1. 1.3 The Muscular System The organ system whose primary function is movement and flexibility

2. Kinds of Muscle 3 types: – Smooth Muscle Found in the digestive tract and in the walls of blood vessels – Cardiac Muscle Found only in your heart – Skeletal Muscle Is attached to your bones for movement Helps protect your inner organs

3. Kinds of Muscle Muscle action – Voluntary: you can control Skeletal Muscles – Involuntary: you cannot control Smooth and Cardiac Muscle Sometimes skeletal muscles – You can blink whenever you want to, but your eyes will blink on their own

4. Movement Signals travel from your brain to your skeletal muscle cells – Muscle cells then contract, or get shorter Muscles attach to bones – Tendons Strands of tough connective tissue – When a muscle that connects 2 bones gets shorter, the bones are pulled closer to each other Ex: Tendons attach the biceps to a cone in your shoulder and a bone in your forearm – When the biceps muscle contracts, your forearm bends toward your shoulder

5. Movement Muscles work in pairs – One muscle in the pair bends part of the body Called a flexor Ex: biceps – The other muscle straightens part of the body Called an extensor Ex: triceps http://www.purchon.com/biology/flash/elbow.swf

6. Use It or Lose It Muscles weaken when they are not exercised – Ex: Muscles in a cast Exercised muscles are stronger and larger – Strong muscles can help other organs Ex: Contracting muscles squeeze blood vessels which increases blood flow so the heart doesn’t have to work as hard – 2 types of exercises increase muscle strength and endurance Resistance exercise – Strengthens skeletal muscles – People work against the resistance, or weight, of an object – Ex: Using your own weight as resistance in sit-ups Aerobic Exercise – Steady, moderately intense activity – Increases muscle strength – Mostly strengthens the heart an increases endurance – Ex: Jogging, cycling, skating, swimming, walking

7. Muscle Injury Strain – An injury in which a muscle or tendon is overstretched or torn – Often happen because a muscle has not been warmed up – Happen when muscles are worked too hard Tendonitis – Tendons are overworked by people who exercise too much and the body cannot repair an injured tendon before the next exercise – The tendon becomes inflamed – Long rest is needed for it to heal

8. Steroids Anabolic Steroids – Short-term effects Muscles stronger Increased body size Bad acne Decreased sperm count in males – Cause long-term health problems Damage the heart, liver, and kidneys Cause high blood pressure If taken before the skeleton is mature, can cause bones to stop growing