The muscular system functions to enable movement, maintain body temperature and posture. There are three main types of muscle: skeletal muscle which is voluntary and attached to bones, smooth muscle which is involuntary and inside organs, and cardiac muscle which makes up the heart. Skeletal muscle contracts to pull bones, working with the skeletal system, and contains bundles of fibers. Exercise causes muscle soreness by building up chemicals during activity and damaging fibers, leading to growth as the muscles heal.

1. Muscular System Life Science, Ms. Wells

2. Function: Movement Work with skeletal system to move body contract = shorten/tighten Muscles PULL bones, never push muscle cells are called muscle fibers Often work in pairs/groups for one movement

3. Function: Body Temperature HOMEOSTASIS: Muscle contraction releases heat to keep your body the right temperature Shivers: fast muscle contractions to raise body temperature

4. Function: Maintain Posture Most muscles always hold a little bit of contraction/tension Tension = “muscle tone” Keep you standing up straight (posture)

5. Types of Muscle Skeletal Muscle Smooth Muscle Cardiac Muscle Skeletal = you control it (called VOLUNTARY) Smooth/Cardiac = you don’t control it (called INVOLUNTARY)

6. Skeletal Muscle Attached to your skeleton Voluntary Structure = bundles of fibers Examples: quadriceps, biceps, triceps, abs, etc.

7. Skeletal Muscle: Bundles of Fibers

8. Smooth Muscle Inside organs Involuntary (automatic movements) Shorter fibers than skeletal muscle Example: pushes food through stomach and intestines

9. Cardiac Muscle Fibers have branched shape (like tree branches) that form webs and layers Make up the heart <3

10. Cardiac Muscle: Branched Fibers

11. Muscle Types: Fiber Shapes

12. Tendons Attach muscles to bones White skinny part of muscle “Gristle”

13. Muscles and Exercise Soreness DURING exercise: chemicals build-up as you use up energy (lactic acid) Soreness AFTER exercise: tears and damage to muscle fibers Healing and replacement of damaged cells = muscle growth

14. Skeletal Muscle Development Skeletal muscles “mature” and strengthen as you grow up Increase coordination Babies can’t lift head (neck muscles still weak)

15. THE END