Exam 2: Chapter 6

Question 1

Steps of target selection

Answer 1

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

Question 2

In sympathetic NS: needs ___ to innervate

Answer 2

Neurotrophin (NT-3)

Question 3

KO NT-3 in mice

Answer 3

No SCG external ear innervation.

Blood vessels make NT3 in external ear

Question 4

What reduces NT3 dependence?

Answer 4

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

Question 5

Tumors can come from

Answer 5

Pancrease FGF uptake

Question 6

Non-sympathetic: INNER ear

Answer 6

Semicircular = BDNF (Trk B)
Cochlea = NT3 (Trk C)

Question 7

Inner ear:

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

Answer 7

1) no innervation

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

Question 8

FGF in tectum, we talked about this

1) Axon FGF insensitive
2) Fill tectum with FGF

Answer 8

FGF lower in tectum to say we made it

1) Never gets to tectum
2) keeps going

Question 9

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

Answer 9

Backup system.

Question 10

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

Answer 10

Visual axons –> MGN –> AC

Question 11

Experiment: cut auditory axons, but late in the game

Answer 11

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

Question 12

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

Answer 12

Visual connections to both LGN and MGN

Question 13

Ligand and Receptors:

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

Answer 13

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

Question 14

Retina/Tectum craziness of Roger Sperry’s Frog Eyes

Answer 14

Retina/Tectum

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

Question 15

1) Retina: EphA3

2) Tectum: Engrailed/Ephrin A

Answer 15

1) Temporal side

2) Caudal/Rostral side

Question 16

1) Retina: Ephrin B

2) Retina: Eph B

Answer 16

1) Dorsal

2) Ventral

Question 17

Bonhoeffers Chemical Cues: AP mapping

Experiment: Treat cells with PI-PLC

Answer 17

Nasal goes to A or P
But Temporal Anterior only

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

Question 18

Temporal injection in Retina:

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

Answer 18

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

Question 19

Nasal injection in Retina:

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

Answer 19

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

Question 20

Engrailed in Tectum

Answer 20

At posterior/caudal, attracts nasal

Question 21

Ephrin-B in Xenopus

Answer 21

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

Question 22

Eph-B in Mouse

Answer 22

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

Question 23

Ephrins in the cortex

Answer 23

thalamus layer 4 attracted by Eprhin A5 ad NT3.

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

Question 24

Ephrin mediates branching in ____

Answer 24

dendrite

Question 25

Ephrin inhibits branching in___

Answer 25

axons

Question 26

Somatographic maps

Answer 26

spatial representation of physical features in nervous system

Question 27

Netrin + what happens when its gone?

Answer 27

some MNs target muscles expressing increased netrin levels. Abolish netrin/netrin receptor = target defects

Question 28

Connectin + what happens when its gone?

Answer 28

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

Question 29

Fas 2/3

Answer 29

Cell adhesion | No major issues if KO, but misexpress = targeting error

Question 30

Semaphorin 2

Answer 30

wrong thing has it = targeting problem

Question 31

Conclusion for all these KO with no big effects?

Answer 31

Relative concentration matters more than presence/absence in target selection

Question 32

Normal muscle 6 and 7 innervation from TN and RP3

Answer 32

6 and 7 both get RP3, TN doesn't innervate either

Question 33

Muscle 6 and 7 innervation from TN and RP3: Increase Fas2 on 6

Answer 33

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

Question 34

Muscle 6 and 7 innervation from TN and RP3: | Increase netrin OR Fas 2 OR decrease Sema 2

Answer 34

TN now innervates 6 and 7

Question 35

Muscle 6 and 7 innervation from TN and RP3: Incrase netrin OR fas 2 and increase Sema 2 (raise/lower together)

Answer 35

TN no innervation, RP3 normal Shows ratio is what is important here

Question 36

Muscle 6 and 7 innervation from TN and RP3: | Decrease netrin OR increase Sema2

Answer 36

RP3 no innervation

Question 37

Neuronal defasiculation: 1) Ko beta-1a 2) KO beta-1a and KO fas2-/-

Answer 37

1) can't defasiculate | 2) KO both defasiculation and fasiculation, so it keeps going and can defasiculate again

Question 38

How does axonal branching occur?

Answer 38

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

Question 39

Goldfish visual system 1) 1/2 tectum 2) 1/2 Retina

Answer 39

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

Question 40

Wilder Penfield Mapping cortical function

Answer 40

homunculi is creepy | Parts of body next to each other tend to have locations next to each other

Question 41

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

Answer 41

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

Question 42

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

Answer 42

1) DRG neurons survive, A innervates in FT areas | 2) DRG axon degenerate F --> F, T --> T

Question 43

Rodent Barrel Cortex Somatotopic Map: 1) Extra whisker 2) Damage/missing whisker 3) Tie 2 whiskers together

Answer 43

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

Question 44

Olfactory mapping

Answer 44

Messy looking, relies on odorant Epithelium --> Glomeruli

Question 45

Odorant receptor protein is on

Answer 45

Axons/dendrites of olfactory neurons

Question 46

Experiment: 1) Normal olfactory mapping 2) P2 receptor deleted 3) Give M71 receptor 4) P2 --> P3

Answer 46

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