The Muscular System

You are strong!

• If all your muscles were working together, you could lift about 20 cars!

Your body has about 700 muscles

Muscles make up about 40% of your body weight.

Muscles weigh more than fat

Who will sink and who will float?

Muscle fiber under a microscope.

Voluntary and involuntary muscles

The heart has involuntary muscle because we cannot control it.

Muscles in our arms and legs are voluntary and are skeletal muscles.

Nerve cells called motor neurons control muscles from signals from the brain.

Massage

Massage is good for your muscles and body, and can make you feel relaxed and happy.

Massage your pectoralis minor

If you type a lot on a computer, or ride a motorcycle a lot, this muscle can get very tight.

tendons

Tendons connect muscle to bone.

Your muscles need oxygen and glucose (sugar).

Why do our muscles “burn” when we exercise a lot?

• Lactic acid in your muscles causes that pain.

“Hitting the wall” happens when you have no glycogen.

Muscle cramps

Muscle cramps can have many causes, such as dehydration, not enough blood flowing to the muscle, or being tired.

Muscles move by contracting and relaxing

To take one step, you use 200 muscles.

Muscles cannot push, they can only pull.

When you push something, it’s because another muscle is pulling.

The largest muscle in your body is your gluteus maximus. Your butt!

When you’re cold, your muscles contract involuntarily.

He is shivering.

You can make your muscles grow!

When you lift weights, you tear your muscles. When they heal, they grow back stronger and bigger.

It takes a long time to grow muscles.

But they can shrink too. This is muscle atrophy.

This woman broke her leg, so she could not use her right leg for a long time.

Her right leg got smaller.

Your muscles need protein

Muscles usually work together with other muscles, not alone.

Muscular Dystrophy

A genetic disease that causes muscles to deteriorate.

Exercise and therapy can help.

Questions

• What nutrient do we need to build muscle?• What is an example of an involuntary muscle?• What connects muscle to bone?• About how many muscles do you have in your body?• What kind of energy does your muscles need?• What do your muscles do when you are really cold?• What kind of exercise can make our muscles grow?• What is the largest muscle in your body?• What happens if you don’t use your muscles?