The Muscular System Key Concepts What types of muscles are found in the body? Why do skeletal muscles work in pairs?

Key Terms Involuntary muscle Voluntary muscle Skeletal muscle Tendon Striated muscle Smooth muscle Cardiac muscle

There are about 600 muscles in the human body

Types of Muscles Involuntary Muscles – Muscles that are not under your conscious control – involved in breathing and digesting food Voluntary Muscles – Muscles that are under your conscious control – smiling, turning a page, getting out of a chair Three types of muscle tissue: Skeletal, smooth and cardiac

Skeletal muscle Attaches to and moves bones Looks striated or banded under a microscope Move only when you want them to: voluntary React quickly and tire quickly Tendon – strong connective tissue that attaches muscle to bone

Smooth Muscle Smooth – found on the inside of many internal organs – Ex. Stomach Involuntary Help to control breathing, blood pressure, and movements of the digestive system No striations or bands React slowly, tire slowly

Cardiac Muscle Found only in the heart Some characteristics of both skeletal and smooth Involuntary Striated Does not tire Contracts repeatedly heart beat

Muscles at Work Skeletal muscles only contract when they receive a message from nervous system. Muscles do work only by contracting or shortening. For movements need 2 muscles or groups of muscles (always work in pairs) Ex. Biceps and triceps work together to bend and straighten your arm.

Muscular Strength and Flexibility Exercise makes individual muscle cells grow in size – that makes the whole muscle thicker The thicker the muscle the stronger it is Stretching makes muscles more flexible Prepares muscles for exercise or play

Muscle Injuries Muscle strain or pulled muscle – when muscles are overworked or overstretched Tendons can also be overstretched or partially torn Muscle cramp – whole muscle contracts strongly and stays contracted