synaptic transmission Flashcards
what is an EPSP (excitatory postsynaptic potential)?
depolarising change in the postsynaptic membrane potential, making the inside of the neuron more positive and bringing it closer to the threshold for generating an action potential
EPSPs occur when neurotransmitters bind to receptors on the postsynaptic neuron which allows Na+ to flow into the neuron or Ca2+ to enter
what is an IPSP (inhibitory postsynaptic potential)?
a hyperpolarizing change in the postsynaptic membrane potential, making the inside of the neuron more negative and moving it farther from the threshold for generating an action potential
receptors typically open Cl- or K+ channels
excitatory transmission
makes the neuron more likely to fire an action potential
inhibitory transmission
makes the neuron less likely to fire an action potential
structure of the synapse
axon terminal
synaptic cleft
synaptic vesicles
active zones (site of transmitter release)
postsynaptic density- receptors and proteins
stages of chemical transmission
- synthesis of transmitter/packaging transmitter into vesicles
- fusion of vesicles to membrane to release transmitter
- receptor activation to convert the transmitter into a postsynaptic signal
- removal of transmitter
fusion of vesicles to release transmitter (exocytosis)
vesicles enter a state of docking/priming which is facilitated by SNARE proteins which form the SNARE complex (anchors the vesicle to active site)
action potential opens voltage gated calcium channels nect to the active zone to produce max rise in calcium
calcium binds to synaptotagmin (calcium sensor which interacts with membranr and SNARE complex)
vesicle membrane fuses with plasma membrane and release of transmitter
vesicle fuses into presynaptic membrane, neurotransmitter enters cleft via concentration gradient
spontaneous subthreshold activity at motor nerve endings
miniature endplate potentials (MEPPs) at the neuromuscular junction are spotaneous depolarisations of the postsynaptic membrane which occur without a stimuli
quantal release- smallest amount of transmission at a synapse
imilar to miniature postsynaptic potentials (mPSPs) in neurons and are caused by the spontaneous release of neurotransmitters (acetylcholine) from
presynaptic vesicles
MEPPs are caused by the spontaneous fusion of synaptic vesicles with the presynaptic membrane at the motor nerve endings, resulting in the release of small amounts of acetylcholine (ACh)
AP- synchronous release
glutamate AMPA receptors - excitatory transmitters in CNS
glutamate transmitter molecules being to glutamate receptors e.g AMPA receptor (ligand-gated ion channel) which is sodium permeable
this depolarises post-synaptic membrane (ESPS)
what are the different glutamate receptors?
NMDA
AMPA
kainate
(all ionotropic glutamate receptors)
3 groups of metabotropic glutamate receptors
difference between iGluRs and mGluRs?
iGluRs uses ion channels (fast) and mGluRs use second messengers (slower)
gamma amino butyric acid (GABA) - inhibitory transmitters in CNS
ionic receptors= GABAa (permeable to chloride= influx in negative charge hyperpolarises
metabotropic= GABAb
what are the two main ways of terminating a neurotransmitter?
enzymatic degredation and reuptake
enzymatic degredation
e.g acetylcholine binds to ach receptors (nicotinic and muscarinic) and then is broken down by acetylcholiesterase into acetyl and choline
reuptake
e.g glutamate is released and taken into surrounding membranes by transporter molecules (excitatory amino acid transporter) expressed on astrocytes in pre/postsynaptic membranes
can be recycled into a vesicle or astrocyte converts glutamate into glutamine
