Muscle 5 Flashcards
What is sliding filament theory based on?
Muscle proteins that slide past each other to generate movement
How is the length of muscle affected when muscle contracts?
When muscle contracts, it shortens
What remains constant in length during muscle contraction?
The A band
What does the A band contain?
Thick filaments of myosin
What is the I band rich in?
Thin filaments
What changes in length during muscle contaction?
The I band and the length of the sarcomere
How is the H zone affected by muscle contraction?
It gets smaller or disappears
What does the Sliding filament theory state?
That the sliding of actin past myosin generates muscle tension
How is the length of filaments affected during muscle contraction?
The filaments do not change in length but instead slide past each other
How are the A band, I band, Z lines, and H zones affected during muscle contraction?
- A band: Remains constant
- I band shortens
- Z lines move closer together
- H zone gets smaller or disappears
What is the Cross Bridge?
The head and hinge region of the myosin filament
What pulls the actin filaments towards the H zone?
The cross bridges or myosin heads
What is the mechanism of contraction?
The binding of actin to myosin forming cross-bridges that generate filament movement
What is the energy of ATP converted into during the cross bridge cycle?
Mechanical energy: Force and movement
What is the Attached State of the Cross-Bridge Cycle?
When the myosin head is attached to actin
What does the attached state represent?
The end of the previous cycle
What did the actin and myosin previously release during the attached state?
ADP
What happens in the first step of the cross-bridge cycle?
ATP binds to the myosin head causing the myosin to detach from the actin
What happens after myosin detaches from the actin in cross bridge cycling?
The ATP is hydrolyzed causing the myosin heads to return to their resting conformation
What do the products of hydrolysis of ATP in the cross bridge cycle do?
Remain attached to the relaxed myosin head
What is the result of ATP hydrolysis during the cross bridge cycling?
The myosin moves and attaches to a new actin monomer
What happens once The myosin binds to a new actin monomer in cross bridge cycling?
The organic phosphate is released from the myosin head, triggering a power stroke causing the myosin to pull the actin filament
What happens once the power stroke occurs?
ADP is released from the myosin head and the myosin is in the attached state attached to the actin monomer
What does the ATP binding to the myosin head do in cross bridge cycling?
Reduces the affinity of myosin for actin causing it to release from actin
What triggers a powerstroke?
The release of inorganic phosphate
What causes rigor Mortis?
The lack of ATP to release the myosin head from the attached state
How do Cardiac and Skeletal msucle control the cycle of contraction?
By preventing cross bridge formation involving tropomyosin and increased calcium levels
