Sliding_filament_theory

Sliding_filament_theory - Sliding Filament Theory A...

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Sliding Filament Theory A Pictorial Guide on Muscle Contraction and The Neuromuscular Junction To Accompany Lecture By Noel Ways ADP P ATP ADP P ADP P
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Nucleus Sarcolemma Nucleus Invaginations of Sarcolemma leading to Transverse Tubules Transverse Tubules Sarcoplasmic Reticulum Sarcomere Z Line (Disk) Z Line (Disk) Myosin Actin Myofiber (Muscle Cell) Note that this illustration depicts only ONE muscle cell. Page 2 Myofibril, containing thin and thick myofilaments (actin and myosin, respectively) A myofibril is divided into sarcomeres. Each sarcomere is an indi- vidual contractile unit.
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Sarcoplasmic Reticulum ADP ADP ATP ADP ATP ATP ADP ATP ADP ADP ATP ADP ATP ATP ADP ATP ADP ATP Active Transport Calcium Pumps Calcium Gates Closed Calcium Gates Opened Transverse Tubules Transverse Tubules When the calcium gates are opened, the calcium that is pumped in immediately returns to the sarcoplasm; even though the calcium pumps are on-going. Page 3 The Sarcoplasmic Reticulum has active transport calcium pumps and calcium gates. When the calcium gates are closed, calcium is sequestered within the sacoplasmic reticulum and it’s terminal cisterns.
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T r o p n i Tro m y s in Myosin Binding Site Actin Protein The thin myofilaments are made of the protein actin. Each actin protein has a myosin binding site. Actin proteins are arrainged in a double helix. Around the actin double helix is another protein complex called the tropomyosin-tropoin complex. The tropomyosin-troponin complex has two configurations depending upon weather calcium ( ) is bonded to the troponin or not. When calcium is absent the tropomyosin-troponin complex covers the myosin binding sites of the actin. When calcium is present, calcium binds to the troponin causing the tropomyosin- troponin complex to take on a new configuration, whereby the myosin binding sites of the actin are exposed. A muscle contraction is depended upon the exposure of the myosin binding sites. When the myosin binding sites are hidden by the tropomyosin-troponin complex, a contraction cannot take place. When the myosin binding sites are exposed, a contrac- tion can take place.
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Sliding_filament_theory - Sliding Filament Theory A...

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