Ch. 12: Peripheral Nervous System Flashcards
What is a spinal nerve?
One place where every axon comes together
What is the pattern when the “spinal” or “segmental” nerve os damaged?
Myotomal or Dermatomal
What nervous system controls peripheral nerves?
Sympathetic
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
- Ventral/anterior - front of body + arms & legs
- Distal axon projections (superficial and deep)
- “Peripheral” pattern when damaged - part of more than one dermatome, myotome
What is a Dermatome?
Dermis innervated by a single spinal nerve
What is a Myotome?
Muscle innervated by a single spinal nerve
How does peripheral nerves get their blood supply?
aterial branches
What is the difference between Myelinated and Unmyelinated axons?
Both are myelinated
Myelinated are extra myelinated
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
How do you classify axons based on Diameter and Conduction speeds?
How many Nerve Plexuses are there?
What are they?
- Cervical plexus (C1-C4): motor, sensory, sympathetic.
-
Brachial plexus (C5-T1): motor, sensory, sympathetic.
- Median nerve shares branches from C5-T1
- Lumbar plexus (L1-L4): motor, sensory, sympathetic.
- Sacral plexus (L4-S4): motor, sensory, parasympathetic.
What is Convergence in the Afferent Direction?
One peripheral nerve gets axons from many different spinal levels.
What is Convergence in the Efferent Direction?
One spinal level sends axons to many different peripheral nerves.
What does damage to a peripheral nerve mean for motor output?
Paralysis
or at least major weakness in one or more muscles
What does damage to a spinal nerve mean for motor output?
minor weakness in one or more muscles
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)
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)
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.
Are Neuromuscular Junctions excitatory or inhibatory?
Excitatory - EPSP only!
Ach (either release it or don’t) - depolarizes and aids in health
What are dysfunctions of peripheral nerves?
- Sensory changes
- Autonomic changes
- Motor changes
- Changes following denervation
Changes following denervation:
Fibrillations
- Spontaneous depolarization of single denervated muscle fibers.
- Cannot see or feel
- Can only exam with a needle detector
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
Mononeuropathy
1 peripheral nerve, at 1 spot
