Topic 3: 2

Question 1

post synaptic density

Answer 1

receptors on post synaptic neurons are located in high density in regions called the post synaptic density

Question 2

discrete synapse

Answer 2

AKA clustered synapse
axon branches out to form discrete endings called terminal buttons, which forms the active zone where neurotransmitter is released

Question 3

Diffuse synapse

Answer 3

AKA widespread synapse

axon forms swellings called varicosities, neurotransmitter released from active zones along the varicosities

Question 4

Criteria for chemical synaptic signalling

Answer 4

cell machinery for synthesis of neurotransmitter in presynaptic nerve terminals
storage of neurotransmitter in secretory vesicles
regulated release of neurotransmitter into synaptic cleft
specific receptors on postsynaptic membrane to bind neurotransmitter (except for gas molecules)
means of termination for neurotransmitters

Question 5

Linking pre and post synaptic structures

Answer 5

CAMs

neuroligin and neurexin hook up to each other across the synapse

Question 6

vesicle storage of neurotransmitter has 3 advantages

Answer 6

neurotransmitter can be concentrated in the vesicles, increasing reception chance
preserved from enzyme degradation
release regulated

Question 7

non peptidergic neurotransmitters

Answer 7

smaller
manufactured in axon terminal
immediately packaged into vesicles which have been transporter down terminal using microtubules

Question 8

peptidergic neurotransmitters

Answer 8

manufactured in cell body

immediately packaged into vesicles synthesised in cell body, then transported down the terminal using microtubules

Question 9

NP- transport into vesicles

Answer 9

involves secondary active transport 
v class ion pump in membrane of vesicle pumps H+ into vesicle using ATP to concentrate H+ (primary active transport) 
Transporter moves H+ out of vesicle down conc gradient (facilitated diffusion) 
Simultaneously moves transmitter from terminal into vesicle via anti porter (secondary active transport)

Question 10

neurotransmitter release

Answer 10

vesical fuse with membrane at active zone and expel neurotransmitter into synaptic cleft (regulated by Ca++ entry into terminal via voltage gated channels at active zones only)
only vesicles bound to docking proteins are released
vesicle membrane then endocytosed and recycles

Question 11

P neurotransmitters vesicles not at active zones

Answer 11

Ca++ plays a role in concentrating them at active zones

Question 12

Steps BEFORE fusion for transmitter release

Answer 12

vesicles trafficked to active zone
loosely tethered at active zone
transiently docked here by cytoskeletons
primed to form partial SNARE
Use Ca++ levels to fuse with membrane, by forming a complete SNARE complex that allows fusion of two membranes

Question 13

two safety valve mechanisms for transmitter release

Answer 13

Ca++ needed

primed

Question 14

P vs NP transmitter synapse release

Answer 14

P transmitters taken to active zones by Ca++
P transmitters less efficient, slower responses and only to repetitive stimulation- takes a train of APs to cause transmitter binding

Question 15

Controlling synaptic efficiency

Answer 15

controlling size of depolarisation controls amount of Ca++ entering, which controls how many vesicles fuse with membrane

Question 16

excitatory response

Answer 16

depolarisation

RMP less negative

Question 17

inhibitory response

Answer 17

hyperpolarisation

RMP more negative

Question 18

Voltage vs transmitter gated ion channels

Answer 18

voltage gated are selective for a specific ion while transmitter gated are selective only for the type of charge

Question 19

excitatory gated channels

Answer 19

net post synaptic depolarisation depends on the amount of Na+ entering the cell versus amount of K+ leaving
net influx of positive charge compared to efflux leads to depolarisation of the RMP

Question 20

inhibitory transmitter gated channels

Answer 20

net post synaptic hyper polarisation depends on net amount of Cl- entering the cell or K+ leaving through their respective transmitter gated channels
More Cl- entering than X- leaving causes hyperpolarisation
More K+ leaving than Na+ or X+ entering causes hyperpolarisation

Question 21

terminating transmitter action

Answer 21

uptake by adjacent glial cells or reuptake by presynaptic terminal (peptide transmitters do not have these)
enzyme degradation
diffusion of transmitter away from synaptic cleft