1. Muscular System

2. The muscular system is mostly made up of muscles that allow your body to move and be flexible
Other muscles move materials inside your body
Muscle is the tissue that contracts and relaxes – this makes movement possible
Muscle is made up of muscle cells

3. Three Types of Muscle

4. Your body has three kinds of muscle tissue: skeletal muscle, cardiac muscle and smooth muscle
Each muscle type has a specific job in your body
Because you are able to control the movement of skeletal muscles, these muscles are called voluntary muscles
You are not able to control the movement of smooth muscles and cardiac muscles
Muscles that are not under your control are called involuntary muscles

5. Smooth Muscle

6. Smooth muscle is found in internal organs and blood vessels
It helps move materials through the body
Arteries and veins contain a layer of smooth muscle that can contract and relax
This controls blood flow through the blood vessel
Smooth muscle movement in your digestive system helps move food through your intestines

7. Cardiac Muscle

8. Cardiac muscle is the tissue that makes up the heart
Your heart never gets tired because cardiac muscle cells are able to contract and relax without ever getting tired
In order to supply energy to all the cells, cardiac muscles have many mitochondria
Contractions of the cardiac muscle push blood out of the heart and pump it around your body

9. Skeletal Muscle

10. Skeletal muscle is attached to your bones and allows you to move
The tough strand of tissue that connects a muscle to a bone is a tendon
When a muscle contracts, or shortens, the attached bones are pulled closer to each other
Most skeletal muscles work in pairs around a joint
One muscle in the pair, called the flexor, bends a joint
The other muscle, the extensor, straightens the joint
When one muscle of a pair contracts, the other muscle relaxes

11. Injuries and Disorders of the Muscular System

12. Some muscle diseases are hereditary
Diseases that affect muscle function can also affect other body systems
Muscular dystrophy is a hereditary disease that causes skeletal muscles to become weaker over time – it affects how muscle proteins form
A strain is a muscle injury in which muscle is over stretched or torn
Muscle tissue swells and can hurt
Tendinitis can occur when tendons become inflamed or torn when muscles are overused

13. Benefits of Exercise

14. Exercise is any activity that helps improve physical fitness and health
Benefits the muscular system, cardiovascular system and the skeletal system
Exercises that raise your heart rate to a certain level for at least 60 minutes improve fitness of the heart
Weight training helps bones stay dense and strong
Resistance exercise helps improve muscle strength by building muscle power – involve short bursts of intense effort – lifting weights and pushups
Endurance exercise allows muscles to contract for a longer time without getting tired – jogging and biking
Flexibility refers to full range of motion of a joint