Wiring a Nervous System

Question 1

guidepost cels

Answer 1

direct outgrowing axons and change their direction

==>alter intracellular signaling with growth cones

Question 2

pioneer neurons

Answer 2

first to grow in uncharted territory

growth cones are active filopodia

Question 3

follower neurons

Answer 3

much simpler growth cones (fewer filopodia)–>latch to pioneers trail and form fasicles

Question 4

some pioneer neurons

Answer 4

are transitory–they die and are replaced by permanent neurons

Question 5

path finding neurons

Answer 5

developming neurons that respond to growth cones (lamellipodia and filopodia)

when they reach target they differentiate into pre syn terminals

Question 6

trophic molecules

Answer 6

support growth and survival

Question 7

tropic molecules

Answer 7

guide

Question 8

extracellular matrix proteins

Answer 8

laminin, collagen, fibronectin

Question 9

function of emp

Answer 9

interact with integrins on axon

• -regulate extend of adhesion of growth cones
• -allow to extend and pull axons along with them

Question 10

cell adhesion molecules are used for

Answer 10

pioneer and follower neurons

Question 11

what are cell adhesion molecules

Answer 11

CAM
Ca-indep
–act as both ligand and R
-hemophilic and heterophilic interactions

promote adherence amongst axon processes

Question 12

chemoattractants/chemorepellants

Answer 12

slit
ephrin
netrin
semaphorin
neurotrophin

Question 13

receptors

Answer 13

roundabout
Eph
DCC
neuropilins & plexins complex
TRR

Question 14

Initial differentiation & axon extension of retina ganglion cells

Answer 14

RGC differentiate as wave, but neuroepitheliam next to wave is INHOSPITABLE because of chondrotin sulfate proteoglycan expression

–>RGC extend axon into optic fiber layer at inner surface of retina

–>Netrin/DCC & cell adhesion molecules attract axons to optic disc

–>run in optic stalk

Question 15

how do RGCs known where to extend their axons?

Answer 15

integrins and cadherins!

and inhib actions of Slit-Robo in outer retina areas

Question 16

Netrin

Answer 16

glial cells surrounding optic disc

Question 17

DCC

Answer 17

R expressed by axons

Question 18

RGC at brain after optic stalk

Answer 18

course towards ventral midline

• ->optic chiasm
• ->temporal retina (ipsilateral) & nasal retina (contralateral)
• ->transition to targets
• ->optic tracts
• ->target (retinotopic maps)

Question 19

why can they project axons into optic chiasM?

Answer 19

decrease SHH at optic recess (which normally inhibits)

Question 20

temporal and nasal retina

Answer 20

ephrin B2/Eph B

NCAM/Sema3d

Question 21

Gap 43

Answer 21

allows to go from chiasm–>optic tract

Question 22

Slit/Robo

Answer 22

repellants to keep axons ont ract

Question 23

CSP6

Answer 23

keep axons from inappropriately crossing di/telencephalon

Question 24

what keeps axons in optic tract

Answer 24

cadherins and integrins

Question 25

fibroblast growth factor

Answer 25

encourages axon extension | if low, encourages axon to stop and stay

Question 26

Nasal RGC terminate in

Answer 26

posterior tectum

Question 27

temporal RGCs terminate in

Answer 27

anterior tectum

Question 28

ephrin A

Answer 28

highest in posterior tectum- repels temporal axons that express RGC meanwhile, eph A highest in temporal area

Question 29

ephA

Answer 29

repels nasal, so since there is low epha in posterior axes-- nasal goes to posterior

Question 30

dorsal RGC go to

Answer 30

medial region

Question 31

ventral RGc go to

Answer 31

lateral region

Question 32

ephrin B/eph B establish

Answer 32

dorsal/ventral axes

Question 33

heparin sulfate proteoglycans

Answer 33

bind to regulate both location and signaling of slit/robo complexes

Question 34

Slit

Answer 34

robo R | secreted by cells in midline to repel axons

Question 35

Nextrin

Answer 35

binds with DCC | attracts axons early on

Question 36

Robo/DCC

Answer 36

blocks netrin response

Question 37

if robo/slit unopposed

Answer 37

no decussation

Question 38

as axons reach midline,

Answer 38

expression of RObo 3 increased

Question 39

ROBO 3

Answer 39

blocks ROBO 1 but does not interat with Netrin-->netrin/slit predominatea and cross midline

Question 40

as cross, get increase sensitivty to

Answer 40

sema 3 repellant | further dissuades axons from turning back around

Question 41

growth cone will turn towards a netrin gradient if

Answer 41

CAMP is high

Question 42

inhibition of CAMp by pka

Answer 42

turns netrin from attraction to repulsion

Question 43

horizontal gaze palsy with progressive scoliosis

Answer 43

mutation in robo3 abnormal morpholgy of abducents nucleus (hypoplasia) absence of normal decussation of corticospinal tract and/or ascending sensory information