KD - Target Innervation Flashcards
What do guidance signals guide?
Growing processes in the embryo
What are different classes of guidance signals? (4)
- Attractive
- Repulsive
- Short range
- Long range
Act via concentration gradients
Interpreted by a growth cone
Guidance signals can be…
“non-diffusible”:
- Short range
- Substrate derived: ECM
- Presented on target cells: cadherins, ephrins
“diffusible”:
- Can act as gradients
- Long range
- Netrin, semaphorins
How do we know about guidance signals?
Guidance signals are identified through explant, cell culture experiments, and genetic studies
How are guidance signals sensed?
Via Growth cones
What are some properties of growth cones? (3)
1) At the tip of growing axons and dendrites
2) Hand-like structures with receptors on the surface
3) Senses guidance cues
Why do not all neurons cross during development?
Due to long-range repulsion
What is the role of adhesion molecules in synapse formation?
Stabilise formed connections
Presynaptic neurexins vs Postsynaptic neuroligins
Presynaptic neurexins: organise the synaptic vesicle docking zone
Postsynaptic neuroligins: recruit PSD (scaffolding protein) which recruit neurotransmitter receptors
How is the decision made to maintain or abandon synapses?
Influenced by factors like neurotrophins and electrical activity
- Determine the final pattern of synaptic contacts.
Who discovered developmental cell death?
Victor Hamburger
- Discovered limb removal results in reduced numbers of motor and sensory neurons in the chick spinal cord (1934)
Once neural circuits are formed, what regulates them? (3)
- The target – continued release of trophic factors; activity
- Learning and memory
- Disease
