Synaptic plasticity

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  • Created by: Jess
  • Created on: 14-05-14 20:50
How many synapses does homosynaptic short-term synaptic plasticity involve?
One.
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What is synaptic facilitation?
A mechanism by which when there is lots of activity in a neuron the response gets larger.
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What is synaptic depression?
A mechanism by which when there is a lot of activity in a neuron the amplitude of the response gets smaller.
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Briefly outline the mechanism for paired-pulse synaptic facilitation.
Ca influx. Release of transmitter from some vesicles and priming of other vesicles. 1st AP caused an increase in the number of primed vesicles. Ca influx due to the 2nd AP leads to more transmitter release.
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Repetitive firing can lead to spike broadening, what effects does this have on the cell?
Longer presynaptic depolarisation, more presynaptic Ca influx, more transmitter release, increased synaptic response.
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Briefly outline the presynaptic model for paired-pulse synaptic depression.
Assume vesicles are primed before the 1st AP. Ca influx due to the AP causes release of docked vesicles. The 1st AP caused depletion of docked vesicles so when the 2nd arrives there are very few. Ca influx leads to release of very few.
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Outline the effects of a 1st and 2nd AP on a low probability synapse.
Low prob that during the 1st AP vesicles will be released. Vesicles are the primed ready giving a greater vesicular release at the 2nd AP.
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Outline the effects of a 1st and 2nd AP on a high probability synapse.
High prob a vesicle will be released during the 1st AP. Very few primed vesicles for release during the 2nd AP leading to a smaller vesicular release.
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What is postsynaptic modulation?
Modulatory input alters the sensitivity of the postsynaptic membrane to transmitter release.
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What is presynaptic modulation?
Modulatory input alters transmitter release. Two types: presynaptic inhibition, presynaptic facilitation.
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Outline how the GABAa receptor is modulated by phosphorylation.
Activation of serotonin receptor (GPCR), activates protein kinase (PKA), phosphorylates GABAa receptor, alters receptor function, can suppress or enhance dependet on phosphorylation site.
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Outline postynaptic modulation by altering the number of postsynaptic receptors.
Insulin promotes the insertion of GABAa receptors from Golgi apparatus, BDNF (brain derived neurotrophic factor) promotes removal of GABAa receptors.
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Outline the mechanism behind heterosynaptic facilitation.
5-HT activates 5-HT receptor (GPCR), activates adenylate cyclase, increase in cAMP conc, activates PKA, phosphorylates K channels reducing K current, broadens AP, Ca channels open longer, more transmitter release.
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Give an example of heterosynaptic facilitation.
Sensitisation of gill withdrawal reflex in the sea hare, Aplysia californica.
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What are the presynaptic mechanisms of synaptic modulation?
Altered vesicle release, altered Ca entry, altered vesicle recycling.
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What are the postsynaptic mechanisms of synaptic modulation?
Altered receptor function, altered receptor number.
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What is the typical tetanus used for LTP?
High frequency burst, 3ms, 100Hz.
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What does LTP do?
Can induce an almost permanent change in connectivity e.g. during learning.
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Where was LTP first discovered?
In the hippocampus.
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What are the two categories of LTP?
NMDA receptor independent and NMDA receptor dependent.
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What are the two categories of long term depression of synaptic function?
NMDA receptor independent and NMDA receptor dependent.
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Card 2

Front

What is synaptic facilitation?

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A mechanism by which when there is lots of activity in a neuron the response gets larger.

Card 3

Front

What is synaptic depression?

Back

Preview of the front of card 3

Card 4

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Briefly outline the mechanism for paired-pulse synaptic facilitation.

Back

Preview of the front of card 4

Card 5

Front

Repetitive firing can lead to spike broadening, what effects does this have on the cell?

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