Chemical Synapse 2 Flashcards
what is the most common chemical synapse
classical NMJ- neuromuscular junction
what are 4 signal processes at NMJ
one motorneuron action potential invades many boutons and produces compound EPSP
each bouton has 1 or more active zone
each active zone releasse 1 vesicle activating many receptors
each receptor channel opens in an all or none manner
what are the two vesicle release mechanisms from active zones of NMJs
quantal release
miniature EPSPs
what are 4 special examples of chemical synapses
transmission at non spiking neuron synapses
voltage dependent NMDARs
transmission mediated by glial cells
retrograde signalling
what is a neuron with nonspiking synapses
photoreceptor on off-bipolar cell
what is the response mechanism of non spiking synapses
not require spike
transmitter is glutamate
there is baseline release at rest (-40mV)
responses not linear
what is the response mechanisms of voltage dependent NMDAR synapses
reversal is ~0mV
mg2+ blocks NMDAR at hyperpolarisation
mg2+ block relieved at depolarisaiton
EPSPs can be bigger with more depolarisaiotn
what are three transmitters mediated by glial cells
glutamate
atp/adenosin
d serine
what are two ways in which glial cells mediate transmission at synapses
have receptors activated by transmitters released from neurons
can release transmitters to act of neurons
what are five transmitters of retrograde signalling
lipid derived gases peptides conventional transmitters growth factors
what is the lipid derived transmitter
endocanibinoids
what are the transmitters of gases
NO
CO
what peptide is a transmitter
dynorphin
what is a conventional transmitter
GABA
which growth factor is a transmitter
BDNF
how does retrograde signalling contribute to LTP formation
calcium influx through NMDARs c2/calmodulin activate NO synthesis NO released and diffuses NO activates GC cGMP enhances vesicle release PDE degrades cGMP
what are 5 functional classifications of synaptic connection
presynaptic inhibition presynaptic facilitation reciprocal inhibition recurrent inhibition reciprocal excitation
what type of synapse does presynaptic inhibiton and presynaptic facilitation occur at
axon-axon
what is the main result of presynaptic inhibiotn
c1 cell indirectly inhibits cell b
what is the mechanism of presynaptic inhibiton
c1 activates receptors on a terminal A terminal cl donductance increases A terminal AP becomes smaller less Ca2+ entry into terminal less transmitter release from A terminal smaller EPSP in cell b
what is the result of presynaptic facilitation
c2 cell indirectly excited cell b
what is the mechanism of presynaptic facilitaiton
c2 activates receptors on terminal terminal k current depressed terminal AP becomes longer more ca2+ entry into terminal more transmitter release bigger EPSP
what is an example of reciprocal inhibition
knee jerk reflex pathway
what is the mechanism of knee jerk reflex
tapping patellar tendon activates 1a fibres from muscle spindles
1a excites motorneurons controlling quadraceps
1a fibres also excite inhibitory motorneurons innervatng the hamstring muscle
