Lec 14: Skeletal muscle contraction

Question 1

Describe how contraction happens in skeletal muscles

Answer 1

myosin binds to actin and slides it, pulling the Z-lines closer together, reducing the width of the I bands. Myosin’s cross-bridges bind to actin, the crossbridges then flex to slide actin. Caclium ions binds to troponin, pulling tropomyosin away from the crossbridge binding site. The energized cross bridge binds, the bound crossbridge flexes, new ATP binds and cross bridge is uncoupled, the bridge gets put back together due to partial hydrolysis of bound ATP

Question 2

Define isometric in relation to single fibre contraction

Answer 2

constant length

Question 3

Define isotonic in relation to single fibre contraction

Answer 3

constant tension

Question 4

ATP production via substrate phosphorylation is supplememted by the availabilty of ….?

Answer 4

creatine phosphate

Question 5

ATP production via oxidative phosphorylation is further supplemented by…?

Answer 5

availability of molecular oxygen bound to intracellular myoglobin

Question 6

Describe slow-oxidative (type 1) fibres

Answer 6

low myosin ATPase, high oxidative capacity, myosin motor is slow. They respond well to repetitive stimultation without becoming fatigued eg muscle of body posture

Question 7

Describe fast-oxidative glycolytic fibres (type 2a)

Answer 7

High myosin ATPase, high oxidative capacity, intermediate glycolytic activity, responds quickly and to repetitive stimulation without becoming fatigued, eg muscles used in walking

Question 8

Describe fast-glycolytic fibres (type 2b)

Answer 8

high myosin ATPase, high glycolytic activity. They dont last very long but produce a lot of force