synaptic plasticity Flashcards
short term plasticity
< 30 min
long term plasticity
days, weeks, months
synaptic facilitation
multiple APs in rapid succession strengthens the synapse by increasing presynaptic calcium availability
synaptic depression
depletion of synaptic vesicles leads to decreased neurotransmitter release thus weakened synapse communication
synaptic augmentation and potentiation
increase Ca in presynaptic neuron, which increased binding of synaptic vesicles with the membrane of the axon terminal
augmentation
short acting, decays in a few seconds
potentiation
lasts several seconds to minutes
long term potentiation (LTP)
long lasting increase in synaptic strength
long term depression (LTD)
long lasting decrease in synaptic strength
AMPA receptors
- ligand gated (glutamate)
- Na enters the cell (depolarization)
NMDA receptors
- ligand gated (glutamate)
- also VG Mg
- Ca and Na enter the cell (depolarization)
habituation
decreased responsiveness to repeated applications of a stimulus
- decreased glutamatergic synaptic transmission
sensitization
heightened response to non-noxious stimuli as a result of previous exposure to a noxious stimulus
- increased activity of neuromodulating interneurons
- increased serotonin at presynaptic terminals of sensory neurons
chemical injury
ions, neurotransmitters
hypoxia
lack of oxygen
infection
microbe comes in
mechanical injury
laceration or cut, traction or stretch on the nervous tissue
neuropraxia
signal transmission is briefly interrupted; no neural death/axonal damage
- completely reversible
- ex: foot falling asleep
axonotmesis
damage to axon only –> happens in PNS, axon can regenerate
neurotmesis
damage to both the axon and CT around it
- worst case scenario
grade 1
neuropraxia
grade 2
intact endoneurium; axon damage
grade 3
intact perineurium, axon and endoneurium damaged
grade 4
intact epineurium; axon, endoneurium, perineurium damaged
grade 5
neurtomesis
grade 6
multifocal mixed injury
- most common form of injury
anterograde/wallerian degeneration
- within minutes: neurofilaments swell and fragment
- replication of mitochondria
- myelin retracts from the axon
- within 12 hours: myelin is swollen and irregular
- within 2-3 days: myelin becomes ellipsoid
proximal / retrograde degeneration
- in opposite direction (toward the cell body)
- only 1-2 nodes of Ranvier backward
way to recover from injury
- regneration
- reinstatement of blood flow
- recovery of synaptic effectiveness
neural regneration
- ONLY IN PNS
- axons can sprout within 6 hours post injury
- growth spurts find endometrial tubes
factors that interfere with regeneration
- distance
- scarring
- location of injury on the axon
- wrong endometrial tubes
sprouting of collaterals
- major mechanism of recovery in CNS
- intact neurons send out new projections to synapse on orphaned postsynaptic cells
denervation hypersensitivity
increase receptors on the postsynaptic neurons
synaptic hyper effectiveness
increase NT from the neighboring healthy neurons
