Neuro9 - 16 Flashcards
What are the two theories of neuronal connectivity?
Weiss resonance theory, sperry chemoaffinity hypothesis
Outline Weiss resonance theory
Random connection growth, non-functionals are eliminated
Outline Sperry chemoaffinity hypothesis
Direct and specific outgrowth
How did Sperry prove his hypothesis?
Cut optic nerve and remove temporal retina in xenopus, allowing just nasal axons to grow back. If Sperry was correct, specific regrowth occurs, if Weiss, they all regrow, and some deleted. Sperry was seemingly correct.
What was the problem with Sperry’s conclusion?
Acons were already there, so there could be some sort of remnant helping guide them
What are guidance cues?
Factors that axons use to find their correct targets
Where are guidance cues thought to be?
Axons
How was the location of guidance cues tested?
Ablation of axons that are thought to be carrying potential cues
What are early axons referred to as?
Pioneers
What do pioneer axons form?
Scaffold
What are late axons referred to as?
Followers
Where are axons scaffolds important in vertebrates?
Subplate neurons
Where is Ti1?
Grasshopper tibia
What path does Ti1 take?
Right at limb boundary, left lateral of Cx1
What does ablation of Cx1 do to Ti1 path finding?
Stalls at limb boundary
