1. Muscular System

2. Muscle An organ that can contract in a organized fashion
Include muscle tissue, blood vessels, nerves, connective tissue.
3 types of muscle:
Skeletal
Smooth
Cardiac
1/3 of your body weight is muscle (average)

3. Skeletal Muscle
Responsible for the movement of your limbs, trunk, and face.
Made of elongated cells called muscle fibers (striated)
Movements are consciously controlled, making them voluntary muscles

4. Smooth Muscle
Forms the walls of stomach, intestines, blood vessels, other internal organs
The movements of these muscles are unconsciously controlled, so they are called involuntary muscles

5. Cardiac Muscle Make up the walls of the heart
Shares some characteristics of skeletal & smooth muscles
They are striated like skeletal muscles
They are involuntary and each cell has one nucleus like smooth muscles

6. What Muscles Need
Muscles need a good supply of blood and nerves to be healthy
Cardiovascular and nervous systems
Active muscles use lots of energy
They require a continuous supply of O2 and nutrients, supplied by arteries
They produce large amounts of metabolic wastes that are removed by veins
Cardiovascular and respiratory systems

7. Muscle Fatigue Muscle cells store glycogen and glycogen stores energy
If glycogen is used up, fat is used for energy
When energy availability fails to keep up with energy use, muscles fatigue
Muscle fatigue: inability of a muscle to contract
Happens because no ATP is available
It is a state of continuous muscle contraction
Can lead to severe muscle cramps

8. Muscle Fatigue Oxygen debt is a temporary lack of available oxygen
Large amounts of O2 are needed to keep cellular respiration producing ATP
After several minutes of heavy exertion, respiratory system cannot bring in enough oxygen to maintain maximum production of ATP
You breathe harder/faster to keep up intake of O2
When oxygen debt occurs:
Your body goes into lactic acid fermentation to create energy
Pain (soreness) in your muscles comes from build up of waste called lactic acid
Soreness persists until wastes are carried away or converted into something else