On a microscopic level, muscle contractions operate under a mechanism where big
ID: 1353643 • Letter: O
Question
On a microscopic level, muscle contractions operate under a mechanism where big bulbous heads of a myosin filament bond to an actin filament, then those myosin heads bend to propel the myosin filament forward. After this “power stroke,” the myosin head detaches, reaches forward and reattaches further along the actin filament to repeat the process. Imagine yourself with a hundred myosin arms climbing up an actin rope in gym class.
Holding a heavy book stationary with your arm extended straight out does no work (because the distance d for your supporting force is zero); yet you will begin to fatigue after a minute, implying energy is being lost. Propose a hypothesis as to why your energy reserve is being expended with consideration given to Work = F·d, the microscopic mechanism for muscle action, and any other concepts you learned about work and energy.
Explanation / Answer
The energy is being lost in breaking mysoin filament to an actin filament.After every power stroke mysoin head detaches, reaches forward& reattaches further along the actin filament to repeat the process.
at the stretch position the nerves continiously send signal to brain. in this process also energy is lost.because of more stress on mussel due to gravitational pull of the heavy stationary book, receptor cells continiously communicate with brain through nervous system. every time brain take some decision for this energy is also required.
work done by blood pressure is more in the stress muscel to provide more energy for holding the book.
in this various ways energy is lost & hence we will begin to fatigue after some time.
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