Muscular System Notes

Muscular System

Muscle Tissues & Function

  • Introduction to the muscular system.
  • Referenced "Simon Says" as a basic example related to muscle function.

Magnificent Muscle Facts

  • The human body has more than 650 muscles.
  • Waste energy from muscle activity helps keep you warm.
  • No two muscles in the body have exactly the same function.
  • Muscles are efficient, using about 35-50% of their potential energy.
  • Muscle fibers are thinner than a human hair and can support up to 1,000 times their own weight.
  • The term "muscle" is derived from the Latin word for "little mouse".

Human Muscles

  • Muscle cells are highly specialized to convert chemical energy (ATP) into kinetic energy.
  • There are three types of muscle tissue:
    • Smooth
    • Cardiac
    • Skeletal

Smooth Muscle Cells

  • Non-striated (lacking a striped appearance).
  • Each cell contains a single nucleus.
  • Contraction is involuntary.
  • Found in the walls of internal organs (e.g., esophagus), facilitating processes like peristalsis.
  • Capable of sustaining prolonged contraction without fatigue (e.g., iris constriction).

Cardiac Muscle Cells

  • Striated, tubular, and branched in structure.
  • Each cell has a single nucleus.
  • Contraction is involuntary.
  • Found in the walls of the heart.

Skeletal Muscle Cells

  • Striated and tubular in structure.
  • Each cell contains multiple nuclei.
  • Contraction is voluntary.
  • Usually attached to the bones of the skeleton.

Skeletal Muscle Function

  • Support: Muscle contraction opposes the force of gravity.
  • Movement: Allows for movement of bones (i.e., arms and legs) as well as eyes and face.
  • Maintain body temperature: ATP breakdown releases heat which spreads throughout the body.
  • Protection: Pads bones and cushions organs.
  • Stabilize joints: Tendons help hold bones to joints.

Cooperation of Skeletal Muscles

  • When muscles contract, they shorten, pulling rather than pushing.
  • Contraction equals work, while relaxation equals no work.
  • Muscles are found in pairs, where one action always has an opposing action.
    • Example: Bicep flex for a bent arm, tricep flex for a straight arm.

Skeletal Muscle Structure

  • Muscles: An organ surrounded by connective tissue and composed of several tissues; it is the largest unit and is attached to bone by tendons.
  • Muscle fibers: Organized into larger bundles and can be up to 20 cm long; connective tissue wraps the fibers.
  • Myofibrils: Thousands of cylindrical subunits within muscle fibers.
  • Myofilaments: Protein structures responsible for muscle contraction; there are two types:
    • Actin: Thin filament
    • Myosin: Thick filament
  • Sarcomere: The functional unit of a muscle, composed of myofilaments.

Hierarchy of Muscle Structure

The hierarchy of muscle structure from largest to smallest:

  1. Muscle
  2. Muscle Fiber
  3. Muscle-fiber bundle
  4. Myofibril
  5. Myofilaments (Actin and Myosin)
  6. Sarcomere
  • Sarcoplasmic reticulum is also part of the structure.
  • Mentioned a YouTube video: "Hidden power of muscles - http://www.youtube.com/watch?v=Q9wRTIZIByk"

Assignment

  • Reading Assignment: Read pages 330-337.
  • Booklet Assignment: Lesson 1 – Check Your Understanding.