1. The Muscular System
9 BIOLOGY

2. The Muscular System 3 Types of muscle:
1.Smooth- involuntary, lines internal organs, no striping, one nucleus per cell
2. Cardiac- involuntary, in the heart only, network arrangement for proper contraction, striped appearance, multi-nucleate
3. Skeletal- voluntary, attached to bones by tendons.

3. Skeletal Muscle Contraction
Muscles arranged in antagonistic pairs
When one contracts, one is relaxed and vice versa.
Muscle fibers:
Arranged in myofibrils of actin and myosin
Sarcomere: functional unit of muscle
Sliding Filament Theory:
1. Once nerve signal reaches muscle, actin filaments slide toward each other causing contraction
2. Nerve signal  release of calcium for relaxation of contraction
3. ATP needed

4. Muscle Contraction

5. Energy for Muscle Contraction
Oxygen available aerobic respiration
Oxygen not available anaerobic
Causes lactic acid build- up, fatigue & soreness

6. Rigor Mortis: State of prolonged muscle contraction
* Upon death, ATP is no longer released to relax contraction, so stiffness occurs.
After 24 hours, tissue degradation begins
Used to determine time of death in forensics

7. Myoglobin Special kind of hemoglobin that is only in muscle cells
Binds only one O2 instead of 4 O2 in hemoglobin
Gives extra oxygen reserves to muscle tissue

8. Myoglobin in Food
Dark meat has more myoglobin, thus more iron than white meat.
Dark meat is generally more nutritious as a result

9. Skeletal Muscle Strength
Slow twitch:
Slow
Endurance
Resist fatigue
Lots of mitochondria
Have myoglobin which gives oxygen reserve
Exercise causes increase of mitochondria, but not size of muscle
Fast twitch:
Fatigue easily
Great strength
For short rapid movements
No myoglobin
Fewer mitochondria
Exercise increases diameter of muscle