Structure of the myofibril

Question 1

What are light bands/I-bands?

Answer 1

• Where actin and myosin do not overlap

Question 2

What are dark bands/A-bands?

Answer 2

• Myosin is present.
• Darkest edges are where myosin and actin overlap.

Question 3

What are the z-lines?

Answer 3

• The line at the centre of each light band.

Question 4

What is a sarcomere?

Answer 4

• The distance between two adjacent z-lines.
• Gets smaller when the muscle fibre contracts.

Question 5

What is a H-zone?

Answer 5

• Lighter coloured region in the centre of each dark band.
• Only myosin present.