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Motor Tracts Flashcards

1
Q

Where do UMNs arise from? Where are they contained?

A

W/in cerebral cortex or brain stem

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2
Q

What do the axons of UMNs synapse w/?

A

W/ LMN or interneurons of SC

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3
Q

What are LMNs?

A

Directly innervate skeletal m.

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4
Q

Where is the cell body of LMNs?

What do they synapse with?

A

Cell body in SC or brainstem

Synapse w/ Sk. M.

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5
Q

What are the two types of lower motor neurons?

A

Gamma and alpha

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6
Q

Where do gamma motor neurons project to?

A

Intrafusal fibers in muscle spindle

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7
Q

Where do alpha motor neurons project to?

A

Extrafusal skeletal muscles

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8
Q

Are alpha or gamma motor nuerons bigger?

A

Alpha

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9
Q

What are Cranial ns? LMNs or UMNs?

A

LOWER MOTOR NEUROSN

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10
Q

What is the direct somatic motor pathway?

A

Cerebral cortex -> SC -> muscles

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11
Q

Why does the direct pathway send some signals down to the brainstem?

A

To help modulate INDIRECT pathways

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12
Q

Name a few places where indirect pathways synapse.

A 
Brainstem
Basal ganglia
Thalamus
Reticular formation 
Cerebellum
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13
Q

Where is the primary motor cortex?

What does it do?

A

In precentral gyrus (area 4)

Initiates voluntary movement (r. Side controls left side of body)

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14
Q

Are the neurons in the primary motor cortex UMNs or LMNs?

A

UMNs

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15
Q

Why are muscles represented unequally on homunculus?

A

Represented according to number of motor units

Those with more motor units need more cortical area

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16
Q

What is the blood supply to the

Lower limb on homunculus?

A

ACA

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17
Q

What is the blood supply to the

Hands/fingers on homunculus?

A

MCA

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18
Q

What is the blood supply to the

Face on homunculus?

A

MCA

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19
Q

Which lobes does the PCA supply?

A

Occipital and temporal lobes

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20
Q

What does the medial corticospinal tract do?

How is this tract different than the lateral?

A

Postural ms. And proximal movements

Neck, shoulder and trunk muscles

does NOT CROSS in Medulla

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21
Q

What does the lateral corticospinal tract do?

A

Limb muscles

Fractionation - finger movements

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22
Q

What is the pathway of the LCST?

A

Cell bodies in cortex
—> thru posterior limb of internal capsule
—> CST tract
—> thru cerebral peduncles
—> thru anterior pons
—> pyramids in medulla
Fibers CROSS in pyramids
—> descend in lateral column of SC (LCST)
—> Synapse with LMNs in anterior horn of spinal cord

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23
Q

How is CST oriented in the

posteiror limb of the internal capsule?

Cerebral peduncles?

Pyramids?

LCST?

A

Arms above, legs below

Arms middle, legs lateral

Arms middle, legs lateral

Arms middle, legs lateral

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24
Q

What is the blood supply to the

posterior limb of the internal capsule?

A

Lenticulate striate a

Anterior choroidal as

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25
Q

What is the blood supply to the

Cerebral peduncles?

A

P1 from PCA

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26
Q

What is the blood supply to the

Pons?

A

Paramedian branches of basilar

AICA

Long circumferential

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27
Q

What is the blood supply to the

pyramids in medulla?

A

Sulcal branches of ASA

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28
Q

What is the blood supply to the

LSCT in SC?

A

Arms = medial = ASA

Legs = lateral = PSA

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29
Q

Where does the CBT arise from?

Where does it descend to?

A

Ventral part of cortical area 4

Brainstem

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30
Q

What does the CBT influence?

A

Influences muscles innervated by CNs that have motor nuclei

5, 7, 9, 10, 11, 12

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31
Q

Where do the axons of CBT cross?

A

At pyramidal decussation

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32
Q

What are the neurons in the CBT, UMNs or LMNs?

A

UMNs

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33
Q

What is the pathway of the CBT?

A 
Ventral art of cortical area 4 
—> thru GENU of internal capsule 
—> CBT,
—> passes thru cerebral peduncles 
—> thru anterior pons (CN 5 and 7) 
—> pyramids, cross
—> thru upper medulla (CN 9, 10, 12)
—> SC
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34
Q

What kind of input does CN 5 have at pons?

A

Bilateral input

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35
Q

What kind of input does CN 7 have at one by CBT?

A

Bilateral to forehead

Contralateral to lower face

36
Q

What kind of input does CN 12 get at upper medulla?

A

Bilateral BUT

MOSTLY contralateral

37
Q

What kind of input does Nucleus ambiguus get?

A

Bilateral BUT

MOSTLY CONTRALATERAL

38
Q

What kind of input does CN 11 get?

Why?

A

Ipsilateral

Bc it stays with medial corticospinal tract

39
Q

What happens if there is damage to CBT,

ABOVE the pons?

A

Ms. Of mastication are ok-bilateral
Ms. Of forehead are ok -bilateral

Contralateral Lower face will droop

40
Q

What happens if there is CBT damage

AT the level of the Medulla?

A

Palate ms weak on contralateral side
Uvula points toward lesion in CBT (away from a lesion to cn 10)

Tongue point away from lesion in CBT
(Toward CN 12 lesion)

41
Q

What happens if there is damage to the CBT at SC?

A

Shoulder droops ipsilaterally to lesion

42
Q

Where are LMNs found in the SC?

A

Anterior horn

43
Q

Where do LMNs project to if they are

Medial?

Lateral?

A

Medail to axial ms.

Lateral to limb ms.

44
Q

What do Ventral LMNs project to?

A

Extensor ms.

45
Q

What do dorsal LMNs project to?

A

Flexor ms.

46
Q

How do indirect pathways activate?

A

Tonically activate antigravity and axial LMNs

47
Q

What are the medial indirect UMN tracts?

A 
TST
Medial Reticulospinal
Lateral Vestibulospinal
Medial vestibulospinal
Medial CST (the modulating fibers to Indirect)
48
Q

What are the lateral indirect UMN tracts?

A

Rubrospinal
Lateral reticulospinal
Lateral CST (modulating fibers to indirect)

49
Q

What do medial LMNs get input from?

A

From all medial indirect UMNs

50
Q

What do lateral LMNs get input from?

A

From all lateral indirect UMN tracts

51
Q

Medial Vestibulospinal spinal tract:

What kind of tract?

Goes from and ends where?

Function?

A

Medial indirect

Medial vestibular nuclei to Cervical and thoracic levels of SC

Coordination of head movements (neck and shoulder ms.)

52
Q

Lateral Vestibulospinal spinal tract:

What kind of tract?

Goes from and ends where?

Function?

A

Medial indirect

Lateral vestibular nuclei to SC’s ipsilateral LMNs innervating postural ms. And limb EXTENSORS

Do extension against gravity

(Will see active in decerebrate posture)

53
Q

Medial Reticulospinal tract:

What kind of tract?

Goes from and ends where?

Function?

A

Medial indirect

Pontine reticular formation to SC’s ipsilateral LMNs innervating postural ms. And limb EXTENSORS

Facilitate postural reflexes

54
Q

Lateral Reticulospinal spinal tract:

What kind of tract?

Goes from and ends where?

Function?

A

Lateral indirect

Medullary RF to SC

Excites FLEXOR MNs and INHIBITS EXT.
inhibits spinal segmental reflexes

55
Q

Tectospinal tract:

What kind of tract?
Goes from and ends where?

Function?

A

Medial indirect

Superior colliculus to Upper SC

Coordinates head w/ eye movements

56
Q

Rubrospinal tract:

What kind of tract?

Goes from and ends where?

Function?

A

Lateral indirect

Red nucleus in midbrain to SC

Innervates upper limb FLEXORS

57
Q

Corticospinal tract:

Function?

A

Fine motor control of hand

58
Q

Corticobulbar tract:

Function?

A

Control of muscles of face, chewing, speech and swallowing

59
Q

What are Lower Motor Neuron sings?

A 
Flaccid paralysis 
Wasting or atrophy 
Hyporeflexia
Areflexia
Hypotonia
Denervation hypersensitivity w/ fasciculations
60
Q

What are Upper Motor Neuron signs?

A

Loss of distal extremity strength and dexterity
Babinski sing
Pronator drift
HYPERtonia
Spasticity
Hyper-reflex is/Clonus
Clasp knife phenomenon (sudden collapse at end of ROM)

61
Q

What lesions cause a LMN sing?

A

Lesions to CNs 3-7, 9-12, and peripheral ns.

62
Q

What is UMN syndrome?

A

Combo loss of:

CST &

loss of regulation from CST’s indirect pathways to brainstem

63
Q

What is spasticity?

What characterizes it?

A

UMN lesion

Rate dependent resistance
And
Collapse of resistance at end of ROM

64
Q

What is Rigidity?

What characterizes it?

A

Basal ganglia disease

Not rate or force dependent
Constant thru out ROM (lead pipe or plastic like)

65
Q

How can you tell where a LMN lesion is?

A

Clinical signs on same side as leasing and at exactly the level involved

66
Q

How can you tell where a UMN lesion is?

A

Above lower medulla, clinical signs = contralateral

In SC = clinical signs ipsilaterally

67
Q

For a spinal cord lesion where will a UMN lesion present?

A

Below the level of lesion

68
Q

What is Decorticate posture caused by?

What characterizes it?

A

Lesion above red nucleus

Thumb tucked under flexed fingers in fisted position
Pronates forearm
Flexion at elbow
Lower extremity in extension w/ foot inversion

69
Q

What is Decerebrate posture caused by?

What tracts are still okay?
What characterizes it?

A

Lesion below and involving Red Nucleus

Reticulospinal and vestibulospinal = extensors

Upper extremity is pronates and extended
Lower extremity is in extension

70
Q

What is Medial Medullary syndrome caused by?

What does if affect and how does it present?

A

Sulcal branches of ASA stroke

Pyramid - contralateral UMN signs

ML (posterior columns) - contralateral loss of sensation to body

CN 12 - LMN , tongue toward side of cn12 lesion

71
Q

What is Lateral Medullary syndrome caused by?

What does if affect and how does it present?

What is another name for it?

A

PICA stroke

ALS - contralateral loss of pain and temp

Spinothalamic - ipsilateral loss of pain and temp to face

Vestibular nuclei - vertigo, nystagmus

Restiform body - ipsilateral ataxia

Hypothalamic spinal tract sympathetic - ipsilateral horner’s

Wallenburgs syndrome

72
Q

If you see….

Loss of pain and temp to body contra
Loss of pain and temp to face ipsi …..

How can you tell if it is lower pons or medulla?

A

If it is in,

Lower pons = cns 6 and 7 hit

Medulla = Nucl. Ambiguus hit = trouble swallowing, hoarse voice etc.

73
Q

What is Weber syndrome caused by?

How does it present?

A

P1 of PCA or Uncal herniation of midbrain

CST affected = contra loss of motor (hemiplegia)

CBT affected - contralateral drooping of face

CN 3 affected - Oculomotor palsy

74
Q

What happens if there is a complete transection of the SC?

A

All sensation 1 or 2 levels below lesion lost

No bladder or bowel control

Spinal shock ==> no DTRs

75
Q

What happens 6 weeks after a trauma causing complete transection of the SC?

A

UMN signs at levels below lesion

LMN signs at level of lesion

76
Q

What happens from a hemisection of SC (Brown Sequards)?

A

ALS hit - contralateral loss of pain and temp to body

GF/CF hit - ipsilateral loss of sensation

CST hit - ipsilateral loss of motor
UMNs signs ipsilaterally
LMN signs at level of lesion

77
Q

What is syringomyelia caused by?

What are the characteristics of it?

A

Formation of cysts w/in central canal of SC

Affects AWC first = ALS = pain and temp lost bilaterally (cape like pattern)

If Ant. Horns affected= LMN signs
If LCST affected = arms first to be affected

78
Q

Where is syringomyelia most common at?

What is it highly associated with?

A

C4, C5

Chiari type 1

79
Q

What is anterior cord syndorme?

What can cause this?

A

Compression or damage to anterior part of SC

Infarction of ASA, intervetebral disc herniation and radiation myelopathy

80
Q

What is central cord syndrome?

What can cause this?

A

Compression or damage to central portion of SC

Due to cervical hyperextension, or
Syringomyelia

81
Q

What is polyneuropahty?

How does the sensory loss distribution present?

Who is this commonly seen in?

A

Involvement of sensory, motor and autonomic axons from distal to proximal due to dying back or impaired axonal transport or demyelination

Stocking/glove distribution of sensory loss

Patients w/ diabetes mellitus

82
Q

What is Amyotrophic lateral Sclerosis?

Presents w/?

A

Destruction of somatic motor neurons (UMNs, brainstem and SC LMNs)

Paresis, hyperstiffness, hyper reflex is, babinski’ s sign, atrophy, fasciculations, fibrillation
Difficulty breathing, swallowing, speaking

83
Q

What is spastic cerebral palsy?

A

Movement dysfunction due to abnormal Supra spinal influences, failure of normal neuronal selection and consequential aberrant msucle development

84
Q

What are the motor disorders assoc. w/ spastic cerebral palsy?

A 
Paresis
Abnormal tonic stretch reflexes
Reflex irradiation
Lack of postural preparation prior to movement
Abnormal co-contraction of muscles
85
Q

What is Central Seven palsy?

How does it present

A

Lesion of the CBT involving CN 7

Forehead will still be able to wrinkle

Contralateral face will droop

86
Q

Why does centralseven palsy present the way it does?

A

Bc Ms. of upper face are controlled bilaterally from both hemispheres

Muscles of lower face are controlled ONLY by CONTRA hemisphere

87
Q

What is Bell’s palsy?

A

Ipsilateral flaccid paralysis of lower AND upper face

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