Notes on Muscles - Anatomy and Physiology (copy)

Course Overview

• Course Title: Anatomy and Physiology I

• Instructor: Dr. Heather Raker, PT, DPT, CBIS

Chapter 11: Muscles

Course Objectives

• Understand the Skeletal Muscles:

  • Skeletal Muscle Structure

  • Contraction of Skeletal Muscle

Interactions of Skeletal Muscle

• Terminology:

  • Origin: The end of a skeletal muscle attached to a fixed structure (usually a bone).

  • Insertion: The end of a skeletal muscle attached to the moving structure (the bone).

  • Agonist (Prime Mover): The muscle whose contraction is responsible for a specific movement.

  • Synergist: Assists the agonist in producing movement.

  • Fixator: A type of synergist that stabilizes the origin, preventing movement at another joint.

  • Antagonist: Opposes the action of the agonist.

Agonist and Antagonist Muscle Examples

• Biceps Brachii (anterior compartment - flexes the forearm) vs Triceps Brachii (posterior compartment - extends the forearm).

• Hamstrings (flexes the leg) vs Quadriceps (extends the leg).

• Flexor Digitorum Superficialis and Profundus (flexes fingers) vs Extensor Digitorum (extends fingers).

Patterns of Fascicle Organization

• Diaphragm: A skeletal muscle not moving the skeleton while aiding in breathing.

• Fascicle Arrangements:

  1. Parallel Muscles: Align with muscle’s long axis; e.g., biceps brachii.

  2. Circular Muscles (Sphincters): Concentric rings controlling openings; e.g., orbicularis oris.

  3. Convergent Muscles: Spread widely and converge; e.g., pectoralis major.

  4. Pennate Muscles (Feather-like): Fascicles angle into a central tendon.

  • Unipennate: One-sided fascicles (e.g., extensor digitorum).

  • Bipennate: Both sides (e.g., rectus femoris).

  • Multipennate: Wrap around the tendon (e.g., deltoid).

Review of Skeletal Muscle

• Every muscle has an origin and an insertion. The muscle's action is determined by its primary role as agonist, synergist, or antagonist. The fascicle arrangement affects the muscle's range of motion and functional capability.

Naming Skeletal Muscles

• Naming Origin: Often derived from Latin and Greek roots reflecting characteristics such as:

  • Location: Gluteal muscles in the buttocks.

  • Size: Muscles named by size, (e.g., maximus, minimus).

  • Direction: Orientation of fibers (e.g., rectus means straight).

  • Origin/Inserts: Named after attachment points (e.g., biceps brachii).

Examples of Muscle Names

• Abductor: Ab (away from) + duct (to move) - Moves away (e.g., abductor digiti minimi).

• Adductor: Ad (toward) + duct (to move) - Moves towards (e.g., adductor digiti minimi).

• Mnemonic Devices: Provided for easier memorization of terms (e.g., anti means against, epi means on top).

Actions of Muscles

• Flexion: Decrease angle

• Extension: Increase angle

• Adduction: Move toward midline

• Abduction: Move away from midline

• Pronation/Supination: Palm down/up rotations

• Dorsiflexion/Plantar Flexion: Foot movements

• Inversion/Eversion: Foot sole movements

Conclusion

• Understanding the skeletal muscles' structure, interaction, naming conventions, and actions is essential for mastering anatomy and physiology of the muscular system.