Biology 204: Introduction to Physiology Muscle Physiology I Striated muscle Unstriated muscle Skeletal muscle Cardiac muscle Smooth muscle Voluntary muscle Involuntary muscle Categorization of muscle. Figure 8-1 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 258. Photomicrographs of skeletal (striated) muscle. Left: A single, teased fiber from the human gastrocnemius muscle. Note cross-banding and multiple, peripherally located nuclei. x 275. Right: Parts of several fibers from the diaphragm. Note that there are bundles of myofibrils in each fiber and that the cross-banding is in register across the myofibrils; however, thin slips of sarcoplasm between myofibrils show no banding. Plastic section. x 650. Figure 6-1 from Leeson, C. Roland, Thomas S. Leeson, &amp; Anthony A. Paparo. Textbook of Histology. 5th ed. Philadelphia: W. B. Saunders, 1985, p. 173. Photomicrographs of striated muscle fibers from the human gastrocnemius muscle. Left: Longitudinal section showing A, I, Z, and H bands. x 1250. Right: Transverse section. Note multiple, peripheral nuclei and numerous myofibrils visible in pale sarcoplasm. Plastic section. x 1000. Figure 6-3 from Leeson, C. Roland, Thomas S. Leeson, &amp; Anthony A. Paparo. Textbook of Histology. 5th ed. Philadelphia: W. B. Saunders, 1985, p. 174. Electron micrograph showing portions of seven myofibrils cut longitudinally from the noncontracted (i.e., relaxed) psoas muscle of a rabbit. The dark A (anisotropic) bands are bisected by the lighter H bands in which there is a thin, dark M band. The I (isotropic) bands are bisected by very dark Z lines. A single sarcomere extends from one Z line to the next Z line. x 13,000. (Courtesy of Dr. H. E. Huxley.) Figure 6-6 from Leeson, C. Roland, Thomas S. Leeson, &amp; Anthony A. Paparo. Textbook of Histology. 5th ed. Philadelphia: W. B. Saunders, 1985, p. 176. Electron micrograph of relaxed rabbit psoas muscle in longitudinal section. The thick myosin filaments extend throughout the length of the A band; the thin actin filaments are found in the I band and extend into the A band as far as the H band. There are two actin filaments between every two myosin filaments. Cross linkages between actin and myosin filaments are visible. x 74,000. (Courtesy of Dr. H. E. Huxley.) Figure 6-7 from Leeson, C. Roland, Thomas S. Leeson, &amp; Anthony A. Paparo. Textbook of Histology. 5th ed. Philadelphia: W. B. Saunders, 1985, p. 177. Muscle Tendon Muscle fiber (a single muscle cell) Enlargement of a cross section of whole muscle. Figure 8-2a from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 259. Connective tissue Muscle fiber Dark A band Light I band Myofibril Enlargement of a myofibril within a muscle fiber. Figure 8-2b from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 259. Surface membrane of muscle fiber Myofibrils Segments of sarcoplasmic reticulum Lateral sacs Transverse (T) tubule I band A band I band The T-tubules and sarcoplasmic reticulum in relationship to the myofibrils. Figure 8-10 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 265. Z line Portion of myofibril A band I band M line Sarcomere Thick filament Thin filament H zone A band I band Cross bridges M line H zone Z line Myosin Thick filament Actin Thin filament Cytoskeletal and protein components of a myofibril. Figure 82c-d from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: ThomsonBrooks/Cole, 2004, p. 259. Cross-sectional arrangement of thick and thin filaments. Figure 8-4 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: ThomsonBrooks/Cole, 2004, p. 260. I band A band I band Cross bridge Thick filament Thin filament Sarcomere Z line H zone I band A band Z line Relaxed H zone shorter I band shorter A band same width Contracted Thick filament Sarcomere shorter Thin filament Changes in banding pattern during shortening: the sliding filament model. Figure 88 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 263. Sliding filament model Click to view animation. Model of dystrophin and its associated proteins at the muscle membrane. Figure 1 from Nawrotzki, Ralph, Derek J. Blake, &amp; Kay E. Davies. The genetic basis of neuromuscular disorders. Trends in Genetics 12(8): 294 298, August, 1996. Myosin molecule Actin binding site Myosin ATPase site Heads Tail Structure of myosin molecules and their organization within a thick filament. Figure 8-5 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 261. Thick filament Cross bridge Myosin molecule Structure of myosin molecules and their organization within a thick filament. Figure 8-5 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 261. Binding site for attachment with myosin cross bridge Actin molecules Actin helix + (See next slide) Composition of a thin filament. Figure 8-6 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 261. Tropomyosin Troponin Thin filament Composition of a thin filament. Figure 8-6 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 261. Tropomyosin Actin Thin filament Troponin Myosin cross bridge Cross-bridge binding sites Cross-sectional view Actin Troponin Cross-bridge binding site Tropomyosin Actin binding site Myosin cross bridge Relaxed Excited Muscle fiber excited; released Ca2+ binds with troponin, pulling troponintropomyosin complex aside to expose cross-bridge binding site; cross-bridge binding occurs Muscle fiber relaxed; no crossbridge binding because the crossbridge binding site on actin is physically covered by the troponintropomyosin complex Longitudinal view Binding of actin and myosin cross bridge triggers power stroke that pulls thin filament inward during contraction Role of calcium in turning on cross bridges. Figure 8-7 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 262. Click to view animation. Actin molecules in thin myofilament Cross bridge activity. Figure 8-9a from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 264. BINDING Myosin cross bridge binds to actin molecule. Z line Myosin cross bridge POWER STROKE Cross bridge bends, pulling thin myofilament inward. DETACHMENT Cross bridge detaches at end of power stroke and returns to original conformation. BINDING Cross bridge binds to more distal actin molecule; cycle repeated. Energized Resting Detachment Binding Bending (power stroke) Cross-bridge cycle: The role of ATP. Figure 813 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 267. Rigor complex Terminal button T tubule Surface membrane of muscle cell Acetylcholine Acetylcholinegated cation channel Lateral sacs of sarcoplasmic reticulum Tropomyosin Troponin Actin Cross-bridge binding Myosin cross bridge Calcium release in excitation-contraction coupling. Figure 8-12 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 266. Calcium release and reuptake Click to view animation. Click to view animation. Cross bridge power strokes are all directed toward the center of the thick filament. Figure 8-9b from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 264. Thin myofilament Thick myofilament Cross bridge activity of one thick filament pulls a total of twelve thin filaments toward the center of the sarcomere. Figure 8-9c from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 264. Extension Triceps contracts Extension and flexion of the elbow joint. Figure 8-20 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: ThomsonBrooks/Cole, 2004, p. 274. Origin of triceps Origin of biceps Flexion Triceps Biceps Insertion of biceps Insertion of triceps Biceps contracts Contractile component (sarcomeres) Series-elastic component (connective tissue/tendon) Load Load Relationship between the contractile component and the series-elastic component in transmitting muscle tension to bone. Figure 8-19 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 273. Lever systems of muscles, bones, and joints. Figure 8-22a from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 276. Fulcrum Lever systems of muscles, bones, and joints. Figure 8-22b from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 276. Fulcrum for lever Biceps Insertion of biceps Stimulation Contraction Relaxation time time Relationship of an action potential to the resultant muscle twitch. Figure 8-14 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 268. Action potential Contractile response Muscle twitch Latent period Spinal cord = Motor unit 1 = Motor unit 2 = Motor unit 3 Schematic representation of motor units in a skeletal muscle. Figure 8-15 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 269. Comparison of motor recruitment in muscles with small motor units and muscles with large motor units. Figure 8-16 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: ThomsonBrooks/Cole, 2004, p. 270. Contractile activity Twitch summation Tetanus Single twitch Stimulation ceases or fatigue begins If a muscle fiber is restimulated after it has completely relaxed, the second twitch is the same magnitude as the first twitch. Action potentials If a muscle fiber is restimulated before it has completely relaxed, the second twitch is added on to the first twitch, resulting in summation. If a muscle fiber is stimulated so rapidly that it does not have an opportunity to relax at all between stimuli, a maximal sustained contraction known as tetanus occurs. Summation and tetanus. Figure 8-17 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 271. Length-tension relationship. Figure 8-18 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 272. Maximum velocity of shortening (zero load) Maximum load (zero velocity of shortening i.e., isometric contraction) Load velocity relationship. Figure 8-21 from Sherwood, Lauralee. <a href="/keyword/human-physiology/" >human physiology</a> : From Cells to Systems. 5th ed. Belmont CA: Thomson-Brooks/Cole, 2004, p. 275.