Muscular System - Key Concepts

Muscular System Overview

  • Skeletal Muscles:
    • Attached to bones
    • Attachments:
    • Direct: epimysium attaches directly to bone
    • Indirect: through tendons/aponeurosis
  • Fascicles: Groups of skeletal muscle cells; contribute to muscle shape and force.

6 Patterns of Muscle Fascicle Arrangement

  1. Convergent: All fascicles converge to a single point.
    • Example: Pectoralis major
  2. Parallel: Fascicles run parallel to muscle's long axis.
    • Example: Sartorius
  3. Circular: Fascicles arranged in concentric circles (sphincters).
    • Example: Orbicularis oris
  4. Unipennate: Fascicles on one side of tendon.
    • Example: Extensor digitorum
  5. Bipennate: Fascicles on both sides of a central tendon.
    • Example: Rectus femoris
  6. Multipennate: Central tendon with branches.
    • Example: Deltoid

Muscle Naming Conventions (7 Ways)

  1. Location: e.g., Frontalis (on frontal bone)
  2. Shape: e.g., Deltoid (triangular)
  3. Size: e.g., Gluteus maximus (largest) vs. gluteus minimus (smallest)
  4. Direction of Fibers: e.g., Rectus (upright) vs. Oblique (angled)
  5. Action: e.g., Flexors & Extensors
  6. Attachments: e.g., Sternocleidomastoid
  7. Number of Origins: e.g., Biceps (two origins) vs. Triceps (three origins)

Muscle Actions

  • Agonists (Prime Movers): Main muscle performing the action.
  • Synergists: Assist the agonist; stabilize origins.
  • Antagonists: Oppose the agonist's action, providing balance to movements.