Module 1- Lecture 6

Question 1

Blocking muscle activity allows the survival of more motor neurons

Answer 1

Curare is a blocker of postsynaptic acetylcholine receptors in the muscles

Question 2

What does Curare block in the muscles?

Answer 2

postsynaptic acetylcholine recpetors

Question 3

The neurotrophic factor hypothesis

Answer 3

1) Neurotrophins are secreted by target to bind to receptors in axon tip. This is internalized and signals pro-survival signals back to soma
2) Neurons approach target (target is a source of neurotrophic factor)
3) There is a limited supply of neurotrophic factor
4) Neurons hat do not receive sufficient levels of this signal degenerate through apoptosis (they die of hunger)

In conclusion: Competition for NGF leads to survival of the fittest!

Question 4

At a normal state, the muscle is releasing ten molecules of neurotrophins all across surface area– for neuromuscular paralysis that has been curare treated, what percent is neuronal survival at?

Answer 4

75% because more neurons still have access to the neurotrophins

Question 5

For neurotrophic factor hypothesis in later stages, is the percent of neuronal survival the same as neuromuscular paralysis in early stages?

Answer 5

No, it drops to like 50% (but in limb bud manipulation, when you have more muscle, 75% will be maintained later in developlemtn)

Question 6

LECTURE 6 STARTS NOW

Question 7

Key points:

Answer 7

1) Molecular cues guide axonal growth cones

Question 8

Molecular cues guide axonal growth cones

Question 9

How is adhesion converted into directional cues in the growth cone?

Answer 9

Changes in the level of intracellular regulatory proteins determine whether the same extrinsic cue attracts or repels the growth cone

Question 10

What are intracellular regular proteins determine whether extrinsic cues attract or repel growth cone?

Answer 10

(Ca2+ gradient, cAMP, PKA, protein synthesis for new factors, etc)

Question 11

In slide– Netrin repels growth cone bc of low PKA levels (inactive) versus PKA active plus cAMP growth cone is attracted to Netrin

Question 12

Do chemical or activity cues guide axons to target? What experiment tested this claim?

Answer 12

Key experiment tah demonstrated it was chemical cues that guide axons to target: can cut axons, and they will grow back in frogs

Question 13

How was this experiment done?

Question 14

In what portion of your eye is the visual field flipped?

Answer 14

Retina

Question 15

Anterior neurons project to ____? What about posterior?

Answer 15

Anterior neurons project to posterior tectum, while posterior neurons project to anterior tectum