Every time you move, Your muscles are doing work. Video The Muscular System Every time you move, Your muscles are doing work. Video

Extend and curl your arm. What muscles are working? Contracting When one muscle is contracting, the other is relaxing…

Three different types of muscles Skeletal Voluntary Attached to bones By thick strands of connective tissue Tendons Connect muscles to bone Allows us to do lots of activities Most muscles work in pairs

Smooth Muscles Not under voluntary control These work automatically when your body needs them to Found with organs that are used in digestion

Cardiac Muscle Found only in the heart Involuntary

Muscle Contraction Contracting Muscles get shorter and thicker They contract because their cells can become shorter Muscle cells/fibers contract when they get a nervous impulse from the brain

Even when muscles aren’t moving, some of their fibers are contracting Muscle tone Slight, constant contraction due to contractions of muscle fibers This helps maintain our posture Keeps our head up, not enough to turn our head, but enough to keep your head up

Energy and Muscle Contraction Muscles use energy when they contract This energy is from a chemical reaction in our muscle cells Use sugar glucose that is made from the food you eat Sugar glucose + Oxygen = energy

If you are really active, O2 can’t keep up with glucose, so a chemical reaction happens that doesn’t need O2. This produces lactic acid This causes your muscles to get tired

Reflexes Reflexes An automatic movement that happens quickly Happen to muscles that we have voluntary control over

Activity In groups, make up a test to test your reaction time (no one should get hurt!) Be prepared to share in front of the class

Caring for your muscles (write down 3 of these) Get regular exercise Eat high protein foods Practice good posture to strengthen back muscles Warm up and cool down to prevent injury Lift correctly

Get out a yellow book and turn to Page 389 In your notes define: Bruises, muscle strains or sprains, tendinitis, hernia, and muscular dystrophy