Exam 5 Flashcards
Retinoic Acid
drives cellular differentiation, regulating transition b/n various classes
BMP
Act as dorsalizing signal to regulate initial specification of neural plate and subsequent differentiation of dorsal part **
Wnt Pathway
regulates cell movement for lengthening neural plate and neural tube *
Sonic Hedgehog
ventralizing signals for motor neuron differentiation*
Delta/Notch signaling
plays a role in neuronal differentation during neurogenesis by regulating neural stem cell decisions to generate either additional stem cells or postmitotic signals *
bHLH
helps determine differentiation of cells
Homeobox transcription factors
regulate segmentation of hindbrain and spinal cord
Reelin
influence detachment of neurons from the radial glia
Function of HOX genes
subset of homeotic genes that encode homeobox transcription factors
Birthdate of neuron
time when precursor/progenitor cell undergoes final cell division and generates a neuroblast
Inside out manner
first born cells are located in the deepest layer (layer 6) and the later born migrate radially to the superficial layer
Symmetric cell division
Produces TWO new stem cells; slow division, self renew
Asymmetric cell division
postmitotic cells that are molecularly distinct from slowly dividing radial glial stem cells
produces stem cell AND a differentiated neuroblast
What does the prosecephalon split into
Telencephalon and Diencephalon
Telencephalon makes
cerebral cortex, hippocampus, basal ganglia, and olfactoru bulb
Diencephalon makes
thalamus and hypothalamus
Rhombencephalon splits into what
metencephalon and myencephalon
Metencephalon
cerebellum and pons
Myelencephalon
medulla
Mesencephalon makes
midbrain tegmentum, superior and inferior colliculi
Function of radial glial cells
instruct cells how to migrate; organizers
PAR
regulate neuronal polarization
Netrin
diffusable axon guidance chemoattractment
Slit
Diffusable axon guidance chemorepellent
Protocadherins
Mediators of synapse specificity
Ephrin/Eph
non diffusable signals for axon guidance and cell to cell recognition codes
Neurexins
Help localize synaptic vesicles, docking proteins, and fusion molecules in the presynaptic active zone
CAM
associated with the bundling or fasciculation of groups of axons
What is the functional consequence for homophillic binding of DSCAM1
generates repulsive signaling which leads to downregulation of DSCAM
What is a neurotrophin
distinct effects on different target neurons; selectively available in different targets to distinguish neurons that innervate them
3 mechanisms of neurotrophins
- neurite outgrowth or retraction
- synapse stabilization or eliminations for activity dependent plasticity
- cell survival or death
What are the neurotrophins
- NGF
- BDNF
- NT-4/5
- NT-3
Receptor for nerve growth factor (NGF)
Trk A
Receptor for brain-deprived neurotrophic factor (BDNF)
Trk B
Receptor for neurotrophin 4 and 5 (NT-4/5)
Trk B
Receptor for Neurotrophin 3 (NT-3)
Trk C
True or False: all neurotrophins activate p75 low affinity neurotrophin receptors
TRUE
What are cells types derived from neural crest cells
Sensory dorsal root ganglion neurons, autonomic ganglion neurons, enteric neurons
Which structures in the mature brain are likely to disappear in patients with holoprosencephaly
Hippocampus, Cerebral Cortex, Basal Ganglia, and Thalamus
What are the steps of neurulation
- formation of the notochord in the mesoderm
- induction of the neuroectoerm in the ectoderm
- folding of the neural plate to form the neural tube
What is the function of the notochord
sends inductive signals to specifiy the ectoderm to differntiate into the neuroectoderm which then gives rise to the entire nervous system
What are three types of neuronal repair
- Peripheral nerve regeneration
- Restoration of damaged CNS neurons
- Wholesale genesis of new neurons
Which of the neuronal repair is most effective
peripheral nerve regeneration
Peripheral nerve regeneration
regrowth of axons from PNS or CNS neurons - peripherally projecting axons are severed
Restoration of damages CNS neurons
- limited
- mostly fails in injured CNS due to overgrowth of glial cells
- local inflammatory response
- glial and immune cells produce signals that inhibit neuron growth and suppress neurite growth
Wholesale genesis of new neurons
- limited
- adult neurogenesis = rare
- nervous tissue must retain population of multipotent neural stem cells in distinct region
What are events for cellular response to PNS injury
- distal portion of injured axon regenerates
- macrophage phagocytose myelin and axonal debris
- schwann cells proliferate and secrete molecules to guide and stimulate growth cone
- axon regrowth to target
What are key molecules involves in PNS injury
- schwann cells
- macrophages
- regenerating sensory or motor neuron
What are events for cellular response to CNS injury
- distal stamp of axons and myelin degenerate
- microglial clear axonal and myelin debris
- reactive gliosis
- glial scar formation & no local production of growth inhibiting molecules
- no regeneration and permanent lesion forms
CNS damage usually happens in what forms
- physical trauma
- hypoxia
- neurodegenerative diseases
What is reactive gliosis
when all three classes of CNS glial cells are activated by proliferation and hypertrophy in response to injury
What are the factors that inhibit axon regrowth
- Physical barrier formed by glial scar
- chemorepellents
- ECM components produced by glial scars
- Myelin associated inhibitors
Chemorepellents that prevent axon regrowrh
semaphorin 3A, ephrin, and slit
What are ECM components produces by glial scarring that prevents axon regrowrh
tenascin and chondortin sulfate proteoglycans
What are the myeline associated inhibitors that prevent axon regrowth
NogoA, MAGm, and OMhp
What are the two neural stem cell niches in adult mammal brains and what do they do
*give rise to post mitotic neurons that can intergrate into existing circuits
1. subventricular zone
2. subgranular zone
Subventricular zone location and function
Location: epithelial lining of anterior lateral ventricles
Function: generate interneurons for olfactory bulbs
Subgranular zone location and function
Location: basal aspect of granule later of dentate gyrus of hippocampus
Function: generate interneurons for hippocampus
What are the cell types that can generate from neural stem cells in adult brains
oligodendrocytes, neurons, and astrocytes