Functions: Movement of the body and all actions. Examples- push blood thru vessels, breath and hold upright.
 
 

Structure: Human body has 640 muscles. 40% of body weight from muscle.
 muscle tissue is made of cells that have 10 or more nuclei in each.   muscle fibers average 1 inch each, groups of fibers create muscle.
 *Muscles are connected to bones in order to move them. They are   connected by tendons (connective tissue).
 
 Voluntary:  muscles one can control. skeletal muscle

 Involuntary: muscles that one can not control, automatic. cardiac    and smooth muscle.

Types: Three types of muscle:
 1. Skeletal: voluntary muscle. can be controlled (nerves)
  covering body. striated, long bundles. react quickly and tire    quickly. attatched to bone by tendons.
 
 2. Smooth: involuntary muscle. inside of the body, lines the walls of    hollow organs such as the stomach and intestines. made of    smooth flat sheets. work automatically for body functions.
 
 3. Cardiac: involuntary muscle. makes the heart beat. built in rythm.    combination of smoth and cardiac muscle. uses large amounts    of O2 and glucose in the blood, muscle must never tire.

Movement: Muscles contract (shorten) and relax to move parts of the   body.
 *Muscles work in pairs: flexor and extensor. One muscle shortens to  bend the part and the other brings back the body to the original    position or straighten.
 * Muscles can also work in complex combinations of many muscles.   *Muscles can be working without any body part moving.
 *Fuel is needed to have muscles work (glucose). Aerobic respiration   takes O2 and glucose to produce ATP with CO2 and H2O as by    products. Anaerobic respiration does not use O2 to create ATP.
 *Longest muscle: sartorius (inner thigh)
 *Biggest muscle: gluteus maximus (bottom)
 *Smallest muscle: stapedius (inner ear)
 * muscles are shaped many different ways.
 
 

Levers: simple machine that works in one movement
 Lever- fixed bar       Bone
 Fulcrum- fixed point      Joint
 Effort- force applied    Muscle contract/relax
 Load- weight on bar or resistance  Body part or outside weight

 First Class Lever- fulcrum in the middle
 

 Second Class Lever- load in the middle
 

 Third Class Lever- effort in the middle