1. How do Muscles Work? Muscles serve FOUR functions for us:
-- motion; they move us
-- 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 slaves roaring the oars in unison.
Each slave had only so much strength, but together gave the ship’s oars incredible power.

5. 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

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

7. 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

8. 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

9. Myofibers Individual muscle fibers are called myofibers (muscle cells)
Arranged in groups of myofibers and these groups are called fascicles
Perimysium surrounds fascicles
Endomysium surrounds individual myofibers

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

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

15. Sarcomere

16. Sarcomere

17. Sarcomere

18. 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