Synaptic Plasticity Flashcards
What is synaptic plasticity?
The ability of the brain to adapt by creating new neural pathways.
The change of synaptic efficiency and strength depends on what?
The activity of the pre and post-synaptic neuron.
Which ‘rule’ determined that synapses could change due to how active or inactive they are?
Hebbs’ rule
For Hebb’s rule, what type of activity will induce a lasting cellular change that adds to its stability?
A persistent or repetitive activity.
Neurons that ____ together, ____ together.
Fire
Wire
Neurons that fire out of ____, lose their ____.
Sync
Link
Hebb’s cell assembly hypothesis proposed a ____ activation of the cell assembly would cause a growth process.
Long
For Hebb’s cell assembly hypothesis, after a growth process has been created, if a fraction of the cells of the assembly were activated by a later stimulus, what would happen to the assembly?
As the growth process has strengthened the connections, a fraction of cells activated in the assembly could cause the whole assembly to be activated.
What can increase the chances of creating an excitatory postsynaptic potential, great enough to fire an AP?
Having two stimulus’ of the same object e.g. seeing and smelling something at the same time.
Repeated association of two synapses from their stimulation, can strengthen the synapse. What would happen if one of the synapse was activated, without the other?
The synapse on it’s own would be sufficient enough to create an excitatory postsynaptic potential, and elicit an AP.
What is the collective system of neural pathways/structural connectivity in a brain or nervous system known as?
Connectome
‘Wiring diagram’
Can include Synaptome + Epigenome.
What is learning the relevant molecular states at each synaptic connection called?
Synaptome
What is learning the relevant changes in the nucleus of each neuron called?
Epigenome
Which significant mechanism that occurs in the hippocampus and cerebral cortex, underlies synaptic strengthening, and is centrally important in processes of learning and memory?
Long term potentiation.
If there is a high frequency stimulation of a neuron, what does this do to the amplitude of an excitatory post synaptic potential?
Increases the potential.
How long would a long term potentiation last, if there is high frequency electrical stimulation?
Hours
How long would a long term potentiation last, if there are multiple high frequency electrical stimulations?
Days or months.
What two receptors are important for long term potentiation?
AMPA
NMDA
Describe the cellular physiology of long term potentiation.
Glutamate released onto inactive cell.
AMPA receptor activated to create excitatory post synaptic potential.
NMDA receptor blocked by Mg2+ (depolarisation from AMPA activation not sufficient to expel this).
Glutamate released onto active cell (membrane depolarised).
AMPA receptor activated.
Mg2+ block on NMDA relieved.
Na+ goes through AMPA + NMDA channels.
Ca2+ goes through NMDA receptors.
Calcium entry through NMDA receptors leads to the activation of what?
Protein kinase C
CaMKII
Protein Kinase C and CaMKII are activated by Ca2+ passing through NMDA receptors. What do these kinases do to AMPA?
Phosphorylates existing AMPA receptors, increasing their effectiveness.
Stimulates insertion of new AMPA receptors into the membrane.
What is the CaMKII molecular switch?
Maintains increased excitability of neurons as CaMKII has an autocatalytic activity and can phosphorylase itself. It therefore no longer needs Calcium and is able to maintain this phosphorylation + the insertion of AMPA receptors, after the depolarising stimulus has receded.
What is the difference between early and late phase long term potentiation?
Early - lasts <1hr. Caused by Ca2+ + the enhancement of AMPA receptors.
Late - >months. Needs new protein synthesis. There can be morphological changes and new synapses. There is also Ca2+ activated signal transduction.
How is long term potentiation involved in presynaptic events?
Postsynaptic neuron can feedback to the presynaptic via Nitric Oxide, resulting in increased glutamate release.
The overload of which ion is essential in exitotoxicity?
Calcium
Low frequency stimulation is linked to what condition?
Long term depression.
What does a low frequency stimulation do to the amplitude of an excitatory post synaptic potential?
Decreases its amplitude.
What happens to AMPA receptors when there is a low level stimulation?
They get de-phosphorylated and removed from the membrane.
What do prolonged low level rises in Ca2+ activate?
Phosphatases.
____ receptor activity in the hippocampus is essential for both long term potentiation and ____ learning.
NMDA
Spatial
Which receptor antagonist has been proven to block hippocampal long term potentiation and blocked learning in the Morris water maze?
AP5-NMDA receptor antagonist.
How does alcohol affect NMDA and memory?
Alcohol is an NMDA antagonist and blocks the normal long term potentiation process.
Which drug class are modulators of GABA a receptors + can lead to anterograde amnesia?
Benzodiazepines.
Which neurotransmitter has a role in memory and learning?
ACh
Scopolamine impairs spatial learning. What type of drug is this?
Muscarinic antagonist.
What type of inhibitors are commonly used in Alzheimers?
Acetylcholinesterase
How can long-term morphine or diamorphine use cause abnormal synaptic plasticity?
Can cause a reduced sensitivity to u-opoid receptors.
How does smoking show up as abnormal synaptic plasticity?
Nicotine binds to nicotinic receptors. Smoking increases the numbers of specific nicotinic receptor subunits in the brains of smokers.
