Ch. 12: Peripheral Nervous System Flashcards Preview

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Flashcards in Ch. 12: Peripheral Nervous System Deck (31):
1

What is a spinal nerve?

One place where every axon comes together

2

What is the pattern when the "spinal" or "segmental" nerve os damaged?

Myotomal or Dermatomal

3

What nervous system controls peripheral nerves?

Sympathetic

4

What are the parts of peripheral nerves?

  • Rami
    • Ventral/anterior - front of body + arms & legs
      • joint into plexuses
    • Dorsal/posterior - just back of body
    • Communicating
      • to and from paravertebral sympathetic ganglia
  • Distal axon projections (superficial and deep)
  • "Peripheral" pattern when damaged - part of more than one dermatome, myotome

5

What is a Dermatome?

Dermis innervated by a single spinal nerve

6

What is a Myotome?

Muscle innervated by a single spinal nerve

7

How does peripheral nerves get their blood supply?

aterial branches

8

What is the difference between Myelinated and Unmyelinated axons?

Both are myelinated

Myelinated are extra myelinated

9

What are the 3 connective sheaths that surround axons?

  • Endoneurium
    • Separates individual axons
  • Perineurium
    • Surrounds bundles of axons (creates "fascicle")
  • Epineurium
    • encloses entire nerve trunk

10

11

How do you classify axons based on Diameter and Conduction speeds?

A image thumb
12

How many Nerve Plexuses are there?

What are they?

  1. Cervical plexus (C1-C4): motor, sensory, sympathetic.

  2. Brachial plexus (C5-T1): motor, sensory, sympathetic.

    • Median nerve shares branches from C5-T1

  3. Lumbar plexus (L1-L4): motor, sensory, sympathetic.

  4. Sacral plexus (L4-S4): motor, sensory, parasympathetic.

13

What is Convergence in the Afferent Direction?

 One peripheral nerve gets axons from many different spinal levels.

14

What is Convergence in the Efferent Direction?

One spinal level sends axons to many different peripheral nerves.

15

What does damage to a peripheral nerve mean for motor output?

Paralysis 

or at least major weakness in one or more muscles

16

What does damage to a spinal nerve mean for motor output?

minor weakness in one or more muscles

17

What does damage to a spinal nerve mean for sensory input?

Sensory loss in a dermatomal pattern

(includes some, but not all, of many peripheral nerves)

18

What does damage to a peripheral nerve mean for sensory input?

Sensory loss in a peripheral nerve pattern

(includes some, but not all, on many dermatomes)

19

Why is movement essential for nerve health?

  • Movement improves blood flow
  • Facilitates gliding of fascicles and nerves
  • Facilitates axoplasmic transport
    • move nutrients from cell bodies to the end
  • "Wrinkling" of axons within endoneurium = neural tension
    • Wrinkle in a shortened position - need to be stretched so they do not stick.

20

Are Neuromuscular Junctions excitatory or inhibatory?

Excitatory - EPSP only!

Ach (either release it or don’t) - depolarizes and aids in health

21

What are dysfunctions of peripheral nerves?

  • Sensory changes
  • Autonomic changes
  • Motor changes
  • Changes following denervation

22

Changes following denervation:

Fibrillations

  • Spontaneous depolarization of single denervated muscle fibers.
    • Cannot see or feel
    • Can only exam with a needle detector

23

Changes following denervation:

Trophic Changes

  • Degenerative tissue changes that result from lack of muscle depolarization, loss of "trophic" substances from nerves and/or distortion of blood flow.
    • Growth, tissue health
    • Atrophy of a muscle

24

Mononeuropathy

1 peripheral nerve, at 1 spot

25

Multiple Mononeuropathy

1+ peripheral nerve, at 1 spot

26

Polyneuropathy

  • Multiple nerves effected in multiple locations
  • Most common: symmetircal loss of sensory, motor & autonomic function
    • starts distal, move prox (stocking & glove)
  • Etiologies
    • Diabetes
    • Nutritional deficits (secondary to alcoholism)
    • Autoimmune disease (ex: Guillain-Barré)

27

Mononeuropathy

Class I injury: Traumatic Myelinopathy

  • Temporary disruption of conduction along axon membrane. Axon remains intact. Demyelination possible.
    • Minor = Puts it to sleep
      • Ex: crossing legs and foot falls asleep
    • More Major = demyelination possible
  • Recovery potential excellent.
  • Physical trauma or internal cellular trauma 

28

Mononeuropathy

Class II injury: Traumatic Axonopathy

  • Axon and myelin degenerate. Connective tissue "tube" remains intact.
    • Wallarian Degeneration
  • Recovery potential very good (especially for short distances). Axon will likely regrow into connective tissue "tube" at the rate of 1-2 mm/day (or about an inch a month).
    • Regenerative sprouting - tube still their to guide them where to grow
  • Demyelinated axons will insert modality gated channels and ligand gated channels to try to get signal back
    • Modality: touch
    • Ligand: sensitive to SNS neurotransmitters (epi & norepi)

29

Mononeuropathy

Class III injury: Severance

  • Axon and myelin degenerate. Connective tissue "tube" is severed or disrupted.
  • Recovery potential fair. Axons will attempt to re-grow, but may not find connective tissue "tube" or may grow into "wrong" tube.
    • Tube is broken

30

Multiple Mononeuropathy

  • Involvement of two or more discrete nerves in different parts of the body.
    • Ex: bilateral carpal tunnel syndrome

31

What is Myasthenia Gravis a disorder of?

Disorder of Neuromuscular Junction