WEEK 2- MS pt 2 Flashcards
true or false Nerve fibres and cell bodies outside the CNS are part of the CNS
false PNS
what structire connects CNS to PNS
nerves
PNS is involved with long or short distance transmission
long
at rest neurons have a positive or negative charge
negative
make sure you understand sodium channels during ap slide 5
!
what is a refractory period
period where action potential is not possible. Prevents
backwards propagation.
what are two ways you can increase conduction velocity of neurons
○ Increasing diameter
of Axon
○ Insulate Axon - Myelination
what is myelin
multiple layers of close glial membranes
which glial cell makes up myelin in the PNS
schwaan
true or false: all axons are covered with teh same maount of myelin
false, Different axons are covered with different number of layers of Schwann cell membranes
true or false an unmyelamted axon sends a message must faster than a myelnated one
false
The action potential in an unmyelinated axon depolarizes all of the membrane and so consumes more energy, much slower transmission.
what helps with the speed of the signal in a myelnated axon
the nodes of ranvier = signal jumps from one gap to the next
what is a node de ranvier
Gap in myelin which allows charge to enter/leave nerve cell to generate AP
t or F nodes of ranvier do not contain ion channels
f they do
how far apart are nodes of ranvier in an axon
1-2 mm
what are two condiitons that involve damage to myelin sheath
multiple sclerosis
guillian barre syndrome
briefly describe multiple sclerosis and
guillian barre syndrome
Auto-immune diseases that cause damage to the myelin sheath and eventual axon loss
in multiple sclerosis and
guillian barre syndrome the nerve conduction is ….
Slowed down
in multiple sclerosis and
guillian barre syndrome causes
gradual weakness, paralysis and sensory loss
true or false peripheral nerves are only made uo of sensory nerves
false , motor also
what are the two types of peripheral nerve injury
axon cut
axon crush
which of the two (axon cut vs crush) is faster regenration
crush
axon cut can cause something called distal axon segment degenretaion… explain
○ Occurs within 24 hours of cut
○ Axonal degeneration is followed by degradation of the myelin sheath and infiltration by
macrophages. The macrophages, aided by Schwann cells clear the debris.
○ The outer myelin sheath (neurilemma tube) does not degenerate and remains as a hollow
tube.
what is one way to speed up recovery of axon cut
Surgical reattachment of distal segment speeds up recovery
why is axon crush faster at regenertaing than axon cut
full degeneration of distal segment does not occur
true or false in axon cut the proximal end (closest to injury) is the part of axon taht degenerates
faslse = the distal
what happens as a step of peripheral nerve regenration
axonal sprouting
how much time does it take for sprouting to occur
96 hours
what are sprouts called at proximal end of axon
neurites
when does a neurite grow into the neurilemma tube
If a sprout reaches the neurilemma tube, it grows into it and advances about 1-3 mm per day.
what are neurites attracted by
growth factors by shwaan cells
t or f regeneration is always complete explain
false = axons can split into many paths
what happens if the sprouts cannot reach the neurilemma tube
they may form a neuroma,
or grow into other tissues.
true or false Axons must grow distances much greater than they did during development
in the embryo in the regenrtaion process
true
t or false the cns is always intact when there are changed in peripheral nerve injuries
false
do Axons regenerate along Schwann cell paths and stay in only one path?
no, they do not stay in one path
They can branch out and go down in a random manner
surgical reattachment use what?
sutures
what 3 things can compromosie the results of surgical nerve repair
Tension, scar formation and missing
nerve tissue
t or f after a 45 min surgery, the nerve is good as new
false : The technique takes many hours and
often does not line up perfectly
true or false the branching out of axons after surgical intervention is much more controlled vs non surgical reattachment
true
how can oT and PT help
● Sensory desensitization and re-education
● Relearning movement and sensation to help strengthen new patterns of
signals in the brain
