The Basic Processes of Neurodevelopment

Question 1

What are the 6 processes?

Answer 1

Cell birth
Cell migration
Cell differentiation and maturation
Synpatogenesis
Cell death and synaptic pruning
Myelination

Question 2

What does cell birth refer too?

Answer 2

The production of new neurons

Question 3

How many neurons are found in one hemisphere?

Answer 3

10 billion cells

Question 4

What is the peak of neural development?

Answer 4

250,000 neurons are born per minute

Question 5

Where does cell birth take place?

Answer 5

The neural tube - in the cerebral spinal fluid

Question 6

What are stem cells?

Answer 6

Immature cells

Question 7

What do stem cells form?

Answer 7

They divide, some stay and continue to be a stem cell and some become Progenitor (precursor cells)

Question 8

What can the progenitor cell be?

Answer 8

Either a neuroblast (will become a neuron) or a glioblast (will become glia)

Question 9

What happens once the progenitor cells are formed?

Answer 9

They are formed in the centre of the neural tube but won’t stay there - start to migrate out of this location of birth (migration)

Question 10

What does migration refer too?

Answer 10

The movement of newly formed neurons and glia to their final destinations

Question 11

Why does migration occur?

Answer 11

Because they need to populate different parts of the brain

Question 12

When do the neurons reach their destination?

Answer 12

Some don’t reach it till adulthood

Question 13

How does migration occur?

Answer 13

Chemical signals - signals which attract them to migrate to a particular location

Physical support - from radial glia

Question 14

What are radial glia?

Answer 14

Special cells which are temporarily there for physical support - cells climb along the radial glia with the help of extensions

Axons extend to the outer part of the tube - immaturing neurons use them to find a way and to migrate towards layers

Question 15

What is the function of radial glia?

Answer 15

Scaffolding - help them migrate in a particular way

Question 16

Where do the cells migrate too?

Answer 16

First neurons which migrate stay closer to the inner surface

the rest stand on their shoulders, climbing higher and higher, filling all the layers of the cortex

Question 17

Why is it important migration takes place undisturbed?

Answer 17

Because the cortex has different layers of cells with different functions - need the neurons to migrate to the correct place

Question 18

What happens when neurons meet their point of destination?

Answer 18

They start to differentiate

Question 19

What does differentiation mean?

Answer 19

Expressing particular genes that will allow them to become a cell
Start to form an axon and dendrites that give them a distinctive shape

Question 20

How do they differentiate?

Answer 20

Dendritic arborisation - branching

Growth of dendritic spines

Question 21

Why are dendritic spines there?

Answer 21

To increase the surface area of the dendrites, the more spines we have, the more area we have on the dendrites

other neurons can make other contact - synapsing on other neurons - more available places for them to make contact

Question 22

What is the difference in Brocas area in a newborn compared with older children?

Answer 22

More dendritic branches in the cells in brocas area in the older child - more differentiation

Question 23

What causes the neuron to differentiate in a particular way?

Answer 23

The destination - final region

Question 24

What do immature cells acquire when differentiating?

Answer 24

The characteristics of the cells in the region of implantation, If implanted early - if neurons reach maturity, we cannot do that, they will always have characteristics they came from

Question 25

Why is the area of destination important?

Answer 25

They will acquire the characteristics of the area that brain has

Question 26

What does morphology of neurons refer too?

Answer 26

Many different neurons found in different locations depending on where you look Can have lots of different neurons in the brain

Question 27

What does synaptogenesis refer too?

Answer 27

The formation of synapses / connections between neurons

Question 28

When does synaptogenesis occur?

Answer 28

Begins after the neuron has differentiated occurs throughout life as a response to our experiences, slows down later on neurons are constantly forming new connections and disregarding old ones

Question 29

What does synaptic pruning mean?

Answer 29

Neurons are constantly forming new connections and disregarding old ones - have more than we need

Question 30

What is the growing end of an axon called?

Answer 30

A growth cone - searching for contact

Question 31

How are contacts made between neurons?

Answer 31

Neurons have a growth cone, these develop extensions known as filopodia - make contact with another cell

Question 32

What are growth cones attracted too?

Answer 32

Chemicals released from target cells: cell adhesion molecules tropic molecules - attract or repel growth cones

Question 33

What are filopodia?

Answer 33

The extensions on the growth cone

Question 34

What happens when axons reach their targets?

Answer 34

They form synapses with several cells - but have more connections than they will even need

Question 35

What does neural darwinism mean?

Answer 35

Some connections will be strengthened and some will be eliminated - lots of competition in regards to synapses Most successful connections will survive

Question 36

What instructs neuron to survive?

Answer 36

Proteins secreted by target cells promote the survival and growth - survival signals

Question 37

What factors aid survival of neurons?

Answer 37

Neurotophic factors

Question 38

What happens if a neuron doesn't receive a survival signal?

Answer 38

It will degenerate and die through apoptosis

Question 39

What is apoptosis?

Answer 39

Programmed cell death, silent, good death, happens as we have more than we need

Question 40

Function of apoptosis

Answer 40

Enables the exact matching of the number of incoming axons to the number of receiving cells if things going well, apoptosis is inhibited

Question 41

What is necrosis?

Answer 41

Loud, powerful, damaging death which occurs after injury

Question 42

How can immature neurons avoid apoptosis?

Answer 42

Neurotrophin (growth factors) from its target cell Active communication with other neurons which leads to strengthening of their synapses

Question 43

What does synaptic pruning mean?

Answer 43

Dendritic branches are not fixed, they extend, retract or even disappear spines can appear or disappear over a short period of time these are related to learning or experience

Question 44

What does myelination mean?

Answer 44

The process by which glia produce the fatty sheath which covers the axons of neurons occurs in the spinal cord then in the hindbrain, midbrain and forebrain - front to back

Question 45

Function of myelination

Answer 45

Speed up transition of neural impulses Aids motor behaviour - correlation between myelination and ability to grasp

Question 46

How long does myelination take?

Answer 46

It is a slow process - occurs gradually for decades - depending on the region - Cortex till 18 but prefrontal cortex takes longe

Question 47

Difference between myelination in the PNS and the CNS

Answer 47

PNS - Schwann cells - dedicate themselves exclusively to the axon, 2 Schwann cell on one part of the axon CNS - oligodendroglia (have a few branches) - not all of the branches are on one axon, each branch wraps around a different segment of a different axon. Lots of axon segments covered by one oligodendroglia