1. The Muscular System
Chapter 15 Lesson 3

2. Functions of the Muscular System
Body movements
Pump blood through body
Move food through digestive system
Control movement of air in/out of lungs

3. How do Muscles Work? By two complementary – or opposing – actions
Contraction: shortening of a muscle
Triggered by nerve impulses. These impulses stimulate muscle fibers.
Extension: stretching of a muscle

4. What Makes a Muscle?
A muscle is composed of bundles of fibers (muscle fibers).
Major muscles are made up of hundreds of bundles
Muscle fibers are made up of even smaller units called myofibrils.
Each myofibril is made up of microscopic filaments called actin & myosin (these control muscle contraction).

5. Types of Muscles 3 basic types:
Smooth muscles are the type of muscle concerned with the movements of internal organs (intestines, bladder, walls of blood vessels). These muscles are also called involuntary muscles because they work without a person’s conscious control.
Skeletal muscles are the stiped/striated muscles attached to bones that cause body movements (more than 600 in your body!) These muscles are voluntary and under conscious control.
Flexors: muscles that close a joint
Extensors: muscles that open a joint
Cardiac muscle is a special type of striated tissue that forms the walls of your heart (heart beats about 100,000 x day!). These muscles are involuntary.

6. Care of the Muscular System
“Use it or lose it” applies to muscles. An unused muscle will atrophy, or waste away.
To maintain muscle tone (natural tension in the fibers of a muscle) you need to be keep active and eat balanced nutritious meals.
* this should be a lifelong goal
Exercise is especially important for aging adults to prevent loss of mobility, balance, and risk of falls.

7. Problems of the Muscular System
Myasthenia Gravis: disorder in which bones become weak and easily fatigued. Most commonly affects eye muscles, which may cause drooping eyelids and/or double vision.
Muscular Dystrophy: an inherited disorder characterized by a progressive wasting away of skeletal muscles. Can be slowed if caught early, by regular exercise.

8. Muscle Strain
AKA “pulled muscle” is a tearing or stretching of muscle fibers as a results of suddenly pulling them too far. (Treatment = RICE)

9. Bruise
Discolored area under skin caused by leakage of blood after an injury. Ice and NSAID can help alleviate pain/swelling.

10. Tendinitis
Inflammation of a tendon, usually caused by overuse. Pain, tenderness, and restricted movement of the muscle attached are often common.

11. Hernia
Protrusion of an organ or tissue through a weak area in the muscle. .