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Flashcards in Synaptic Transmission Deck (51):
0

What protein forms a gap junction?

Connexin (6 subunits from a connexon = hemichannel)

1

What are 3 roles of electrical synapses?

1) network activity (synchronization of electrical activity/info across many neurones)
2) communication between glia
3) coordination of growth in embryonic development (Bear et al)

2

Which type of synapse has a role in epilepsy?

Electrical

3

Which type of synapse is the most common form of communication in the CNS?

Chemical

4

Chemical synapses occur between a presynaptic element, most commonly _______, and postsynaptic elements such as ________

Axon terminals

Dendrites, soma, axon terminals

(I.e. Axoaxonic, axosomatic, axodendritic)

5

Why is chemical transmission greatly flexible?

Many different NTs and receptors
Can modulate expression of NT and receptors
=> huge modulatory activity

6

What is the distance across the synapse for a) electrical synapses?
and b) chemical synapses?

Electrical - 0.35nm

Chemical - 30-50nm

7

What is the synaptic delay at:
a) electrical synapse?
b) chemical synapse?

a) none

b) min 0.3ms, usually 1-5ms

8

What is the direction of transmission for chemical and electrical synapses?

Chemical - unidirectional

Electrical - bidirectional

9

What are the 4 types of major NT?

Ach
Amines
AAs
Peptides

10

Small molecule NTs are synthesised in______ and stored in _____?

Synaptic terminal using enzymes from cell body

Small clear vesicles (40-60nm)

11

Large NTs are synthesised in _____ and stored in _____?

Cell body using RER and Golgi

Large dense core vesicles (90-250nm)

12

Where does Ca enter the presynaptic terminal?

Active zone

13

What is a MEPP?

Miniature end plate potential
=> spontaneous release of a single vesicle (quanta) (not due to AP)

14

What is/what causes an EPP?

Multiple MEPPs due to AP dependent release of many vesicles

15

Are axo-dendritic synaptic connections usually inhibitory or excitatory?

Excitatory

16

Are axo-somatic synaptic connections usually inhibitory or excitatory?

Inhibitory

17

Synapses where influence neurone firing the greatest?

At the initial segment / axon hillock

18

Which type of synaptic connection is modulatory and controls NT release?

How does it control NT release?

Axo-axonic

Controls Ca influx in presynaptic neurone

19

What is the name of the axo-axonic connection that increases NT release?

Presynaptic facilitation

(Decreases K+ current, increases Ca current)

20

What is integration?

Summation of all EPSPs and IPSPs

21

Where does integration occur?

Axon hillock

22

What is convergence?

Many neurones synapse onto one neurone

23

What is divergence?

One neurone communicates with many via axon collaterals

24

What is temporal summation?

Summation of PSPs arriving in quick succession (only needs one synaptic input)

25

What is spatial summation?

Summation of PSPs from different inputs across membrane surface

26

How does frequency affect NT release?

Increased frequency = increased release

27

What NTs require higher frequency APs for release?

Peptides

28

Why is an AP?

Self-propagating wave of depolarization

29

What is the normal direction of an AP?

Orthodromic

30

Synaptobrevin is what type of SNARE and what does it do?

V-SNARE

Binds T-SNAREs: SNAP-25 and syntaxin forming SNARE complex (docking and priming)

31

Which SNARE protein is a Ca sensor?

What does it trigger?

Synaptotagmin

SNARE complex formation and Fusion (Ca dependent)

32

What do synapsins do?

Restrain vesicles - bind NT to cytoskeleton

33

How are vesicle released from synapsins?

Ca dependent phosphorylation of synapsin

34

What occurs in targeting and docking?

Vesicle moves towards and binds to active zone

35

What is priming?

Vesicles are prepared for fusion

36

What is fusion?

Pore opening

37

What is the process (each step) of NT release from vesicles?

1) vesicles restrained (synaspsin)
2) targeting + docking
3) priming
4) fusion
5) exocytosis
6) endocytosis

38

How long does it take for vesicles to be recycled after release?

30-60 sec

39

What is the role of Clathrin proteins and dynamin?

Endocytosis;
- Clathrin binds and distorts vesicle membrane, pulls it into cell
- once fully invaginated dynamin "pinches off" vesicle
(Energy dependent GTP -> GDP)

40

What do zinc endonucleases and clostridium toxins do?

Cleave SNARE proteins actively involved in fusion

41

What are clostridium toxins?

Botulinum and tetanus

42

Which toxins is synaptobrevin cleaved by?

Tetanus and botulinum B, E, F + G

43

Which toxins are snap-25 and syntaxin cleaved by?

Snap25: botulinum A + E

Syntaxin: botulinum C

44

What does botulinum toxicity cause?

Blocks neuro transmission at peripheral Cholinergic synapses

45

Do vesicle transporters have high or low specificity?

LOW (many NTs use same transporter)

46

Do membrane tansporters have high or low specificity?

High (each NT has dif transporter)

47

What are vesicular transporters?

What else do they require to function?

Proton dependent antiporters
(NT in, H+ out)

ATPase: transports H+ into vesicle creates electro chem gradient

48

What is a membrane transporter?

Which NTs have these?

Na- dependent symporter

Choline, 5-HT, DA, GABA, glutamate

49

What is disinhibition?

Inhibition of inhibitory neurones

Generation of excitation by transient inhibition of a tonically active neurone

50

Describe how disinhibition works in the basal ganglia to excite the motor cortex

1) striatum excited (by excitatory input from cortex)
2) increased inhibition of globes pallidus
3) decreased inhibition of VL/VA of thalamus (it is disinhibited)
4) allows excitation of motor cortex