BIOL 0800 Reading- Chapter 9 Flashcards
(121 cards)
What is a myoblast?
Undifferentiated, mononucleated cells that formed into a single cylindrical and multinucleated cell
What are satellite cells?
Undifferentiated stem cells that repair muscle in response to strain or injury
What are tendons?
Attach muscles to bones; bundles of collagen fibers
What are myofibrils?
Filaments that are part of small cylindrical bundles that make up striations
What are thick filaments of the sarcomere?
Made of myosin
What are the thin filaments of the sarcomere?
Composed mostly of actin, troponin, and tropomyosin
What is the A band?
The wide, dark band produced by thick filamins in the middle of the sarcomere
What is the Z line?
Where the thin filament is anchored to interconnecting proteins
What defines the limits of one sarcomere?
To adjacent Z lines
What is the I band?
The light band that’s between the A bands of adjacent sarcomeres that results from thin filaments and interconnecting proteins, but no overlapping thick filaments
What’s the H zone?
The narrow, light band in the middle of the A band, where the two thin filament sets don’t overlap
What’s the M line?
The proteins that link together the central region of adjacent thick filaments, in the center of the H zone
What is titin?
The elastic protein that extends from the Z line to the M line (interconnecting)
How are thin and thick filaments arrange?
Hexagonal thin around one thick; triangular thick around one thin
What are crossbridges?
Projections that bridge the space between overlapping thick and thin filaments; part of the myosin molecules on the thick filaments; the velcro heads
What is the sliding-filament mechanism of contraction?
When the overlapping thick and thin filaments in each sarcomere move past each other, propelled by crossbridge movement: shortens the sarcomere
What does the ability of a muscle fiver to generate force and movement depend on?
Interaction of the contractile proteins actin and myosin
What comprises the myosin molecule?
Two heavy chains and four light chains: produces two globular heads and a long tail
How are myosin molecules oriented in the thick filament?
Opposite directions, so tails point in, so that when the heads swivel, they drag the thin filaments in towards the center
What is the crossbridge cycle?
Attachment of crossbridge to thin filament, movement of crossbridges to produce tension, detachment of crossbridge from thin filament, energizing the crossbridge so it can attach to a thin filament again and repeat the cycle
What initiates crossbridge cycling?
Entry of calcium into the cytoplasm
What happens when the energized myosin binds to actin?
The strained conformation is released, to produce movement of the bound crossbridge and the release of a phosphate and ADP
How is the analogy of energy storage/release in myosin like a mousetrap?
Cock the spring (ATP hydrolysis), and spring the trap (bind to actin)
Why is ATP needed a second time when actin and myosin are bound?
To break the crossbridge bond to reenergize the crossbridge and start the cycle all over again