Molecular Pathways (Spurway and Wackerhage, 2006)

Question 1

1. Anabolic Signal
   - Stretch

Answer 1

• Can stimulate growth response, but so can isometric

Question 2

1. Anabolic Signal
   - Swelling

Answer 2

• Due to shift of water into muscle
• Leads to integrin signalling = increased PS

Question 3

1. Anabolic Signal
   - Tension

Answer 3

• Titin kinase = tension sensor
• Integrins and dystrophin come under load and trigger PS signal?

Question 4

1. Anabolic Signal
   - Muscle damage

Answer 4

• Occurs after resistance exercise
• Also happens to marathon runners but hypertrophy doesn’t occur

Question 5

2. Skeletal Muscle Growth Factors
   - IGF-1

Answer 5

• Increases in response to GH and testosterone, decreases in response to glucocorticoids
• Promotes MPS, but effect is modulated by IGF binding proteins
• Response to training is inconclusive

Question 6

2. Skeletal Muscle Growth Factors
   - Myostatin

Answer 6

• Negative regulator of growth
• Resistance training may increase expression of myostatin inhibitors
• GH supresses myostatin

Question 7

3. Global Transcriptional Regulation
   - IGF-1

Answer 7

• IGF-1 binding activates PKB
• PKB results in downstream activation of mTOR and p21

Question 8

3. Global Transcriptional Regulation
   - Myostatin

Answer 8

• Myostatin activates Smad2/3, blocks PKB
• Myostatin inhibitors would therefore inhibit Smad2/3 and activate PKB

Question 9

4. Activation of mTOR Signalling Cascade

Answer 9

• Anabolic signal –> increased IGF-1 expression –> increased PKB phosphorylation –> activation of mTOR signalling cascade
• myc increases ribosomal biogenesis
• S6K1 increases PS

Question 10

5. Satellite Cell Proliferation

Answer 10

• Stem cells that proliferate in response to exercise
• Fuse with fibres to increase nuclear content, otherwise DNA content wouldn’t increase with fibre size
• IGF-1 promotes, myostatin inhibits
• Proliferation and nuclear uptake increase in response to resistance training