Plasticity and Regeneration

Question 1

Neurogenesis

Answer 1

the growth and development of nerve tissues

Question 2

What is the germ layer that gives rise to the nervous system?

Answer 2

Ectoderm which forms in week 3 of gestation

Question 3

Neural Tube Development

Answer 3

Question 4

The neural crest are migratory cells that

Answer 4

give rise to diverse cell types: melanocytes etc

Question 5

Stem Cells Definition

Answer 5

capable of self-renewal, indefinite number of cell divisions, can differentiate into any cell type

Question 6

Progenitor Cells Definition

Answer 6

more specialised than stem cells, can differentiate towards a limited number of cell types

go through a limited number of cell divisions priot to differentiation

Question 7

Neural Epithelial cells are stratified cells.

True or False?

Answer 7

False

columnar cells

Question 8

Cells of the neural crest are

Answer 8

stem cells
give rise to all cell types in the nervous system including neurons, oligodendrocytes and astrocytes

Question 9

Neural Progenitor cells emerge after

Answer 9

neural stem cell asymmetric self-renewal

Question 10

Neural Progenitor Cells:

Answer 10

Question 11

What regulates the differentiation of neuroblasts?

Answer 11

the notch receptor of the notochord regulates the differentiation of progenitor cells

notch signaling promotes the formation of astrocytes while it inhibits the formation of neurons and oligodendrocyte

Question 12

The growth cones are

Answer 12

the growing tips of axon

Question 13

Growth Cone and Filopodia: Next step after differentiation in development in the CNS:

Answer 13

• growth cones are growing tips of
  axons
• growth cones are rich in
  microtubules and mitochondria and
  other organelles: which are the
  driving force for growth
• growth cones extent to filopodia and
  sense environmental signals
• within the growth cone and filopodia
  myosin molecules act a motor of
  actin filaments
• the filopodia receive environmental
  signals through the receptor and
  respond by either advancing,
  retracting or turning

Question 14

Filopodia are

Answer 14

slender cytoplasmic projections

Question 15

Chemoattraction vs Chemorepulsion:

Answer 15

guidance of commissural neurons across the ventral midline

commissural neuron axons cross the midline that separates the two hemispheres of the developing brain

the protein netrin-1 is such a chemoattractant = causes formation of neurons that cross the midline/between two hemispheres hence commissural

Slit signal is a chemorepulsion

INSERT DIAGRAM

Question 16

Which of the terms neuroblast/glioblast, neurostem cells, progenitor cells and neuroepithilial cells are interchangable?

Answer 16

• Neuroblasts/glioblasts and
  progenitor cells are the same
• neurostem cells and neuroepithelial
  cell

Question 17

Delta-Notch Signaling Pathway determines and label

Answer 17

whether a neuroepithelial cell will follow the glial or neuronal pathway

Question 18

Cellular events in neuronal development are and regulated by

Answer 18

• in embryonic development approx
  double the number of neurons are
  produced compared to the mature
  brain and spinal cord
• increased apoptosis ensures the
  removal of excess neurons
• this process is regulated through the
  action of neurotrophins nerve
  growth factor (NFG), brain derived
  growth factor (BDNF) and the
  fibroblast growth factor (GFG)

Question 19

Cortex formation begins in —— development, and when are the six layers of the neocortex formed?

Answer 19

• embryonic development
• six (unequal) layers are formed at
  birth

Question 20

Which of the six layers in cortex development has the most myelin and hence axons?

Answer 20

layer six
decreases on the way to layer one

Question 21

How does the cortex develop?

Answer 21

Inside out cortical development

Question 22

Inside-out Cortical Development:

Answer 22

• newly formed neurons migrate
  towards the cortical plate with the
  help of radial glial cells
• migration is achieved through the
  action of cytoskeletal microtubules
• this leads to the formation of the 6
  cortical layers of the cerebellum
• this movement is called radial glial
  migration
• first lower layers develop
  *radial glial cells are differentiated
  neuroepithelial cells

insert diagram

Question 23

Adult Neurogenesis:
- locations

Answer 23

• subventricular zone (SVZ)
• hippocampal dentate gyrus

Question 24

Ventricular System:

Answer 24

Question 25

Adult Neurogenesis: - why not common? - what allows neurogenesis

Answer 25

- neurons are post-mitotic cells but two exceptions (SVZ, hippocampus) - neural crest cells are found and hence stem cells which can still regenerate

Question 26

Adult Neurogenesis Process: Replace Olfactory Neurons:

Answer 26

- neural crest stem cells = neuroblasts - differentiate into immature neurons - migrate to the olfactory bulb along the Rostral Migratory Stream - then integrate into the already formed neuronal network - migration is guided by the cellular environment, molecular and chemical signals - migration also depends on cytoskeletal rearrangements

Question 27

CNS vs PNS Regeneration:

Answer 27

- Neurons of the CNS have a different outcome following injury compared to PNS - in CNS oligodendrocyte myelinate axons but in PNS schwann cells myelinate - axons can still grow even if damaged but oligodendrocytes will not regenerate myelin sheath but schwann cells will reform the sheath - in CNS hindered as it is a compromise to keep networks stable as there is immediately phagocytic activity and invasion of astroctyes - glial scar is formed and axon in CNS can not grow

Question 28

The Critical Period Concept:

Answer 28

- time during postnatal neural development where neuronal plasticity depends on environmental signals - more accurate to have different critical periods for different brain functions - ***critical periods are charcaterised by increased plasticity - strictly: sensitive period, the time when a sensory signal is received and followed by a period of increased neuronal plasticity - if something is learnt outside of the critical period the learning will not be as great later in life

Question 29

Examples of Critical Period in Development:

Answer 29

- language skills - accent learning - bird imprinting: hatchling immediately attached to a moving entity and important for survival of new bird - primates can see early social interactions are essential for social development

Question 30

Cortical Plasticity:

Answer 30

- adult brain characterised by low incidence of regeneration - some degree of ***plasticity in the somatosensory cortex located in the postcentral gyrus - when fingers are amputated there are changes in the cortical area to reflect that, cortical areas corresponding to missing fingers now respond to stimulations from adjacent skin areas - cortical plasticity diminishes with age

Question 31

Primary Somatosensory Cortex:

Answer 31

- somatotopic representation of the different body areas of the cortex - resembles a homunculus - some body regions have a high number of sensory receptors and are assigned a larger cortical area while other regions with low density of sensory receptors correspond to a smaller cortical area

Question 32

Computational Theories of Memory:

Answer 32

- recording new memories rely on the emergence of newly formed neuronal cells in the hippocampal dentate gyrus - older memories are encoded in the pre-existing neuronal network

Question 33

Axon guidance is regulated by specific signalling cues that cause chemoattraction or chemorepulsion. True or False?

Answer 33

True

Question 34

Neuronal differentiation relies on the formation of growth cones, microtubule supported cell migration, signalling pathways, apoptosis of surplus cells. True or False?

Answer 34

True

Question 35

Neurogenesis in the hippocampus has been shown to assist formation of new memories. True or False?

Answer 35

True (hippocampal dentate gyrus)

Question 36

Some neuronal axons (PNS) are characterised by regenerative capacity, while few cortical neurons exhibit plasticity even in the adult CNS. True or False?

Answer 36

True

Question 37

Neurogenesis begins early in embryonic development with the formation of the neural tube and the differentiation of neural stem cells towards glial cells and neurons. True or False?

Answer 37

True