chapter 11

Chapter 11: The Muscular System

Learning Outcomes
11.1 Fascicle Arrangement

  1. Describe the arrangement of fascicles in the various types of muscles and explain the resulting functional differences.

  2. Classify muscles into the following categories based on fascicle arrangement:
       - Parallel muscles: Fascicles run parallel to the long axis of the muscle. These muscles can be flat (e.g., oblique, forearm, thigh) or cylindrical (e.g., biceps brachii).
         - Example: Biceps brachii.
         - Function: Tension developed during a contraction depends on the total number of myofibrils.
          More myofibirls more tension
       - Convergent muscles: Muscle fibers spread out like a fan that converge at a single attachment site.
         - Example: Pectoralis muscles. Pectoralis minor
         - Attachments: Muscle may pull on tendons, aponeuroses, or raphe (slender band of collagen fibers).
         - Function: Fibers pull in various directions depending on the activity.

   - Pennate muscles: Muscle fibers pull at an angle relative to the tendon.
     - Comparison with parallel muscles: While they do not move tendons as far, they contain more myofibrils and develop more tension.
     - Types of pennate muscles:
       - Unipennate: All fascicles on the same side of the tendon (e.g., extensor digitorum).
       - Bipennate: Fascicles on both sides of a central tendon (e.g., rectus femoris).
       - Multipennate: Tendon branches within muscle (e.g., deltoid).

   - Circular muscles (sphincters): Surround body openings and hollow organs, acting as valves in the digestive and urinary tracts.
     - Example: Orbicularis oris of the mouth. External sphincter for urination
     - Function: Contraction decreases the diameter of the opening.

11.2 Levers

  1. Describe the classes of levers, and explain how they make muscles more efficient.

    affect speed force range of movement

    joint is the fulcrum

    muscle is applied force
       - Almost all skeletal muscles attach to bones at their points of origin.
       - Levers: Rigid structures that move at a fixed point called the fulcrum.
       - Joints serve as fulcrums, allowing for force application:
         - First-Class Lever: Fulcrum lies between applied force and load (e.g., neck extension).
         - Second-Class Lever: Load is between applied force and fulcrum (e.g., calf muscles during ankle extension).
         - Third-Class Lever: Applied force is between load and fulcrum. This type is the most common in the body and maximizes speed and distance at the expense of effective force. Bicep brachii flexion

11.3 Origins and Insertions

  1. Predict the actions of a muscle based on its origin and insertion.
       - Origin: Fixed point of attachment; generally proximal.
       - Insertion: Movable point of attachment.
       - Muscle actions: Movements resulting from muscle contractions (e.g., flexion, adduction).
       - Various muscle interactions maximize efficiency:

    Effect on muscle and bone
         - Agonist (prime mover): Main muscle producing the action. (Bicep brachii)
         - Antagonist: Muscle that opposes the action of the agonist. (Traps and Lats)
         - Synergist: Assists a larger agonist muscle in performing the action. (Rotator cuff)
         - Fixator: A type of synergist that assists an agonist by stabilizing another joint.

   - Opposing muscle actions: Agonists and antagonists work in pairs (e.g., flexors and extensors).

Adduction:

11.4 Naming Skeletal Muscles

  1. Explain how the name of a muscle can help identify its location, appearance, or function.
       - The body has approximately 700 skeletal muscles with names that convey descriptive information:
         - Regional indicators: Terms such as "brachial" (arm), "femoris" (thigh), etc.

    Structural indicators:
         - Position/direction: Descriptors indicating superficial/internal locations (e.g. "externus", "internus").
         - Specific actions: Names indicating a specific action performed (e.g. "flexor" for bending movements).

  2. First part of name of muscle usually is its orgin ( strenocladomastiod)

  3. Size ( gluteus Maximus)

  4. Facicles ( bicep= 2 facicles

  5. Shape( plates a) flare

  6. Latissusmis is widest

Action

Movement is sometimes in the name of

Direction could be apart of name

11.5 Axial and Appendicular Muscles

  1. Compare and contrast the axial and appendicular muscles.
       - Axial Muscles: Account for 60% of skeletal muscles.
         - Functions include positioning head and vertebral column, moving rib cage, and forming pelvic floor.
       - Appendicular Muscles: Stabilize and move pectoral and pelvic girdles and limbs.

Axial Muscles: Overview
11.6 Principal Axial Muscles (Identification & Details)

   - Muscles of the head and neck:
     - Facial expression, mastication, and swallowing (e.g., orbicularis oris, buccinator, masseter).
   - Muscles of the vertebral column:
     - Include erector spinae and others (flexing and rotating the neck and back).

   - Note: For specific details on origins, insertions, actions, and innervation of each muscle described, refer to individual muscle sections.

Appendicular Muscles: Overview
11.7 Principal Appendicular Muscles Identification & Actions

   - Muscles of the shoulders and upper limbs: Include muscles that position the girdle and move the limbs (e.g., deltoid, pectoralis major).
   - Muscles of the pelvis and lower limbs: Allow a range of movements (e.g., gluteus maximus and quadriceps).

Effects of Exercise
11.8 Functional Relationships

  1. Explain the functional relationship between the muscular system and other body systems.
       - Cardiovascular: Delivers oxygen, removes waste.
       - Respiratory: Responds to oxygen demand from muscles.
       - Integumentary: Helps disperse heat from muscle activity.
       - Nervous & Endocrine: Direct responses of all systems involved.