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Neurology Year 3 > Ascending and Descending Pathway > Flashcards

Ascending and Descending Pathway Flashcards

1
Q

Generally what are ascending pathways main modality?

A

Sensory

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2
Q

Generally what are descending pathways main modality?

A

Motor

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3
Q

What column is involved with Fine Touch and conscious proprioception?

A

Dorsal Column / Medial Lemniscus system

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4
Q

What divides the upper and lower fasciculus in the DCML?

A

T6

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5
Q

Cutaneous receptors below T6 trigger an AP which travels along what?

A

Fascicule Gracilis

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6
Q

Cutaneous receptors above T6 trigger an AP which travels along what?

A

Fascicule Cutanea

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7
Q

Fibres from below T6 synapse where?

A

Nuclei Grascilis - within medulla

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8
Q

Fibres from above T6 synapse where?

A

Nuclei Cutanea - within medulla

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9
Q

At what level do neurones from the DCML cross over?

A

Level of the medulla.

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10
Q

Where within the brain do 2nd order neurones synapse?

DCML

A

Ventral Posterolateral Nuclei - within the thalamus

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11
Q

Where within the brain do 3rd order neurones synapse?

DCML

A

Primary somatosensory cortex

Post Central Gyrus

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12
Q

3rd order neurones travel within this to reach the primary somatosensory cortex.
DCML

A

Posterior Internal Capsule

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13
Q

If originating above T6 where do 1st order neurones synapse?

DCML

A

Nucleus Cutanea - within medulla

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14
Q

What tract deals with Pain Temperature and deep pressure?

A

Spinothalmic tract / Anterolateral Column

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15
Q

Generally what cutaneous receptors deal with pain?

A

Nociceptors

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16
Q

Where do 1st order neurones synapse within the spinothalmic tract?

A

Posterior horn

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17
Q

At what level do neurones of Spinothalmic tract cross over?

A

At the level it synapses they cross over before climbing anterolaterally.

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18
Q

Where do second order neurones synapse within the spinothalmic tract?

A

Pass through straight to the ventral Posterolateral Nucleus

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19
Q

Where are motor action potentials generated?

A

Precentral Gyrus

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20
Q

From where do Upper Motor Neurones originate and where do they synapse?

A

Originate at precentral gyrus

Synapse within anterior horn.

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21
Q

Within the Midbrain where do UMN pass?

A

Cerebral Peduncles

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22
Q

Where within the medulla do the UMN pass?

A

Pyramids of the medulla, located on the anterior portion.

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23
Q

What percentage of UMN cross laterally at the level of the medulla?

A

85%

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24
Q

If the UMN cross laterally at the level of the medulla what are they referred to as?

A

Lateral Corticospinal tract

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25
Q

If the UMN don’t cross and descend ipsilateral to side of origin what are the UMN referred to as?

A

Anterior Corticspinal tract

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26
Q

Where do UMN of the anterior corticospinal tract cross over to synapse?

A

At level of synapse they cross over to the opposite anterior horn to join the lateral corticospinal tract.

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27
Q

Once synapsed where do both the lateral and anterior corticospinal tracts exit the spinal column?

A

From the anterior horn.

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28
Q

What is the function of the Tectospinal Tract?

A

Mediate reflex head and neck movement due to visual stimuli

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29
Q

What is the function of the Reticulospinal tract?

A

Influences voluntary movement

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30
Q

What is the function of the Vestibulospinal tract?

A

Excitatory input to antigravity extensor muscles

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31
Q

List some of the key jobs of the dorsal column medial lemniscus.

A 
Stereogensesis - ability to recognise by touch
Vibration detection
Fine touch - two point discrimination
Conscious proprioception
Weight discrimination
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32
Q

What helps to sharpen the stimuli perception within the Doral column / medial lemniscus?

A

Contrast enhancement and lateral inhibition

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33
Q

What is the basis behind contrast enhancement and lateral inhibition?

A

The most active neurone inhibits adjacent neurones via inhibitory interneurones.
Thus amplifying the action potential of the active neurone.

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34
Q

What does the posterior parietal cortex do?

A

Receives and integrates inputs from post central gyrus and other sensory areas e.g. visual auditory and subcortical.
Pieces together the jigsaw

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35
Q

Damage to the posterior parietal cortex would result in what?

A

Neglect syndrome - failure to recognise or use one half of the body.
Difficulties with understand arithmetic and numbers.

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36
Q

What are the two types of Lower Motor Neurone?

A

Alpha - innervate the bulk of the muscle responsible for producing force.
Gamma - innervate the sensory muscle spindle fibres

37
Q

LMN supplying axial muscle groups are found where in the lateral horn?

A

Medially

38
Q

LMN supplying distal muscle groups are found where in the lateral horn?

A

Laterally

39
Q

LMN supplying flexor muscle groups are found where in the lateral horn?

A

Dorsal

40
Q

LMN supplying extensor muscle groups are found where in the lateral horn?

A

Ventral

41
Q

What is the Spinal Central Pattern Generator

A

An excitatory interneurone that displays pacemaker activity creating a rhythmic alternating activity that controls movement within a limb.

42
Q

Describe how a Spinal Central Pattern Generator could in theory control walking from spinal level.

A

If two antagonistic circuits containing flexion and extension produced a viable rhythm it could produce locomotion.

43
Q

What is the motor control hierarchy and where is it controlled?

A

Strategy - Basal Ganglia - Aims of the movement.
Tactics - Sequence of muscle contraction and relaxations
- Motorcortex cerebellum
Execution - Brain Stem and Spinal Chord
- Activation of motor and interneurones

44
Q

List the descending tracts

A 
Corticospinal
Rubrospinal
Corticobulbar
Tectospinal
Reticulospinal
Vestibulospinal
45
Q

How can descending tracts be divided?

A

Pyrimidal and Extrapyramidal

Lateral and Ventromedial

46
Q

Where are cell bodies located in the corticospinal tract?

A

Motor cortex BA4 BA6

47
Q

What proportion of descending fibres cross at the level of the medulary pyramid?

A

85 % Lateral

15 % Ventral

48
Q

Describe Lateral Descending tracts.

A

Under control of cerebral cortex

Voluntary control of distal musculature

49
Q

Describe Ventromedial Descending tracts.

A

Under control of the brain stem

Key for postural control and locomotion.

50
Q

What is the name of a minor lateral descending tracts?

A

Rubrospinal

51
Q

Where are the cell bodies of the rubrospinal tract located?

A

Red Nucleus

52
Q

Where does the red nucleus recieve input from?

A

Motor Cortex and the cerebellum

53
Q

Where do the fibres of the rubrospinal tract decussate at?

A

Level of the ventral tegmental - Base of the midbrain

54
Q

How does the rubrospinal chord descend once it has crossed over?

A

With the ventrolateral spinal chord to join the lateral corticospinal tract.

55
Q

What is the function of the Rubrospinal tract?

A

Exert control over upper limb flexor muscles inhibit extensor

56
Q

A lesion of the lateral column would result in what?

A

Loss of shoulder elbow wrist fingers being able to move independently
Loss of accuracy in voluntary movements
No really affect on posture

57
Q

The Rubrospinal can compensate for a damaged corticospinal tract. T/F

A

Yes it able to compensate to some extent for the loss of the corticospinal tract, but the corticospinal can not compensate for loss of the rubrospinal.

58
Q

What are the pyramidal tracts?

A

Corticospinal

Corticobulbar

59
Q

Describe the corticobulbar tract?

A

Controls the face head and neck by innervating the cranial nerve nuclei

60
Q

What cranial nerve nuclei are not innervated by the corticobulbar tract?

A

CN XII

Lower part of Cranial Nerve VII

61
Q

Where do corticobulbar tracts leave the brain or the spinal column?

A

Within Brainstem

62
Q

Axons of the lateral vestibulospinal tract do what?

A

Aid extensor MNs of the antigravity muscles.

Holds upright and balanced posture.

63
Q

Axons of the medial vestibulospinal tract do what?

A

Control neck and back muscles to guide the head movement.

64
Q

Where do the cell Bodies of the Vestibulospinal tract sit?

A

Vestibular nuclei - receives input from cerebellum and CN VIII

65
Q

How far do axons of the lateral vestibulospinal tract descend?

A

As far as the lumbar spinal chord

66
Q

Do the axons o the vestibulospinal tract cross over ?

A

No they descend ipsilaterally

67
Q

How far do axons of the medial vestibulospinal tract descend?

A

As far as the cervical spinal chord

68
Q

What is the function of the Tectospinal tract?

A

Reflex postural control of the neck and head in response to visual stimuli.

69
Q

What is the function of the vestibulospinal tract?

A

Reflex postural control of the back neck and head in response to vestibular stimuli.

70
Q

Where do the cell bodies of the tectospinal tract reside?

A

Superior Colliculus

71
Q

What is the function of the superior colliculus?

A

Receives input from the retina visual, auditory and somatosensory cortex to create a map of the external world.

72
Q

Do axons of the tectospinal tract cross over and if so where?

A

Axons decussate at the dorsal tegmental , midbrain.

73
Q

Where within the spinal chord do axons of the tectopsinal chord descend?

A

Close to the midline

74
Q

How far do axons of the tectospinal chord descend?

A

To level of the cervical spinal chord

75
Q

How can the reticulospinal tract be subdivided?

A

Pontine (Medial)

Medullary ( Lateral (

76
Q

What is the function of the reticulospinal tract?

A

Locomotion and postural control

77
Q

Where do the cell bodies of both reticulospinal tracts sit?

A

Within the reticular formation which sits at the core and runs the length of the brainstem.

78
Q

How do fibres of the Pontine reticulospinal tract descend?

A

Ipsilatteraly

79
Q

How do fibres of the medullary reticulospinal tract descend?

A

Bilaterally

80
Q

What is the function of the Medullary reticulospinal tract?

A

Opposes action of the pontine tract by releasing antigravity muscles from pontine control.

81
Q

What is the function of the pontine reticulospinal tract?

A

Facilitates lower limb extensor contraction.

82
Q

How can you tell if there is a peripheral lesion of the corticobulbar tract?

A

Complete unilateral forehead and lip drooping

Lower MN CVII is affected

83
Q

How can you tell if there is a central lesion affecting thecorticobulbar tract?

A

Lip droops

Forehead is spared

84
Q

What are the extrapyramidal tracts?

A

Rubrospinal
Reticulospinal
Vestibulospinal
Tectospinal

85
Q

Describe a decorticate lesion

A

Lesion occurs above the midbrain

86
Q

Describe a decerebrate lesion

A

Lesion occurs below the midbrain

87
Q

What can be seen in a decorticate lesion?

A

Rubrospinal when unconscious
Arms folded inwards
Hands turned inwards
Feet and legs extended

88
Q

What can be seen in a decerebrate lesion?

A 
Reticulospinal when unconscious 
Plantar flexed
Flexed and pronated hands an wrist 
Arms extended and adducted 
Neck arched

Neurology Year 3 (29 decks)

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