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Flashcards in Axonal Growth Lec03 Deck (79):
1

____ changes shape at decision points

growth cone

2

how do neurons start (before polarization)?

round, with no obvious processes

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3

___ defines the polarity of the neuron

the axon

4

where are growth cones located?

the tip of the axon

5

what are lamellapodium? 

what do they contain? 

fan shaped sheet at the tip of the axon

contain actin filaments and microtubles

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6

what are filopodia? what do they contain?

fine processes extending out from lamellapodium

have actin filaments

7

___ growth cone form and disappear rapidly

filopodia

8

___ dictates direction of growth - in lamellipodia / filopodia

Filamentous actin (F-actin) 

9

____ gets incorporated into F-actin at leading edge

 Gobular actin (G-actin)

10

F-actin Binding Proteins cause ___ and ___

retrograde flow & growth cone turning (by causing depolymerixation)

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11

 attractive cue increases ___ and decreases ___ 

↑ polymerization/assembly, ↓ retrograde flow (goes toward the attractive cue)

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12

functional difference ebtween MT and F-actin 

MT are responsible mostly for axon elongation

f-actin dictates direction

13

 ___ make the cytoskeleton core

Microtubules (they are strong and stable)

14

Acetylated microtubles only in ____

axons

15

 Tyrosinated microtubules ↑ in ____

lamellipodia

16

where is f actin found?

in lamellipodium and filpodia

17

Contact repellants include

Semaphorins and Ephrins

18

Contact attractants include

1. peipheral ECM

2. CAM

3. Cadherins

19

___ are attractants inthe periphery, but are not well understood in the CNS?

what are examples of each?

ECM molecules

attractants - laminins, collagens, fibronectin

not well understood? repellants? -- proteolgycens, glycoproteins, hyaloruonan

20

homolphilic binding of Cam 

triggers cytoplasmic kinases of growth cone

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21

what is Ca independent signaling? dependent

indepdent - CAM

 

Depdendent - caDherins

22

homophilic binding of cadherins triggers

intracellular signals --> actin binding &
organization

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23

axon guidance signsla re either ___ or ___

1. nondiffusable and short range

2. or diffusable and long range

24

the contact attraction and repulsion signals are ___

nondiffusable and short range

25

the chemoattractants and chemorepulsive signals are 

diffusable and long range

26

what does the binding of axon guidanc emolecules to receptors on growth cones activate?

signaling cascades that result in the reognization of growth cone cytoskeletons --> controlling the  direction and rate at which the growth cone moves

27

attractive interactions (contact attractants and chemoattractants) promote ____

actin polymerization

28

repellant interactions promote ____

actin depolymerization and growth cone collapse

29

lamins, collagens, and fibronectins bind to ___

integrin receptors

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30

___ has been associated with bundling (fasiculation) of groups of axons as they grow

L1 CAM

31

where can cadherins be found

on the suface of growth cones, growing axons, surrounding cells or targets

32

where are semapghorins found?

can be secreted or anchored to the cell surface

(secreted are probably attached to the cell surface or the ECM --> not really diffusable)

33

where do sempahorins bind to?

cell surface --> plexin family receptors

secreted --> bind neurophilins

34

what is the difference between the two classes of ephrins?

ephrin A has gpi linked ot surface

ephrin b is a single pass transmembrane protein

 

each has its own receptors on growth cone 

35

why do temporal retina axons go to the anterior tectum?

ephrins A2 and A5 are lower in anterior

 

-> posterior A2 and A5 repulses the temporal axons since they have high A3

36

nasal retina go to the posterior tectum because

axons from the nasal retina are blind to ephrin and lack the eph receptor

 

so they don't be repulsed by ephrins A2 and A5 found highly in the posterior tectum

37

chemorepulsion molecules include

slits

netrins if they have UNC 5 receptors

38

chemoattractant molecules include

netrin if they have DCC receptors

39

what is secreted at the embyro midline

chemorepulsants, so netrins and slits

40

what are slits receptors

robo

41

what receptors make netrin attractants

DCC

42

what receptors make netrin repiulsants

UNC 5

43

before crossing the midline ___ attracted to netrin at midline

DCC

44

after crossing the midline --> 

cell upregualtes robo receptors, repulsion from the midline

45

what silences DCC signaling?

the robo that is upregulated after crossing

46

what does KO of netrin eliminate?

the crossing of commisural axons

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47

why do netrin and silts have to work together?

because the cells have to cross at a very specific site in the spinal cord

also cant recross

48

synaptogensis in CNS

 Presynaptic process (from growth cone) recognizes target cell via ____

cadherin

49

start of synaptgensis at the NMJ?

1. mtoor axon approaches and amkes contact with a myotube

50

in synaptogensis at NMJ

after mtoor axons approaches the myotube.... what happens?

nerve terminal and mytotubual diffeerentiate

nerve terminal becomes motor terminal

muscle forms post synpatic apparatus

51

what is the differenation of muscle induced by?

agrin --> activating MuSK --> causing clustering and increased expression of acetylcholine receptors

52

what does MuSK do?

causes clustering and increased expression of acetylcholine receptors

53

in NMJ synaptogensis, both the motor nerve and muscle make

ecm components to form a basa lamina (to stabilize the synaptic structure)

54

axons arising from t1 in the superior cervical ganglia form synapses on cellbodies of neurons that 

project to targets in the eye

55

axons arising from t4 in the superior cervical ganglia form synapses on cellbodies of neurons that 

project to targets in the ear

56

how do the correct pre and post synaptic neurons in superior cervical ganglion find eachother

they have a higher affinity than the wrong combinations

57

CNS synaptogensis

 

what recognizes the appropriate site on target cell

 

nascent presynaptic process via cadherin/protocadherin family

58

CNS synaptogensis

immediately after nascent process recognizes the target cell -->

synaptic vesicles and active zone components accumulate

59

CNS synaptogensis

what is recruited in the developing synapse tob ring in moilecules?

neurexin and neuroglin

60

where is neurorxin found?

what is its function

presynatpic

function -- localizes cytoskeltal elements, vesciles, active zone proteins, and Ca channels TO PRESYNAPTIC MEMBRANE 

61

where is neuroglin found? 

what is its function?

postsynp. membrane

function -- recruits NT receptors and other postsynatpic proteins

62

After synaptogenesis, target cells secrete

 limited amounts of neurotrophic factors.

63

which neurons survive after synaptogensis?

those that receive enough trophic factors

64

Neurotrophins control the 

# of target cells contacted and # of synapses formed

65

what happens if there is NGF in check sensory ganglion?

 

if there is none?

yes NGF -- explosion of axon extensions

no NGF -- neuron death

66

___ respond to all growth factors

dorsal root ganglion 

67

nodose ganglia respond best to

NT3

68

Sympathetic ganglia respond best to ___? and not at all to ___?

best to -- NGF

not at all to BDNF

69

neutrophin receptors include -- 

Trk and p75 receptors

70

Trk receptors ahve a high affinity for

processed/cleaved neutrphins

71

p75 have a high affinity for

unprocessed enutrophin

72

intially, skeletal muscle and some aprsymp neurons are innveratvated by

multiple neurons

(this is eventually pruned)

73

with synapse elimation at the nmj, comeptition is dependent on 

electricial activity in both pre and post synaptic cells 

74

blocking electrical acitivity in either pre or post synaptic cells results in

persistence of polyneuronal innervation

75

axonal branching patterns are refined via

competition and synapse elimination

76

BDNF, NT3, NT 4/5 are all

growth factors

77

what is evidence for the trophic function of NGF?

no NGF --> neuronal death 

excessive NGF --> survival of excess neurons

NGF are present (and produced) in target cells)

NGF

78

neutrophic interactions depend on

neurotrophins secreted by target cells

the neurorophin receptors present

intracellualr signaling cascade present

79

neutrophic interactions determine--

number of neurons, shape of neurons, patterns of neuronal connections