Co-Ordination And Control (Muscle)

Question 1

What is the Z line within a scaromere of a microfibril?

Answer 1

Bands of connective material which thin (actin) filaments are attached.

Question 2

What is the M line within a sarcomere of a microfibril?

Answer 2

Bands of connective material which thick (myosin) filaments are attached. They are found within the middle of the sacromere.

Question 3

What is the A bands within a sarcomere of a microfibril?

Answer 3

Thick (myosin) filaments extend the length of the central parts of the sarcomere. Thick and thin bands overlap. This band appears the darkest.

Question 4

What is the H zone within a sarcomere of a microfibril?

Answer 4

Only thick (myosin) filaments are found here. This band looks intermediate in colour.

Question 5

What is the I band within a sarcomere of a microfibril?

Answer 5

Only thing (actin) filaments found here. This band looks the lightest.

Question 6

What happens to the sarcomere when the muscle contracts?

Answer 6

• actin filaments are pulled between the myosin filaments towards the centre of the sarcomere (individual filaments remain the age length)
• I bands and H zone become narrower
• sarcomere becomes shorter
• Z lines become closer
• A bands remain the same length

Question 7

What is the Sliding Filament Theory?

Answer 7

• Action potential arrives. Reaching threshold value so sarcolemma becomes depolarised
• Ca2+ ions released into cytoplasm
• Ca2+ ions uncover binding site on actin filaments
• Myosin molecules attach to actin filaments forming acto-myosin bridges
• Myosin head rotates pulling actin filament over mysoin. Towards the centre of the sacromere.
• ATP binds with mysoin head, its hydrolysed and energy released causes the head to detach from the actin filament
• This process of attachment, rotation and detachment is repeated.