1. Muscle Size and Strength

2. MUSCLES There are more than 620 skeletal muscles in the human body. Not only do muscles work with bones to produce movements, but they are also stabilizing agents for joints and they help humans stand erect.

3. Three Types of Muscles 1. Skeletal muscles are often called striated because of the bands or stripes that are visible in these cells under a microscope.

4. Three Types of Muscles The smallest skeletal muscle in the human is the stapedius, which is about 1 millimeter long. It attaches to the stirrup bone, which helps conduct vibrations from the eardrum to the inner ear.

5. Three Types of Muscles One of the largest skeletal muscles is the latissimus dorsi, the broad, flat muscles of the back that moves the arms.

6. Three Types of Muscles 2.Smooth Muscles: Line the digestive tract and are responsible for peristaltic movements. They also line the walls of arteries. They contract and relax to accommodate a continuous flow of blood. All hollow organs and tubes in the body contain smooth muscle.

7. Three Types of Muscles 3. Cardiac or heart: Combines the strength of skeletal muscle with the endurance of smooth muscle.

8. Voluntary or Involuntary? Voluntary Muscles are within a person’s conscious control. Skeletal muscles are voluntary muscles. Involuntary Muscles always operate automatically. Cardiac and smooth muscles are involuntary muscles.

9. Muscle Energy Most of the energy in muscle fibers is produced in mitochondria. The more mitochondria in the muscle fiber, the more energy the muscle can produce, as long as there is enough oxygen.

10. Muscle Contractions A muscle contraction is initiated by a nerve impulse from the central nervous system. There are 3 stages: 1.A latent period in which the muscle is preparing to contract after receiving the electrical signal from the nerve. 2.The actual contraction 3.A period of relaxation in which the muscle returns to its original length or tension.