1. Muscular System
What Moooooves YOU?

2. Purpose:
Allows our bodies to move
“Moves” some vital organs

3. How many muscles are in our bodies?
More than 630 muscles

4. Three Categories/Types of Muscle:
1. Skeletal
2. Cardiac
3. Smooth

5. 1. Skeletal Muscle
Function: Attaches to bones of skeleton via tendons, allowing body to move
(Tendons are a connective tissue)
Voluntary – You can control them at will
Examples: Biceps, Triceps, Quadriceps

6. 2. Cardiac Muscle
Function: Forms the walls of the heart

7. Cardiac Muscle

8. 3. Smooth Muscle Forms sheets, layers, or tubes
Function: Forms walls of inner body parts
Examples: Stomach & bladder
Involuntary Muscles – work automatically
Under microscope do not show any patterns or stripes

9. Smooth Muscle

10. Muscle Makeup
Muscles are groups of cells (or fibers)

11. Muscle Cells Each muscle cell (fiber) contains several myofibrils
Myofibrils are bundles of filaments containing actin and myosin strands

12. Muscle Cells
Appear to have stripes or “striations” because of the myrofibrils

13. Myosin and Actin Protein filaments
Myosin and Actin are parallel to one another and do not touch
When stimulated, Actin releases a Calcium ion

14. Actin and Myosin
When the Calcium ion is released, Myosin binds to the Actin and “inches forward” causing your muscle to contract

15. How do muscles work? A chemical reaction causes muscles to contract
Muscles can only PULL. They NEVER PUSH.
Muscles work together in groups.
Muscle actions are controlled by messages from your brain along nerves called “motor nerves”
When muscles contract they release energy which produces heat

16. Why do we shiver when cold?
Shivering is produced by rapid muscle contractions
When the body is cold, muscles contract rapidly, which releases heat and warms the body.