Anatomy 35 – Chapter 9: Myology

  • Types of Muscle Tissue:

    • Skeletal Muscle:

    • Appearance: Striated, multiple peripheral nuclei

    • Location: Attached to bones and skin

    • Function: Voluntary movement, generates body heat

    • Cardiac Muscle:

    • Appearance: Striated, branched cells, single nucleus, intercalated discs

    • Location: Walls of heart (myocardium)

    • Function: Involuntary heart beating

    • Smooth Muscle:

    • Appearance: Non-striated, single nucleus

    • Location: Walls of hollow organs, encircles blood vessels

    • Function: Involuntary movement (e.g., digestion, vessel control)

  • Skeletal Muscle Facts:

    • Approximately 605 skeletal muscles
    • Comprises nearly half of body weight

  • Muscle Development:

    • Myoblasts: Muscle cell precursors
    • Muscle Components:
    • Muscle → Fascicle → Muscle fiber (cell) → Myofibril → Sarcomere → Myofilaments (thick and thin)

  • Connective Tissue Components:

    • Epimysium: Surrounds entire muscle
    • Perimysium: Surrounds fascicles
    • Endomysium: Surrounds individual muscle fibers

  • Neuromuscular Junction:

    • Connection between motor neuron and muscle
    • Components: Axon terminal, synaptic cleft, vesicles with neurotransmitters, receptors on muscle

  • Muscle Fiber Anatomy:

    • Sarcolemma: Electrically excitable membrane
    • T-tubules: Conduct action potentials into cell
    • Sarcoplasmic Reticulum: Stores Ca++ for muscle contraction

  • Muscle Contraction:

    • Sliding Filament Theory:
    • Myosin binds to actin, pulling Z-lines closer together
    • A-band remains the same, I-band and H-zone decrease

  • Sarcomere Structure:

    • Z line: Connects thin filaments
    • M line: Connects thick filaments
    • Components: A bands, H zone, I bands
    • Length of filaments does not change during contraction

  • Muscle Attachment:

    • Origin, Insertion, Belly (body):
    • Muscles stretch from one bone to another, crossing joints
    • Types of Muscles:
    • Agonist: Prime mover
    • Synergist: Assists prime mover
    • Antagonist: Opposes prime mover

  • Levers in Muscle Mechanics:

    • First Class Lever: Fulcrum in the middle
    • Second Class Lever: Resistance in the middle
    • Third Class Lever: Effort in the middle

  • Muscle Fiber Organization:

    • Muscle Shapes:
    • Parallel, Convergent, Circular, Pennate (unipennate, bipennate, multipennate)