peripheral nervous system and neuromuscular junction

Question 1

define peripheral neuropathies

Answer 1

damage/disease affecting PNS nerves

Question 2

what may peripheral neuropathies impair

Answer 2

sensation, movement, gland or organ function

Question 3

symptoms of sensory sensation affected

Answer 3

tingling, pain, numbness

Question 4

symptoms of motor movement affected

Answer 4

weakness to hands and feet

Question 5

symtoms of autonomic (involuntary) affected

Answer 5

changes in heart rate or blood pressure

Question 6

causes of peripheral neuropathies

Answer 6

metabolic, toxic, inflammatory, traumatic, genetic; idiopathic is unknown origin

Question 7

mono and poly peripheral neuropathies

Answer 7

mono (single nerve affected), poly (several nerves affected)

Question 8

3 PNS connective tissue structures

Answer 8

endoneurium, preneurium, epineurium

Question 9

endoneurium: location and function

Answer 9

around each individual neuron/axon; loose collagen fibrils

Question 10

perineurium: location and function

Answer 10

around a fascicle (bundles of neurons/axons); gives main tensile strength to nerve

Question 11

epineurium: location and function

Answer 11

around the entire nerve; dense and collagenous; blood supply; some fatty tissue

Question 12

PNS nerve injury classification: what class injuries are connective tissue layers not affected

Answer 12

classes 1 or 2

Question 13

PNS nerve injury classification: what class injuries are connective tissue layers affected

Answer 13

classes 3, 4 and 5

Question 14

define neurapraxia

Answer 14

a reversible conduction block following selective demyelination of the axon sheath; the endoneurium and axon are still intact so no axonal discontinuity

Question 15

example of neurapraxia

Answer 15

nerve compression

Question 16

define axonotmesis

Answer 16

demyelination and axon loss but the epineurium and perineurium remain intact; still some continuity within the nerve; degeneration occurs below and slightly proximal to the site of injury; Wallerian degeneration

Question 17

define neuromesis

Answer 17

most severe form of nerve injury associated with complete nerve division and disruption from soma, commonly seen after toxic or ischemic injuries; damage to the epineurium (around the entire nerve) means no nerve growth and support cells are destroyed; Wallerian degeneration

Question 18

diagram of long-distance axon regeneration and substantial functional recovery in adult PNS neurones

Answer 18

diagram from slide 37

Question 19

define Wallerian degeneration

Answer 19

process that results when a nerve fibre is cut or crushed, and the part of the axon distal to the injury degenerates

Question 20

define neuroma

Answer 20

where axon doesn’t re-establish precise former connection

Question 21

main diagnostic techniques for peripheral nerve disorders

Answer 21

electromyography, nerve conduction study, somatosensory evoked potential

Question 22

what does an electromyography distinguish between and how

Answer 22

myopathies (intrinsic to muscle) and muscle weakness due to nerve pathology (neurogenic) by looking at waveforms of motor unit action potentials

Question 23

electromycography of denervated muscle caused by nerve injury

Answer 23

other nerves take over muscle fibres so larger signal produced and reduced interference pattern; start contracting by themselves

Question 24

electromycography of myopathy caused by damage to muscle fibres

Answer 24

smaller signals and unstable membranes so infrequent fibrillations; full interference pattern

Question 25

what does a nerve conduction study do

Answer 25

evaluates speed of nerve impulses

Question 26

nerve conduction velocity units

Answer 26

m/s

Question 27

nerve conduction amplitude units

Answer 27

mV

Question 28

what does a nerve conduction study distinguish between

Answer 28

axonapathies and demyelinating neuropathies

Question 29

nerve conduction study: axonapathies

Answer 29

lower amplitudes

Question 30

nerve conduction study: demyelinating neuropathies

Answer 30

delayed proximal response as affects conduction

Question 31

nerve conduction study: demyelinating and conduction block

Answer 31

delayed proximal response as affects conduction, and lower in amplitude

Question 32

somatosensory evoked potential

Answer 32

evaluation at site of lesion (CNS or PNS) in somatosensory pathways by assessing amplitude and latency of responses as opposed to skin or muscle

Question 33

somatosensory evoked potential vs electromyography

Answer 33

very small amplitude of nerve responses in uV, so constant averaging over many responses negates noise; electromyography (mV) at muscle