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Chapter 10

Chapter 10. 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. The scientific study of muscles is known as myology.

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Chapter 10

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  1. Chapter 10 Muscle Tissue Lecture Outline

  2. 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

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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

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

  11. 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

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

  13. Connective Tissue Components • Tendons and aponeuroses are extensions of connective tissue beyond muscle cells that attach muscle to bone or other muscle. • A tendon is a cord of dense connective tissue that attaches a muscle to the periosteum of a bone (Figure 11.22). • An aponeurosis is a tendon that extends as a broad, flat layer (Figure 11.4c). Principles of Human Anatomy and Physiology, 11e

  14. Nerve and Blood Supply • Each skeletal muscle is supplied by a nerve, artery and two veins. • Each motor neuron supplies multiple muscle cells (neuromuscular junction) • Each muscle cell is supplied by one motor neuron terminal branch and is in contact with one or two capillaries. • nerve fibers & capillaries are found in the endomysium between individual cells Principles of Human Anatomy and Physiology, 11e

  15. 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

  16. Sarcolemma, T Tubules, and Sarcoplasm • Skeletal muscle consists of fibers (cells) covered by a sarcolemma (Figure 10.3b). • The fibers contain T tubules and sarcoplasm • T tubules are tiny invaginations of the sarcolemma that quickly spread the muscle action potential to all parts of the muscle fiber. • Sarcoplasm is the muscle cell cytoplasm and contains a large amount of glycogen for energy production and myoglobin for oxygen storage. Principles of Human Anatomy and Physiology, 11e

  17. Transverse Tubules • T (transverse) tubules are invaginations of the sarcolemma into the center of the cell • filled with extracellular fluid • carry muscle action potentials down into cell • Mitochondria lie in rows throughout the cell • near the muscle proteins that use ATP during contraction Principles of Human Anatomy and Physiology, 11e

  18. Myofibrils and Sarcoplasmic Reticulum • Each fiber contains myofibrils that consist of thin and thick filaments (myofilaments) (Figure 10.3b). Principles of Human Anatomy and Physiology, 11e

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

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

  25. 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

  26. 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

  27. 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

  28. Principles of Human Anatomy and Physiology, 11e

  29. Principles of Human Anatomy and Physiology, 11e

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

  31. 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

  32. 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

  33. 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

  34. 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

  35. 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

  36. 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

  37. 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

  38. 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

  39. 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

  40. 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

  41. 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

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

  43. Neuromuscular Junction (NMJ) or Synapse • NMJ = myoneural junction • end of axon nears the surface of a muscle fiber at its motor end plate region (remain separated by synaptic cleft or gap) Principles of Human Anatomy and Physiology, 11e

  44. Structures of NMJ Region • Synaptic end bulbs are swellings of axon terminals • End bulbs contain synaptic vesicles filled with acetylcholine (ACh) • Motor end plate membrane contains 30 million ACh receptors. Principles of Human Anatomy and Physiology, 11e

  45. Events Occurring After a Nerve Signal • Arrival of nerve impulse at nerve terminal causes release of ACh from synaptic vesicles • ACh binds to receptors on muscle motor end plate opening the gated ion channels so that Na+ can rush into the muscle cell • Inside of muscle cell becomes more positive, triggering a muscle action potential that travels over the cell and down the T tubules • The release of Ca+2 from the SR is triggered and the muscle cell will shorten & generate force • Acetylcholinesterase breaks down the ACh attached to the receptors on the motor end plate so the muscle action potential will cease and the muscle cell will relax. Principles of Human Anatomy and Physiology, 11e

  46. Pharmacology of the NMJ • Botulinum toxin blocks release of neurotransmitter at the NMJ so muscle contraction can not occur • bacteria found in improperly canned food • death occurs from paralysis of the diaphragm • Curare (plant poison from poison arrows) • causes muscle paralysis by blocking the ACh receptors • used to relax muscle during surgery • Neostigmine (anticholinesterase agent) • blocks removal of ACh from receptors so strengthens weak muscle contractions of myasthenia gravis • also an antidote for curare after surgery is finished Principles of Human Anatomy and Physiology, 11e

  47. Muscle MetabolismProduction of ATP in Muscle Fibers • Muscle uses ATP at a great rate when active • Sarcoplasmic ATP only lasts for few seconds • 3 sources of ATP production within muscle • creatine phosphate • anaerobic cellular respiration • aerobic cellular respiration Principles of Human Anatomy and Physiology, 11e

  48. MUSCLE METABOLISM • Creatine phosphate and ATP can power maximal muscle contraction for about 15 seconds and is used for maximal short bursts of energy (e.g., 100-meter dash) (Figure 10.13a). • Creatine phosphate is unique to muscle fibers. Principles of Human Anatomy and Physiology, 11e

  49. MUSCLE METABOLISM • The partial catabolism of glucose to generate ATP occurs in anaerobic cellular respiration (Figure 10.13b). This system can provide enough energy for about 30-40 seconds of maximal muscle activity (e.g., 300-meter race). • Muscular activity lasting more than 30 seconds depends increasingly on aerobic cellular respiration (reactions requiring oxygen). This system of ATP production involves the complete oxidation of glucose via cellular respiration (biological oxidation) (Figure 10.13c). Principles of Human Anatomy and Physiology, 11e

  50. Creatine Phosphate: Details • Excess ATP within resting muscle used to form creatine phosphate • Creatine phosphate 3-6 times more plentiful than ATP within muscle • Its quick breakdownprovides energy for creation of ATP • Sustains maximal contraction for 15 sec (used for 100 meter dash). • Athletes tried creatine supplementation • gain muscle mass but shut down bodies own synthesis (safety?) Principles of Human Anatomy and Physiology, 11e

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