HBY 554: 2/27: Synaptic Plasticity

Hebbs postulate

-where the term synaptic plasticity comes from -when cells are active, they end up becoming more active in the future (use it or lose it) -set themselves up to be more efficient to be better performers

sensitization of the sensorimotor neuron modulation lasts approx. how long? (similar to short term gill withdrawal produced by single shock to tail)

1 hour

In what 2 ways does CREB work?

1. Transcription factor/changing the activity of actual DNA (change through PKA activity being more persistent; receptor/channel changes) 2. sprouting new dendrites (structures/morphological changes)

steps in facilatory interneuron/sensory/motor neuron

1. tail is shocked and serotonin is released from the facilatory interneuron end to the pre-synaptic terminal of the sensory neurons 2. Serotonin binds to the serotonin g-protein receptors on the membrane 3. This activates the g-protein and causes it to disassociate from receptor and bind to other signaling molecules like adenyl cyclase 4. adenyl cyclase produce cAMP from ATP 5. cAMP binds to regulatory subunits of pKA, liberation catalytic subunits of PKA 6. These catalytic phosphorylate channels (like K+ channels, opening fewer) and allows for a greater influx of Ca2+ into the presynaptic terminal via their channels (due to phosphorylation). 7. This increase of Ca2+ causes more NTs to be released.

explain 2 examples of habituation with clothes and DLAR smell

1. when you first put clothes on, you can feel the cloth on your skin but throughout day, it mutes out 2. When you first go to DLAR, it smells but by the end of the week your nose pathways have been stimulated enough that you don't need to carry this message on forever.

2 post-synaptic cell receptors involved in LTP

AMPA and NMDA receptors

which post synaptic receptor has a more dominant current flow and of which ion?

AMPA/Na+

PKA activation of ___ produces long-lasting changes in synapse structure

CREB

whats stimulates increased degradation of PKA regulatory suits, allows pKA to be persisistently active

CREB

Ins synaptic facilitation, cells have identical strength but because of the ___, it's able to increase the strength in the second ap

Frequency

Eric Kandel used mollusks Aplysia to study what?

Long-term synaptic plasticity that underlie simple forms of learning

silent synapses only have what receptor?

NMDA receptors

Hebb's postulate in terms of LTP

Only strengthening the synapses that are stimulated

extensions of the CA3 pyramidal cell body is called ___ ___

Schaffer collaterals

what happens to AMPA receptors as a results of low calcium concentration in the postsynaptic cell? What happens to glutamate sensitivity?

They can becomes internalized and the glutamate sensitivity decreases

T/F: Maintenance of LTP occurs due to changes of gene expression and protein synthesis

True

what is a functional synapse?

a synapse that has both AMPA and NMDA receptors

in LTP, degrading the PKAs regulatory subunits allows it to be more ___

active

What kind of muscles can have facilitation and then depression?

anaerobic because it needs such exaggerate stimulation

What is the molecular mechanisms for why NMDA receptors by themselves won't work for synaptic transmission?

b/c NMDA receptors by themselves won't be able to bring any of the Na+ or Ca+ due to the mg2+ block which can only be unblocked by the depolarization of the membrane, which can only occur with AMPA receptors, known for being permeable to Na+

augmentation

bringing something back/recovery

increase in NT level= increase that synapse will experience ___

depression

in LTD, why/how do post-synaptic phosphates get activated?

due to low frequency stimulation which leads to low amplitude rise in calcium concentration

synaptic facilitation results from prolonged ___ of Ca2+ levels in the pre-synaptic terminal

elevation; doesn't get to recover so NT builds further

Drugs that block protein synthesis prevent LTP, but not the maintenance of it.

false, it prevents the maintenance of LTP, but not LTP itself

T/F: Schaefer collaterals have to be stimulated together

false, they can be stimulated separately

T/F: LTD and LTP have the same intracellular pathways, and if false, why?

false, they use different kinases to engage their respective responses in the post synaptic cell

LTP response is strongly correlated to the ___ of ___ ___

formation of new synapses

what NTs do sensory neurons release onto motor neurons

glutamate

What 2 types of cell are there in the hippocampal circuitry?

granule and pyramidal cells

repeated siphon stimulation causes the withdrawal reflex to weaken over time, also known as ___

habituation

Molecular mechanism for LTP

has both NMDA and AMPA receptors, Na+ flows into NMDA receptor. Increased amount of Na+ causes a depolarization of the membrane, which allows for the Mg2+ in the NMDA receptor to unplug and allows for the flow of Ca2+ and Na+. This increased influx of Ca2+ allows for the initiation of LTP to occur.

LTP associativity

if one pathway has a strong pathway and pathway puts a tiny amount of effort at the same time, they both can get strengthened.

in LTP, what can CREB do in terms of the amount of protein structures

increase the amount of protein structures, which can increase the sensitivity of the synapse

sensitization modifies the circuit habituated circuit as a shock will do what?

it will pair the aversive and non-aversive pathway and cause the facilatory neuron to release serotonin onto the presynaptic terminal of the sensory neuron

Habituation

less responsive to repeated occurrence of a stimulus

LTP: State dependency

need the pairing of the pre and post synapse to increase EPSPs

Short-term plasticity: Synaptic depression is related to the amount of ___ released and too much could cause ___

neurotransmitters, depression

short term synaptic plasticity is cells receiving a different quantity of ___

neurotransmitters; abundance or depletion of ligands

in habituation, over time from the siphon being touched, the sensory and motor neuron get depressed and their is decreased response due to a reduction in what?

number of synaptic vesicles available for release in axon terminals

LTP: Specificity

only the pathway that is active/action potential occurrence will cause the synapse to be strengthened

Sensitivation

pairing an aversive and non-aversive pathway to help make re-engage the non-aversive pathway to be more responsive to stimulus

Short term plasticity: synaptic facilitation is a ___-___ event where something gets helped along/moved along

pre-synaptic

the modulatory/facilitatory interferon actually connects to the ___-___ side of a mechanism

pre-synaptic

CREB is a transcription factor, which means

proteins involved in the process of converting, or transcribing, DNA into RNA.

Synaptic faction happens at what speed and is it reversible?

quickly and yes for the most part

In Synaptic depression, post-synaptic cells lose the amplitude of their ___

response

Short term plasticity: Post tetanic potentiation

response happens after stimulation has been removed so it takes longer to initiate the change also longer In response (delay onset)

in between which 2 neurons can their be habituation

sensory and motor (glutamate synapse)

the interneuron to sensory neuron is what kind of NT synapse?

serotoninergic

what is the mechanism behind how long-term synapticity works?

stimulation creates changes to how it'll behave in the future; change receptor expression and kinase expression

vesicle depletion hypothesis

there can be so much release of NT, that vesicles can actually be depleted of NT over time and won't be replenished until the mobilization of vesicles from a reserve pool

The ability of the synapse is...

to change in response to stimulus

Short term plasticity: synaptic facilitation is a ___ increase in synaptic strength that occurs when 2 or more action potentials invade the ___-___ terminal is close succession

transient, pre-synaptic

T/F: All neurons have to have facilitation before depression

true

T/F: When you change receptors due to long term plasticity on membrane, you change how the cell behaves to a fixed amount of neurotransmitters

true