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Musculoskeletal

Musculoskeletal. muscles. Chapter 4 SEHS. Muscle Tissue Lecture Outline. INTRODUCTION. Motion results from alternating contraction (shortening) and relaxation of muscles; the skeletal system provides leverage and a supportive framework for this movement.

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Musculoskeletal

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  1. Musculoskeletal muscles

  2. Chapter 4 SEHS Muscle Tissue Lecture Outline

  3. INTRODUCTION • Motion results from alternating contraction (shortening) and relaxation of muscles; the skeletal system provides leverage and a supportive framework for this movement. • The scientific study of muscles is known as myology. Principles of Human Anatomy and Physiology, 11e

  4. Chapter 10Muscle Tissue • Alternating contraction and relaxation of cells • Chemical energy changed into mechanical energy Principles of Human Anatomy and Physiology, 11e

  5. OVERVIEW OF MUSCLE TISSUE • Types of Muscle Tissue • Skeletal muscle tissue is primarily attached to bones. It is striated and voluntary. • Cardiac muscle tissue forms the wall of the heart. It is striated and involuntary. • Smooth (visceral) muscle tissue is located in viscera. It is nonstraited (smooth) and involuntary. • Table 4.4 compares the different types of muscle. Principles of Human Anatomy and Physiology, 11e

  6. 3 Types of Muscle Tissue • Skeletal muscle • attaches to bone, skin or fascia • striated with light & dark bands visible with scope • voluntary control of contraction & relaxation Principles of Human Anatomy and Physiology, 11e

  7. 3 Types of Muscle Tissue • Cardiac muscle • striated in appearance • involuntary control • autorhythmic because of built in pacemaker Principles of Human Anatomy and Physiology, 11e

  8. 3 Types of Muscle Tissue • Smooth muscle • attached to hair follicles in skin • in walls of hollow organs -- blood vessels & GI • nonstriated in appearance • involuntary Principles of Human Anatomy and Physiology, 11e

  9. Functions of Muscle Tissue • Producing body movements • Stabilizing body positions • Regulating organ volumes • bands of smooth muscle called sphincters • Movement of substances within the body • blood, lymph, urine, air, food and fluids, sperm • Producing heat • involuntary contractions of skeletal muscle (shivering) Principles of Human Anatomy and Physiology, 11e

  10. Properties of Muscle Tissue • Excitability • respond to chemicals released from nerve cells • Conductivity • ability to propagate electrical signals over membrane • Contractility • ability to shorten and generate force • Extensibility • ability to be stretched without damaging the tissue • Elasticity • ability to return to original shape after being stretched Principles of Human Anatomy and Physiology, 11e

  11. SKELETAL MUSCLE TISSUE • Each skeletal muscle is a separate organ composed of cells called fibers. Principles of Human Anatomy and Physiology, 11e

  12. Skeletal Muscle -- Connective Tissue • Superficial fascia is loose connective tissue & fat underlying the skin • Deep fascia = dense irregular connective tissue around muscle • Connective tissue components of the muscle include • epimysium = surrounds the whole muscle • perimysium = surrounds bundles (fascicles) of 10-100 muscle cells • endomysium = separates individual muscle cells • All these connective tissue layers extend beyond the muscle belly to form the tendon Principles of Human Anatomy and Physiology, 11e

  13. Connective Tissue Components Principles of Human Anatomy and Physiology, 11e

  14. Muscle Fiber or Myofibers • Muscle cells are long, cylindrical & multinucleated • Sarcolemma = muscle cell membrane • Sarcoplasm filled with tiny threads called myofibrils & myoglobin (red-colored, oxygen-binding protein) Principles of Human Anatomy and Physiology, 11e

  15. Myofibrils & Myofilaments • Muscle fibers are filled with threads called myofibrils separated by SR (sarcoplasmic reticulum) • The sarcoplasmic reticulum encircles each myofibril. It is similar to smooth endoplasmic reticulum in nonmuscle cells and in the relaxed muscle stores calcium ions. • Myofilaments (thick & thin filaments) are the contractile proteins of muscle Principles of Human Anatomy and Physiology, 11e

  16. Sarcoplasmic Reticulum (SR) • System of tubular sacs similar to smooth ER in nonmuscle cells • Stores Ca+2 in a relaxed muscle • Release of Ca+2 triggers muscle contraction Principles of Human Anatomy and Physiology, 11e

  17. Filaments and the Sarcomere • Thick and thin filaments overlap each other in a pattern that creates striations (light I bands and dark A bands) • The I band region contains only thin filaments. • They are arranged in compartments called sarcomeres, separated by Z discs. • In the overlap region, six thin filaments surround each thick filament Principles of Human Anatomy and Physiology, 11e

  18. Sarcomere • Figure 10.5 shows the relationships of the zones, bands, and lines as seen in a transmission electron micrograph. • Exercise can result in torn sarcolemma, damaged myofibrils, and disrupted Z discs (Clinical Application). Principles of Human Anatomy and Physiology, 11e

  19. Thick & Thin Myofilaments • Supporting proteins (M line, titin and Z disc help anchor the thick and thin filaments in place) Principles of Human Anatomy and Physiology, 11e

  20. Thick & Thin Myofilaments Overlap Dark(A) & light(I) bands (electron microscope) Principles of Human Anatomy and Physiology, 11e

  21. The Proteins of Muscle • Myofibrils are built of 3 kinds of protein • contractile proteins • myosin and actin • regulatory proteins which turn contraction on & off • troponin and tropomyosin • structural proteins which provide proper alignment, elasticity and extensibility • titin, myomesin, nebulin and dystrophin Principles of Human Anatomy and Physiology, 11e

  22. The Proteins of Muscle -- Myosin • Thick filaments are composed of myosin • each molecule resembles two golf clubs twisted together • myosin heads (cross bridges) extend toward the thin filaments • Held in place by the M line proteins. Principles of Human Anatomy and Physiology, 11e

  23. The Proteins of Muscle -- Actin • Thin filaments are made of actin, troponin, & tropomyosin • The myosin-binding site on each actin molecule is covered by tropomyosin in relaxed muscle • The thin filaments are held in place by Z lines. From one Z line to the next is a sarcomere. Principles of Human Anatomy and Physiology, 11e

  24. http://www.youtube.com/watch?v=0kFmbrRJq4w Principles of Human Anatomy and Physiology, 11e

  25. http://www.blackwellpublishing.com/matthews/myosin.html Principles of Human Anatomy and Physiology, 11e

  26. Human back muscles • http://www.scivee.tv/node/2413 Principles of Human Anatomy and Physiology, 11e

  27. Structural Proteins • Structural proteins keep the thick and thin filaments in the proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix. • Titin helps a sarcomere return to its resting length after a muscle has contracted or been stretched. • Myomesin forms the M line. • Nebulin helps maintain alignment of the thin filaments in the sarcomere. • Dystrophin reinforces the sarcolemma and helps transmit the tension generated by the sarcomeres to the tendons. • Table 10.1 reviews the type of proteins in skeletal muscle. Principles of Human Anatomy and Physiology, 11e

  28. The Proteins of Muscle -- Titin • Titan anchors thick filament to the M line and the Z disc. • The portion of the molecule between the Z disc and the end of the thick filament can stretch to 4 times its resting length and spring back unharmed. • Role in recovery of the muscle from being stretched. Principles of Human Anatomy and Physiology, 11e

  29. Structural Proteins • The M line (myomesin) connects to titin and adjacent thick filaments. • Nebulin, an inelastic protein helps align the thin filaments. • Dystrophin links thin filaments to sarcolemma and transmits the tension generated to the tendon. Principles of Human Anatomy and Physiology, 11e

  30. Sliding Filament Mechanism Of Contraction • Myosin cross bridgespull on thin filaments • Thin filaments slide inward • Z Discs come toward each other • Sarcomeres shorten.The muscle fiber shortens. The muscle shortens • Notice :Thick & thin filaments do not change in length Principles of Human Anatomy and Physiology, 11e

  31. Overview: From Start to Finish Basic Structures • Nerve ending • Neurotransmitter • Muscle membrane • Stored Ca+2 • ATP • Muscle proteins Principles of Human Anatomy and Physiology, 11e

  32. How Does Contraction Begin? • Nerve impulse reaches an axon terminal & synaptic vesicles release acetylcholine (ACh) • ACh diffuses to receptors on the sarcolemma & Na+ channels open and Na+ rushes into the cell • A muscle action potential spreads over sarcolemma and down into the transverse tubules • SR releases Ca+2 into the sarcoplasm • Ca+2 binds to troponin & causes troponin-tropomyosin complex to move & reveal myosin binding sites on actin--the contraction cycle begins Principles of Human Anatomy and Physiology, 11e

  33. Contraction Cycle • Repeating sequence of events that cause the thick & thin filaments to move past each other. • 4 steps to contraction cycle • ATP hydrolysis • attachment of myosin to actin to form crossbridges • power stroke • detachment of myosin from actin • Cycle keeps repeating as long as there is ATP available & there is a high Ca+2 level near the filaments. Principles of Human Anatomy and Physiology, 11e

  34. Steps in the Contraction Cycle • Notice how the myosin head attaches and pulls on the thin filament with the energy released from ATP Principles of Human Anatomy and Physiology, 11e

  35. ATP and Myosin • Myosin heads are activated by ATP • Activated heads attach to actin & pull (power stroke) • ADP is released. (ATP released P & ADP & energy) • Thin filaments slide past the thick filaments • ATP binds to myosin head & detaches it from actin • All of these steps repeat over and over • if ATP is available & • Ca+ level near the troponin-tropomyosin complex is high Principles of Human Anatomy and Physiology, 11e

  36. Excitation - Contraction Coupling • All the steps that occur from the muscle action potential reaching the T tubule to contraction of the muscle fiber. Principles of Human Anatomy and Physiology, 11e

  37. Relaxation • Acetylcholinesterase (AChE) breaks down ACh within the synaptic cleft • Muscle action potential ceases • Ca+2 release channels close • Active transport pumps Ca+2 back into storage in the sarcoplasmic reticulum • Calcium-binding protein (calsequestrin) helps hold Ca+2 in SR (Ca+2 concentration 10,000 times higher than in cytosol) • Tropomyosin-troponin complex recovers binding site on the actin Principles of Human Anatomy and Physiology, 11e

  38. Overview: From Start to Finish • Nerve ending • Neurotransmittor • Muscle membrane • Stored Ca+2 • ATP • Muscle proteins Principles of Human Anatomy and Physiology, 11e

  39. CARDIAC MUSCLE TISSUE - Overview • Cardiac muscle tissue is found only in the heart walland top of Aorta (see Chapter 20). • Its fibers are arranged similarly to skeletal muscle fibers. • Cardiac muscle fibers connect to adjacent fibers by intercalated discs which contain desmosomes and gap junctions (Figure 4.1e). • Cardiac muscle contractions last longer than the skeletal muscle twitch due to the prolonged delivery of calcium ions from the sarcoplasmic reticulum and the extracellular fluid. • Cardiac muscle fibers contract when stimulated by their own autorhythmic fibers. • This continuous, rhythmic activity is a major physiological difference between cardiac and skeletal muscle tissue. Principles of Human Anatomy and Physiology, 11e

  40. Cardiac versus Skeletal Muscle • More sarcoplasm and mitochondria • Larger transverse tubules located at Z discs, rather than at A-l band junctions • Less well-developed SR • Limited intracellular Ca+2 reserves • more Ca+2 enters cell from extracellular fluid during contraction • Prolonged delivery of Ca+2 to sarcoplasm, produces a contraction that last 10 -15 times longer than in skeletal muscle Principles of Human Anatomy and Physiology, 11e

  41. SMOOTH MUSCLE • Smooth muscle tissue is nonstriated and involuntary and is classified into two types: visceral (single unit) smooth muscle (Figure 10.18a) and multiunit smooth muscle (Figure 10.18b). • Visceral (single unit) smooth muscle is found in the walls of hollow viscera and small blood vessels; the fibers are arranged in a network and function as a “single unit.” • Multiunit smooth muscle is found in large blood vessels, large airways, arrector pili muscles, and the iris of the eye. The fibers operate singly rather than as a unit. Principles of Human Anatomy and Physiology, 11e

  42. Two Types of Smooth Muscle • Visceral (single-unit) • in the walls of hollow viscera & small BV • autorhythmic • gap junctions cause fibers to contract in unison • Multiunit • individual fibers with own motor neuron ending • found in large arteries, large airways, arrector pili muscles,iris & ciliary body Principles of Human Anatomy and Physiology, 11e

  43. INTRODUCTION • The voluntarily controlled muscles of the body make up the muscular system. • The muscular system and muscle tissue contribute to homeostasis by producing movement, stabilizing body position, regulating organ volume, moving substances within the body, and producing heat. • This chapter discusses how skeletal muscles produce movement and describes the principal skeletal muscles. Principles of Human Anatomy and Physiology, 11e

  44. Chapter 11The Muscular System • Skeletal muscle major groupings • How movements occur at specific joints • Learn the origin, insertion, function and innervation of all major muscles • Important to allied health care and physical rehabilitation students Principles of Human Anatomy and Physiology, 11e

  45. Muscle Attachment Sites:Origin and Insertion • Skeletal muscles shorten & pull on the bones they are attached to • Origin is the bone that does not move when muscle shortens (normally proximal) • Insertion is the movable bone (some 2 joint muscles) • Fleshy portion of the muscle in between attachment sites = belly Principles of Human Anatomy and Physiology, 11e

  46. Tenosynovitis • Inflammation of tendon and associated connective tissues at certain joints • wrist, elbows and shoulder commonly affected • Pain associated with movement • Causes • trauma, strain or excessive exercise Principles of Human Anatomy and Physiology, 11e

  47. Lever Systems and Leverage • A lever is a rigid structure that moves around a fixed point, the fulcrum (F) • The lever is acted on by two different forces: (Figure 11.1b). • resistance (load) (L), which opposes movement • effort (E) which causes movement Bones serve as levers and joints serve as fulcrums. • Leverage, the mechanical advantage gained by a lever, is largely responsible for a muscle’s strength and range of motion (ROM), i.e., the maximum ability to move the bones of a joint through an arc. Principles of Human Anatomy and Physiology, 11e

  48. Levers Principles of Human Anatomy and Physiology, 11e

  49. Levers are categorized into three types – • First class levers (EFL) e.g. a seesaw – the head on the vertebral column (Figure 11.2a) • Second-class (FLE) eg. a wheelbarrow(Figure 11.2b) • Third-class (FEL) (Figure 11.1b) e.g. forceps - the elbow joint (Figure 11.2c). Principles of Human Anatomy and Physiology, 11e

  50. Lever Systems and Leverage • Muscle acts on rigid rod (bone)that moves around a fixed point called a fulcrum • Resistance is weight of bodypart & perhaps an object • Effort or load is work doneby muscle contraction • Mechanical advantage • the muscle whose attachment is farther from the joint will produce the most force • the muscle attaching closer to the joint has the greater range of motion and the faster the speed it can produce Principles of Human Anatomy and Physiology, 11e

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