1. Lesson 20 Terms and Definitions
Human Body Systems
Lesson 20 Terms and Definitions

2. Q: What is force and what does it have to do with muscle strength?

3. 3 types of Muscles

4. Involuntary Muscles
Cardiac and Smooth muscles are both involuntary muscles.
Involuntary Muscles operate automatically.
Heart beats automatically
Food is digested automatically

5. Cardiac Muscles
Cardiac Muscle (heart muscle) pumps blood through the circulatory system.
Involuntary, very strong
Striated

6. Smooth Muscles
Smooth Muscle lines the digestive tract, and blood vessels creating wave like motions.
Involuntary

7. Voluntary Muscles Skeletal muscles Within someone’s conscious control.
Only involuntary action is through a reflex.

8. Skeletal Muscles
Skeletal Muscles work together with bones to cause the movement of the body.
Voluntary, VERY strong
Striated
620 skeletal muscles

9. Skeletal muscles Energy in muscle fibers comes from mitochondria.
The more mitochondria = the more energy (as long as there is enough O2)

10. Muscle Contractions
Contraction STARTS by a nerve impulse from the central nervous system.
Receives an electrical signal from nerve and is preparing to contract.
Actual Contraction (2/3’s its size).
Relaxation when muscle returns to it’s original length.

11. Videos Discovery Education The Human Body: Pushing the Limits
Segments:
Muscles: Superhuman Strength (6min)
Muscle Memory: Learning While you sleep (4 min)
Other movie in the Chapter 20 folder

12. Size vs Strength Lab Force – the push or pull of an object
newton (N) – unit of measurement of force
(Number of kilograms) x 9.8 = newtons