Transmitter release (week 7)

Question 1

how fast can action potentials travel

Answer 1

120/meters per second

Question 2

what are some of the receptors that neurotransmitters bind to

Answer 2

ionotropic, nicotinic and glutamate, (cation conducting are usually excitatory)

Question 3

which receptors are anion conducting

Answer 3

ionotropic, glycine and GABA2

Question 4

what are the subunits making up the transmitter gated ion channels

Answer 4

2 alpha
1 beta
1 gamma
1 delta

Question 5

which subunits does ACh bind to

Answer 5

the two alpha subunits

Question 6

explain the Transmitter-gated ion channels(cys-loop superfamily).

Answer 6

Eg.The nicotinic acetylcholinereceptor (nAChR)

integral ion channel
* agonist binding to the receptorinduces a rapid conformationalchange to open the channel
* the channel is selective forcertain ions.
* signalling is extremely rapid(milliseconds)

Question 7

does a minature end plate potential result from the release of a single vesicle of packaged ACh

Answer 7

yes
the release of a singular vesicle will cause the binding of multiple ACh molecules to the receptors causing an increase in the in the MEPPs

Question 8

what does vesamicol do

Answer 8

it inhibits vesicular uptake of ACh and consequently decreases the amplitude of mepps (miniature end plate potentials)

Question 9

what does alpha latroxin do

Answer 9

it causes the uncontrolled release of vesicles causing many spikes in the mepps and then the depletion of the presynaptic neuron.

Question 10

what does a-LTX form

Answer 10

a cation (Na+/ Ca+) conducting pore channel

Question 11

what is endocytosis by kiss and run

Answer 11

the vesicles go back up and is ready to be used again for neurotransmitters to fill up

Question 12

what is endocytosis by the clathrin pathway

Answer 12

coating membranes

Question 13

what is essential for neurally evoked neurotransmitter release

Answer 13

Calcium

Question 14

how does calcium enter the presynaptic neuron

Answer 14

voltage gated calcium ions

Question 15

how fast is calcium triggering of vesicles

Answer 15

very fast around ~0.1 ms

Question 16

what blocks the voltage-gated calcium channel

Answer 16

magnesium

Question 17

what does high mg2+ and low Ca2+ result in

Answer 17

reduces the epp to below the threshold for firing an action potential

Question 18

what is tubocurarine

Answer 18

a non depolarising neuromuscular junction

Question 19

what is botulinum toxin and how does it work

Answer 19

Botulinum toxin blocks the release of acetylcholine, a neurotransmitter that plays a key role in muscle contraction. It does this by preventing the fusion of synaptic vesicles with the cell membrane, inhibiting the release of acetylcholine into the synaptic cleft.

Question 20

what are the steps on how botox work

Answer 20

1)attachment
2) toxin enters by endocytosis
3) light chain in cytoplasm
4) Proteolytic cleavage of synaptobrevin

Question 21

what is synaptobrevin

Answer 21

a vesicle associated membrane protein (VAMP)

Question 22

simplified model of vesicular release

Answer 22

1)Docking - A complex of synaptobrevin, syntaxin and SNAP 25 forms to bring the vesicle into the zone adjacent to the calcium channel
2) Priming - synaptotagmin is recruited to the complex
3) Fusion - Calcium influx triggers fusion and release