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Muscle funccellularlevel animal systems
This document summarizes the functions of muscular tissue at the cellular level. It discusses the three main types of muscle tissue - skeletal, cardiac, and smooth muscle - and their distinct locations, functions, appearances, and methods of control. For each type of muscle tissue, it provides details on structure, contraction mechanisms, and proteins involved. It also examines the sliding filament model of muscle contraction and how calcium regulates the exposure of actin binding sites to trigger muscle shortening.
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Muscle funccellularlevel animal systems
- 1. MO Figure MuscleFunction at the Cellular Level Michael Patrick O'Neill/Science Source.
- 2. Functions of MuscularTissue • Like nervous tissue, muscles are excitable or "irritable” they have the ability to respond to a stimulus • Unlike nerves, however, muscles are also: Contractible (they can shorten in length) Extensible (they can extend or stretch) Elastic (they can return to their original shape)
- 3. Functions of MuscularTissue • Muscle makes up a large percentage of the body’s weight • Their main functions are to: Create motion – muscles work with nerves, bones, and joints to produce body movements Stabilize body positions and maintain posture Store substances within the body using sphincters
- 4. Three Types ofMuscular Location Function Appearance Control Skeletal skeleton movement, heat, posture striated, multi-nucleated (eccentric), fibers parallel voluntary Cardiac heart pump blood continuously striated, one central nucleus involuntary Visceral (smooth muscle) G.I. tract, uterus, eye, blood vessels Peristalsis, blood pressure, pupil size, erects hairs no striations, one central nucleus involuntary Tissue
- 5. Three Types ofMuscular Tissue (a) Skeletal muscle (b) Cardiac muscle (c) Visceral smooth muscle
- 6. Location Function AppearanceControl Skeletal skeleton movement, heat, posture striated, multi-nucleated (eccentric), fibers parallel voluntary Cardiac heart pump blood continuously striated, one central nucleus involuntary Visceral (smooth muscle) G.I. tract, uterus, eye, blood vessels Peristalsis, blood pressure, pupil size, erects hairs no striations, one central nucleus involuntary Skeletal Muscle
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- 8. Skeletal Muscle Skeletalmuscle fibers are very long “cells” - next to neurons (which can be over a meter long), perhaps the longest in the body The Sartorious muscle contains single fibers that are at least 30 cm long A single skeletal muscle fiber
- 9. Motor neuron Sarcolemma Skeletal Muscle The terminal processes of a motor neuron in close proximity to the sarcolemma of a skeletal muscle fiber
- 10. Skeletal muscle fibers A muscle fiber consists of a single cell. • The cell is long and multinucleated. • The cytoplasm is called the sarcoplasm. • Contains a specialized ER, called the sarcoplasmic reticulum, that stores calcium. • Contains myofibrils made up of thick and thin filaments.
- 11. The Skeletal MuscleFiber Increasing the level of magnification, the myofibrils are seen to be composed of filaments Thick filaments Thing filaments
- 12. The Skeletal MuscleFiber • The basic functional unit of skeletal muscle fibers is the sarcomere: An arrangement of thick and thin filaments sandwiched between two Z discs A scanning electron micrograph of a sarcomere
- 13. The Skeletal MuscleFiber • Muscle contraction occurs in the sarcomeres The “Z line” is really a Z disc when considered in 3 dimensions. A sarcomere extends from Z disc to Z disc.
- 14. Muscle Proteins •Myofibrils are built from three groups of proteins Contractile proteins generate force during contraction Regulatory proteins help switch the contraction process on and off Structural proteins keep the thick and thin filaments in proper alignment and link the
- 15. Muscle Proteins •The thin filaments are comprised mostly of the structural protein actin, and the thick filaments are comprised mostly of the structural protein myosin
- 16. Muscle Proteins •In the thin filaments actin proteins are strung together like a bead of pearls • In the thick filaments myosin proteins look like golf clubs bound together
- 17. Muscle Proteins Inthis first graphic, the myosin binding sites on the actin proteins are readily visible. The regulatory proteins troponin and tropomyosin have been added to the bottom graphic: The myosin binding sites have been covered
- 18. Muscle Proteins Inthis graphic the troponin-tropomyosin complex has slid down into the “gutters” of the actin molecule unblocking the myosin binding site Myosin binding site exposed The troponin-tropomyosin complex can slide back and forth depending on the presence of Ca2+
- 19. Muscle Proteins •Ca2+ binds to troponin which changes the shape of the troponin-tropomyosin complex and uncovers the myosin binding sites on actin
- 20. Muscle Proteins •Besides contractile and regulatory proteins, muscle contains about a dozen structural proteins which contribute to the alignment, stability, elasticity, and extensibility of myofibrils • Titan is the third most plentiful protein in muscle, after actin and myosin - it extends from the Z disc and accounts for much of the elasticity of myofibrils • Dystrophin is discussed later as it relates to the disease of muscular dystrophy
- 21. The Sliding-Filament Mechanism • With exposure of the myosin binding sites on actin (the thin filaments)—in the presence of Ca2+ and ATP—the thick and thin filaments “slide” on one another and the sarcomere is shortened
- 22. The Sliding-Filament Mechanism • The “sliding” of actin on myosin (thick filaments on thin filaments) can be broken
- 23. Figure 1 Slidingfilament model Thick (myosin) and thin (actin) filaments slide past one another during muscle contraction. As a result, the sarcomere shortens.
- 24. Figure 2 Sarcomeres C. F. Armstrong/Science Source. Z-discs form dark lines in electron micrographs and give skeletal muscle a striated appearance.
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- 26. Figure 4 Muscleanatomy
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- 29. Muscle energy storage Glycogen • Glucose polymer. Glucose is used in cellular respiration to make ATP. Creatine phosphate • Transfers a phosphate to ADP to form ATP.
- 30. Figure 5 Muscleinnervation Muscle fibers can be innervated by a single neuron, which increases contraction strength at the expense of fine control, or by multiple neurons, which allows finer control but with little strength.
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- 33. Figure 6 Excitation-contractioncoupling
- 34. Figure 7 Regulationof contraction In resting muscle, tropomyosin covers myosin-binding sites on actin. The troponin complex holds tropomyosin in place. Ca2+ binding to troponin causes tropomyosin to shift, which exposes the myosin-binding sites. Myosin binds actin, and the muscle contracts.
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- 38. MO Figure SkeletalSystem and Locomotion Art Wolfe/Science Source
- 39. Skeletal systems Endoskeleton:inside the animal Exoskeleton: outside the animal Hydrostatic skeleton: composed of pressurized water in internal compartments.
- 40. Figure 1 Hydrostaticskeletons © 2006 Nature Publishing Group Alvarado, A & Tsonis, P. Bridging the regeneration gap: genetic insights from diverse animal models. Nature Reviews Genetics 7, 873–884 (2006) doi:10.1038/nrg1923. Used with permission. This Hydra moves using a hydrostatic skeleton.
- 41. Figure 2 Peristalticmovement Caused by alternating radial and longitudinal muscle contractions against a fluid-filled coelom.
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- 44. Figure 3 Exoskeletons © 2002 Nature Publishing Group GDC seeks members of new Appointing Body. British Dental Journal 193, 431– 433 (2002), doi:10.1038/sj.bdj.4801590. Used with permission. Arthropod exoskeletons contain chitin.
- 45. Figure 4 Thehuman skeleton
- 46. Figure 5 Antagonisticmuscle pairs Coordinated movement enables flexion and extension of a limb.
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- 49. Figure 6 Balanceand locomotion During walking and running, the feet are used for balancing, pushing off, and maintaining momentum.
- 50. Figure 7 Terrestriallocomotion Stephen Dalton/Science Source. Energy stored in tendons enables this frog to jump.
Editor's Notes
- #8 All muscle start as these spindly shaped cells from myoblasts – skeletal muscle cells fuse to form large fibers… Satellite cells are small mononuclear progenitor cells with virtually no cytoplasm found in mature muscle. They are found sandwiched between the basement membrane and sarcolemma (cell membrane) of individual muscle fibres, and can be difficult to distinguish from the sub-sarcolemmal nuclei of the fibres. Satellite cells are able to differentiate and fuse to augment existing muscle fibres and to form new fibres. These cells represent the oldest known adult stem cell niche, and are involved in the normal growth of muscle, as well as regeneration following injury or disease.
- #9 It’s difficult to find the sartorius muscle in some people (cadavers)
- #12 Sarcomeres are multi-protein complexes composed of three different filament systems. The thick filament system is composed of myosin protein which is connected from the M-line to the Z-disc by titin. It also contains myosin-binding protein C which binds at one end to the thick filament and the other to actin. The thin filaments are assembled by actin monomers bound to nebulin, which also involves tropomyosin (a dimer which coils itself around the F-actin core of the thin filament) and troponin. Nebulin and titin give stability and structure to the sarcomere.
- #13 Z-line (from the German "Zwischenscheibe“). Each myofibril is made up of thin filament proteins and thick filament proteins, arranged (configured) in sarcomeres.
- #14 Each myofibril is made up of thin filament proteins, and thick filament proteins, arranged (configured) in sarcomeres
- #21 Titin is the largest known protein, consisting of 34,350 amino acids. Titin, also known as connectin is a protein that is important in the contraction of striated muscle tissues. Dystrophin, not Titin, is the protein absent in muscular dystrophy.
- #26 This interactive can be found as a separate file in your downloaded folder. This slide is a placeholder only. The image is a screen shot taken from the digital book.