Lecture Notes: The Muscular System

Introduction

• Overview of previous topics:
  • Structure of muscle tissue
  • Process of muscle contraction
• Focus: Learning about major muscles in the body

Muscle Classification by Function

• Muscles contract but do not expand; they only pull, not push.
• Complex motion requires cooperation of multiple muscles.

Types of Muscle Roles

1. Prime Movers (Agonists):
   • Primary responsibility in producing a particular motion.
2. Antagonists:
   • Oppose a particular movement, providing resistance for delicate motions.
3. Synergists:
   • Assist prime movers by adding force or reducing undesired movements.
   • Act as stabilizers.
4. Fixators:
   • A type of synergist that immobilizes a bone, maintaining posture.

• Note: A muscle can perform more than one role depending on the motion.

Muscle Naming Criteria

1. Location:
   • Example: Temporalis muscle near the temporal bone.
2. Shape:
   • Example: Trapezius muscle is trapezoidal.
3. Size:
   • Terminology includes maximus, minimus, longus, brevis (large, small, long, short).
   • Example: Gluteus maximus and minimus.
4. Direction of Muscle Fibers:
   • Rectus (parallel), Transversus (perpendicular), Oblique (angled).
   • Example: Rectus femoris.
5. Number of Origins:
   • Biceps (two origins), Triceps (three), Quadriceps (four).
6. Locations of Attachments:
   • Origin and insertion points detailed in names.
   • Example: Sternocleidomastoid.
7. Type of Motion:
   • Flexor, extensor, adductor, etc.

Muscle Shapes and Fascicle Arrangements

• Circular: Fascicles form concentric rings (e.g., muscles around eyes/mouth).
• Convergent: Spread out but converge to a tendon (e.g., pectorals).
• Fusiform: Muscle tapers to tendons at both ends (e.g., biceps).
• Parallel: Fascicles run parallel to the long axis (e.g., sartorius muscle).
• Pennate: Fascicles at oblique angles.
  • Unipennate: Fascicles on one side of the tendon.
  • Bipennate: Fascicles on both sides, resembling a feather.
  • Multipennate: Resembles several feathers into one tendon.

Range of Motion and Power

• Muscles can contract ~30%.
• Parallel fascicles = more shortening, less power.
• Oblique fascicles = less shortening, more power.

Conclusion

• A brief exploration of major muscles via images.
• Emphasis on gaining a vague familiarity, rather than memorization.
• Upcoming topic: Neurons and the nervous system.

• Contact info: Professor Dave, open for questions via email.