The Muscular System

1. Chapter 15, Section 2

2. Movement
 In the process of moving, energy is used, work is done.
 More than 600 muscles in the body
 Some muscles in your body are always moving.
 Breathing
 Heart beating
 Digestive system working

3.  Muscle control
 Voluntary muscles—muscles you are able to control
 Examples: face, hand ,arm
 Involuntary muscles—muscles that you can’t control
 Work all day long, all your life
 Pump blood through vessels and move food through digestive
system

4. Classification of Muscle Tissue
 Skeletal muscle tissue
 Voluntary muscles that move bone
 More common than other muscle types
 Attached to bones by tendons
 Striated (appear striped under microscope)

5.  Cardiac muscle tissue
 Found only in heart
 Striated
 Contracts about 70 times per minute all your life
 Smooth muscle tissue
 Non-striated
 Involuntary
 Found in bladder, intestines, blood vessels, other
internal organs

6. Working Muscles
 You move because pairs of skeletal muscles work
together.
 When one muscle of a pair of muscles contracts, the
other muscle relaxes or returns to its original length.
 Muscles always pull; they never push

7. Changes in Muscles
Over time, muscles become larger or smaller depending
on whether or not they are used.
Muscles that are given regular exercise respond quickly
to stimuli.
Some of the change in muscle size is because of an
increase in the number of muscle cells.

8.  However, most of the change in muscle size is because
individual muscle cells become larger.
 Muscles that aren’t worked, become smaller in size.

9. How muscles move
 Muscles need energy to contract and relax.
 Your blood carries energy-rich molecules to your
muscle cells, where chemical energy is released.
 As muscle contracts, this released energy changes to
mechanical energy (movement) and thermal energy
(heat).