Block II: CC1 Flashcards
WHta is the endoneurium?
is a supporting structure around individual axons within each fascicle.
WHat is a fascicle?
number of axons together in a circular structure surrounded by perineurium
WHta is the perineurium?
Collagenous tissue binding each fascicle with elastic fibers and mesothelium cells
Whta si the epineurium?
Collagen, elastic fibers and fatty tissue binding individual fascicles together. Outmost layer of supportive tissue. Contains vasa nervorum.
Rate nerve fibers by size (um)
Aa > AB > Ay > Ag > B >C
Rate nerve fibers by conduction speed (ms-1)
Aa > AB > Ay > Ag > B >C
Which fibers are myelinated?
Aa (thickest)
AB
Ay
Ag (thinnest)
B
Which fibers are NOT myelinated?
C
General functions of Aa?
Motor, propioception
General functions of AB?
Touch, pressure, vibration
General functions of Ay
Motor to muscle spindle
General functions of Ag
Touch, coldness, fast pain
General functions of B
Pre-ganglionic autonomic
General functions of C
Touch, warmth, itch, slow pain; post-ganglionic autonomic
What is slow transport in axonal transport?
0.5-10mm/day
-unidirectional always anterograde
-moves enzymes, cytoskeletal components and new axoplasm down the axon during repair and regeneration of damaged axons
-Damaged nerve fibers regenerate at a speed governed by slow axonal transport
what is fast transport in axonal transport?
20-400mm/day
-bi-directional
-anterograde transport: organelles, enzymes, synaptic vesicles and small molecules
-Retrograde: for recycle material and pathogens- rabies, herpes simplex, tetanus, polio viruses.
What is wallerian degeneration?
Following focal interruption of axons (as trauma or vasculitis). From injury downward. atrophic muscle
What is axonal degeneration?
Dying -back phenomenon from metabolic derangement of the neuron. Injuty occurs in the whole nerve, but dies from distal to proximal. atrophic muscle.
What is segmental demyelination?
affects myelin, slowing the conduction velocity. patched pattern
What is neuraplaxia?
Class I nerve injury
-milder form of damage
-nerve does not suffer major changes after injure, myelin regenerates
-cause:compression or ischemia
-good prgnosis
What is axonotmesis?
-class II nerve injury
-axonal damage results in loss of continuity and wallerian degeneration distally.
-Basal lamina and endoneurial tissue is intact
-recovery depends on nerve regeneration (1-3mm/d)
What is neuronotmesis?
Class III nerve injury
-results in separation of entire nerve including supportive tissue, ranging from endoneurial and schwann cell tube transection to total nerve serverance
-limited axonal regeneration
-neuroma formation and aberrant regeneration is common
What type of fibers are injured in patient has trouble with motor and sensory axons responsible for propioception, vibration and light tough?
Large myelinated axons
What type of fibers are injured in patient has trouble with sensory fibers responsible for light touch, pain, temperature, and preganglionic autonomic fucntions?
thinly myelinated axons