axon growth and guidance

Question 1

How many neurons and connections

Answer 1

10’11 neurons 10’14 connections

Question 2

Weiss resenonce theory

Answer 2

random then non functional removed. it is wrong

Question 3

Sperry chemoreceptivce theory

Answer 3

axons with id tags with directed and specific outgrowth. is right

Question 4

name the 4 types of growth cone

Answer 4

long/short atractive/repelant

Question 5

what was found from insect experiments into the growth cone?

Answer 5

Pathways are stereotyped embryo to embryo and segment to segment.

Question 6

Cajals groth cone

Answer 6

is the growing tip of the axon.

Question 7

what are CAMs and CDCs egs

Answer 7

cell adhesion molecules eg IgG and NCAM and calcium dependant cahderin molecues.

Question 8

give examples of experiments that prove Sperry right

Answer 8

Chick embryo notocord reversed still got to targets. Frog cut and removed optic nerve it regrew to original position. grass hopper ti1 uses cx1 as a gidance cell.

Question 9

decribe pineer and follower cells

Answer 9

pioneer cells use cell cues and floor plate interaction to lay the scaffold, then follower or secondary cells use cell adhesion moleucles on the axons to giude them to their destination both are steriotyped.

Question 10

how does c axon sensitivity change

Answer 10

becomes sensitive to repellant after crossing floor plate, before floor plate sensitive to netrin. Semaphorins and slits protein inhibit after floor plate.

Question 11

X levels determine if axon will be comissural, What is X

Answer 11

X is slits receptor.

Question 12

FASII

Answer 12

causes fascicluation, regulated by BEAT.

Question 13

ROBO

Answer 13

Roundabout-encodes for slits receptor lots on non crossing axons. vetebrate homologue ROBO1

Question 14

Commisureless (COMM)

Answer 14

Expressed in C neuons then turned off after crossing. Comm controls ROBO-encodes traficing protein that stops ROBO getting to the cell surface.

Question 15

COMM in veterbrates

Answer 15

trick question you cheeky monkey, However Rig 1 or ROBO3 is expressed only precrossing blocks ROBO 1 until midline.

Question 16

Keep working you’re doing well furry kitten

Answer 16

keep on going otherwise you might get bittern

Question 17

Structure of lamella and filopodia f actin

Answer 17

lamela actin bundles crosslinked net. Filopodia polarised bundles that form larger bundles.

Question 18

Chat about treadmilling (not the gym)

Answer 18

in a resting growth cone treadmilling occurs. If it reaches a target molecular clutch stops the actin movement. a actinmyosin tubule pulls the myosin tuble to the end.

Question 19

Ephrins

Answer 19

non-permissive used in early patterning.detected by eph receptors. Together they make the longitudinal lateral grid for topograhic mapping. ephrins posterior (hi) and anterior. Ephs tempral (hi) to nasal. Ephrins cause repulsion between cells. cause rhombomeres. Can channel axon growth but still need permissive.

Question 20

Semaphorins

Answer 20

membrane bound or secreated sema3. Cause growth cone to turn or inhibit guidance.

Question 21

Lamin

Answer 21

localised in optic nerve permissive but not directive

Question 22

long and short work together example

Answer 22

Sema1 short and Sema2 long direct Ti1

Question 23

Netrin

Answer 23

secreated protien that can associated with extracellular matrix

Question 24

Target derived factors

Answer 24

determine morphology and connection. GDNF turns off Pea 3 so cutaneous maximus and lats have internueron pecs and triceps dont <-monosynaptic.

Question 25

BMP

Answer 25

BMP repels c axons. made by roof plate BMP7 causes growth cone collapse. uesd early on to control neuronal fate.

Question 26

Cycloamine blocks my signal but I require smo who am I.

Answer 26

I am sonic hedgehog

Question 27

Fas3

Answer 27

fasiculin 3 is expressed in axons and the muscle it inervates

Question 28

Circuit compleation relies on target feedback tell me more.

Answer 28

muscle expressed neurotrophin 3 induces TF Er81 by proprioceptors.