Most muscles work together in pairs. One muscle pulls while the other muscle relaxes. When you bend your arm the biceps muscle pulls and the triceps muscle relaxes. When you make your arm straight, the biceps muscle relaxes and the triceps muscle pulls.

Muscles are very important. They help you do almost everything — from pumping blood throughout your body to lifting your heavy backpack. You control some of your muscles and others, like your heart, do their jobs without you thinking about them at all.

 You use 17 muscles when you smile.  You use 43 muscles when you frown.

 Provides voluntary movement of body  Enables breathing, blinking, and smiling  Allows you to hop, skip, jump, or do push-ups  Maintains posture  Produces heat

CCauses heart beat DDirects circulation of blood RRegulates blood pressure SSends blood to different areas of the body

PProvides movement of internal organs MMoves food through digestive tract EEnables bladder control CCauses involuntary actions RReflex actions AAdjusts opening of pupils CCauses hair to stand on end: goosebumps.

TThere are three main types of muscle tissue SSkeletal (striated) CCardiac (heart) SSmooth (visceral)

Muscle Type Cardiac Function Movement of bone Walls of internal organs + in skin Location Attached to bone Heart SmoothSkeletal Control Mode Beating of heart InvoluntaryInvoluntary Movement of internal organs Voluntary

_______- Muscle that bends the joint when contracted. _________- Muscle that straightens the joint when contracted. ___________ muscle is short, firm, tight and thicker around. ________ muscle is stretched, long, loose and thinner around. Flexor Extensor Relaxed Contracted

MMuscles are bundles of cells and fibers. MMuscles work in a very simple way. All they do is tighten up--that is, contract--and relax. YYou have two sets of muscles attached to many of your bones which allow them to move. TThere are 630 active muscles in your body and they act in groups. MMuscles can only pull. They never push.