Neuroscience Flashcards
NS DEV - What is Semaphorin-3A an example of?
Chemoattractant, secreted by cells near the plial surface
NS DEV - What does Semaphorin-3A induce?
Helps establish neural polarity and orientation of cortical neurons
NS DEV - Tests examining the function of Semaphorin-3A
Mutant mice lacking Semaphorin-3A exhibited disrupted orientation of cortical neurons.
NS DEV - What is the key neuronal element for axonal growth?
Growth Cones
NS DEV OR - Who discovered Growth Cones?
Ramon y Cajal
NS DEV What are growth cones?
Sensory structures that receive directional cues from the environment and motor structure that drives axon elongation
NS DEV What are the main components of the growth cones?
Microtubules, Mitochondria and other organelles.
NS DEV How do growth cones sense their environment?
Through Filopodia
What are between Filopodia?
Lamellipodia, which are motile units and give the growth cone its ruffled appearance.
Which 3 ways does Actin drive filopodia movement?
- Actin polymerization, pushing filopodia forward
- Force generated by retrograde flow of actin
- Filopodium contacting adhesive cues, contracting, and pulling the growth cone forward
OR = What hypothesis did Roger Sperry have involvement in?
Chemospecificity Hypothesis
How did Roger Sperry experiment regarding chemospecificity?
Cut optic nerve in frog.
Rotated the frogs eye 180 degrees before the nerves regenerated.
Once healed, presented the frog with fly above head, would jump down, presented below, it would jump up.
RETINAL AXONS HAD REINNERVATED THEIR ORIGINAL TECTAL TARGETS
Where can guidance cues be presented?
Cell surface, Extracellular matrix or as soluble forms
What do guidance cues do?
Either promote or inhibit filopodia growth
Where do growth cones diverge with ganglion cells?
Optic Chiasm
What is able to act as a Scaffold for axons?
A pioneer axon
What happens once a growth cone reaches its target?
Synapse forms
What are neurotrophic molecules
Signal molecules released from targets that keep neurons alive.
E.G Nerve Growth factor, Brain derived Neurotrophic Factor, Neurotrophin 3.
Function of Netrins
Netrin-1 can act as both a chemoattractant and repellent
What does Netrin-1 removal lead to?
Misrouting of Axons
What does Netrin-1 removal lead to?
Misrouting of Axons
Function of SLITS
Chemorepellents, mediated by ROBO and Roundabout receptors
Function of Ephrins
Cell surface signalling molecules, short range, bind to Trks.
Act as repellents and Attractants
Morphogens definition
Specify cell fate during embryonic development
Attractive morphogens
HGF, FGF and GDNF
What are guidance cues?
Signaling molecules that influence cell biological mechanisms by which growth cones extend, turn and retract.
SYNAPSE FORMATION
- Growth cone approach newly fused myotube
- Forms unspecialised contact
- Nerve terminal accumulates synaptic vesicles, basal lamina forms in the synaptic cleft.
- Multiple axons converge on a single site.
- All axons but one are eliminated and surviving terminal matures.
Synaptic pruning
Developmental process by which the brain refines and removes extrasynaptic/redundant synapses within the brain. Whilst others get strengthened and retained.
How do neurons establish?
By trophic regulation, interactions continue to modulate the formation of synaptic connections.
How does synaptic pruning occur?
Through autophagy via microglia which engulf and digest unwanted or unnecessary synaptic connections = elimination.
What does pruning promote?
Strengthening of other synaptic connections.
How has Schizophrenia been linked to synaptic pruning?
Believed that Schizophrenia arises due to synaptic pruning faults. TOO MUCH PRUNING
Which chromosome defect has been linked to Schizophrenia?
Chromosome 6, in which a single nucleotide polymorphism affects the C4 gene.
What involvement does the microtubule cytoskeleton have in Filopodium growth?
Regulates elongation of the axon
What involvement does the actin cytoskeleton have in Filopodium growth?
Regulates changes in the growth cone
How is growth cone growth and movement generated?
By cytoskeleton rearrangements; polymerisation and depolymerisation of actin and tubulin.
Examples of non-diffusable guidance molecules?
Integrins, CAMs, cadherins and ephrins
Diffusable guidance molecules?
Netrins, Slits
Examples of neurotrophic receptors?
Trk - Tyrosine Kinase, promote cell survival, activated by neurotrophins.
p75 receptor - promotes cell death and is inhibited by neurotrophins.
Genetic factors involved in Schizophrenia?
C4 gene splits into C4a and C4b of the complement system.
Too many copies of C4a increase the risk of Schizophrenia.