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Transcript of Muscles- contractions
Myosin- protein in a thick filament; cell is shaped like a golf club with two heads
Sarcomere- the basic contractile unit, a muscle fiber Sliding filament model- actin and myosin slide against each other which cause the sarcomeres to shorten.
Sarcomeres then tighten which causes the myofibrils to tighten which causes the whole muscle to tighten On the Cellular Level... Basically... When the muscle is activated, it shortens or
When a muscle is relaxing, it lengthens The shortening of a sarcomere in a myofibril produces the shortening of the microfibril
And in turn, the muscle fibre
The light bands become shorter and the dark bands stay the same length What do the sarcomeres do? Dark Bands and Light Bands When a muscle contracts, sarcomeres become smaller.
The filaments don’t change in length
Instead, they slide past each other (overlap)
Actin filaments slide between myosin filaments and the zone overlap is larger In conclusion... Types of Contractions Isometric- (equal distance) amount of tension increases during contraction process, but length of muscle doesn’t change
- Responsible for constant length of postural muscles in body
Isotonic contractions- (equal tension) amount of tension produced by muscle is constant during contraction, but length of muscle decreases- Movement of arms or fingers
More Types of Contractions Concentric- isotonic contractions in which muscle tension increases as muscle shortens
Eccentric- isotonic contractions in which tension is maintained as muscle lengthens
- Muscle injuries can occur from repetitive eccentric contractions, such as in a hamstring from running downhill
Repetition - One ATP molecule is split by each cross bridge in each cycle
Cross-bridges- the actin myofilament bind to the heads of the myosin myofilaments to form this
- During a contraction 1000’s of cross bridges in each sarcomere go through the cycle
- Many cross bridges attach to one b/c many go through the cycle but are out of synch