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Neuroscience > Lecture 4: PNS Injury and Repair > Flashcards

Lecture 4: PNS Injury and Repair Flashcards

1
Q

where are upper motor neurons?

A

originate in the cerebral cortex and brainstem and govern the activity of lower motor neurons

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2
Q

where are lower motor neurons

A

once it reaches the anterior horn of the spinal cord

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3
Q

what are the 2 types of lower motor neurons

A

alpha motor neurons

gamma motor neurons

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4
Q

what are alpha motor neurons

A

LMNs that innervate extrafusal muscle fibres for muscle contraction

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5
Q

what are gamma motor neurons

A

LMNs that innervate intrafusal muscle fibres (muscle spindles)

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6
Q

what is a motor unit

A

The alpha motor neuron and the skeletal muscle fibres it innervates

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7
Q

do we have more alpha motor neurons or muscle fibres in the body

A

way more muscle fibres

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8
Q

Spinal nerves are made up of which two types of roots

A

posterior (sensory Afferent ) roots

anterior (motor efferent) roots

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9
Q

if a spinal nerve is injured, would there be motor or sensory issues

A

both

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10
Q

what do Spinal nerves split to become

A

posterior and anterior rami

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11
Q

what is a dermatome

A

an area of skin that is mainly supplied by afferent nerve fibres from the dorsal root of a spinal nerve

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12
Q

what is a peripheral nerve

A

terminal branches of the PNS

Mixed (motor and sensory)

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13
Q

where is the damage in an Upper Motor Neuron Syndrome

A

Damage to the descending tract before it synapses in the anterior horn of the spinal cord

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14
Q

where is the damage in a Lower Motor Neuron Syndrome

A

Damage to alpha motor neuron at or distal to the anterior horn

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15
Q

what are 3 symptoms of an upper motor neurone lesion

A

(proximal to anterior horn)

hypertonia

hyperreflexia

positive babinski and Hoffman’s test

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16
Q

what are the 6symptoms of a lower motor neuron lesion

A

(at or distal to the anterior horn)

Weakness/paralysis/paresis

hypotonia

hyporeflexia

negative babinski and Hoffman’s test

a lot of atrophy

abnormal nerve conduction tests and EMG

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17
Q

if there was a lesion on the right side of the brain in the cerebral cortex or the brain stem, what would we excect to see

A

spastic paresis (hypertonia) on the opposite side (contralateral) and below lesion

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18
Q

what would we expect to see if there was a lesion on the spinal cord

A

hypertonia on the same side (ipsilateral) and below lesion

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19
Q

what would we see if the lesion was at the lower motor neuron or the muscle?

A

flaccid paralysis (hypotonia) ipsilaterally (same side) at the level of injury

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20
Q

what type of neuron is injured during a stroke

A

upper motor lesion

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21
Q

what are the 4 symptoms of stroke

A

Usually have some paresis

positive Babinski/Hoffman’s

  • Hyperreflexia
  • Hypertonia
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22
Q

what type of neuron is injured during a spinal cord injury

A

primary upper motor neuron, but can have Lower motor neurons or mixed depending on location of injury

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23
Q

what are the 4 symptoms of a spinal cord injury

A

Hypertonia and hyperreflexia

Weakness below level of lesion (often bilateral)

Sensory loss below level of lesion

Bladder and bowel involvement

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24
Q

what is Amyotrophic Lateral Sclerosis (ALS) (3 things)

A

Destroys both UMNs and LMNs

dramatic ↓ Number of motor units

negative prognosis (death)

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25
Q

what is an Alpha Motor Neuron Injury

A

LMN syndrome

Wasting and weaknes

no sensory involvement

26
Q

what is a Spinal Nerve Injury

A

Weakness in distribution of nerve root

Associated sensory symptoms in same distribution (dermatome)

27
Q

what is Peripheral Nerve Injury

A

LMN

Weakness and sensory loss in distribution of affected nerve(s)

28
Q

what is Guillain-Barre Syndrome (GBS)

A

peripheral nerve issue, lower motor neurone presentation

Preceded by acute infectious illness

Destruction of myelin sheath with axonal damage

Rapidly progressing motor and sensory impairments

29
Q

what are the 3 classifications of peripheral nerve injuries

A

neuropraxia

axonotmesis

neurotmesis

30
Q

what is neuropraxia

A

Focal myelin injury

axon is intact

most mild

31
Q

what is axonotmesis

A

Injury to axon and myelin but supporting connective tissue intact

crush injury

32
Q

what is neurotmesis

A

Injury to myelin, axon and supporting connective tissue

Complete nerve laceration

33
Q

what is Wallerian degeneration

A

when a nerve fiber is cut or crushed (axonotmesis or neurotmesis) and part of the distal axon degenerates

can happen with axonotmesis or neurotmesis

34
Q

what are the 2 types of peripheral nerve recovery

A

Axonal Repair and Regrowth

Collateral Sprouting

35
Q

what does regrowth of the axon result in

A

reinnervation of the target muscle

Regeneration is faster closer to injury site and slower further away

36
Q

what are the 2 key players in axonal regrowthand their function

A

Macrophages clear away degenerating parts

Schwann cells act as a guide and stimulate regrowth

37
Q

How do Schwann cells support axonal regrowth?

A

Growth cone extends to search for target

Provide a framework to help guide growing axons

Secrete neurotrophic signals that promote axon growth

38
Q

do Crush injury (axonotmesis) always result in Wallerian degeneration

A

no but its always in neurotmesis

39
Q

why do crush injuries (axonotmesis) not always result in wallerian degeneration

A

Schwann cell framework less disrupted which help guide the regenerating proximal segment

Recovery is often more rapid (and complete) in a crush vs. cut injury

40
Q

how are severed nerves reconnected

A

if severe, surgery is needed

41
Q

are Schwann cells unable to regrow with extensive damage

A

no. new Schwann cells can regrew

42
Q

what happens if there is a severe injury and distal end is not available for reapposition

A

outcomes tend to be poor

43
Q

who is Henry Head

A

he Surgically transected his own radial nerve

44
Q

Can We Fast-Track peripheral nerve regeneration?

A

not good enough evidenve to suggest a positive effect of exercise on nerve regeneration

45
Q

what is collateral sprouting

A

motor unit sprouts new axons to reinnervate damaged muscle fibres, so motor unit increase in size

46
Q

progressive muscle weakness, hyporeflexia, and paralysis. She suddenly developed weakness and tingling sensations in her legs and arms that gradually progressed over the course of a few days. She eventually found it difficult to walk and perform her ADLs.

Do you think this is an UMN or LMN condition?

A

lower motor neuron

hyperreflexia

weakness

47
Q

progressive muscle weakness, hyporeflexia, and paralysis. She suddenly developed weakness and tingling sensations in her legs and arms that gradually progressed over the course of a few days. She eventually found it difficult to walk and perform her ADLs.

What condition do you think Emily has?

A

Guillain-Barre Syndrome (GBS)

48
Q

where do we see damage with polio

A

anterior horn cells

49
Q

what was recovery with polio due to

A

motor unit collateral sprouting

50
Q

true or false
Damage to the post-central gyrus would impact upon an individual’s ability to perceive tactile sensation.

A

true

51
Q

true or false:
Peripheral nerves, such as the median nerve, are branches from multiple spinal cord levels

A

true

52
Q

do Nerve bundles consist of motor neurons only, A single axon, or a collection of motor and sensory neurons

A

a collection of motor and sensory neurons

53
Q

A lesion affecting the lateral aspect of the post-central gyrus would most likely produce what

A

Impairment in contralateral sensory function for the face and neck

54
Q

A patient presents with selective loss of pain and temperature sensations of both hands. Other sensory modalities and voluntary motor activity is intact. What is the most likely cause of this problem?

A

A lesion of the anterior white commissure at the level of the cervical spinal cord

55
Q

An individual is experiencing muscle weakness with no sensory dysfunction. Even with this limited clinical information, you would NOT expect the patient to have:

An anterior root injury

Compression to a peripheral nerve

A myopathy (disease affecting muscle tissue)

Damage to lower motor neuron cell bodies

A

Compression to a peripheral nerve

56
Q

Henry is able to detect pain in his left lower extremity, but is unable to perceive light (discriminative) touch in his left lower extremity. If Henry has no damage above/superior to his medulla, he most likely has a lesion affecting his:

A

Left (ipsilateral) posterior column medial lemniscus (PCML) tract/dorsal column

57
Q

If an individual experienced compression to their right thoracic 10th (T10) spinal nerve, you would expect to see:

A

Motor and sensory impairments consistent with a myotome and dermatome distribution

58
Q

Axonotmesis refers to:

A

Nerve crush

59
Q

A client has had a stroke affecting the left internal capsule. What would you be most likely to observe?

A

Spastic paralysis of the right arm

60
Q

As a result of collateral sprouting, the following changes occur to the motor unit:

A

The motor unit size increases

Neuroscience (20 decks)

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