Muscles

Question 1

What defines fibre (speed) type?

Answer 1

Rate of sarcomere shortening

Question 2

What are the 14 events of a muscle contraction?

Answer 2

1. Nerve impulse arrives at axon terminal of motor neuron and triggers release of Acetylcholine.
2. Acetylcholine diffuses across synaptic cleft to receptors and triggers muscle action potential.
3. Acetylcholinesterase in synaptic cleft destroys Acetylcholine.
4. AP travels to transverse tubule to open Ca channels in sarcoplasmic reticulum (SR). Ca floods sarcoplasm.
5. Ca binds to troponin exposing myosin binding site.
6. Myosin binds to actin at 45o.
7. ATP binds to myosin and induces dissociation from actin.
8. ATPase on myosin hydrolysis ATP to access energy.
9. Myosin head moves away from actin. ADP & Pi remain bound to myosin.
10. Myosin head moves to 90o and binds to a new action molecule.
11. Myosin head makes power stroke by releasing Pi and pulls action which goes 45o towards centre of sarcomere.
12. Myosin head releases ADP & troponin releases from tropomyosin and slides back to position to block myosin binding site.
13. Continues until myosin head reaches z-disk.
14. Ca channels in SR close and Ca active transport pumps use ATP to restore low level of Ca in sarcoplasm.

Question 3

How is a stride created?

Answer 3

Muscles turn on/off

Question 4

Describe muscle fibre fatigue

Answer 4

Slow twitch- fatigue resistant
Fast twitch- fatigue resistant for a short time

Question 5

What determines max V?

Answer 5

ATP utilisation rate (=ML/s)

Question 6

What is the difference between type 1 and 2 isoforms?

Answer 6

Type 1 isoforms get rid of ADP faster than type 2 isoforms.
Type 1 myosin retains ADP for longer than type 2 myosin

Question 7

In what order are muscle fibre types used in?

Answer 7

All type 1 fibres used before type 2