actin

actin troponin

actin troponin

tropomyosin

actin troponin

tropomyosin

actin troponin

tropomyosinmyosin binding site

Ca2+Ca2+ Ca2+ Ca2+

Ca2+Ca2+ Ca2+ Ca2+

Calcium ions are released from the sarcolemma after stimulation from the T system

Ca2+Ca2+

Ca2+

Ca2+

Ca2+Ca2+

Ca2+

Ca2+

the calcium ions bind to the troponin and changes its shape

Ca2+Ca2+

Ca2+

Ca2+

the calcium ions bind to the troponin and changes its shape

Ca2+Ca2+

Ca2+

Ca2+

Ca2+Ca2+

Ca2+

Ca2+

Ca2+Ca2+

Ca2+

Ca2+

the troponin displaces the tropomyosin and exposes the myosin binding sites

Ca2+Ca2+

Ca2+

Ca2+

Ca2+Ca2+

Ca2+

Ca2+

Ca2+Ca2+

Ca2+

Ca2+

the bulbous heads of the myosin attach to the binding sites on the actin filaments

Ca2+Ca2+

Ca2+

Ca2+

Ca2+ Ca2+

Ca2+

Ca2+ Ca2+

Ca2+

the myosin heads change position to achieve a lower energy state and slide the actin filaments past the stationary myosin

Ca2+ Ca2+

Ca2+

APi PiPiAPi PiPiAPi PiPi

Ca2+ Ca2+

Ca2+APi PiPi

APi PiPi

APi PiPi

Ca2+ Ca2+

Ca2+APi PiPi

APi PiPi

APi PiPi

ATP binds to the bulbous heads and causes it to become detached

Ca2+ Ca2+

Ca2+

APi PiPiAPi PiPi

APi PiPi

ATP binds to the bulbous heads and causes it to become detached

Ca2+ Ca2+

Ca2+

APi Pi

Pi

APi Pi

Pi

APi Pi

Pi

hydrolysis of ATP provides the energy to “re-cock” the heads

Ca2+ Ca2+

Ca2+

APi Pi

Pi

APi Pi

Pi

APi Pi

Pi

hydrolysis of ATP provides the energy to “re-cock” the heads

Ca2+ Ca2+Ca2+

APi Pi

Pi

APi Pi

Pi

APi Pi

Pi

Ca2+ Ca2+Ca2+

APi Pi

Pi

APi Pi

Pi

APi Pi

Pi

calcium ions are re-absorbed back into the T system

APi Pi

Pi

APi Pi

Pi

APi Pi

Pi

calcium ions are re-absorbed back into the T system

APi Pi

Pi

APi Pi

Pi

APi Pi

Pi

the troponin reverts to its normal shape and the tropomyosin move back to block the myosin binding sites

APi Pi

Pi

APi Pi

Pi

APi Pi

Pi

the troponin reverts to its normal shape and the tropomyosin move back to block the myosin binding sites

APi Pi

Pi

APi Pi

Pi

APi Pi

Pi

the troponin reverts to its normal shape and the tropomyosin move back to block the myosin binding sites

APi Pi

Pi

APi Pi

Pi

APi Pi

Pi

phosphocreatine regenerates ATP

APi Pi

PiAPi PiPi

APi PiPi

phosphocreatine regenerates ATP

APi PiPiAPi PiPi

APi PiPi

phosphocreatine regenerates ATP

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