L10 GOK

Question 1

What is a growth cone ?

Answer 1

a motile structure at the distal tip of an elongating neural axon

it searches for and detects molecular signposts that are
displayed throughout developing tissues

The growth cone responds to these signs by advancing, pausing and turning until it reaches its proper destination.

Question 2

growth cone description ?

Answer 2

thin flat fan like sheet with many spikes radiating from it

Question 3

Description of different components of GC structure

Answer 3

Lamellipodia = fan-shaped sheet
Filopodia = spikes

Question 4

Filpedia contain what ?

Lamellipodia contain ?

Answer 4

F - actin

L - microtubles

Question 5

How do GC move ?

Answer 5

microtubules grow/ shrink by adding / subtracting subunit from their distal ends

microtubules move into the filopedia and push them forward

Question 6

GC detect which extrinsic cues on the way to its target ?

Answer 6

soluble - long range
surface bound - short range

attractive / repulsive

Question 7

what do these signals cause in the GC ?

Answer 7

trigger changes in membrane ans cytoskeleton dynamics

turn GC

Question 8

what are a major target fro guidance cues ?

Answer 8

the actin and microtubule network

Rho-GTPases which activate intracellular signalling pathways
 Regulate actin-binding and microtubule-binding proteins
 Controls the organisation and distribution of actin filaments and microtubules.

Question 9

Repulsive cues switch on what to cause what ?

Answer 9

Ephrin A switch on RhoA GTPase to reduce GC protusion and cause actin depolymerisation

Question 10

attractive cues switch on what and cause what ?

Answer 10

Netrin1 switch on GTPase Rac1 and Cdc42 increase GC protusion and causes actin polymerisation

Question 11

4 guidance mechanisms

Answer 11

Contact attraction

2) Chemoattraction
3) Contact repulsion
4) Chemorepulsion

Question 12

spinal comissural neurons guidnace describe

Answer 12

BMP repluses axons away from roof plate toward midline

Netrin- DCC attracts axon to floor plate

slit and Robo receptors prvent recrossing at the midline

Wnt attracts rostrally

Question 13

guide post cells of sc comissural fibres

Answer 13

floor plate cells an intermediate for GC axons on the way to their destination

Question 14

is netrin soluble or surface bound ?
attractive effects of netrin through
repulsive effects of netrin through ?

Answer 14

soluble
DCC
UNC5

Question 15

guidance cues divided into 2 types ?

Answer 15

Canonical guidance cues (most well established)

Non-canonical cues

Question 16

cannonical guidance cues families plus receptors

Answer 16

semaphorins, - neurophilins NPN
netrins - UNC5 DCC
EPhrins
Slits - Robo

Question 17

non-cannonical guidance cues

Answer 17

Morphogens - BMP and Wnt , SHH

Growth factors - - GDNF, FGFs, HGF and Neurotrophins

Question 18

Crossing at midline

Answer 18

netrin activates DCC receptor on axon
axon drawn to midline
once in midline upregulation of robo receptor expression
Slit causes replusion via robo
Axon becomes unresponsive to netrin despite DCC expression

Question 19

loss of DCC receptors cause what ?

Answer 19

mirror movements voluntary movement of one limb
accompanied by involuntary movement of other limb, due corticospinal axons
failing to decussate = each hemisphere connected both sides of SC

Question 20

netrin bifunctionality depends on what ?

Answer 20

composition of receptors on axon

intracellualr signalling in GC - Inhibit CAMP using PKA to convert to repulsive