Presynaptic Flashcards
how are signals transmitter between neurons
via synapses
synaptic transmission
what is the reticular theory
the NS was made of continuous mesh of nerve cell processes (axons and dendrites)
how neurons actually work
individual contiguous cells - neurons
not continuous
2 types of synapse
chemical and electrical
size of synaptic cleft
20nm
concentration can change rapidly
chemical synapse
signals transmitter through chemical messengers . neurotransmitters
synaptic vesicle structure
balls of lipid membrane
40 nm in diameter
individual neuorn releases …
one type of neurotransmitter
e.g glutamatergic GABAergic dopaminergic
what are neurotransmitters transported into vesicles via
proton antiporters
what generates a proton gradient across vesicle membrane
ATPase
what is the proton gradient used for
vesicle transporters use gradient to drive the transport of transmitters into secretory vesicles by coupling the translocation of transmitter to H+
function of membrane protein on synaptic vesicle
multitude of membrane bound proteins
* docking at presynaptic membrane
* release of neurotransmitter
* filling vesicle with neurotransmitter
transporter of GABA
VGAT
transporter of glutamate
VGLUTs
transporter of ACh
VAChT
transporter of MA
VMATs
what is crucial for neurotransmitter release
calcium entry
triggered by AP
what type of calcium channels are on presynaptic vesicle
voltage dependent calcium channel s
role of SNARE proteins
Bring synaptic vesicle close to membrane
how are vesicle brought and fused to the membrane
brought by SNARE proteins
close to membrane = dock to membrane
docking and calcium sensing proteins
calcium triggered exocytosis
endocytosis vis Cathrin coated vesicles
what is the cable transmission of neurons
axon
what part of the axon does an AP initiate
Axon initial segment (AIS)
structure of Axon initial segment
- high density of voltage gated ion channels
- membrane proteins
- unique repertoire of sub membranous cytoskeletal scaffolds
- generate and shape ap before they are propagated
what boundary does Axon initial segment lie
between somatodendritic and axonal compartments
what are axon collaterals
side branches of the axon that allow the neuron to send information to others
where are synapses located
boutons terminaux
en passant boutons
probability of synaptic release
stochastic (rendom)
probability 0-1
not the same at all synapses
synaptic and changed by physiological factors
what is increased by increased probability of release at synapses
synaptic strength goes up
at Probability of release 0 = no synaptic communication
calculate Pr (probability of release)
Pr = mean number of synapses releasing per trial / total number of synapses
how to change probability of release
change local intracellular calcium conc
ways to alter presynaptic calcium entry
- change extracellular calcium conc
- apply blockers of presynaptic calcium channels
- activate presynaptic receptors that alter calcium channel activity
short term synaptic plasticity
short lived changes in the strength of synaptic coupling that reflect the prior experience/ activity of the synapse
what underpins short term synaptic plasticity
dynamic changes in release probability
what’s the Schaffer collateral commissural pathway (SCCP)
connection between CA3 and CA1 pyramidal neurons
experiment into short and long term plasticity
Schaffer collateral commissural pathway in hippocampus
how to fins an excitation post synaptic potential (EPSP) recording
- place extracellular stimulating electrode on the axons of CA3 neurone
- place an extracellular stimulating electrode in the dendritic region of CA1
- record the EPSP
frequency =
1/ time period
what do low frequency responses mean in SCCP experiment
stable response - little plasticity
what do changes in paired pulse ration reflex
transient change in release probability
paired pulse facilitation
second response (when stimulated) is bigger than the first
paired pulse depression
second response lower than first
do synapses with a low Pr tend to exhibit paired pulse facilitation or paired pulse depression
paired pulse facilitation
do synapses with a high Pr tend to exhibit paired pulse facilitation or paired pulse depression
paired pulse depression
Why are you more likely to get facilitation when the synapse has low Pr?
Readily release pool
vesicle that did not release NTs the first time are ready for second AP to be release
more vesicles and more NTs
why do synapses with high Pr get depression
Fewer vesicles - fewer Nts left as they were release in first AP
what determines short term plasticity
number of vesicles release (presynaptic)
Low probability of release (Pr) effect on vesicle release
few vesicles released
more vesicles released in response to second action potential = FACILITATION
high probability of release (Pr) effect on vesicle release
many vesicle released
fewer vesicles available for RRP = DEPRESSION
lower calcium release and its effect on paired pulse depression
less calcium entry
lower release probability after the first stimulation
less paired pulse depression
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