Anatomy & Physiology 2 Unit 3

 Skeletal muscles:  Muscles that move bones of the skeleton  These allow you to move, walk, dance, run, etc  These muscles are all voluntary, meaning you can move them on your own, when you want to  The cells are very long and cylindrical (can be up to 1ft long), have obvious striation and are multinucleate  Skeletal muscles attach to bones by tendons

 Cardiac Muscles:  Found only in the heart  These muscles have their own “beat”  They are involuntary, meaning you don’t control your heart beat, it controls itself  The cells branch into chains, have striations and are uninucleate

 Smooth Muscles:  Makes up your intestines, arteries and many other body organs  Most of these are involuntary, but some are voluntary to some degree  The cells are long and thin, have no striations and are uninucleate

 Provides movement  Maintains posture  Stabilizes joints  Generates heat

 A muscle fiber is composed of many myofibrils surrounded by the sarcolemma  The myofibril is a unique organelle composed of a thin filament (actin) and a thick filament (myosin)  These are what cause muscle contraction

 Muscles work by contracting and relaxing  Skeletal muscles work by contracting against the bone and pulling bone  All muscles work in pairs, meaning when one contracts the other relaxes and vice versa

 When the muscle contracts the actin and myosin “catch” on one another  When the muscle is relaxed the actin and myosin “release” each other

 Isotonic Contractions  Typical shortening and lengthening contractions  Examples: squats, curls, smiling, picking up a child  Isometric Contractions  Occurs when the muscles do not shorten and lengthening but still contracting ▪ Examples: moving or holding furniture, holding a child

 When muscles are used for a long period of time they fatigue and oxygen debt (can’t take oxygen in fast enough for the muscles) occurs  However, they will continue to function, but under a different system  This system has a “pay back” period and lactic acid accumulates in the cells

 Flexion – bending knees or elbows  Extension – straightening the knee or elbow  Rotation – shaking your head “no”  Abduction – fanning fingers or toes apart  Adduction – opposite of abduction  Circumduction – moving a limb in a circle

 Direction – rectus (straight), oblique (slant)  Relative size – maximus (largest), minimus (smallest)  Location – temporalis (temporal bone), frontalis (frontal bone)  Number of origins – biceps (two origins), triceps (three origins), quadriceps (four origins)

 Location of origin and insertion – sternocleidomastoid (attaches to the sternum, clavicle and mastoid bones)  Shape of muscle – deltoid (triangular)  Action of muscle – flexor, extensor and adductor

 Muscular Dystrophy  Disease that causes the slow wasting away of skeletal muscle  Can be inherited  Mostly common in males  Strained Muscles  Caused by weak muscles that are not used to exercise  Usually not a problem and takes a few days to heal