Muscular System Overview

Anatomy and Physiology I - Chapter 11: The Muscular System

Overview of the Muscular System

• Skeletal muscles = nearly 50% of body weight.
• Divided into:
  • Axial Muscles: Support and position the axial skeleton.
  • Appendicular Muscles: Support, move, and brace the limbs.

Interactions of Skeletal Muscles (11.1)

• Most muscles pull on bones (cross at joints).
• Terms:
  • Origin: Point where muscle attaches to stationary bone.
  • Insertion: Point where muscle attaches to movable bone.
  • Agonist (Prime Mover): Main muscle causing action (e.g., biceps in arm flexion).
  • Antagonist: Opposing muscle relaxing during action (e.g., triceps during flexion).
  • Synergist: Assists agonist (may stabilize; called a fixator).

Patterns of Fascicle Organization

1. Parallel: Run along muscle's length; shorten by ~30%.
2. Convergent: Broad area converges at tendon; direction of pull can change.
3. Pennate: Short fascicles attach to long tendons; strongest configuration.
   • Types:
     • Unipennate: One side of tendon.
     • Bipennate: Both sides of tendon.
     • Multipennate: Multiple directions to tendons.
4. Circular: Concentric rings around openings (sphincters).

Lever System of Muscle and Bone Interactions

• Lever: Bone acts as a lever, pivoting at a Fulcrum (joint).
• Muscles provide applied force to overcome load preventing movement.

Naming Skeletal Muscles (11.2)

• Knowledge of terminology aids in memorization:
  • Regions, positions, fascicle organization, structural characteristics, actions.
• Mnemonic Devices for Latin Roots:
  • ad: to, toward → ADvance
  • ab: away from → n/a
  • ductor: moves → conDUCTOR
  • anti: against → antisocial
  • epi: on top of → n/a
  • longissimus: longest → longer than "long"
  • maximus: large → max
  • uni: one → UNIcorn
  • bi/di: two → DIcast
  • tri: three → TRIple

Individual Muscles (11.3, 11.4, 11.5, and 11.6)

• Specific muscles will be covered in the lab, omitted in this summary.