Muscular System

Muscular System Notes
Note: You only have to write what looks like this.

Muscles
Muscles provide the tug on the bones needed to bend, straighten, and support joints. Muscles can pull on bones, but they can't push them back to their original position, so the muscles work in pairs.

• The flexor muscle contracts to bend the joint. 
• The extensor contracts to straighten (or extend) the limb at the same joint.

Muscles get their signals to contract and relax from the brain.

Smooth Muscles
Smooth muscles — also called involuntary muscles — can't be controlled by you. Your brain and body tell these muscles what to do without you even thinking about it. But smooth muscles are at work all over your body. In your stomach and digestive system, they contract (tighten up) and relax to allow food to make its journey through the body. 


You'll find smooth muscles at work behind the scenes in your eyes, too. These muscles keep the eyes focused.

Cardiac Muscle
The muscle that makes up the heart is called cardiac muscle. The thick muscles of the heart contract to pump blood out and then relax to let blood back in after it has circulated through the body.


Just like smooth muscle, cardiac muscle works all by itself with no help from you. A special group of cells within the heart are known as the pacemaker of the heart because it controls the heartbeat.

Skeletal Muscle
Skeletal muscles are voluntary muscles, which means you can control what they do.  These muscles help to make up the musculoskeletal system — the combination of your muscles and your skeleton.
Skeletal muscles are held to the bones with the help of tendons. Tendons are cords made of tough tissue, and they work as special connector pieces between bone and muscle. 


Skeletal muscles come in many different sizes and shapes to allow them to do many types of jobs. 
Some of your biggest and most powerful muscles are in your back, near your spine. These muscles help keep you upright and standing tall.

They also give your body the power it needs to lift and push things. Muscles in your neck and the top part of your back aren't as large, but they are capable of some pretty amazing things: Try rotating your head around, back and forth, and up and down to feel the power of the muscles in your neck. These muscles also hold your head high.

Face Muscle
Facial muscles don't all attach directly to bone like they do in the rest of the body. Instead, many of them attach under the skin. This allows you to contract your facial muscles just a tiny bit and make dozens of different kinds of faces. 

Your tongue is actually made of a group of muscles that work together to allow you to talk and help you chew food. Stick out your tongue and wiggle it around to see those muscles at work.

Major Muscles

• In each of your shoulders is a deltoid muscle. Your deltoid muscles help you move your shoulders every which way — from swinging a softball bat to shrugging your shoulders when you're not sure of an answer.

• Down under your ribcage are your rectus abdominus muscles, or abdominals. They're often called abs for short.

• When you make a muscle in your arm, you tense your biceps muscle. When you contract your biceps muscle, you can actually see it push up under your skin.

• Your quadriceps , or quads, are the muscles on the front of your thighs. Many people who run, bike, or play sports develop large, strong quads.

• And when it's time for you to take a seat? You'll be sitting on your gluteus maximus, the muscle that's under the skin and fat in your behind!