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Sliding Filament Theory

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Sliding Filament Theory  The process starts with the sarcoplasmic reticulum is stimulated to release calcium ions into the muscle. Then the calcium ions bind to the troponin-tropomyosin and drags off the cross bridges of the myosin Cross bridges bind to actin with ATP Cross bridges pull on actin so it slides to the middle of the sarcomere which contracts the muscle Cross bridges detract from the actin and ATP changes into ADP+P Muscle fiber relaxes Calcium close and transport pump carries calcium through transport pump into the sarcoplasmic reticulum  https://www.ptdirect.com/training-design/anatomy-and-physiology/skeletal-muscle-the-physiology-of-contraction
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3 Muscle Types

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Description and Diagram of the 3 Muscle Types Cardiac Muscle- Involuntary The cardiac muscle is located in the walls of the heart. Function: The cardiac muscle is responsible for pumping blood throughout the body. Structure: -Partially striated -Branched -Mononucleated Smooth Muscle- Involuntary The smooth muscle is located in the walls of internal organs (stomach, intestines, bladder, blood vessels...etc.) Function: movement of contents in the internal walls of organs, changes in the diameter of blood vessels and airways. Structure: -Non-striated -Mononucleated -Spindle-shaped -Unbranched Skeletal Muscle- Voluntary The skeletal muscle is attached to bones or skin. Function: Heat production, posture, movement Structure: -Cross striated -Multinucleated -Unbranched
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Labeled Diagram

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Muscle Contraction

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Once an action potential (AP) is generated at the motor end plate it will spread like an electrical current along the sarcolemma of the muscle fiber  The AP will also spread into the T-tubules, exciting the terminal cisternae of the sarcoplasmic reticula   This will cause Calcium (Ca+2 ) gates in the SR to open, allowing Ca+2 to diffuse into the sarcoplasm  Calcium will bind to troponin (on the thin myofilament), causing it to change its shape. This then pulls tropomyosin away from the active sites of actin molecules.  The exposure of the active sites allow the sliding of the filaments  Calcium (Ca+2 ) gates in the SR open, allowing Ca+2 to diffuse into the sarcoplasm  Myosin heads are “energized” by the presence of ADP + PO4 3- at the ATP binding site (energy is released as phosphate bond of ATP breaks)  Once the active sites are exposed, the energized myosin heads hook into actin molecules forming cross-bridges  Using the stored energy...
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Function

Description of the Four Characteristics of Muscle Excitability - ability to receive and respond to a stimulus Contractility - ability to shorten Extensibility - ability to stretch Elasticity - ability of a muscle fiber to resume its resting length after contraction or stretching What do these four characteristics allow the muscles to do? These 4 characteristics allow muscles to perform important functions, including movement, maintaining posture, supporting soft tissues within body cavities, guarding entrances and exits of the body, and maintaining body temperature.
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