Muscle 5

Question 1

What is sliding filament theory based on?

Answer 1

Muscle proteins that slide past each other to generate movement

Question 2

How is the length of muscle affected when muscle contracts?

Answer 2

When muscle contracts, it shortens

Question 3

What remains constant in length during muscle contraction?

Answer 3

The A band

Question 4

What does the A band contain?

Answer 4

Thick filaments of myosin

Question 5

What is the I band rich in?

Answer 5

Thin filaments

Question 6

What changes in length during muscle contaction?

Answer 6

The I band and the length of the sarcomere

Question 7

How is the H zone affected by muscle contraction?

Answer 7

It gets smaller or disappears

Question 8

What does the Sliding filament theory state?

Answer 8

That the sliding of actin past myosin generates muscle tension

Question 9

How is the length of filaments affected during muscle contraction?

Answer 9

The filaments do not change in length but instead slide past each other

Question 10

How are the A band, I band, Z lines, and H zones affected during muscle contraction?

Answer 10

• A band: Remains constant
• I band shortens
• Z lines move closer together
• H zone gets smaller or disappears

Question 11

What is the Cross Bridge?

Answer 11

The head and hinge region of the myosin filament

Question 12

What pulls the actin filaments towards the H zone?

Answer 12

The cross bridges or myosin heads

Question 13

What is the mechanism of contraction?

Answer 13

The binding of actin to myosin forming cross-bridges that generate filament movement

Question 14

What is the energy of ATP converted into during the cross bridge cycle?

Answer 14

Mechanical energy: Force and movement

Question 15

What is the Attached State of the Cross-Bridge Cycle?

Answer 15

When the myosin head is attached to actin

Question 16

What does the attached state represent?

Answer 16

The end of the previous cycle

Question 17

What did the actin and myosin previously release during the attached state?

Answer 17

ADP

Question 18

What happens in the first step of the cross-bridge cycle?

Answer 18

ATP binds to the myosin head causing the myosin to detach from the actin

Question 19

What happens after myosin detaches from the actin in cross bridge cycling?

Answer 19

The ATP is hydrolyzed causing the myosin heads to return to their resting conformation

Question 20

What do the products of hydrolysis of ATP in the cross bridge cycle do?

Answer 20

Remain attached to the relaxed myosin head

Question 21

What is the result of ATP hydrolysis during the cross bridge cycling?

Answer 21

The myosin moves and attaches to a new actin monomer

Question 22

What happens once The myosin binds to a new actin monomer in cross bridge cycling?

Answer 22

The organic phosphate is released from the myosin head, triggering a power stroke causing the myosin to pull the actin filament

Question 23

What happens once the power stroke occurs?

Answer 23

ADP is released from the myosin head and the myosin is in the attached state attached to the actin monomer

Question 24

What does the ATP binding to the myosin head do in cross bridge cycling?

Answer 24

Reduces the affinity of myosin for actin causing it to release from actin

Question 25

What triggers a powerstroke?

Answer 25

The release of inorganic phosphate

Question 26

What causes rigor Mortis?

Answer 26

The lack of ATP to release the myosin head from the attached state

Question 27

How do Cardiac and Skeletal msucle control the cycle of contraction?

Answer 27

By preventing cross bridge formation involving tropomyosin and increased calcium levels