Topic 7 Muscular system: Sliding Filament Model

Question 1

• Initially, myosin head is bound to the actin filament from the previous contraction. When ATP binds to the myosin head, myosin and actin unbind. When ATP is converted to ADP + Pi, the myosin head is cocked back
• After death, ATP production ceases. The cross bridges remain locked in place because no ATP is available to bind to myosin head and make it unbind

Answer 1

1. ATP binds to myosin head

Question 2

• Binds to troponin -> pulls back tropomyosin -> exposes attachment sites

Answer 2

2. Ca2+ exposes binding site on actin

Question 3

• Between myosin heads and actin filaments form

Answer 3

3. Cross bridges

Question 4

• The sliding motion of actin brings Z-lines together (contraction, power stroke)

Answer 4

4. ADP + Pi are released

Question 5

• To myosin head, causing cross bridges to unbind – new phosphorylation breaks cross bridge

Answer 5

5. New ATP attached

Question 6

• The strength of contraction of a single muscle fiber cannot be increased, but the strength of overall contraction can be increased by recruiting more muscle fibers. Muscle fibers of a single muscle don’t all contract at once

Answer 6

Note