Muscle Contraction and Sliding Filament Theory (Nursing)

by Jasmine Clark

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    00:01 Now switching gears, let's talk about how an contraction actually occurs.

    00:07 In the sliding filament mechanism of our muscles, myosin is going to pull on actin, causing the thin filament to slide inward.

    00:17 It's important to note that in a muscle contraction, neither the thin or the thick filament themselves shorten, but instead it is the arrangement of the thin and thick filaments in the sarcomere that changes.

    00:34 After the myosin pulls on the actin the Z discs are going to move toward each other and the sarcomere is going to short and as a whole.

    00:45 Thanks to the structural proteins, we can now transmit this force across the entire muscle and resulting in an entire or a whole muscle contraction.

    00:57 So now let's discuss the contraction cycle.

    01:00 During the contraction cycle, there are going to be several steps that occur that allow for the sliding filament mechanism to occur.

    01:09 The first step in the contraction cycle involves the binding of calcium to the regulatory protein troponin.

    01:17 This binding causes troponin to move the tropomyosin, so that the myosin head of the thick filament can bind to the actin or thin filament.

    01:31 As well during this step, we also have ATP hydrolysis.

    01:37 ATP will be converted to ADP and inorganic phosphate.

    01:43 While this hydrolysis step happens the ADP and the inorganic phosphate remain attached to the myosin head.

    01:51 And the myosin head is said to be energized or cocked into the ready position.

    02:00 The next major step in the contraction cycle is going to be crossbridge formation.

    02:06 During crossbridge formation, the now available myosin binding sites on the actin thin filament are bound by the myosin head.

    02:18 In this step, the ADP and the inorganic phosphate are still attached.

    02:25 Following this step, the ADP and the inorganic phosphate are removed from the myosin head.

    02:32 This triggers the myosin to move or pull the thin filament past the thick filament toward the center of the sarcomere.

    02:43 This step is referred to as the power stroke.

    02:48 The final step in the contraction cycle involves that returning everything back to its original state.

    02:56 We also refer to this as the crossbridge detachment step.

    03:01 In this step, we are going to attach a new ATP molecule to the myosin head.

    03:08 This causes or triggers the myosin head to detach from the actin thin filament.

    03:16 And then we can start the process all over again.

    About the Lecture

    The lecture Muscle Contraction and Sliding Filament Theory (Nursing) by Jasmine Clark is from the course Musculoskeletal System – Physiology (Nursing).

    Included Quiz Questions

    1. The myosin protein pulls on the actin protein.
    2. The Z discs move closer together.
    3. The thin filament moves.
    4. The sarcomere shortens.
    5. The Z discs move apart.
    1. Binding of calcium
    2. Crossbridge formation
    3. Power stroke
    4. Crossbridge detachment
    5. Binding of potassium

    Author of lecture Muscle Contraction and Sliding Filament Theory (Nursing)

     Jasmine Clark

    Jasmine Clark

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