Lecture 15

Question 1

Which are the thin and thick filaments in a sarcomere

Answer 1

The thin filaments are made of actin and are isotonic (let light through). The thick filaments are myosin which are unisotonic

Question 2

Which two proteins bind to actin

Answer 2

Troponin and tropomyosin. Troponin goes through a conformational change when bound to calcium

Question 3

Describe excitation contraction coupling

Answer 3

An action potential is triggered in the muscle fibre
The action potential moves down the T-tubules
DHPR’s sense depolarisation and cause rhyanodine receptors on the SR to open
Ca2+ is released and initiates the cross bridge cycle
Ca2+ is pumped back into the SR by sarcoplasmic and endoplasmic reticulum calcium ATPase (SERCA)

Question 4

What are the three factors that determine force of contraction?

Answer 4

1. Frequency of action potentials
2. Number of motor units activated
3. Active length of muscles