The Muscular System

Muscles produce movement or generate tension by contracting (shortening in length).

Within a single muscle fiber there are thousands of contractile units called sarcomeres that are arranged end to end.

There are three types of muscles: skeletal, cardiac, and smooth muscles.

Skeletal muscles contact oinly when activated by their motor nerve.

Cardiac and smooth muscles do not attach to bones and can contract spontaneously and be influenced by nerves.

Cardiac muscles are only found in the heart and is the main force for blood to be pumped from the heart

Smooth muscles are found in the digestive tract, urinary tract, and some blood vessels.

Check out this video about how muscles work:

http://www.youtube.com/watch?v=ren_IQPOhJc




Reference:

Johnson, M. D. (2010). Human Biology: Concepts and Current Issues (5th ed.). San Francisco: Pearson Education.