Skeletal and Muscular Systems

Skeletal System The framework for your body 206 bones “Os-” bone; “Osteo-” bone

Osteocytes are bone cells

Bone contains: Minerals – especially calcium which provides for the hardness of bone Collagen fibers which provides strength of bone

Bone has an excellent blood supply

Joint “art-” and “arthr-” mean joint Ligaments stabilize joints Cartilage caps the bones at the joint for a smooth surface

Cartilage “chondr-” means cartilage Healing capability is poorer than bone

Skeleton Function Framework Support Movement Protection Blood cell production from bone marrow Storage of minerals & fat

Disorders of Skeleton-Osteoporosis

Incidence Common in the U.S. Responsible for many fractures each year

Cause Inadequate calcium Females, older more commonly Sedentary lifestyle Poor diet Pregnancy giving calcium to fetus Menopause lead to calcium withdrawal from bone

Prevention/Treatment Weight-bearing exercise Calcium in diet Estrogen replacement therapy after menopause Drugs, such as Fosamax

Arthritis Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the joints in the body leading to their gradual destruction

Arthritis Osteoarthritis is the wear and tear arthritis due to joint damage and injuries

Sprain Joint injury that stretches or tears supportive ligaments A severe sprain can result in a dislocation

Fracture Generally bones heal well with proper alignment, stabilization, and without infection

Fractures Hairline or greenstick Simple Compound = Open Comminuted

Muscular System “Myo-” means muscle Muscle tissue is capable of contraction

Smooth muscle Found in the wall of tubular structures such as intestine Involuntary Smooth appearance microscopically Peristalsis is a wave like contraction of smooth muscle

Cardiac Muscle Heart muscle Involuntary Striated, or striped when observed microscopically

Skeletal Muscle Muscle attached to the skeleton Voluntary Striated microscopically

Skeletal Muscle Tendons attach muscle to bone

Microscopic Muscle Myofiber = muscle cell Myofibril = the striated parts of the muscle cell Myofilaments = the proteins that make up the myofibrils

Myofilaments The two main proteins that comprise the myofilaments are: –Myosin – very thick protein –Actin – very thin protein

Sarcomere The actin and myosin in the muscle cells are arranged in small groups called SARCOMERES Since contraction occurs at the microscopic level of the sarcomere, the sarcomere is the functional unit of contraction

Sliding Filament Theory This describes the mechanics of muscle contraction The myosin “heads” grab on to the actin protein and pull the actin towards the center of the sarcomere, making the sarcomere shorter.

ATP ATP is necessary for muscle contraction Running out of ATP leads to muscle fatigue

Motor Neuron Skeletal muscle will not contract unless a motor neuron (movement nerve cell) stimulates it to contract

Motor Unit A motor neuron plus how every many skeletal muscle cells it serves is a motor unit A motor unit that has one neuron to one muscle cell allows for very precise movements A motor unit that has one neuron to 400 muscle cells does not provide precise control