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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
If the UMN don't cross and descend ipsilateral to side of origin what are the UMN referred to as?
Anterior Corticspinal tract
26
Where do UMN of the anterior corticospinal tract cross over to synapse?
At level of synapse they cross over to the opposite anterior horn to join the lateral corticospinal tract.
27
Once synapsed where do both the lateral and anterior corticospinal tracts exit the spinal column?
From the anterior horn.
28
What is the function of the Tectospinal Tract?
Mediate reflex head and neck movement due to visual stimuli
29
What is the function of the Reticulospinal tract?
Influences voluntary movement
30
What is the function of the Vestibulospinal tract?
Excitatory input to antigravity extensor muscles
31
List some of the key jobs of the dorsal column medial lemniscus.
``` Stereogensesis - ability to recognise by touch Vibration detection Fine touch - two point discrimination Conscious proprioception Weight discrimination ```
32
What helps to sharpen the stimuli perception within the Doral column / medial lemniscus?
Contrast enhancement and lateral inhibition
33
What is the basis behind contrast enhancement and lateral inhibition?
The most active neurone inhibits adjacent neurones via inhibitory interneurones. Thus amplifying the action potential of the active neurone.
34
What does the posterior parietal cortex do?
Receives and integrates inputs from post central gyrus and other sensory areas e.g. visual auditory and subcortical. Pieces together the jigsaw
35
Damage to the posterior parietal cortex would result in what?
Neglect syndrome - failure to recognise or use one half of the body. Difficulties with understand arithmetic and numbers.
36
What are the two types of Lower Motor Neurone?
Alpha - innervate the bulk of the muscle responsible for producing force. Gamma - innervate the sensory muscle spindle fibres
37
LMN supplying axial muscle groups are found where in the lateral horn?
Medially
38
LMN supplying distal muscle groups are found where in the lateral horn?
Laterally
39
LMN supplying flexor muscle groups are found where in the lateral horn?
Dorsal
40
LMN supplying extensor muscle groups are found where in the lateral horn?
Ventral
41
What is the Spinal Central Pattern Generator
An excitatory interneurone that displays pacemaker activity creating a rhythmic alternating activity that controls movement within a limb.
42
Describe how a Spinal Central Pattern Generator could in theory control walking from spinal level.
If two antagonistic circuits containing flexion and extension produced a viable rhythm it could produce locomotion.
43
What is the motor control hierarchy and where is it controlled?
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
List the descending tracts
``` Corticospinal Rubrospinal Corticobulbar Tectospinal Reticulospinal Vestibulospinal ```
45
How can descending tracts be divided?
Pyrimidal and Extrapyramidal | Lateral and Ventromedial
46
Where are cell bodies located in the corticospinal tract?
Motor cortex BA4 BA6
47
What proportion of descending fibres cross at the level of the medulary pyramid?
85 % Lateral | 15 % Ventral
48
Describe Lateral Descending tracts.
Under control of cerebral cortex | Voluntary control of distal musculature
49
Describe Ventromedial Descending tracts.
Under control of the brain stem | Key for postural control and locomotion.
50
What is the name of a minor lateral descending tracts?
Rubrospinal
51
Where are the cell bodies of the rubrospinal tract located?
Red Nucleus
52
Where does the red nucleus recieve input from?
Motor Cortex and the cerebellum
53
Where do the fibres of the rubrospinal tract decussate at?
Level of the ventral tegmental - Base of the midbrain
54
How does the rubrospinal chord descend once it has crossed over?
With the ventrolateral spinal chord to join the lateral corticospinal tract.
55
What is the function of the Rubrospinal tract?
Exert control over upper limb flexor muscles inhibit extensor
56
A lesion of the lateral column would result in what?
Loss of shoulder elbow wrist fingers being able to move independently Loss of accuracy in voluntary movements No really affect on posture
57
The Rubrospinal can compensate for a damaged corticospinal tract. T/F
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
What are the pyramidal tracts?
Corticospinal | Corticobulbar
59
Describe the corticobulbar tract?
Controls the face head and neck by innervating the cranial nerve nuclei
60
What cranial nerve nuclei are not innervated by the corticobulbar tract?
CN XII | Lower part of Cranial Nerve VII
61
Where do corticobulbar tracts leave the brain or the spinal column?
Within Brainstem
62
Axons of the lateral vestibulospinal tract do what?
Aid extensor MNs of the antigravity muscles. | Holds upright and balanced posture.
63
Axons of the medial vestibulospinal tract do what?
Control neck and back muscles to guide the head movement.
64
Where do the cell Bodies of the Vestibulospinal tract sit?
Vestibular nuclei - receives input from cerebellum and CN VIII
65
How far do axons of the lateral vestibulospinal tract descend?
As far as the lumbar spinal chord
66
Do the axons o the vestibulospinal tract cross over ?
No they descend ipsilaterally
67
How far do axons of the medial vestibulospinal tract descend?
As far as the cervical spinal chord
68
What is the function of the Tectospinal tract?
Reflex postural control of the neck and head in response to visual stimuli.
69
What is the function of the vestibulospinal tract?
Reflex postural control of the back neck and head in response to vestibular stimuli.
70
Where do the cell bodies of the tectospinal tract reside?
Superior Colliculus
71
What is the function of the superior colliculus?
Receives input from the retina visual, auditory and somatosensory cortex to create a map of the external world.
72
Do axons of the tectospinal tract cross over and if so where?
Axons decussate at the dorsal tegmental , midbrain.
73
Where within the spinal chord do axons of the tectopsinal chord descend?
Close to the midline
74
How far do axons of the tectospinal chord descend?
To level of the cervical spinal chord
75
How can the reticulospinal tract be subdivided?
Pontine (Medial) | Medullary ( Lateral (
76
What is the function of the reticulospinal tract?
Locomotion and postural control
77
Where do the cell bodies of both reticulospinal tracts sit?
Within the reticular formation which sits at the core and runs the length of the brainstem.
78
How do fibres of the Pontine reticulospinal tract descend?
Ipsilatteraly
79
How do fibres of the medullary reticulospinal tract descend?
Bilaterally
80
What is the function of the Medullary reticulospinal tract?
Opposes action of the pontine tract by releasing antigravity muscles from pontine control.
81
What is the function of the pontine reticulospinal tract?
Facilitates lower limb extensor contraction.
82
How can you tell if there is a peripheral lesion of the corticobulbar tract?
Complete unilateral forehead and lip drooping | Lower MN CVII is affected
83
How can you tell if there is a central lesion affecting thecorticobulbar tract?
Lip droops | Forehead is spared
84
What are the extrapyramidal tracts?
Rubrospinal Reticulospinal Vestibulospinal Tectospinal
85
Describe a decorticate lesion
Lesion occurs above the midbrain
86
Describe a decerebrate lesion
Lesion occurs below the midbrain
87
What can be seen in a decorticate lesion?
Rubrospinal when unconscious Arms folded inwards Hands turned inwards Feet and legs extended
88
What can be seen in a decerebrate lesion?
``` 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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