Myofibrils and basis of contraction

Question 1

What 2 proteins make up the sarcomere?

Answer 1

Actin and myosin

Question 2

How does an action potential travel from motor neurone into muscle fibre?

Answer 2

Via T tubules

Question 3

What occurs when action potential reaches sarcoplasmic reticulum?

Answer 3

Calcium channels open and calcium ions diffuse into sarcoplasm

Question 4

What do the calcium ions bind to and what effect does it have?

Answer 4

Troponin, this moves the tropomyosin molecule which exposes the myosin binding site on the actin filament

Question 5

What happens when myosin head attaches to actin?

Answer 5

Myosin head changes shape, pulling the actin filaments, releases ADP

Question 6

What effect does ATP have on myosin head?

Answer 6

Changes its shape causing it to detach from actin

Question 7

How does the myosin heads then return to its normal position?

Answer 7

ATP is broken down by ATPases

Question 8

What activates ATPases?

Answer 8

Calcium ions