Brain development

Question 1

What are guidance signals interpreted by?

Answer 1

Growth cone

act via concentration gradients of morphogens

Question 2

What are non-diffusible guidance signals ?

Answer 2

short range
sub derived
ECM or on target cells (cadherins and ephrins)

Question 3

What are diffusible guidance signals ?

Answer 3

Long range
act as gradients
Netrins, semaphorins

Question 4

What are growth cones ?

Answer 4

hand like structures
at the tip of growing axons and dendrites
receptor on surface
senses guidance cues

Question 5

What is the role of the cytoskeleton in responding to guidance cues ?

Answer 5

Microtubules reinforce the structure, pilloponea project out
Actin filaments for movement
polymerisation = direction o growth cone

Question 6

How do we know about guidance signals ?

Answer 6

Cell culture experiments

Question 7

How do repulsion and attraction work together?

Answer 7

Long attraction interplay of attraction and repulsion to drive growth to midline
Switch to repulsion at midline to be pushed forward

Question 8

How are synapses formed ?

Answer 8

Adhesion mols stabilise formed connections
Presynaptic neurexins: org SV docking zone
Post neuroligins: recruit PSD

Question 9

What determines the synapses worth keeping?

Answer 9

Neurotrophins + electrical activity

Question 10

How do axons navigate ?

Answer 10

Via intermediate targets

Axons grow along another as guides

Question 11

What are the transient structures of brain development ?

Answer 11

Notochord, floor plate and roof plate

Question 12

What does the anterior end turn into after neurogenesis ?

Answer 12

The brain

Question 13

What does the neural tube near somites turn into after neurogenesis ?

Answer 13

Spinal cord

Question 14

What structure is a major part of the PNS ?

Answer 14

Neural crest

Question 15

How do neurones become different ?

Answer 15

High degree of patterning in neural tube

Patterning along the anterior (rostal) and posterior (caudal) length of tube

Question 16

What are morphogens ?

Answer 16

Activate/ repress transcription factors
Are secreted molecules (extracellular)
Work via gradients

Question 17

What part of the brain distinguishes humans from other animals ?

Answer 17

The size of the cortex, especially frontal lobe.

Distinguishes personality and decision making

Question 18

What causes differentiation ?

Answer 18

Morphogen gradients
Distance from secreting cells (gradients) / availability of ligand and presence of receptors determines the response of the cell

Question 19

What are the 5 steps of neurogenesis ?

Answer 19

Neural plate develops from overlying ectoderm
Plate folds inward and closes neural tube
Floorplate about notochord
Where tube closes = roof plate
Neural crest plate on top

Question 20

What are hox genes ?

Answer 20

Family of transcription factors

Establishes segmentation along anterior-posterior axis

Question 21

How is the cortex built ?

Answer 21

Migration

Neuroepithelium progenitor cells in neural tubes (neural precursor cells) form the ventricular zone

Question 22

What do radical glia do?

Answer 22

Connect ventricular and pial surface

Question 23

What are neuroblasts ?

Answer 23

precursors of a nerve cell, undifferentiated

which migrate to pial surface to make the marginal zone

Question 24

Why is the cortex described to be built inside out ?

Answer 24

Newer neuroblasts migrate past the older ones

Question 25

What are the two places the glia remain?

Answer 25

1. Remain attached to lumen + become ependymal cells (product of spinal fluid)
2. Move to marginal layer + form astrocytes or oligodendrites

Question 26

What do astrocytes do?

Answer 26

Repair and maintenance