L1 - neurotransmitter release Flashcards
what is SSRRRD
Synthesis Storage Release Receptors Reuptake Degradation
list the types of NT release
spontaneous
asynchronous
calcium independant
synchronous
what is spontaneous NT release
small amounts of NT release that is calcium dependant but doesnt trigger action potential
what is asynchronous NT release
AP may be triggered but not in time with NT release.
Ca dependant also
describe calcium independent NT release
NT release via revere transportation of a transporter
what is synchronous NT release
calcium dependant release of NT triggers AP
describe process of synchronous NT release
- depolarisation of presynaptic neurone (beginning in axon travelling to presynaptic terminal)
- triggers opening of VGCCs - Ca influx
- causes vesicular movement and priming
- vesicles dock via snare proteins
- vesicle fusion with presynaptic membrane
- NT released and vesicle recycled
describe process of presynaptic neurone depolarisations
- EPSPs and IPSPs from dendrites further upstream summate at the cell body
- if the EPSPs are sufficient and reach the threshold -55mv an AP is generated in the axon hillock (spike initiation zone)
- AP travels down axon jumping between nodes of ranvier
why are APs initaited in the Axon hillock / spike initiation zone?
high concentration of VG Na and K channels
why do nodes of ranvier conduct AP well?
high concentration of VG Na and K channels
how does the AP change from the presynaptic axon to terminal and why
width in axon -> 2ms
width in presynaptic terminal -> 350ms
the presence of Ca channels increases the width of the AP
why does Ca infulx?
Conc trandient and voltage gradient
list the names of the subfamilies of calcium channels
Cav1 (L)
Cav2 (N)
Cav3 (T)
describe opening of Cav1 channels
stay open for long time, dont inactivate quickly
describe opening of Cav2 channels
open and inactivate at a speed between Cav1 and Cav3
describe opening of Cav3 channels
stay open for very short period (fastly inactivating)
explain the difference between C channel opening times
the faster inactivating, briefly open Cav2&3 are involved in NT release
the longer open, slower inactivating Cav 1 is involved in muslce contraction
describe general negative feedback pathway of NTs
NT binds to GPCR coupled receptors (Go) which interacts with and blocks VGCC reducing the amount of Ca entering the terminal
describe the general positive feetback mechanism of NTs
NTs bind to Ligand gated ion channels on presynaptic membrane, allowing more Ca entry
what receptor is involved in long term potentiation, describe it
NMDA glutamate (presynaptic, LGIC, allows Ca entry)
name a calcium independant type of NT release
reverse transportation of a transporter
what is the difference between ion channels at the NOR and presynaptic terminals
NOR -> Na and K
terminal -> Na, K and Ca
which G protein subtype regulates NT release? where is it found
Go
presynaptic membrane
what is priming?
vesicular movement and molecular changes that allow vesicle fusion to occur
what are SNARES
proteins found on vesicles and cell membranes
65 residue domains`
name the 3 snare proteins
synaptobrevin
syntaxin-1
SNAP25
where is synaptobrevin found?
does it have TMDs
how many SNARE motifs
vesicle membrane
yes 1
1
where is syntaxin-1 found
how many TMDs
how many SNARE motifs
cell membrane, on top of SNAP25
0
1
where is SNAP 25 found
does it have TMDs
how many SNARE motifs
cell membrane
yes
2
describe synaptotagmin components
where is it found ?
+ve amino acids (+ve charged)
Ca binding motifs
PIP2 binding motifs
within snare complex
describe function of synaptotagmin
- Ca binds to synaptotagmin
- triggers binding of synaptotagmin to PIP2
- leads to structural change opening up snare complex and membranes, releasing NT
describe process of vesicle fusion
- Ca binds to synaptotagmin
- triggers binding of synaptotagmin to PIP2
- leads to structural change opening up snare complex and membranes, releasing NT (exocytosis)
what happens during vesicle recycling
readdition of synaptobrevin and transporters to vesicle membrane
describe co release
when two different NTs are released from the same terminal
the NTs can either be in the same vesicle, or separate vesciles for each NT
what is segregation
where one axon has two different presynaptic terminals releasing different NTs`
example of two NTs that are co released? and where from
ATP and NA in sympathetic vas deferens
what controls Ca2+ release from ER / SR
ryanodine receptors (ca2+ mediated Ca2+ release)
IP3 receptors
define EPSP
excitatory post synaptic potential. This is a subthreshold positive change in
potential derived from an excitatory neuronal input through changes in Na+
conductance. These can summate to initiate the action potential at the axon hillock
define IPSP
inhibitory post synaptic potential. This is a subthreshold negative change in
potential derived from and inhibitory neuronal input, usually thorough increase Cl- or
K
+ conductance. These can also summate to make the potential more negative, and
thus an action potential less likely to occur.
what occurs at the axon hillock>
summation of EPSPs and IPSPs
what features of the axon hillock that allow AP to be generated here
located very close to axon so is able to summate inputs from soma
has high density of Na+ and K+ channels, so if the threshold for AP is reached many can open at once triggering an AP
