Chapter 1, Section 2, Pages 14 - 19 The Muscular System Chapter 1, Section 2, Pages 14 - 19

What are Muscles? Muscles are organs that relax, contract, and provide force to move your body parts.

3 Types of Muscle Tissues

Classification of Muscle Tissue Skeletal Muscles Voluntary Muscles that move the bones Most common muscle type Attaches to bones by thick bands of tissue called tendons They are striated (appear striped) Tire more easily than involuntary muscles

Muscle Tissue Continued… Cardiac Muscle Found only in the heart It is striated Contracts about 70 times per minute every day of your life It’s an involuntary muscle.

Muscle Tissue continued… Smooth Muscles Located in your intestines, bladder, blood vessels and other internal organs Nonstriated Involuntary muscles that slowly contract and relax

Working Muscles Pairs of skeletal muscles work together One muscle contracts, the other relaxes Muscles always pull (never push) For example, when you bend your arm, your bicep muscle contracts (tightens) while your triceps muscle relaxes (returns to its original length)

Changes in Muscle Muscles can become larger or smaller, depending whether or not they are used. Muscles that are exercised become stronger, and sometimes, larger. Muscles that are not used, become smaller, soft, flabby and will lack strength. Athlete vs. nonathlete

How muscles Move Muscles need chemical energy to contract and relax Blood carries energy-rich molecules to muscle cells Chemical energy is stored and released Muscle contractions = release of energy changes to mechanical energy (movement) and thermal energy (heat) When the supply of energy-rich molecules in a muscle is used up, the muscle becomes tired and needs to rest. During resting period, blood supplies more energy-rich molecules to muscle cells. The heat produced by muscle contractions helps keep your body temperature constant.

Major Muscles Muscle Location Hamstring Back of Thigh Abdominals Stomach Bicep Front of upper arm Deltoid Shoulder Quadriceps Front of Thigh Trapezius Upper back Muscle Location Calf Muscle Back of lower leg Pectorals Chest Obliques Sides of stomach Gluteus Maximus Butt Triceps Back of upper arm