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632: Neuroanatomy-Neuroscience > Peripheral Nervous System > Flashcards

Peripheral Nervous System Flashcards

1
Q

What forms the peripheral nervous system?

A
  • axons of sensory, motor, and autonomic neurons
  • specialized sensory endings
  • entire postganglionic autonomic neruorns
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2
Q

What do peripheral nerves consist of?

A

parallel bundles of axons surrounded by three connective tissue sheaths: endoneurium, perineurium, and epineurium

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3
Q

What connective tissue separates individual axons?

A

endoneurium

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4
Q

What connective tissue surrounds fascicles?

A

perineurium

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5
Q

What connective tissue encloses the entire nerve trunk?

A

epineurium

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6
Q

What do peripheral nerves supply?

A

both the viscera (autonomic) and somatic structures

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7
Q

Are somatic peripheral nerves usually sensory, motor, or mixed?

A

mixed

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8
Q

What do the cutaneuous branches of somatic peripheral nerves supply?

A

the skin and subcutaneous tissues

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9
Q

What do the muscular branches of somatic peripheral nerves supply?

A

the muscles, tendons, and joints

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10
Q

What are peripheral axons classified according to?

A

speed of conduction and diameter

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11
Q

What do the junctions of anterior rami form?

A

nerve plexuses

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12
Q

What are the 4 nerve plexuses?

A
  • Cervical
  • Brachial
  • Lumbar
  • Sacral
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13
Q

The cervical plexus arises from the anterior rami of C_ to C_

A

C1 - C4

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14
Q

What does the cervical plexus supply?

A
  • sensory information from the posterior scalp to the clavicle
  • motor innervation of the anterior neck muscles and diaphragm
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15
Q

The brachial plexus arises from the anterior rami of C_ to T_

A

C5 - T1

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16
Q

What does the brachial plexus supply?

A

The entire motor and sensory innervation of the upper limb

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17
Q

The lumbar plexus arises from the anterior rami of L_ to L_

A

L1 - L4

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18
Q

What does the lumbar plexus supply?

A

The skin and muscles of the anterior and medial thigh

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19
Q

The sacral plexus arises from the anterior rami of L_ to S_

A

L5 - S4

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20
Q

What does the sacral plexus supply?

A

the posterior thigh and most of the leg and foot

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21
Q

Why is movement essential for nerve health?

A

It optimizes the health of nerves by promoting blood flow throughout the nerves and the flow of axoplasm through the axons

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22
Q

What does movement cause the axoplasm to do?

A

thin and flow more easily, facilitating axoplasmic transportation

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23
Q

Where do motor axons synapse with muscle fibers?

A

at neuromuscular junctions

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24
Q

Is summation of action potentials is required to depolarize the postsynaptic membrane at the neuromuscular junction?

A

No

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25
Q

What are the 3 signs of peripheral nerve damage?

A
  • Sensory
  • Autonomic
  • Motor
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26
Q

What are the 4 types of abnormal sensations?

A
  • Hyperalgesia
  • Dysesthesia
  • Paresthesia
  • Allodynia
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27
Q

Following peripheral nerve damage, what do autonomic changes depend on?

A

the pattern of axonal dysfunction

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28
Q

If a single nerve fiber is damaged when do signs occur?

A

Only when the nerve is completely severed

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29
Q

If many peripheral nerves are damaged, what problems may arise?

A
  • difficulty regulating blood pressure
  • heart rate
  • sweating
  • bowel and bladder functions
  • impotence
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30
Q

Motor signs of peripheral nerve damage include what?

A

paresis or paralysis

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31
Q

Following peripheral nerve damage what occurs?

A
  • rapidly progressing muscle atrophy

- muscle fibers begin to develop a generalized sensitivity to ACh along the muscle membrane

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32
Q

What occurs when muscle fibers begin to develop a generalized sensitivity to ACh along the muscle membrane?

A

Fibrillation, which is spontaneous contraction of individual muscle fibers

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33
Q

How are fibrillations observed?

A

Only through needle EMG, not on the skin

34
Q

What types of tropic changes occur when a peripheral nerve is denervated?

A
  • muscles atrophy
  • skin becomes shiny
  • nails become brittle
  • subcutaneous tissues thicken
35
Q

Due to blood supply changes, loss of sensation, and lack of movement following peripheral nerve damage what is a common occurrence?

A
  • ulceration of cutaneous and subcutaneous tissues
  • poor healing of wounds and infections
  • neurogenic joint damage
36
Q

Describe Mononeuropathy

A

It is a form of peripheral neuropathy that involves a single nerve and is considered a focal dysfunction

37
Q

Describe Multiple mononeuropathy

A

It is a form of peripheral neuropathy that involves several nerves and is considered a multifocal dysfunction

38
Q

Describe Polyneuropathy

A

It is a form of peripheral neuropathy that involves many nerves and is a generalized disorder that typically has a distal and symmetrical presentation

39
Q

What types of traumas may injure peripheral nerves?

A
  • repetitive stimuli
  • prolonged compression
  • wounds
40
Q

What are the 3 classifications of traumatic peripheral nerve injury?

A
  • Traumatic myelinopathy
  • Traumatic axonopathy
  • Severance
41
Q

What does traumatic myelinopathy refer to?

A

The loss of myelin limited to the site of injury

42
Q

Peripheral myelopathies interfere with what?

A

the function of large-diameter axons

43
Q

What causes traumatic myelinopathy?

A

Focal compression of a peripheral nerve (such as nerve entrapment or repetitive mechanical stimuli)

44
Q

What syndrome is a common form of traumatic myelinopathy?

A

carpal tunnel syndrome

45
Q

What does traumatic axonopathy disrupt? What does this cause?

A

axons, which causes wallerian degeneration distal to the lesion

46
Q

What size of axons are affected by axonopathies?

A

All sizes of axons, which means reflexes, somatosensation, and motor functions are all significantly reduced or absent.

47
Q

Following traumatic myelinopathy are axons able to regenerate? Why or why not?

A

Yes, because myelin and connective tissues remain intact.

48
Q

When does traumatic severance occur?

A

when nerves are physically divided by excessive stretching or a laceration

49
Q

What does traumatic severance result in?

A

The immediate loss of sensation and/or muscle paralysis in the area supplied

50
Q

Following traumatic severance can the peripheral nerves regenerate?

A

Yes, if the proximal and distal nerve stumps are apposed and scarring does not interfere

51
Q

What does multiple mononeuropathy involve? What does this produce?

A

Two or more nerves in different parts of the body, which produces a random, asymmetrical presentation of signs

52
Q

When multiple mononeuropathy typically occur?

A

When diabetes or vasculitis (inflammation of blood vessels) cause ischemia of the nerves

53
Q

What are the hallmark signs of polyneuropathy?

A

symmetrical involvement of sensory, motor, and autonomic fibers, often progressing from distal to proximal

54
Q

Where do symptoms of polyneuropathy typically occur?

A

In the feet and then appear in the hands. These are the areas of the body supplied by the longest axons

55
Q

Are polyneuropathies the result of trauma or ischemia?

A

No

56
Q

Polyneuropathies can be of what 3 origins?

A
  • toxic
  • metabolic
  • autoimmune
57
Q

What are the most common causes of polyneuropathies?

A
  • diabetes
  • nutritional deficiencies secondary to alcoholism
  • autoimmune diseases
58
Q

Polyneuropathy in what syndrome is characterized by more severe effects on the motor system than the sensory system?

A

Guillain-Barré

59
Q

What is the major difference between Guillain-Barré polyneuropathy and most neuropathies?

A

Paresis is worse proximally

60
Q

What is the most commonly inherited form of polyneuropathy?

A

Charcot-Marie-Tooth disease

61
Q

What does Charcot-Marie-Tooth disease typically cause?

A

Paresis of muscles distal to the knee with resulting foot drop, step-page gait, frequent tripping, and muscle atrophy

62
Q

What is the typical onset of Charcot-Marie-Tooth disease?

A

adolescence or in young adults

63
Q

What is Myasthenia gravis?

A

an autoimmune disease that damages ACh receptors at the neuromuscular junction, repeated use of a muscle leads to increasing weakness.

64
Q

What are myopathies?

A

disorders intrinsic to muscles

65
Q

What is an example of a myopathy?

A

Muscular dystrophy

66
Q

Describe muscular dystrophy

A

Random muscle fibers degenerate, leaving fewer muscle fibers than normal which results in less force being produced than by a healthy motor unit

67
Q

Are sensation and autonomic function affected in muscular dystrophy? Why or why not?

A

No, because the nervous system is not affected by myopathy

68
Q

Are coordination, muscle tone, and reflexes affected in muscular dystrophy?

A

Not until muscle atrophy becomes so severe that muscle activity cannot be elicited.

69
Q

Dysfunction of peripheral nerves and the muscles they innervate can be evaluated by what?

A

electrodiagnostic studies

70
Q

How can electrodiagnostic studies be diagnostic?

A

By recording electrical activity from nerves and muscles by nerve conduction and EMG studies reveal the pathologic location

71
Q

Nerve conduction studies can be used to differentiate among what 4 things?

A
  • Primarily myelinopathy and axonopathy processes
  • Upper motor neuron and lower motor neuron paresis
  • Mononeuropathy and polyneuropathy
  • Local conduction block and Wallerian degeneration
72
Q

What can differentiate between nerve and muscle disorders?

A

Electromyography (EMG)

73
Q

How can myelinopathies be diagnosed via motor nerve conduction studies?

A

Indicated by long distal latency times, slow conduction velocity, and normal amplitude

74
Q

How can axonopathies be diagnosed via motor nerve conduction studies?

A

Indicated by severely prolonged distal latency and a marked decrease in amplitude. Conduction velocity is normal.

75
Q

What are the 3 clinical signs of peripheral neuropathy revealed in patients 50 years of age and older?

A
  • Absence of ankle jerk reflex despite facilitation
  • Impaired vibration sense of the great toe
  • Impaired position sense of the great toe
  • presence of two or three signs correlate highly with electrodiagnostic evidence of peripheral neuropathy
76
Q

What increases as the severity of neuropathy increases?

A

reports of a pins and needles sensation

77
Q

What should individuals with peripheral neuropathy that affects sensation do daily?

A

inspect the involved areas to monitor for wounds and for a reddening of the skin that persists more than a few minutes

78
Q

What has endurance exercise following peripheral nerve damage been shown to do?

A

enhance sensory and motor recovery

79
Q

What has resistance training following peripheral nerve damage been shown to do?

A

delay functional recovery

80
Q

What devices are frequently used to stabilize weight-bearing joints following peripheral nerve injury?

A

Orthoses

632: Neuroanatomy-Neuroscience (26 decks)

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