Brain Wiring

Question 1

What are the five positions of cellular proliferation?

Answer 1

1. Ist position - A cell in the ventricular zone extense a process that reaches upward toward the pia
2. 2nd position - The nucleus of the cell migrates upward from the ventricular surface towards the pial surface the cell’d DNA is copies
3. 3rd position - The nucleus containing two complete copies of the genetic instructions, setteles back to the ventricular surface
4. 4th posiiton - the cell retracts its arm from the pial surface
5. fifth position - The cell divides in two

The cell than divides vertically or horiziontally

Question 2

What is the result of a cell dividing horizontally? When does this happen in development?

Answer 2

The daughter cell lying furthest away from the ventricular surface migrates away to take up its position in the cortex, where it never divides again. The other daughter cells stays in the ventricular zone to divide more.

Happens in later development

Question 3

What is the result of a cell dividing vertically? When does this happen in development?

Answer 3

Both daugher cells remain in the ventricular zone to divide again and again,

Happens early in development

Question 4

What happens to notch-1 and numb transcription factors during vertical or horizontal division?

Answer 4

Vertical - Notch-1 and numb are equally divided among daughters, allowing them to continue dividing

Horizontal - Notch-1 migrates with the cell that goes to the cortex, numb remains with the cell that will divide again.

Question 5

What type of cells make the scaffolds that neuroblasts climb up during cell migration?

Answer 5

radial glial cells

Question 6

What are young migrating neurons called?

Answer 6

neuroblasts

Question 7

In what order does the cortex build itself through cell migration?

Answer 7

1.Subplate
Cortical plate becomes below
2. layer IV
3. Layer V

etc. etc.

Question 8

Which protein regulates the assembly of the cortex as a transcription factor?

Answer 8

reeler

Question 9

What order do cells of the brain differentiate?

Answer 9

1. Neuronal differentiation
2. Astrocyte differentiation
3. Oligodendrocyte differentiation

Question 10

What repels growing pyramidal cell axons and attracts apical dendrites? Where is it secreted?

Answer 10

Secreted into the marginal zone.

Semaphorin 3A

Question 11

What causes cytoarchitectural differences in adult brain cortex?

Answer 11

The arrival of thalamic axons to the cortex

Question 12

What are the three phases of axon development?

Answer 12

1. Pathway selection
2. Target selection
3. Address selection

Question 13

What does the glycoprotein laminin do? (hint, part of extracellular matrix)

Answer 13

Axon expresses special surface molecules called intergrins that bind laminins from extracellular matrix, this promotes axonal elongation. This can direct axonal growth

Question 14

What is it called where axons grow and stick together?

Answer 14

fasciculation

Question 15

What allows fasciculation of axons to happen?

Answer 15

Cell-adhesion molecules (CAM)

Question 16

What type of molecule attracts a growing axon? What is an example?

Answer 16

Chemoattractant

Netrin

Question 17

What is an example of a chemorepellant?

Answer 17

slit, chases axons away

Question 18

What must axons have in order to be affected by slit?

Answer 18

The protein robo

Question 19

What is the chemoaffinity hypothesis?

Answer 19

That growing axons express proteins that are matched complementary with chemical markers on their targets to establish precise connections.

Question 20

What are the steps of synapse formation?

Answer 20

1. Postsynaptic receptos begin clustering under growth cone
2. Agrin is depositied in the extracellular space at point of contact
3. Layer where receptors are is called basal lamina
4. Muscle specific kinase binds to agrin which causes rapsyn to gather posysynaptic ACh receptors at the synapse
5. Nueregulin regulates the amount of receptors expressed
6. Entry of calcium into the growth cone causes it to trigger transmitter release and finally mature (through a couple weeks cytoskeleton and others change)

Question 21

How do neutrophins such as nerve growth factor (NGF) save neurons from apoptosis?

Answer 21

Switching off the genetic program for apoptosis that all neruons have

Question 22

What causes selective cell death in brain development neurons?

Answer 22

Competition for trophic factors

Question 23

What is the condition where eyes are not perfectly aligned?

Answer 23

Strabismus

Cortical cells are not binochular with strabismus, ocular dominance groups are sharply segregated to left or right eye

Question 24

What two diffuse modulatory systems effect plasticity?

Answer 24

• Cholinergic basal forebrain complex

- Epinephrinergic locus coeruleus

Question 25

What three things cause critical periods to end?

Answer 25

1. Axon growth ceases
2. Synaptic transmissions mature
3. Plasticity dimishes when cortical activation is constrained