Sliding filament model

Question 1

What is the sliding filament model?

Answer 1

• muscle contraction is usually described using the sliding filament model
• in order to contract and cause movement, the actin and myosin filaments within the myofibrils have to slide past each other

Question 2

What happens during contraction?

Answer 2

• the myosin filaments pull the actin filaments inwards towards the centre of the sacromere

Question 3

What happens to the:

• light band
• dark band
• Z lines
• H-zone

during contraction?

Answer 3

• light band becomes narrower
• dark bands remain the same width
• the z lines move closer together, shortenin the sacromere
• the H-zone becomes narrower

Question 4

Why does this happen to the dark band during contraction?

Answer 4

stays the same width because:

• as the myosin filaments themselves have not shortened
• but now overlap the actin filaments by a greater amount

Question 5

What is relaxation?

Answer 5

when the sacromeres return to their original length, the muscle relaxes

Question 6

How is a great amount of force produced?

Answer 6

the simulataneous contraction of lots of sacromers means that the myofibrils and muscle fibres contract

this results in enough force to pull on a bone and cause movement