Chemical Synapse 2

Question 1

what is the most common chemical synapse

Answer 1

classical NMJ- neuromuscular junction

Question 2

what are 4 signal processes at NMJ

Answer 2

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

Question 3

what are the two vesicle release mechanisms from active zones of NMJs

Answer 3

quantal release

miniature EPSPs

Question 4

what are 4 special examples of chemical synapses

Answer 4

transmission at non spiking neuron synapses
voltage dependent NMDARs
transmission mediated by glial cells
retrograde signalling

Question 5

what is a neuron with nonspiking synapses

Answer 5

photoreceptor on off-bipolar cell

Question 6

what is the response mechanism of non spiking synapses

Answer 6

not require spike
transmitter is glutamate
there is baseline release at rest (-40mV)
responses not linear

Question 7

what is the response mechanisms of voltage dependent NMDAR synapses

Answer 7

reversal is ~0mV
mg2+ blocks NMDAR at hyperpolarisation
mg2+ block relieved at depolarisaiton
EPSPs can be bigger with more depolarisaiotn

Question 8

what are three transmitters mediated by glial cells

Answer 8

glutamate
atp/adenosin
d serine

Question 9

what are two ways in which glial cells mediate transmission at synapses

Answer 9

have receptors activated by transmitters released from neurons
can release transmitters to act of neurons

Question 10

what are five transmitters of retrograde signalling

Answer 10

lipid derived
gases
peptides
conventional transmitters
growth factors

Question 11

what is the lipid derived transmitter

Answer 11

endocanibinoids

Question 12

what are the transmitters of gases

Answer 12

NO

CO

Question 13

what peptide is a transmitter

Answer 13

dynorphin

Question 14

what is a conventional transmitter

Answer 14

GABA

Question 15

which growth factor is a transmitter

Answer 15

BDNF

Question 16

how does retrograde signalling contribute to LTP formation

Answer 16

calcium influx through NMDARs
c2/calmodulin activate NO synthesis 
NO released and diffuses
NO activates GC
cGMP enhances vesicle release
PDE degrades cGMP

Question 17

what are 5 functional classifications of synaptic connection

Answer 17

presynaptic inhibition
presynaptic facilitation
reciprocal inhibition
recurrent inhibition
reciprocal excitation

Question 18

what type of synapse does presynaptic inhibiton and presynaptic facilitation occur at

Answer 18

axon-axon

Question 19

what is the main result of presynaptic inhibiotn

Answer 19

c1 cell indirectly inhibits cell b

Question 20

what is the mechanism of presynaptic inhibiton

Answer 20

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

Question 21

what is the result of presynaptic facilitation

Answer 21

c2 cell indirectly excited cell b

Question 22

what is the mechanism of presynaptic facilitaiton

Answer 22

c2 activates receptors on terminal
terminal k current depressed
terminal AP becomes longer
more ca2+ entry into terminal
more transmitter release
bigger EPSP

Question 23

what is an example of reciprocal inhibition

Answer 23

knee jerk reflex pathway

Question 24

what is the mechanism of knee jerk reflex

Answer 24

tapping patellar tendon activates 1a fibres from muscle spindles
1a excites motorneurons controlling quadraceps
1a fibres also excite inhibitory motorneurons innervatng the hamstring muscle

Question 25

what is recurrent inhibition

Answer 25

neurons inhibit themselves in negative feedback fashion

Question 26

what is reciprocal excitation

Answer 26

neurons excite each other in positive feedback manner

may be mechanism for maintaining long lasting neuronal activities