1. Muscular System
Anatomy & Physiology

2. Introduction 600 muscles that make up 40-45% of your body weight
Made up of bundles of muscle fibers (long, slender cells) held together by connective tissue
When stimulated by nerves they contract (become short and thick) which causes movement

3. Properties
Excitability-the ability to receive and respond to a stimulus
Contractility-the ability to shorten
Extensibility-the ability to be stretched
Elasticity-the ability to resume resting length after being stretched
Automaticity-the ability of a muscle to contract without a nerve supply

4. Functions Movement To hold the body erect/posture
Locomotion/manipulation
Heartbeat
Moving substances through hollow organs
To hold the body erect/posture
Body heat – 85% of body heat
Joint stabilization
Some Internal organ protection

5. Types of Muscles
Cardiac, Visceral/smooth, & Skeletal

6. Types of Muscle Skeletal Smooth – unstriated – involuntary - visceral
Found in hollow organs like - digestive tract, blood vessels, and ducts leading from glands.
Purpose is to move fluids through these structures
Cardiac
Myocardium
Like striated muscle in appearance but like smooth muscle in function.

8. Cardiac Muscle Forms walls of the heart
Contracts to circulate the blood
Striated with lots of mitochondria
Involuntary
Efferent nerves control the rate of contraction
Afferent nerves sense pain, spasm, & stretch
Contracts at a steady rate, except for brief, rapid bursts

9. Visceral/Smooth muscle
Found in the internal organs
Walls of hollow, visceral organs
No striations
Involuntary
Efferent neurons are less important
Afferent nerves are concerned with pain, spasm, and stretch
Steadies constant contractions, automaticity

10. Skeletal Muscles 40% of the body
Attaches to and cover the bony skeleton
Longest fibers
Striated
Voluntary
Efferent nerves send impulses for contraction
Afferent nerves send message to inform brain of degree of contraction
Contracts rapidly, tires easily; tremendous power, adaptable
Causes body movement

11. Methods of Attachment to Bone

12. Tendon Strong, tough connective tissue cord Example
Achilles tendon-attaches the gastrocnemius muscle on the calf of the leg to the heel bone

13. Fascia A tough, sheet-like membrane Covers and protects tissues
Example-lumbodorsal fascia which surrounds the deep muscles of the trunk & back

14. Aponeurosis
Flat sheet of fibrous connective tissue that connects muscle to bone or to other tissues

16. Origin & Insertion
When muscles attach to bones, one end becomes the origin and one end becomes the insertion
Origin – the end that does not move; usually proximal to insertion. Where the muscle begins.
Insertion – the end that moves when muscle contracts. Where the muscle ends.

17. Physiology of Skeletal Muscle Contraction

18. Muscle Tone Steady partial contraction is present at all times
State of tension when awake
State of readiness to act; enables muscles for immediate response
Does not produce an active movement
Keeps muscles firm and healthy
Stabilizes the joints
Maintains posture

19. Muscle Tone continued Loss of muscle tone
Can occur in severe illnesses such as paralysis & palsy
When muscles are not used for a long period of time – atrophy, waste away (degeneration & loss of mass)
Complete immobilization of muscle (complete bed rest or in a cast or loss of neural stimulation) – strength decreases 5% per day; paralysis=atrophy to ¼ the initial size; muscle tissue is replaced by fibrous connective tissue – muscle rehab is impossible; delayed with electrical stimulation

20. Muscle Tone continued
Lack of use can result in contracture (permanent contraction of the muscle due to spasm or paralysis)
Severe tightening of a flexor muscle
Results in bending of a joint
Fingers, wrists, and knees, as well as other joints can be affected

21. Muscle Tone continued Muscle fatigue
Muscle is unable to contract
Tension drops to zero
Spasm – sudden involuntary contraction of a muscle
Clonic – a spasm alternating with relaxation
Tonic – sustained

22. Muscle Tone continued Tetanus – a smooth, sustained contraction
Tetany – the result of low calcium
Increases the excitability of neurons
Loss of sensation, muscles twitching, convulsions
If untreated-spasms of the larynx, respiratory paralysis, and death can occur

23. Characteristics Kinesiology Muscles work in antagonistic pairs
Biceps brachii – elbow flexion
Triceps brachii – elbow extension
Contraction and relaxation
Muscle innervation
neuromuscular