Sliding filament theory

Question 1

What are the thick and thin myofibrils made of?

Answer 1

Thick - myosin

Thin -actin

Question 2

What is a myofibril made up of?

Answer 2

Sarcomeres

Question 3

What happens in contraction?

Answer 3

Actin moves between myosin shortening the sarcomere

Question 4

Step 1 , 2 and 3 of the theory?

Answer 4

Impulse arrives at neuromuscular junction,
Ca2+ released from sarcoplasmic reticulum into sarcoplasm
Ca2+ attach to troponin molecules

Question 5

Step 4,5 and 6 of the theory?

Answer 5

Troponin molecules and attached tropomyosin shift their position exposing myosin binding sites on the actin filaments
Myosin heads bind with myosin binding sites on actin forming cross bridges
ADP and Pi on the myosin head are released

Question 6

Step 7,8 and 9 of the theory?

Answer 6

Myosin changes shape
Myosin head nods forward
Actin moves over the myosin

Question 7

Step 10,11 and 12 of the theory?

Answer 7

ATP molecule binds to the myosin head
Head detacheds
ATPase on myosin head hydrolyses the ATP forming ADP and Pi
Myosin head changes shape

Question 8

Steps 13 and 14 of the theory?

Answer 8

Myosin head returns to upright position

Cycle starts again