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Developmental Neurobiology 🧠 > Exam 2: Chapter 6 > Flashcards

Exam 2: Chapter 6 Flashcards

1
Q

Steps of target selection

A

1) Defasiculation
2) Branch, get trapped
3) Topographic location
4) Cell layer
5) Connect to targets

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2
Q

In sympathetic NS: needs ___ to innervate

A

Neurotrophin (NT-3)

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3
Q

KO NT-3 in mice

A

No SCG external ear innervation.

Blood vessels make NT3 in external ear

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4
Q

What reduces NT3 dependence?

A

NGF –> TrkA receptor –> P75 –> increase NGF dependence, decrease NT3

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5
Q

Tumors can come from

A

Pancrease FGF uptake

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6
Q

Non-sympathetic: INNER ear

A 
Semicircular = BDNF (Trk B)
Cochlea = NT3 (Trk C)
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7
Q

Inner ear:

1) KO both TrkB and Trk C
2) Swap NT3 for BDNF

A

1) no innervation

2) NT3 same spot, but off, can sub in, both not all equal

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8
Q

FGF in tectum, we talked about this

1) Axon FGF insensitive
2) Fill tectum with FGF

A

FGF lower in tectum to say we made it

1) Never gets to tectum
2) keeps going

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9
Q

Why make visual connections to somatosensory that we pull out later?

A

Backup system.

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10
Q

Experiment:
A) Destroy LGN
AND
B) Destroy auditory axons

A

Visual axons –> MGN –> AC

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11
Q

Experiment: cut auditory axons, but late in the game

A

stays on the right side, thanks to EphrinA2/A5 expression barrier

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12
Q

Experiment on LGN/MGN: KO Ephrin As and cut auditory

A

Visual connections to both LGN and MGN

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13
Q

Ligand and Receptors:

1) NT3
2) NGF
3) BDNF
4) Lots of neurotrophin

A

1) NT3 TrkC
2) NGF Trk A
3) BDNF Trk B
4) Neurotrophins to p75

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14
Q

Retina/Tectum craziness of Roger Sperry’s Frog Eyes

A

Retina/Tectum

1) Dorsal –> Ventral/Lateral
2) Ventral –> Dorsal Medial
3) Nasal –> Posterior/Caudal
4) Temporal –> Anterior/Rostral

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15
Q

1) Retina: EphA3

2) Tectum: Engrailed/Ephrin A

A

1) Temporal side

2) Caudal/Rostral side

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16
Q

1) Retina: Ephrin B

2) Retina: Eph B

A

1) Dorsal

2) Ventral

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17
Q

Bonhoeffers Chemical Cues: AP mapping

Experiment: Treat cells with PI-PLC

A

Nasal goes to A or P
But Temporal Anterior only

Experiment: Destroys Ephrin A, temporal axons lose preference.
Significance: Force is repulsion

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18
Q

Temporal injection in Retina:

1) Wild Type
2) KO Ephrin As
3) Eph3A under control of Brn3c

A

1) Anterior
2) axons go crazy
3) different levels, split into two stop groups

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19
Q

Nasal injection in Retina:

1) Wild Type
2) KO Ephrin As
3) Eph3A under control of Brn3c

A

1) Posterior
2) axons go crazy
3) different levels, split into two stop groups

20
Q

Engrailed in Tectum

A

At posterior/caudal, attracts nasal

21
Q

Ephrin-B in Xenopus

A

axons carry Ephrin B LIGAND to the receptor
(Eph B –> Ephrin B)
Reverse

22
Q

Eph-B in Mouse

A

dorsal axons also attracted to Wnt
carry EphB
(Ephrin B –> Eph B)

23
Q

Ephrins in the cortex

A

thalamus layer 4 attracted by Eprhin A5 ad NT3.

IF you don’t need to stop in layer 4, repelled by Ephrin A

24
Q

Ephrin mediates branching in ____

A

dendrite

25
Q

Ephrin inhibits branching in___

A

axons

26
Q

Somatographic maps

A

spatial representation of physical features in nervous system

27
Q

Netrin + what happens when its gone?

A

some MNs target muscles expressing increased netrin levels.

Abolish netrin/netrin receptor = target defects

28
Q

Connectin + what happens when its gone?

A

CAM type, in subset of muscles and neurons
pairs axons and target site

KO- does little if KO, but mis-expressed, leads to targeting errors

29
Q

Fas 2/3

A

Cell adhesion

No major issues if KO, but misexpress = targeting error

30
Q

Semaphorin 2

A

wrong thing has it = targeting problem

31
Q

Conclusion for all these KO with no big effects?

A

Relative concentration matters more than presence/absence in target selection

32
Q

Normal muscle 6 and 7 innervation from TN and RP3

A

6 and 7 both get RP3,

TN doesn’t innervate either

33
Q

Muscle 6 and 7 innervation from TN and RP3:

Increase Fas2 on 6

A 
More green (attractive factors) 
So TN and RP3 innerate, and RP3 fails to get 7
34
Q

Muscle 6 and 7 innervation from TN and RP3:

Increase netrin OR Fas 2 OR decrease Sema 2

A

TN now innervates 6 and 7

35
Q

Muscle 6 and 7 innervation from TN and RP3:

Incrase netrin OR fas 2 and increase Sema 2 (raise/lower together)

A

TN no innervation, RP3 normal

Shows ratio is what is important here

36
Q

Muscle 6 and 7 innervation from TN and RP3:

Decrease netrin OR increase Sema2

A

RP3 no innervation

37
Q

Neuronal defasiculation:

1) Ko beta-1a
2) KO beta-1a and KO fas2-/-

A

1) can’t defasiculate

2) KO both defasiculation and fasiculation, so it keeps going and can defasiculate again

38
Q

How does axonal branching occur?

A

Pause looks like microtubules all over, but then builds stably off growth cones.

39
Q

Goldfish visual system

1) 1/2 tectum
2) 1/2 Retina

A

Takes on new axons.
Reprobes environment

1) as it grows, middle becomes middle again
2) if cut nasal, middle will take it, no wasted space

40
Q

Wilder Penfield Mapping cortical function

A

homunculi is creepy

Parts of body next to each other tend to have locations next to each other

41
Q

Cortex vs. Thalamus: What do we do with free space

A

Cortex: use it
Thalamus: no way, sensory neurons good, phantom limb sensation. Only remap when the neurons die

42
Q

Experiment:

1) Peripheral Damage (remove middle cortex)
2) Central amputation (remove middle cortex and Sensory neurons)

A

1) DRG neurons survive, A innervates in FT areas

2) DRG axon degenerate F –> F, T –> T

43
Q

Rodent Barrel Cortex Somatotopic Map:

1) Extra whisker
2) Damage/missing whisker
3) Tie 2 whiskers together

A

Rodent Barrel Cortex Somatotopic Map:

1) Extra whisker- Extra Barrel
2) Damage/missing whisker- other barrels bigger
3) Tie 2 whiskers together - barrels fuse

Significance? Flexibility early on

44
Q

Olfactory mapping

A

Messy looking, relies on odorant

Epithelium –> Glomeruli

45
Q

Odorant receptor protein is on

A

Axons/dendrites of olfactory neurons

46
Q

Experiment:

1) Normal olfactory mapping
2) P2 receptor deleted
3) Give M71 receptor
4) P2 –> P3

A

1) Get to p2 glomerulus in olfactory bulb
2) Go to blub, but can’t find P2
3) Go to middle between M71/P2
4) Get a little closer since P3 is near P2

Developmental Neurobiology 🧠 (11 decks)

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