple segments of the spinal cord

58
Q

Where do the dorsolateral tract projections go to

A

They sometimes project directly to alpha motor neurons
Project to the distal muscles eg— fingers

59
Q

Where do the projections of the ventromedial tracts go to

A

Proximal muscles muscles of trunk and limbs

60
Q

What is the basal ganglia

A

A group of structures beneath the cortex that act as a gate keeper for control of the motor system

61
Q

What is the cerebellum

A

The cerebellum is a large brain structure that acts as a parallel processor enabling smooth coordinated movements and important in a range of cognitive tasks

62
Q

What does the cerebellum do in relation to motor neurons

A

The cerebellum has no direct projections to lower motor neurons but does modulate activity of upper motor neurons

63
Q

What inputs does the cerebellum get from the cortical tract

A

Mostly from the motor cortex which are copies of the motor commands and somatosensory and visual areas of parietal cortex

64
Q

What inputs does the cerebellum get from to spinal tract

A

Proprioceptive information about limb position and movement

65
Q

What inputs do the cerebellum get from the vestibular tract

A

Rotational and acceleratory head movements

66
Q

What are the function of the cerebellum

A

It knows what the current motor command is
It knows about actual body positions
It projects back to the motor cortex
Computes motor error and adjusts cortical commands accordingly

Neuro (17 decks)

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