1. Muscular System

2. Introduction:
Over 600 muscles make up the muscular system

3. Muscles are made of bundles of muscle fibers that are held together by connective tissue.

4. Properties (Characteristics) of Muscles
Excitability or irritability: ability to respond to a stimulus such as a nerve impulse.

5. Contractibility When muscle fibers are stimulated by nerves, they contract or become short and thick. This causes movement.

6. Extensibility: ability to be stretched

7. Elasticity: allows the muscle to return to its original shape after it has contracted or stretched.

8. Three Main Types of Muscle Tissue:

9. Cardiac
Form walls of heart
Contract to circulate blood
Involuntary: function without conscious thought or control

10. Visceral (Smooth)
Found in the internal organs of the body such as the digestive system, respiratory system, blood vessels, and eyes.
Contract to cause movement in these systems
Involuntary: function without conscious thought or control

11. Skeletal Attached to bones Cause body movement
Voluntary: person has control over their action

12. Functions of Skeletal Muscle:
Attach to bones to provide voluntary movement
Produce heat and energy
Help maintain posture
Protect internal organs

13. Methods of Attachment to Bones:
Tendon
Strong, tough connective tissue cord
Example: Achilles tendon which attaches the gastrocnemius muscle on the calf of the leg to the heel bone.

14. Fascia
Tough, sheetlike membrane
Covers and protects tissue
Example: lumbodorsal fascia which surrounds the deep muscles of the trunk and back

15. Origin and Insertion
When muscles attach to bones, one end becomes the origin and one end the insertion
Origin: end that does not move
Insertion: end that moves when muscle contracts

16. Movements of Muscles: Adduction: moving body part toward the midline
Abduction: moving body part away from midline

17. Flexion: decreasing the angle between two bones or bending a body part
Extension: increasing the angle between two bones or straightening a body part

18. Rotation: turning a body part around its own axis; turning the head from side to side
Circumduction: Moving in a circle at a joint; Example – swinging the arm in a circle with the trunk flexed forward at the waist.

19. Toe-down motion of the foot at the ankle
Dorsiflexion:
Turn your foot or toes upward.
Plantar Flexion:
Toe-down motion of the foot at the ankle

20. Muscle Tone:
Muscles are partially contracted at all times even though they may not be in use.
This state of partial contraction is known as muscle tone.
Also described as a state of readiness to act.

21. Can occur in severe illness such as paralysis
Loss of muscle tone
Can occur in severe illness such as paralysis
When muscles are not used for a long period of time, they can atrophy or waste away
Lack of use can result in a contracture
Severe tightening of a flexor muscle
Results in bending of a joint
Foot drop is a common contracture
Many joints such as fingers, wrists, and knees can be affected.

22. Increase in muscle tone Can occur with brain damage
Resistance is felt in muscles; rocking motion can help to normalize tone