Target Selection and Topographic Maps

Question 1

What type of muscles do medial MNs innervate?

Answer 1

Axial

Question 2

What type of muscles do lateral MNs innervate?

Answer 2

Distal

Question 3

What type of receptor is Eph?

Answer 3

Tyrosine kinase

Question 4

Where does FGFR1 guide axons?

Answer 4

To axial muscle

Question 5

Where does EphB1 guide axons?

Answer 5

To ventral limb mesenchyme

Question 6

Where does EphA4 guide axons?

Answer 6

To dorsal limb mesenchyme

Question 7

Which receptor does EphrinB bind to?

Answer 7

EphB1

Question 8

What is the concentration gradient of EphrinB and what is its effect?

Answer 8

High dorsally, low ventrally

Repels axons to ventral side of limb

Question 9

Which receptor does EphrinA bind to?

Answer 9

EphA4

Question 10

What is the concentration gradient of EphrinA and what is its effect?

Answer 10

High ventrally, low dorsally

Repels axons to dorsal side of limb

Question 11

What is the effect of attractive cues?

Answer 11

Actin assembly and microtubule stabilisation on ipsilateral side

Question 12

What is the effect of repulsive cues?

Answer 12

Actin assembly and microtubule stabilisation on contralateral side

Question 13

Which molecules regulate the cytoskeleton?

Answer 13

Rho family GTPases

Question 14

Name 3 Rho family GTPases and describe their effects

Answer 14

Cdc4 - lamellipodia and filopodia - growth cone extension
Rac - filopodia - growth cone extension
Rho - stress fibres - growth cone retraction

Question 15

What are the key features of topographic maps?

Answer 15

Neighbouring cells in one area connected to neighbouring cells in another area
Order of neurons maintained

Question 16

What are the key features of discrete maps?

Answer 16

Cells expressing same receptor type map to same place - glomeruli

Question 17

Which parts of the retina and tectum are connected by axons?

Answer 17

Temporal retina to rostral tectum - nasal retina to caudal tectum
Posterior retina to anterior tectum - anterior retina to posterior tectum

Question 18

Describe Sperry’s experiment

Answer 18

Rotated frog eye before axon growth

Axons still went to correct part of tectum - respond to cues in tectum

Question 19

What is the ephA gradient in the retina?

Answer 19

High temporally, low nasally

Question 20

What is the ephrinA gradient in the tectum?

Answer 20

High caudally, low rostrally

Question 21

What is the ephB gradient in the retina?

Answer 21

High ventrally, low dorsally

Question 22

What is the ephrinB gradient in the tectum?

Answer 22

High medially, low laterally