How do Muscles Work?

1. How do Muscles Work? • Muscles serve FOUR functions for us: -- motion; they move our skeleton -- stability and posture -- controlling organ function -- generate body heat

2. Characteristics of Muscle Tissue • Excitability – ability of the muscles to be stimulated by nerves • Contractility – muscles can contract • Extensibility – muscles lengthen • Elasticity – after shortening or lengthening, muscle can return to its original shape Muscles PULL, they never push!

3. Roman Ship Analogy… • Muscles work much like an old roman ship that used a galley of people rowing the oars in unison. • Each person had only so much strength, but together, they gave the ship’s oars incredible power.

4. Muscles need help… • Muscles need to be connected to the rest of the body -- they need motor nerves -- they need energy and O2 -- H20, CO2 waste & glucose transport • Requires nerves, blood vessels, and the lymphatic system to carry them • These are held in connective tissues called FASCIA Muscles need to use sugar available in blood for energy

5. Fascia Galore! • Fascia is connective tissue that surrounds muscles • Provides protection and stability

6. Superficial Fascia • Closest to the skin and holds muscle to the skin • Also contains adipose tissue • Stores fat and water, provides insulation from heat loss, protects, and is a place for vessels and nerves to carry things in and out of muscles

7. Deep Fascia • Separates muscle groups • Allows muscles to contract without interference from other muscles • Each muscle has its own outer fascia called epimysium which is then surrounded by deep fascia

8. Superficial Fascia Deep Fascia

9. Myofibers • Individual muscle fibers are called myofibers(muscle cells) • Arranged in groups of 10-100 myofibers and these groups are called fascicles • Perimysiumsurrounds fascicles • Endomysiumsurrounds individual myofibers

11. Myofibrils (actin & myosin) • Proteins are arranged in a thread-like appearance in the sarcoplasm • Give skeletal and cardiac muscle tissue their striations muscle cell

13. Skeletal Muscle Fiber Contraction • “Sliding Filament Theory” • When muscle fibers are stimulated to contract, myofilaments (actin and myosin) slide past one another. • This causes sarcomeres (muscle units) to shorten and the whole muscle fiber shortens.

14. Sarcomere

15. Sarcomere

16. Sarcomere

17. Whole Muscle Contraction • The whole length of one muscle fiber must contract; however, the whole muscle does not have to contact. • The number of muscle fibers contracting determines the strength of the contraction.

20. The Effect of Exercise • A regular exercise program will bring about 1. Increased endurance 2. Increased strength of muscles. • Muscle enlarge, not due to increase in number of muscle fibers, but increased amounts of actin and myosin myofibrils inside each muscle fiber making them bigger and stronger. • “Use it or lose it !”

21. Arnold….then and now!

22. Exercise increases muscle size, strength, and endurance • Aerobic (endurance) exercise (biking, jogging) results in stronger, more flexible muscles with greater resistance to fatigue • Makes body metabolism more efficient • Improves digestion, coordination • Resistance exercise like weight lifting increases muscle size and strength

23. Effect of Exercise on Muscles