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Excitable Cells: Neuroscience > Module 9 - synapses > Flashcards

Module 9 - synapses Flashcards

1
Q

what are the 2 types of synapses

A

electrical and chemical

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2
Q

what is one way transmission called

A

rectifying

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3
Q

two way transmission?

A

non-rectifying

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4
Q

advantage of electrical synapses

A

fast and reliable
so used in escape reflexes

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5
Q

what are neurons connected by in electricla synapses

A

connexons in vertabrate
innexins in non-vertabrate

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6
Q

what do connexons/innexins form between neurons

A

gap junction

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7
Q

structure of connexons

A

6 subunits (connexins)
similar to ion channels but much bigger

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8
Q

why is a fly always able to fly away

A

uses electrical transmission whilst we use chemicaltransmission to capture it

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9
Q

what was missing in mutated drosophila who had no escape reflex

A

no innexins so no gap junctions
so the signal is transmitted down the giant fibres, but cant get past synapses

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10
Q

why are chemical synapses the more common and preffered synapse in animals

A

much more adaptable

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11
Q

what did otto loewi find when bathing fluid from one chamber with heart being stimulated was dripped into the next chamber without stimulation

A

the heart still slowed down

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12
Q

what did otto loewi discover as a consequence

A

‘vagus substance’ which ended up being ACh
so found out a water soluble chemical substance was stimulating the heart

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13
Q

why so many mitochondria in nerve terminals

A

vesciular release is very enrgy consuming

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14
Q

what are the 3 SNARE proteins

A
  • synaptobrevin
  • SNAP 25
  • syntaxin
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15
Q

where is synaptobrevin located

A

on the vesicle

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16
Q

where is SNaP 25 and syntaxin located

A

on the membrane

17
Q

what triggers the vesicles to release their contents

A

Ca2+

18
Q

what is calcium sensed by in the vesicle

A

protein called synaptotagmin

19
Q

in muscle, what is synaptic transmission called if it occurs with no AP or Ca2+ release

A

miniature end plate potential (since it is spontaneous release)

20
Q

what is synaptic release with calcium called

A

evoked release/ End plate potential (in muscles)

21
Q

what is one quantum

A

amount of trnsmitter per vesicle

22
Q

what is quantal content

A

avg no. vesicles released in an evoked response

23
Q

how do we calculate quantal content `

A

EPP current/1quantum current

24
Q

what is key for vescle recycling

A

clathrin !!

25
Q

what type of structure does clathrin form around vesicles

A

truncated icosohedral shape
with 20 hexagons and 12 pentagons

26
Q

what 3 things are kept constant by clathrin

A
  • vesicle size
  • number of vesicles
  • size of terminal
27
Q

mechanism of action of botulinum toxin

A

a proteolytic enzyme
that cleaves SNARE proteins
stopping neurotransmitter release

28
Q

how does ω-agatoxin work

A

blocks P/Q voltage gated Ca2+ channels
used by spider to subue its prey

29
Q

how does ω-conotoxin work

A

blocks N-type voltage gated Ca2+ channels
used by cone snails to paralyse prey

30
Q

how do α-neurotoxins work and what types are there

A

block nicotinic ACh receptors or to normal nicotinic receptors
- α-bungarotoxin
- α-cobratoxin

31
Q

how can α-neurotoxins be used

A

not therapeutic
but have high affinity for nicotinc recpeotrs, so used as radioligands

32
Q

how does physostigmine work

A

acts as AChesterase inhibitor
so = no breakdown of ACh

33
Q

how can phygostigmine be used therapeutically

A

muscle weakness
boosts ACh conc,

34
Q

how does tetanus toxin work

A
  • toxin binds and enters in skeletal muscle junction but travels back up motor neurons into the CNS
  • destroys SNARE proteins in inhibitory neurons that release GABA and glycine
  • causes uncontrollable spasms
35
Q

what bacteria causes tetanus

A

clostridium tetani
related to clostridium botulinum - botox

Excitable Cells: Neuroscience (21 decks)

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