1. The Muscular System

2. Muscle Tissues Cardiac –Involuntary striated muscle –Found only in heart –Smooth –Lines blood vessels, digestive organs, urinary system, and parts of respiratory system, pupils of eyes –Involuntary non-striated muscle Skeletal –Voluntary striated muscle –Attached to bones for movement

3. Functions of Skeletal Muscle Produce Movement –Contractions pull on tendons and move bones Maintain posture and body position –Continuous contractions maintain posture Support/protect soft tissues –Abdominal wall –Floor of pelvic cavity Guard entrances and exits –Voluntary control of swallowing, defecation, and urination Maintain body temp –Some energy from contractions lost as heat

4. Gross Anatomy of Skeletal Muscle Each cell is called a “muscle fiber” –Connective Epimysium – collagen fibers surrounding entire muscle Perimysium – divide skeletal muscles into bundles of fibers (fascicles) Endomysium – surrounds fiber Tendons – connect skeletal muscle to periosteum of bones

5. Microanatomy of Skeletal Muscle Sarcolemma – cell membrane Sarcoplasm – cytoplasm Myofibrils – bundles of myofilaments –Thin filaments – actin proteins –Thick filaments – myosin proteins Sarcoplasmic reticulum – smooth ER (stores Ca+) Sarcomeres – repeating units of myofilaments

6. http://legacy.owensboro.kctcs.edu/gcaplan/anat/notes/api%20notes%20j%2 0%20muscle%20contraction.htm

7. Muscle Fiber Contraction

8. Muscle Tone Tone – resting tension Stabilizes the position of your joints Any skeletal muscle not stimulated on a regular basis will atrophy – fibers become smaller and weaker Initially atrophy is reversible Extreme atrophy is permanent

9. Energetics of Muscle Activity Sources of ATP –Aerobic Metabolism ( Krebs  Oxidative Phosphorylation) Provides 30% of ATP needed during peak exertion Waste products  Carbon dioxide and water vapor –Anaerobic Metabolism (glycolysis) Waste products  Lactic acid builds up Ineffective Muscle Fatigue – no contraction despite stimulation –Lack of ATP or lactic acid build up

10. Muscle Performance Force and endurance depends on: Types of muscle fibers –Fast Twitch (white) Powerful contractions Fatigue rapidly (few mitochondria) –Slow Twitch (red) Extended contraction (many mitochondria) Extensive capillary network Myoglobin binds O 2 Physical conditioning ( increase power and endurance)