Muscle Contractions: Micro Level

Muscle Contractions: Micro Level

Author: Aaron Mullally

This lesson will go into more detail describing how a muscle contracts.

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  • Sarcomere

    The functional and contractile units of skeletal and cardiac muscles; created by a specific arrangement of myofilaments called actin and myosin; each sarcomere is bordered by a z-line.

  • Actin

    Referred to as the thin filament of a sarcomere, creates the lighter color within a sarcomere and interacts with myosin to create movement.

  • Myosin

    Referred to as the thick filament of a sarcomere, creates the darker colors within a sarcomere and contains various heads that pull on actin filaments to create movements.

  • ATP

    The primary energy molecule that cells use for energy; composed of adenosine and three phosphate groups; when the bonds that hold the phosphates together are broken energy is released for work.

  • Action potential

    The technical term for a nervous impulse; when a wave of depolarized electrical energy travels down the length of a cell/tissue.

  • Calcium

    A mineral/ion that has many physiologic uses to humans; calcium is stored in the sarcoplasmic reticulum (SR) of skeletal muscles and when released it prepares actin and myosin for interaction.

  • Sarcoplasmic reticulum (SR)

    A specialized form of smooth endoplasmic reticulum (SER) found within skeletal muscles used for calcium storage.

  • Contraction

    A muscle fiber generates tension, causing the muscle to shorten.

  • Twitch

    The way a skeletal muscle contracts, sarcomeres quickly pull inward and create a quick, jerky twitch.

  • Tetanus

    A term used to described a prolonged muscle contraction; often used to describe a person who has been exposed to Clostridium tetani toxin.

  • Sliding filament mechanism

    A theory used to describe how the microfilaments within the sarcomere interact with one another; actin and myosin cling together and slide past one another.

  • Motor unit

    The term used to describe one motor neuron and all of the muscle fibers it innervates at once.