KD - Target Innervation

Question 1

What do guidance signals guide?

Answer 1

Growing processes in the embryo

Question 2

What are different classes of guidance signals? (4)

Answer 2

1. Attractive
2. Repulsive
3. Short range
4. Long range

Act via concentration gradients

Interpreted by a growth cone

Question 3

Guidance signals can be…

Answer 3

“non-diffusible”:
- Short range
- Substrate derived: ECM
- Presented on target cells: cadherins, ephrins

“diffusible”:
- Can act as gradients
- Long range
- Netrin, semaphorins

Question 4

How do we know about guidance signals?

Answer 4

Guidance signals are identified through explant, cell culture experiments, and genetic studies

Question 5

How are guidance signals sensed?

Answer 5

Via Growth cones

Question 6

What are some properties of growth cones? (3)

Answer 6

1) At the tip of growing axons and dendrites

2) Hand-like structures with receptors on the surface

3) Senses guidance cues

Question 7

Why do not all neurons cross during development?

Answer 7

Due to long-range repulsion

Question 7

What is the role of adhesion molecules in synapse formation?

Answer 7

Stabilise formed connections

Question 8

Presynaptic neurexins vs Postsynaptic neuroligins

Answer 8

Presynaptic neurexins: organise the synaptic vesicle docking zone

Postsynaptic neuroligins: recruit PSD (scaffolding protein) which recruit neurotransmitter receptors

Question 9

How is the decision made to maintain or abandon synapses?

Answer 9

Influenced by factors like neurotrophins and electrical activity
- Determine the final pattern of synaptic contacts.

Question 10

Who discovered developmental cell death?

Answer 10

Victor Hamburger
- Discovered limb removal results in reduced numbers of motor and sensory neurons in the chick spinal cord (1934)

Question 11

Once neural circuits are formed, what regulates them? (3)

Answer 11

1. The target – continued release of trophic factors; activity
2. Learning and memory
3. Disease