Chapter 8: Muscular System Anatomy & Physiology 1 Pages 176-210

Ch. 8 Wordbytes Calat- = something inserted Erg- = work Hyper- = over, more Inter- = between Laten- = hidden Myo- = muscle Sarco- = flesh Syn- = together Tetan- = stiff -troph = well fed

8.1 Introduction All movements require muscles Muscles organs composed of specialized cells that use the chemical energy stored in nutrients to contract Muscular actions also: Provide muscle tone Propel body fluids and food Generate the heartbeat Distribute heat

Benefits of weight training: Resistance (weight) training can increase the ratio of muscle to fat in our bodies Benefits of weight training: Muscle burns calories 3x faster than fat = a lean body is more energetically efficient Weight-lifting increases muscle tone and bone density; lowers blood pressure; decreases the risk of developing arthritis, osteoporosis, and diabetes; improves self-esteem; lowers sick days

Three types of muscles: Skeletal Smooth Cardiac

8.2 Structure of Skeletal Muscle Skeletal muscle = organ of skeletal system Composed of skeletal muscle tissue, nervous tissue, blood, and other connective tissue

A. Connective Tissue Coverings Fascia layers of fibrous connective tissue that separate an individual skeletal muscle from adjacent muscles and hold it in position (fig. 8.1) Surrounds each muscle May project to form a tendon Fibers in tendon could intertwine with bone periosteum, attaching muscle to bone May form aponeuroses broad fibrous sheets that attach to bone or coverings of adjacent muscles (figs. 8.17 & 8.19)

2. Epimysium layer of connective tissue that surrounds a skeletal muscle 3. Perimysium layers of connective tissue that extend inward from the epimysium and separate the muscle tissue into small compartments 4. Fasicles bundles of skeletal muscle fibers found in perimysium 5. Endomysium thin covering found around each muscle fiber in a fasicle

Many blood vessels and nerves pass through layers Layers of connective tissue enclose and separate all parts of a skeletal muscle This allows all parts to move independently Many blood vessels and nerves pass through layers

B. Skeletal Muscle Fibers Skeletal muscle fiber single cell that contracts in response to stimulation then relaxes when stimulation ends Each fiber is a thin, elongated cylinder with rounded ends Cell membrane = sarcolemma Cytoplasm = sarcoplasm; contains many small nuclei , mitochondria, & myofibrils

Sarcomeres repeating pattern of units of muscle fibers Myofibrils help with muscle contraction. They contain 2 filaments that produce the bands (striations): Myosin thick Actin thin Sarcomeres repeating pattern of units of muscle fibers

2. Striation pattern has 2 parts: a 2. Striation pattern has 2 parts: a. I bands light bands composed of thin actin filaments directly attached to Z lines b. A bands dark bands composed of thick myosin filaments overlapping thin actin filaments i. H zone region of thick filaments ii. M line thickening 3. Sarcomere extends from one Z line to the next (figs. 8.2 and 8.3)

4. Sarcoplasmic reticulum membranous network of channels and tubules of a muscle fiber 5. Transverse tubules (T tubules) membranous channels that extend inward from a muscle fiber membrane *The sarcoplasmic reticulum and transverse tubules activate the muscle contraction mechanism when the fiber is stimulated

Got muscles?