Neuroplasticity

Question 1

What are some causes of axonal injuries in the PNS

Answer 1

stretch
crush
shear
laceration

Question 2

What are the 3 types axonal injuries in the PNS from least severe to most severe

Answer 2

neuropraxia
axonotmesis
neurotmesis

Question 3

neuropraxia

Answer 3

local myelin damage, axon stays intact
sx: weakness, numb, tingling, hyposensitivity
AP slowed down

Question 4

axonotmesis

Answer 4

continuity of axon lost leads to Wellerian degeneration

may or may not include damage to epineurium, perineurium, and endoneurium

Question 5

what is Wallerian degeneration

Answer 5

axon degeneration that occurs after a PNS axonal injury

Question 6

neurotmesis

Answer 6

complete transection of a nerve and it is unable to grow back
surgery is necessary
still see Wallerian degeneration

Question 7

What are the 6 cellular events after a peripheral n injury

Answer 7

1. Wallerian degeneration (distal to injury)
2. Macrophages clear debris and Schwann cells become phagocytic and engulf degenerating axon and myelin
3. center end of axon (proximal) sprouts into endometrial sheaths left behind by degenerated axon
4. Schwann cells proliferate as axon regrows
   
   • prod of new myelin
   • guide axon regrowth
5. axon re-establishes postsynaptic target (where we see pts improve)
6. axon diameter increases, more myelin created with time

Question 8

When peripheral axons get injured they degenerate ______ to _____

Answer 8

distal to proximal

Question 9

how many mm/day and cm/wk do peripheral axons regrow

Answer 9

1

Question 10

what is collateral sprouting

Answer 10

neighboring PNS neuron sprouts from own neuron to communicate with the postsynaptic target that the injured neuron used to communicate with

Question 11

regenerative sprouting

Answer 11

axon is able to regrow but changes its postsynaptic target

Question 12

what are the 3 causes of CNS axonal injuries

Answer 12

trauma
decreased blood flow (ischemia)
neurodegenerative disease

Question 13

what is the bad news about CNS axonal injuries

Answer 13

axons typically do not regrow after injury

Question 14

what is the good news about CNS axonal injuries

Answer 14

out brain can create new pathways to compensate for axons lost
we only use about 10% of brain until something goes wrong

Question 15

What are some causes for the CNS to not be able to regenerate?

Answer 15

CNS damage triggers necrosis and apoptotic cell death of severed axons
slow cleanup
hostile environment in regenerative events

Question 16

What happens when necrosis and apoptotic cell death occurs

Answer 16

when the brain causes this the damaged cells release neurotoxins into brain and they travel to healthy tissues and kill them too

Question 17

what causes the hostile environment in CNS

Answer 17

astrocytes - glial scarring (these can block any attempt on axon regrowing)
microglial activation (clear away debris but cannot distinguish bw good and bad)

Question 18

What are two areas believed to show potential for neurogenesis in CNS and what kind of cells are going to be able to do this

Answer 18

olfactory bulb
hippocampus
glial cells NOT neuronal cells

Question 19

what is neuroplasticity

Answer 19

the ability for the NS to respond to intrinsic stimuli by reorganizing its structure, function, and connections
can occur in development, response to environment, learning, disease, or therapy

Question 20

what are the 3 things that activate neuroplasticity

Answer 20

environmental
behavioral
neural processes

Question 21

what are the five neuroplasticity mechanisms

Answer 21

chemical
structural
functional
habituation
LT Potentiation and Depression

Question 22

what is chemical neuroplasticity

Answer 22

immediate to ST changes to chemical synapses
increase NT released in synaptic cleft
happens when start using a new pathway repetitively

Question 23

what is structural neuroplasticity

Answer 23

LT changes to neuronal structure
modify existing postsynaptic receptors
create new postsynaptic receptors
increased dendritic and terminal axonal growth
creates a stronger pathway

Question 24

what is functional neuroplasticity

Answer 24

LT changes to neuronal function
neurons change roles, function, and info relayed
this is how we recover from an injury

Question 25

cortical remapping

Answer 25

process in which the cortical map is affected and changed by sitimulus

Question 26

what is the earliest occurrence of cortical remapping

Answer 26

infancy | synaptic pruning

Question 27

what are some examples of cortical remapping in adults

Answer 27

blindness - we heighten other senses esp hand function/sensation to read braille phantom limb - cortical does not understand why limb is not there but eventually realizes

Question 28

habituation

Answer 28

``` decreased response to a repeated, benign stimulus ST < 30 min - change presynaptically - decease excitatory release of NT LT > 30 min - change postsynaptically - decrease receptors ```

Question 29

experience-dependent neuroplasticity

Answer 29

selective stabilization of certain synapses and removal of others in response to experience more complex than habituation manifested through LT potentiation and depression

Question 30

LT potentiation (LTP)

Answer 30

process by which the synaptic connections bw neurons become stronger by frequent activation require high intensity stimulation

Question 31

LTP has two types of postsynaptic receipts and what do they include

Answer 31

AMPA receptors - permeable to Na - ligand receptors, open in response to glutamate linking NMDA receptor - permeable to Na and Ca - contain Mg blockade to make it more picky what goes through

Question 32

LTP NMDA receptors require what to happen

Answer 32

pre and postsynaptic events to happen need rapid fire of AP "coincidence receptors"

Question 33

What is the role of Ca in LTP

Answer 33

secondary messenger than activate secondary intracellular cascade in postysnpatic for structural changes increase post AMPA receptors - more ready to accept glutamate increase growth factors - new synapses

Question 34

what is LT depression (LTD)

Answer 34

conversion of active synapses into silent ones helps "clear the slate" low-intensity, prolonged stimulation

Question 35

how is pharmacology involved in rehab and neuroplasticity

Answer 35

fluoxetine is an antidepressant that facilitates neuroplasticity after brain injury/stroke

Question 36

who has the biggest clout in rehab and neuroplasticity

Answer 36

physical rehabiliation