Plasticity and Regeneration Flashcards
Which embryonic layer gives rise to the nervous system?
Ectoderm
When does neurogenesis happen in an embryo?
between weeks 3-28.
Which steps are essential for neurogenesis embryonically?
Notochord thickening + neural plate formation
Neural crest formation
Neural tube closure
What type of cells are capable of self-renewal, can divide indefinitely + can differentiate into any cell type?
Stem cells
Can progenitor cells divide indefinitely?
No - they can only go through a limited number before their final differentiation.
What type of stem cells give rise at all the cell types in the nervous system?
Neural stem cells
Where are neural stem cells initially found?
In the neural tube
How do neural stem cells differentiate?
They divide asymmetrically - creating both a stem cell and a progenitor cell (different from mitosis which produces 2 identical daughter cells)
What are stem cells?
Cells that are capable of self-renewal, that can undergo an indefinite number of cell divisions AND can differentiate into any cell type.
What is the difference between stem and progenitor cells?
Stem cells can undergo any amount of divisions and become any type of cell.
Progenitor cells can only undergo a limited number of divisions are are on the “specialisation pathway” to become a certain type of final cell.
What is the name of the process that neural stem cells self-renew / divide?
Asymmetric cell division
What is the process by which neurons are formed?
Stem cell - progenitor cell differentiates - to specialised cell (neuron)
When do neural progenitor cells emerge?
After neural stem cell asymmetric self renewal
Where are migratory cells found?
In the neural crest.
Migratory cells can give rise to what different cell types?
Melanocytes
Craniofacial cartilage + bone
Smooth muscle
Peripheral and enteric neurons
Glia cells
Which receptor regulates the differentiation of progenitor cells towards neurons?
Notch receptor
Which pathway does the Notch receptor utilise?
Delta-Notch signalling pathway
Notch signalling pathway promotes the formation of which cell?
Astrocytes
Notch signalling pathway promotes the formation of what?
Astrocytes
Inhibits:
Oligodendrocytes & Neurons
In cortex development, which antagonist of the Notch pathway regulates the differentiation of progenitor cells to neurons?
NUMB protein
Growth ___ are the growing tips of ____.
Cones
Axons
What is found in the growth cones?
Microtubules, mitochondria & other organelles
Which molecule is important in the growth cone?
Myosin - moves the actin filaments
What is the role of filopodia?
To receive environmental signals through receptor + responding by either advance, retract or turn.
How many layers is the neocortex organised into?
6
When are the 6 layers of the neocortex formed?
By birth
What is the main difference between different layers of the cortex?
Degree of myelination of neurons (more on inside, less the further out on the cortex you go)
What cells are the most abundant in the neocortex?
Pyramidal neurons
What functions take place in the cerebral cortex?
Higher intellectual functions (inc motor and sensory)
What embryological structure forms the ventricular system of the brain?
Neural tube
What is important about the ventricular system in terms of neural crest cells?
They can be found here throughout adult life - as they are stem cells they have the ability to regenerate and differentiate into new nervous system cells - important area of research into treating neurodegenerative disorders,
In cortical development, what do newly formed neurons migrate towards?
The cortical plate
In what direction is the cortex developed?
From the inside out - newly formed neurons travel outwards to form the outer layers of the cortex first - they differentiate as they do - giving rise to the different levels of the cortex.
Which cells assist newly formed neurons in migrating towards the cortical plate?
Radial glial cells
What is the name for the movement of neurons to the outer cortical layers in development?
Radial glial migration
What structures helps the neurons undergo radial glial migration?
Cytoskeleton microtubules
What happens when there are problems with radial glial migration due to mutations?
Can cause disruption of the layers of the cortex - e.g. can have a reverse structure or reduction of the number of layers.
Which cell signalling protein is responsible for cell migration? What happens if this has a mutation?
Reelin
Can get inverted layers of the cortex (outside on the inside).
Which protein is responsible for the cytoskeleton component of migration? What happens if there is mutation to this protein?
Doublecortin
Can get some migration, but not enough, resulting in a reduced number of layers
Adult neurogenesis takes place in which two areas of the brain?
Sub-ventricular zone - in the lateral ventricles
Hippocampus
What is important about the ventricular system in terms of neural crest cells?
They can be found here throughout adult life - as they are stem cells they have the ability to regenerate and differentiate into new nervous system cells - important area of research into treating neurodegenerative disorders.
Why does neurogenesis take place in the olfactory bulb?
Because is often a site of damage from viral infections = loss of smell. Is beneficial to have increased neurogenesis here to combat this problem,
What is migration of neurons controlled by?
SIGNALS
Cellular environment (physical scaffolding = microtubules)
Molecular signals
Electrical signals
What is chemoattraction?
Neurons being chemically attracted to move and adhere to a certain part of the brain
What is chemorepulsion?
Neurons being chemically repulsed away from certain parts of the brain - causing them to grow/move in a different direction
Name a protein that is a chemoattractant in the brain.
Netrin-1
What is neuronal pruning?
The differentiation of neurons is controlled - however the number of stem cells is not = huge amount of neurons, some of which are not needed.
Therefore unutilised neurons will undergo apoptosis to avoid having excess numbers of neurons = pruning,
Which signalling molecules regulate apoptosis of neurons?
Neurotrophins - inc:
Nerve Growth Factor (NGF)
Brain Derived Neurotrophic Factor (BDNF)
Fibroblast Growth Factor (FGF)
What is the difference in terms of outcome after injury for neurons of the CNS and the PNS?
CNS neurons are more sensitive to damage than neurons in the PNS.
PNS has greater amounts of regeneration potential than neurons in the CNS.
Why is there a difference between PNS and CNS neuronal recovery outcomes?
Because of the environment they both exist in.
PNS = lots of phagocytes to clear damaged bits of cells - inc amounts of regeneration.
CNS = macrophages are not as good at clearing up the damage. Also Glial cells inhibit axons from growing here.
What is the term for the time in development where neuroplasticity is optimum for learning a certain skill?
Critical period
What characterises critical periods?
Increased plasticity in an area of the brain
Given an example of a critical period
Language learning skills / accent learning
Bird imprinting
Primate = social interactions & development
Amputations of fingers showed changes in which cortical area to prove there is a degree of plasticity? How?
Somatosensory cortex (postcentral gyrus)
Were observed changes to cortical area that showed areas which previously aligned to the now amputated finger instead respond to stimulations from adjacent skin areas.
What is the name for the somatotropin representation of different body areas on the cortex?
Homunculus.
What evidence of neurogenesis exists in relation to memory?
Recording memories - relies on newly formed neuronal cells in the hippocampal dentate gyrus
In which part of the hippocampus is neurogenesis linked?
Dentate gyrus
