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Anatomy & Physiology: Muscle Structure and Function

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Terms in this set (26)

  • Endomysium
    A thin layer of connective tissue that surrounds each individual muscle fiber.
  • Sarcolemma
    The plasma membrane of a muscle cell that encloses the muscle fiber.
  • Sarcomere
    The basic contractile unit of a muscle fiber, defined by the area between two Z discs.
  • Myofibril
    A long, cylindrical organelle within muscle fibers composed of repeating sarcomeres.
  • Z disc
    The boundary structure that defines the ends of a sarcomere and anchors actin filaments.
  • Myosin
    The thick filament protein responsible for muscle contraction by forming cross-bridges with actin.
  • Actin
    The thin filament protein that interacts with myosin during muscle contraction.
  • Tropomyosin
    A regulatory protein that blocks myosin-binding sites on actin filaments when the muscle is relaxed.
  • Troponin
    A regulatory protein complex that binds calcium to initiate muscle contraction by moving tropomyosin.
  • Temporalis muscle
    A muscle of the head involved in elevating and retracting the mandible for chewing.
  • Masseter muscle
    A powerful muscle of mastication that elevates the mandible to close the jaw.
  • Sternocleidomastoid
    A neck muscle that flexes and rotates the head.
  • Pectoralis major
    A large chest muscle that adducts and medially rotates the arm.
  • Rectus abdominis
    A paired muscle running vertically on the anterior abdominal wall, responsible for trunk flexion.
  • Deltoid muscle
    The shoulder muscle responsible for arm abduction.
  • Biceps brachii
    A muscle of the arm that flexes the elbow and supinates the forearm.
  • Gluteus maximus
    The largest muscle of the buttocks, responsible for hip extension and external rotation.
  • Rectus femoris
    A quadriceps muscle that extends the knee and flexes the hip.
  • Tibialis anterior
    A muscle of the anterior lower leg that dorsiflexes and inverts the foot.
  • Calcaneal tendon
    Also called the Achilles tendon; connects the calf muscles to the heel bone.
  • Muscle contraction initiation
    Begins with an action potential triggering acetylcholine release at the neuromuscular junction.
  • Cross-bridge cycle
    The process where myosin heads bind to actin, perform a power stroke, and release to shorten the muscle.
  • Acetylcholine clearance
    The breakdown of acetylcholine by acetylcholinesterase to end muscle contraction.
  • Origin vs insertion
    Origin is the fixed attachment of a muscle; insertion is the movable attachment.
  • Push vs pull in muscles
    Skeletal muscles can only pull on bones to create movement; they cannot push.
  • Directional vocabulary in anatomy
    Terms like medial, lateral, proximal, distal describe locations and directions in the body.