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Biomed > Motor function > Flashcards

Motor function Flashcards

1
Q

What are motor neurons involved in?

A

Pathways which carry efferent impulses from the CNS to the periphery of the head and body which ultimately activate effectors

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2
Q

What are motor neurons needed for?

A
  1. voluntary muscle contraction (somatic nervous system)
  2. involuntary muscle contraction (autonomic nervous system)
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3
Q

What else inputs to motor neurons as they pass through the CNS?

A
  1. eyes
  2. vestibular apparatus
  3. cerebellum
  4. basal ganglion loop system
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4
Q

What order is the hierarchy of motor pathways?

A
  1. primary motor cortex
  2. upper motor neurons
  3. lower motor neurons
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5
Q

Where is the primary motor cortex?

A

in the brain

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6
Q

What are upper motor neurons?

A

Axons from the primary motor cortex descending directly into the brainstem or spinal cord

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7
Q

What do the lower motor neurons do?

A

Receive an impulse from an upper motor neuron and then exit the CNS to cause the contraction of a muscle at the periphery

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8
Q

What lower motor neurons exit at the brainstem?

A

the cranial nerves, which innervate the muscles of the head and neck

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9
Q

Which motor neurons exit from the spinal cord?

A

Spinal nerves which innervate the muscles of the lower body

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10
Q

Which lower motor neurons synapse in the spinal cord?

A

Those which exit the spinal cord from the anterior horn of the grey matter

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11
Q

Each branch of the motor neuron will synapse with what?

A

A motor end plate - the region of the muscle that the neuron communicates with across the synapse

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12
Q

How is voluntary muscle contraction stimulated?

A

Motor neuron releases acetylcholine

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13
Q

Which areas of the frontal lobe are involved in motor movement?

A
  1. primary motor cortex (M1)
  2. premotor cortex (PM)
  3. supplemental motor area (SMA)
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14
Q

What does the premotor cortex do?

A

receives sensory input from parietal lobe and basal ganglia to help plan and prepare movement

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15
Q

What does the supplemental motor area do?

A

Coordinates complex fine movements and posture

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16
Q

Where is the primary motor cortex?

A

in the precentral gyrus of each hemisphere

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17
Q

How is the primary motor cortex arranged?

A

somatopically - body represented in the correct sequence but upside down

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18
Q

What are the main motor pathways divided into?

A
  1. the lateral pathways
  2. the medial pathways
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19
Q

What are the lateral motor pathways?

A
  1. corticospinal tract (from cerebral cortex)
  2. rubrospinal tract
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20
Q

What are the medial motor pathways?

A
  1. reticulospinal tracts
  2. tectospinal tracts
  3. vestibulospinal tract
  4. ventral corticospinal tract (from cerebral hemisphere)
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21
Q

Which are the pyramidal pathways?

A
  1. corticospinal tract
  2. ventral corticospinal tract
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22
Q

Which are the extrapyramidal pathways?

A
  1. rubrospinal tract
  2. reticulospinal tract
  3. tectospinal tract
  4. vestibulospinal tract
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23
Q

What is the function of the medial pathways?

A

To coordinate:
1. balance and posture
2. proximal limb muscles
3. guiding of limbs into positions for planned movement

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24
Q

Where does the vestibulospinal tract start?

A

in the vestibular spinal tract - spans pons and medulla

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25
Q

What do the vestibular nuclei do?

A
  1. receive info about balance from the semi circular canals in middle ear
  2. send info back from vesticulocerebrum to modulate and refine motor output
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26
Q

What doe the vestibulospinal tracts do?

A

Convey balance info to spinal cord where it remains ipsilateral, and controls balance and posture by:
1. innervating ‘anti-gravity’ muscle sin trunk and spine to maintain upright position
2. respond to changes in head position and movement - essential for reflexive adjustment to maintain balance and prevent falls

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27
Q

Where do the reticulospinal tracts arise from?

A

the reticular formation of the pons or medulla

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28
Q

What does the reticular system do?

A

receives sensory input from the spinoreticular tracts, red nuclei, and motor cortex

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29
Q

What do the reticulospinal tracts do?

A

Influence voluntary movement by controlling muscle tone and are involved in the synchronisation of complex movements

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30
Q

Where do the medial reticulospinal tracts arise from?

A

medullary reticular formation

31
Q

What do the medial reticulospinal tracts do?

A

Facilitate voluntary movement and increases muscle tone

32
Q

Where does the lateral reticulospinal tract arise?

A

pons

33
Q

What does the lateral reticulospinal tract do?

A

Inhibits voluntary contraction and reduces muscle tone

34
Q

Where does the venterolateral reticulospinal tract originate?

A

the medulla

35
Q

What does the venterolateral reticulospinal tract do?

A

helps control muscle tone

36
Q

What is the pathway of the tectospinal tracts?

A
  1. begin at superior colliculus in midbrain
  2. neurons then decussate and descend to enter the spinal cord
  3. terminate at cervical levels of spinal cord
37
Q

What is the superior colliculus?

A

a structure which receives input from optic nerves from eyes

38
Q

What do the tectospinal tracts do?

A

control reflex postural movements in response to visual stimuli

39
Q

Where does the anterior corticospinal tract start?

A

in the cortex

40
Q

Where does the anterior corticospinal tract decussate?

A

in the spinal cord at the level of its synapse with a lower motor neuron

41
Q

What is the function of the anterior corticospinal tract?

A

to maintain balance, posture, and purposeful movements involving the axial musculature, esp in the trunk region

42
Q

What is the function of the lateral motor pathways?

A

Mainly to coordinate voluntary movement?
1. fine voluntary movements (esp in hands and fingers)
2. flexor muscles of limbs, control, and coordination

43
Q

Why are the lateral and anterior corticospinal tracts known as the pyramidal tracts?

A

Because they pass through the medullary pyramids

44
Q

What the pathway of the lateral corticospinal tract?

A
  1. starts in cortex
  2. desucates in medulla
45
Q

Which corticospinal tract is larger?

A

The lateral tract

46
Q

What is the function of the lateral corticospinal tract?

A

Maintains posture, balance, and purposeful movements involving axial musculature, especially in the trunk if the region

47
Q

What is the pathway of the corticobulbar tract?

A
  1. originate in primary motor cortex
  2. dessucate in medullary pyramids
  3. terminate on moter nuclei of cranial nerves, where they synapse with lower motor neurons
48
Q

What is the function of the corticobulbar tract?

A

Controls voluntary facial expression, mastication, swallowing, vocalisation of speech. Uses bilateral control to coordinate movement on both sides

49
Q

What are the inputs of the corticospinal and corticobulbar tracts?

A
  1. primary motor cortex
  2. premotor cortex
  3. supplementary motor cortex
  4. somatosensory area
50
Q

What does the input from the somatosensory area do for the corticospinal and corticobulbar tracts?

A

Play a role in regulating the activity of the ascending tracts

51
Q

What is the pathway shared by the corticospinal and corticobulbar tracts?

A
  1. pass through the internal capsule in somatotopic organisation
  2. enter the anterior part of the brainstem at the midbrain
52
Q

What do the red nuclei receive output from?

A

The motor cortex and cerebellum - so info on state of contraction and stretch of muscles can be fed into motor pathways

53
Q

What is the pathway of the rubrospinal tract?

A
  1. originates in red nuclei of midbrain
  2. nerve fibres desucate as they emerge and descend into spinal cord (contralateral innervation)
54
Q

What is the function of the rubrospinal tract?

A

control voluntary flexor muscles of limbs (muscles that bend the limbs)

55
Q

What does the anterior limb of the internal capsule contain?

A
  1. Axons projecting from the thalamus to the motor cortex
  2. corticopontine axons projecting from cortex to pontine nuclei
56
Q

What does the posterior limb of the internal capsule contain?

A

the corticobulbar and corticospinal axons arranged somatopically

57
Q

How does the internal capsule receive its blood supply?

A

through a series of small perforating arteries entering from the base of the brain - clinically imp as is susceptible to compression from haemorrhagic bleeds which can cause lesions of descending tracts

58
Q

Where does the vestibulospinal tract desucate?

A

It doesn’t, it remains ipsilateral

59
Q

Where does the reticulospinal tract desucate?

A

It doesn’t, it remains ipsilateral

60
Q

Where does the tectospinal tract arise?

A

superior colliculus in midbrain

61
Q

Where does the tectospinal tract dessucate?

A

As it leaves the midbrain

62
Q

Where does the tectospinal tract terminate?

A

at the cervical levels of the spinal cord

63
Q

Where does the lateral corticospinal tract arise?

A

in the cortex

64
Q

Where does the lateral corticospinal tract decussate?

A

in the medulla

65
Q

Where does the corticobulbar tract arise?

A

primary motor cortex

66
Q

Where does the corticobulbar tract decussate?

A

in the medullary pyramids

67
Q

What is the innervation of the corticobulbar tract?

A

bilateral to all except facial and hypoglossal

68
Q

What is the corticobulbar innervation to the facial nerve?

A

bilateral to upper, contralateral to lower

69
Q

What is the corticobulbar innervation to hypoglossal nerve?

A

contralateral

70
Q

Where does the rubrospinal tract arise?

A

in the red nuclei of the midbrain

71
Q

Where does the rubrospinal tract decussate?

A

as they emerge from the midbrain

72
Q

What is the basal ganglia?

A

a system of nuclei located deep in the hemisphere and midbrain

73
Q

What is the basal ganglia involved in?

A

regulating movement and reducing unwanted movement through complex loop systems between cortex, basal ganglia, and substantia niagra

74
Q

What is the basal ganglia made up of?

A
  1. caudate nucleus
  2. lentiform nucleus
  3. substantia niagra

Biomed (29 decks)

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