3.8 Development of multicellular organisms 2

Question 1

How many phases are there in neural development?

Answer 1

3

Question 2

What happens in phase 1?

Answer 2

Different cell types develop independently at widely separate location in embryo according to local program and are unconnected.

Question 3

what happens in phase 2?

Answer 3

axons and dendrites grow along specific routes setting up a provisional but orderly network of connections between various parts of the system.

Question 4

What happens in phase 3?

Answer 4

continues into adult life, connections are adjusted and refined through interaction with distant regions via electric signals.

Question 5

Neurons are produced in association with what cells?

Answer 5

glial

Question 6

Neurons and glial cells devlop from where?

Answer 6

ectoderm

Question 7

What consists of the CNS?

Answer 7

brain spinal cord, retina

Question 8

What consists of the PNS?

Answer 8

nerves, sensory nerves

Question 9

The CNS is derived from what?

Answer 9

neural tube

Question 10

The PNS is derived from what?

Answer 10

neural crest.

Question 11

What does the sonic hedgehog do?

Answer 11

Activate latent genes, Transcription repression to activation. Depend on proteoglycans for function.

Question 12

What does BMP do?

Answer 12

pattern formation, differentiation, secretion of extracellular matrix

Question 13

The neural crest cells originate at what end of the neural tube?

Answer 13

dorsal end.

Question 14

What 3 cell types does the neural crest produce?

Answer 14

neurons and glial cells of PNS. Epinephrine cells of adrenal gland. Skeletal and connective tissue components of the head.

Question 15

Fate of the neural crest cells depends on what?

Answer 15

Where they migrate and settle

Question 16

What is the structure of a neuron?

Answer 16

cell body, long axon, and dendrites

Question 17

Where is the growth cone?

Answer 17

Tip of axon/dendrite

Question 18

What forms the axon?

Answer 18

one of the growth cone starts migrating fast and develops axon specific proteins

Question 19

How is growth cone behavior dictated by?

Answer 19

its cytoskeltal machinery

Question 20

What 2 things do growth cones throw out?

Answer 20

filopodia and lamelopodia

Question 21

What two monomeric GTPases control the assembly and disassembly of actin filaments, which control movement of growth cone?

Answer 21

rho and Rac

Question 22

how do growth cones know where to find their way? 2 ways

Answer 22

extracellular matrix environment and chemotactic factors.

Question 23

How does the extracellular matrix environment work via growth cones?

Answer 23

Sensed by receptors present on membrane

Question 24

How do chemotactic factors work via growth cones?

Answer 24

Released by neighboring cells. Attract or repulse.

Question 25

What is contact guidance?

Answer 25

path taken by other cells that growth cones often follow

Question 26

the extracellular matrix is mediated by what molecules?

Answer 26

homophilic cell adhesion molecules

Question 27

What are the 2 classes of homophilic cell adhesion molecules?

Answer 27

immunoglobulin superfamily and cadherin family.

Question 28

Extracellular matrix provides a mechanism for what two things?

Answer 28

selective guidance and recognition

Question 29

Matrix molecules such as laminin favor what?

Answer 29

axonal outgrowth

Question 30

Chondroitin sulfate proteoglycans inhibit what?

Answer 30

growth

Question 31

Dorsal neurons of spinal cord receive and relay sensory info from what

Answer 31

sensory neurons located in the periphery of the body

Question 32

Ventral clusters of spinal cord neurons develop as what?

Answer 32

motor neurons

Question 33

What do motor neurons do?

Answer 33

send out long axons to connect with specific subset of muscles

Question 34

Intermediate location has inter neurons that do what?

Answer 34

connect specific set of nerve cells to each other

Question 35

What are chemotactic factors?

Answer 35

secreted by cells, act as guidance factors at stretegic points along path

Question 36

What are 3 ex of chemotactic factors?

Answer 36

Slit, Semaphorin and Netrin

Question 37

What does the first stage of commissural neuron guidance depend on?

Answer 37

Secretion of netrin by cells of the floor plate

Question 38

binding of netrin to its receptor causes what?

Answer 38

opening of TRPC channels.

Question 39

opening of TRPC channels allows for what?

Answer 39

entry of extracellular calcium

Question 40

After calcium has entered, what does this lead to?

Answer 40

Lead to activation of machinery for filopodia and movement of growth cone.

Question 41

What neurons do not have netrin receptors?

Answer 41

Non commissural neurons

Question 42

Since non commissural neurons in neural tube dont have netrin receptors, what does this mean?

Answer 42

non commissural neurons dont migrate towards floor plate

Question 43

What cells secrete slit?

Answer 43

midline cells

Question 44

Whats the name of the slit receptor that is present on commissural neurons?

Answer 44

roundabout

Question 45

What does slit do?

Answer 45

repels growth cones and blocks entry to the midline

Question 46

What is semaphorin?

Answer 46

a repulsive signal that gets growth cones to become sensitive

Question 47

Why do growth cones travel in a narrow track?

Answer 47

Because they are trapped between 2 sets of repellents

Question 48

Do axonal growth cones reach their target cells?

Answer 48

yes

Question 49

When axonal growth cones reach their target cells what happens?

Answer 49

they halt, communicate and make synapses with target cells

Question 50

Signal from target tissue regulate what?

Answer 50

which growth cones synapse and where

Question 51

What two rules is synaptic remodeling dependent on?

Answer 51

1. Axons from cells in dif regions of retina compete for tectal neurons. 2. Axons from neighboring sites which are excited at same time cooperate/collaborate to retain and strengthen synapses with tectal neurons

Question 52

What two things does activity dependent synaptic remodeling depend on?

Answer 52

electrical activity and synaptic signaling.

Question 53

Posterior retinal neuron axons prefer what type of tectal neurons?

Answer 53

anterior

Question 54

Anterior retinal neurons prefer what type of tectal neurons?

Answer 54

no preference.

Question 55

Neurons that fire together also what together?

Answer 55

wire together

Question 56

Synapses are strengthened by what?

Answer 56

external events that cause 2 or more neurons to be activated at the same time.

Question 57

What triggers lasting change in synaptic strength?

Answer 57

enty of calcium through the NMDA receptor