ch. 9

Overview of Muscular System

  • Muscle Types: Skeletal, Cardiac, Smooth
  • Key Concepts: Transforming chemical energy into mechanical energy, generating ATP

Muscle Cell Terminology

  • Sarcolemma: Cell membrane of muscle cells
  • Electrical Excitability: Property of muscle and nerve cells to generate and propagate electrical signals
    • Resting membrane potential: ~ −70-70 mV

Characteristics of Muscle Tissue

  • Excitability: Ability to respond to stimuli
  • Contractility: Capability to shorten or contract
  • Extensibility: Ability to stretch
  • Elasticity: Returns to original shape after stretching

Functions of Skeletal Muscle

  • Produce skeletal movements
  • Maintain posture
  • Support soft tissues
  • Guard body openings (sphincters)
  • Maintain body temperature
  • Store nutrient reserves (glycogen, calcium)

Structure of Skeletal Muscle

  • Fascicles: Bundle of muscle fibers
  • Connective Tissue Coverings:
    • Epimysium: Surrounds the entire muscle
    • Perimysium: Surrounds fascicles
    • Endomysium: Surrounds individual muscle fibers
  • Neuromuscular Junction: Synapse between nerve and muscle cell

Muscle Cell Composition

  • Muscle Fibers: Multinucleated, long cells
    • Contain myofibrils (thick and thin filaments)
    • Sarcoplasmic Reticulum: Stores calcium, analogous to endoplasmic reticulum
    • Transverse Tubules: Invaginations of the sarcolemma
    • Sarcoplasm: Cytoplasm of muscle fibers, contains myoglobin and mitochondria