Mader Chapter on page 133
1. Skeletal – voluntary (attached to skeleton) 2. Cardiac – involuntary (heart) 3. Smooth – involuntary (walls of hollow internal organs)
1. Produce movement – picking up an object 2. Resist movement – posture, blood pressure (Newton’s 3 rd Law: muscles generate a force (static tension) that exactly opposes and equal but opposite force being applied to a body part 3. Generate heat – contraction of our muscles accounts for > 75% of all heat generated by the body – shivering thermogenesis 4. Stabilizing joints – stabilize & strengthen
A group of many individual cells, all w/same origin and insertion and all with the same function (p. 115) Arranged in bundles called fascicles Each bundle is enclosed in a sheath of fibrous connective tissue called fascia Each fascicle contains 12 to 1000s of individual muscle cells – called muscle fibers The outer surface of the whole muscle is covered with several more layers of fascia – at the ends all come together forming tendons
Tube shaped 3 cm – 30 cm (thigh) Can contain more than one nucleus just under the cell membrane (skeletal) Nearly entire cell is packed with long cylindrical structures in parallel called myofibrils Myofibrils are packed with contractile proteins called actin and myosin When myofibrils contract the muscle cell also contracts
Each skeletal muscle fiber is a long, cylindrical cell w/multiple oval nuclei just beneath the sarcolemma (plasma membrane) surface Fibers are large, 10 to 100 m in diameter, and up to hundreds of centimeters long Sarcoplasm, similar to cytoplasm of other cells, but has numerous glycosomes (=organelle full of glycogen) and a unique oxygen-binding protein called myoglobin, similar to hemoglobin
A single myofibril within one muscle cell (in your biceps) can contain > 100,000 sarcomeres arranged end to end. 100,000 sarcomeres all shortening at once produces a muscle contraction Understanding muscle shortening is simply understanding how a single sarcomere works
From Z to shining Z
2 kinds of proteins 1) Myosin – thick filaments regular intervals with a different protein 2) Actin – thin filaments that are structurally linked to the Z-line Myosin filaments are completely contained within the sarcomere Muscle contractions depend on the interaction of these 2 filaments
1. Nerves activate skeletal muscles 2. Activation releases calcium 3. Calcium starts the sliding filament mechanism 4. Contraction ends when nerve activation ends Sliding filament model of contraction
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1. Lots of mitochondria form ATP by aerobic cellular respiration 2. Muscles contain creatine phosphate (high E storage supply) used to regenerate ATP indirectly 3. ATP produced anaerobically when oxygen supply is limited
Continued intake of oxygen (panting) to complete the metabolism of lactic acid (built up anaerobically) Lactic acid is transported to the liver and broken down into carbon dioxide and water