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Steps of Muscle Contraction definitions

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  • Neuromuscular Junction
    The site where a motor neuron communicates with a muscle fiber, initiating muscle contraction.
  • Acetylcholine
    A neurotransmitter released at the neuromuscular junction to trigger muscle contraction.
  • Sarcolemma
    The cell membrane of a muscle fiber that conducts action potentials.
  • T-tubules
    Invaginations of the sarcolemma that help propagate action potentials into the muscle fiber.
  • Sarcoplasmic Reticulum
    A specialized endoplasmic reticulum in muscle cells that stores and releases calcium ions.
  • Calcium Ions
    Ions released from the sarcoplasmic reticulum that bind to troponin to initiate contraction.
  • Troponin
    A protein that binds calcium ions, causing tropomyosin to expose myosin binding sites on actin.
  • Tropomyosin
    A protein that blocks myosin binding sites on actin filaments in resting muscle.
  • Cross-bridge
    The connection formed when myosin heads bind to actin filaments during muscle contraction.
  • Power Stroke
    The action of myosin pulling actin filaments toward the center of the sarcomere.
  • ATP Hydrolysis
    The process of breaking down ATP to ADP and inorganic phosphate, providing energy for muscle contraction.
  • Depolarization
    A change in cell membrane potential that makes the inside of the cell more positive.
  • Repolarization
    The process of restoring the resting membrane potential after depolarization.
  • Acetylcholinesterase
    An enzyme that breaks down acetylcholine in the synaptic cleft, ending muscle contraction.
  • Myofibril
    A basic rod-like unit of a muscle cell, composed of repeating sarcomeres.