Lecture 5 Flashcards
The neurone II : Synaptic transmission
pre-synaptic neurone
- has axon terminal
- pre synaptic membrane
- vesicles with NT molecules
- Ca++ ion channels
synaptic cleft
between pre and post synaptic neurone
post-synaptic neurone
post-synaptic membrane
various ion channels
process of pre-synaptic neurone
AP arrives
Ca++ channels open
Ca++ ion enter axon terminal
vesicles fuse with pre synapticc membrane
change shape
molecules release into synaptic cleft
synaptic cleft process
NT mols diffuse across
post synaptic neurone process
NT bind to ion channels at receptor site
ion channels open
ion enter neurone
post-synaptic potential ( PSP ) - wave of ions being generated in post-synaptic cell
NT mols removed from receptor site
channels close
ion drift down dendrites –> soma –> axon hillock
when do voltage gated ion channels open ?
when change in membrane potential
eg.
K+ channel and Na+ channels in axon hillock and axon
Ca++ channels in membrane of axon terminal
all of these respond to a positive charge on the inside of the membrane (depolarisation )
when do Transmitter gated ion channels open ?
when NT molecule binds with channels receptor site
eg.
ion channels in post-synaptic membrane
2 basic forms of transmitter gated ion channels
Ionotropic Channels
Metabotropic channels
Which transmitter gated ion channel opens directly
ionotropic
which transmitter gated ion channel opens indirectly
metabotropic
what type of ion channels are in post-synaptic membrane ?
only transmitter gated
key and lock method
NT mols fit into specific receptor sites
diff channels respond to different NT’s because they have diff shaped receptors
Type of NT determined which channel opens
type of channel determined type of ion can enter
type of ion (+ or -)determines how cell behaves
type of NT determines…
type of channel opening
type of channel determines….
type of ion that can enter
type of ion. ( +or-) determines…
cell behaviour / response
voltage gated channels respond to what
voltage change - signals
eg. K+ channel
eg. Na+ channel
transmitter gated channels respond to what
chemicals ( NT’s )
electrical change
excitatory synapse
positive ions enter
depolarisation
EPSP
new AP triggered by axon hillock becomes more likely
Inhibitory synapse
negative ions enter ( hyperpolarisation )
IPSP
new AP becomes less likely
what makes synapse exitatory or inhibitory
NT released by axon terminal ( most, not all neurones have one type of NT )
ion channel and receptor present in post-synaptic membrane
how do you make NT stop having an effect on the cell ?
actively removing them on post synaptic cell
( they don’t change hen they bind to the receptor )
Two types of NT removal
degration
re-uptake
degration
special enzymes in the synaptic cleft break down (inactive) NTs
change shape
NT no longer fits
components are partly recycled to make new NT’s
re-uptake
receptor molecules at pre-synaptic axon terminal take up NT’s
( the same neurone grab NT’s + pulls back into pre-synaptic cell)
return them into pre-synaptic cell
