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Copyright © 2010 Pearson Education, Inc. Muscles Part I H. Biology II Adapted 2014-2015 Overview of Muscular Tissue Skeletal Muscle Tissue Contraction.

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Presentation on theme: "Copyright © 2010 Pearson Education, Inc. Muscles Part I H. Biology II Adapted 2014-2015 Overview of Muscular Tissue Skeletal Muscle Tissue Contraction."— Presentation transcript:

1 Copyright © 2010 Pearson Education, Inc. Muscles Part I H. Biology II Adapted Overview of Muscular Tissue Skeletal Muscle Tissue Contraction and Relaxation of Skeletal Muscle Fibers Muscle Metabolism Control of Muscle Tension Types of Skeletal Muscle Fibers Exercise and Skeletal Muscle Tissue Cardiac Muscle Tissue Smooth Muscle Tissue Regeneration of Muscle Tissue Development of Muscle Aging and Muscular Tissue

2 Copyright © 2010 Pearson Education, Inc. Muscular System 9-2 Three Types of Muscle Tissues Skeletal Muscle usually attached to bones voluntary- under conscious control striated Smooth Muscle walls of most viscera, blood vessels, skin involuntary - not under conscious control not striated Cardiac Muscle wall of heart involuntary - not under conscious control striated

3 Copyright © 2010 Pearson Education, Inc. Table 9.3

4 Copyright © 2010 Pearson Education, Inc. Special Characteristics of Muscle Tissue Excitability (responsiveness or irritability): ability to receive and respond to stimuli Contractility: ability to shorten when stimulated Extensibility: ability to be stretched or extended without damage Elasticity: ability to recoil to resting length (bounce back)

5 Copyright © 2010 Pearson Education, Inc. Functions of a Muscle Tissue Movement: Skeletal- locomotion, vision, facial expression Cardiac- blood pumping Smooth- food digestion Posture: (skeletal) Joint Stability: (skeletal) Heat Generation:(skeletal) A. shivering to increase heat production B. contract muscle to provide heat

6 Copyright © 2010 Pearson Education, Inc. Structure of a Skeletal Muscle Skeletal Muscle organs of the muscular system skeletal muscle tissue nervous tissue blood Each muscle is served by one artery, one nerve, and one or more veins Connective tissues and muscle tissue: 1.fascia – covers the muscle 2.tendon – attaches the muscle 3.aponeuroses – muscle to muscle

7 Copyright © 2010 Pearson Education, Inc. Macroscopic Anatomy of skeletal muscles Skeletal muscle fiber (cell) Muscle Fascicle Surrounded by perimysium Surrounded by endomysium endomysium perimysium Skeletal muscle Surrounded by epimysium epimysium tendon Play IP Anatomy of Skeletal muscles (IP p. 4-6)

8 Copyright © 2010 Pearson Education, Inc. Figure 9.1 Bone Perimysium Endomysium (between individual muscle fibers) Muscle fiber Fascicle (wrapped by perimysium) Epimysium Tendon Epimysium Muscle fiber in middle of a fascicle Blood vessel Perimysium Endomysium Fascicle (a) (b)

9 Copyright © 2010 Pearson Education, Inc. Anatomy of a Skeletal Muscle Coverings of a muscle Epimysium 1. Epimysium - outer Perimysium 2. Perimysium - middle. Endomysium 3. Endomysium - inner Organization of Muscle muscle fascicles muscle fibers myofibrils thick and thin filaments

10 Copyright © 2010 Pearson Education, Inc. Anatomy of a Skeletal Muscle 9-4 Coverings of a muscle Epimysium 1. Epimysium – dense regular connective tissue surrounding the entire muscle Perimysium 2. Perimysium – fibrous connective tissue surrounding a fascicle. Endomysium 3. Endomysium – thin areolar connective tissue surrounding each muscle cell Organization of Muscle muscle fascicles fascicles – bundle of muscle cells muscle fibers muscle fibers – a muscle cell myofibrils myofibrils – a long, filamentous organelle found within muscle cells that has a banded appearance thick and thin filaments (myofilament)- thick and thin filaments (myofilament)- actin &myosin filaments sarcomere sarcomere – contractile unit of muscle

11 Copyright © 2010 Pearson Education, Inc. Skeletal Muscle Tissue The number of skeletal muscle fibers is set before you are born Most of these cells last a lifetime Muscle growth occurs by hypertrophy An enlargement of existing muscle fibers Testosterone and human growth hormone stimulate hypertrophy Satellite cells retain the capacity to regenerate damaged muscle fibers

12 Copyright © 2010 Pearson Education, Inc. Microscopic Anatomy of Skeletal Muscle Fiber 9-5 sarcolemma sacroplasm sarcoplasmic reticulum transverse tubule triad cisterna of sarcoplasmic reticulum transverse tubule myofibril actin filaments myosin filaments sarcomere

13 Copyright © 2010 Pearson Education, Inc. Skeletal Muscle Tissue-Microscopic Anatomy Sarcolemma The plasma membrane of a muscle cell Transverse (T tubules) Tunnel in from the plasma membrane Muscle action potentials travel through the T tubules Sarcoplasm, the cytoplasm of a muscle fiber Sarcoplasm includes glycogen used for synthesis of ATP and a red-colored protein called myoglobin which binds oxygen molecules Myoglobin releases oxygen when it is needed for ATP production

14 Copyright © 2010 Pearson Education, Inc. Skeletal Muscle Tissue- Microscopic Anatomy Myofibrils Thread like structures which have a contractile function Sarcoplasmic reticulum (SR) Membranous sacs which encircles each myofibril Stores calcium ions (Ca ++ ) Release of Ca ++ triggers muscle contraction Filaments Function in the contractile process Two types of filaments (Thick and Thin) There are two thin filaments for every thick filament Sarcomeres Compartments of arranged filaments Basic functional unit of a myofibril

15 Copyright © 2010 Pearson Education, Inc. Triad Relationships T tubules conduct impulses deep into muscle fiber Integral proteins protrude into the intermembrane space from T tubule and SR cisternae membranes T tubule proteins: voltage sensors SR foot proteins: gated channels that regulate Ca 2+ release from the SR cisternae

16 Copyright © 2010 Pearson Education, Inc. Sarcomere Smallest contractile unit (functional unit) of a muscle fiber The region of a myofibril between two successive Z discs Composed of thick and thin myofilaments made of contractile proteins Each myofibril contains 10,000 sarcomeres end to end.

17 Copyright © 2010 Pearson Education, Inc. Check for Understanding 1:

18 Copyright © 2010 Pearson Education, Inc. Check for Understanding 2:

19 Copyright © 2010 Pearson Education, Inc. Microanatomy of a Muscle Fiber (Cell) sarcolemma transverse (T) tubules sarcoplasmic reticulum terminal cisternae myofibril thin myofilament thick myofilament triad mitochondria Play IP Anatomy of Skeletal muscles (IP p. 7) nuclei myoglobin

20 Copyright © 2010 Pearson Education, Inc. Muscle fiber myofibril Thin filamentsThick filaments Thin myofilament Myosin molecule of thick myofilament sarcomere Z-line

21 Copyright © 2010 Pearson Education, Inc. Sarcomere 9-6 I band A band H zone Z line M line

22 Copyright © 2010 Pearson Education, Inc. Skeletal Muscle Tissue Z discs Separate one sarcomere from the next Thick and thin filaments overlap one another A band Darker middle part of the sarcomere Thick and thin filaments overlap I band Lighter, contains thin filaments but no thick filaments Z discs passes through the center of each I band H zone Center of each A band which contains thick but no thin filaments M line Supporting proteins that hold the thick filaments together in the H zone

23 Copyright © 2010 Pearson Education, Inc. Skeletal Muscle Tissue Muscle Proteins Myofibrils are built from three kinds of proteins 1) Contractile proteins Generate force during contraction 2) Regulatory proteins Switch the contraction process on and off 3) Structural proteins Align the thick and thin filaments properly Provide elasticity and extensibility Link the myofibrils to the sarcolemma

24 Copyright © 2010 Pearson Education, Inc. Contractile Proteins Myosin Thick filaments Functions as a motor protein which can achieve motion Convert ATP to energy of motion Projections of each myosin molecule protrude outward (myosin head) Actin Thin filaments Actin molecules provide a site where a myosin head can attach Tropomyosin and troponin are also part of the thin filament In relaxed muscle Myosin is blocked from binding to actin Strands of tropomyosin cover the myosin-binding sites Calcium ion binding to troponin moves tropomyosin away from myosin-binding sites Allows muscle contraction to begin as m yosin binds to actin

25 Copyright © 2010 Pearson Education, Inc. Structural Proteins Titin Stabilize the position of myosin accounts for much of the elasticity and extensibility of myofibrils Dystrophin Links thin filaments to the sarcolemma

26 Copyright © 2010 Pearson Education, Inc. The Sliding Filament Mechanism Myosin heads attach to and “walk” along the thin filaments at both ends of a sarcomere Progressively pulling the thin filaments toward the center of the sarcomere Z discs come closer together and the sarcomere shortens Leading to shortening of the entire muscle In the relaxed state, thin and thick filaments overlap only slightly During contraction, myosin heads bind to actin, detach, and bind again, to propel the thin filaments toward the M line As H zones shorten and disappear, sarcomeres shorten, muscle cells shorten, and the whole muscle shortens

27 Copyright © 2010 Pearson Education, Inc. Sliding Filament Mechanism When sarcomeres shorten, actin and myosin filaments slide past one another VIDEOVIDEO#1 VIDEO #2

28 Copyright © 2010 Pearson Education, Inc. Figure 9.6 I Fully relaxed sarcomere of a muscle fiber Fully contracted sarcomere of a muscle fiber I A ZZ H IIA ZZ 1 2

29 Copyright © 2010 Pearson Education, Inc. Figure 9.3 Flexible hinge region Tail Tropomyosin TroponinActin Myosin head ATP- binding site Heads Active sites for myosin attachment Actin subunits Actin-binding sites Thick filament Each thick filament consists of many myosin molecules whose heads protrude at opposite ends of the filament. Thin filament A thin filament consists of two strands of actin subunits twisted into a helix plus two types of regulatory proteins (troponin and tropomyosin). Thin filament Thick filament In the center of the sarcomere, the thick filaments lack myosin heads. Myosin heads are present only in areas of myosin-actin overlap. Longitudinal section of filaments within one sarcomere of a myofibril Portion of a thick filament Portion of a thin filament Myosin molecule Actin subunits

30 Copyright © 2010 Pearson Education, Inc. Contraction & Relaxation of Skeletal Muscle

31 Copyright © 2010 Pearson Education, Inc. Microscopic Contraction Events

32 Copyright © 2010 Pearson Education, Inc. Contraction & Relaxation of Skeletal Muscle The Contraction Cycle The onset of contraction begins with the SR releasing calcium ions into the muscle cell Where they bind to actin opening the myosin binding sites

33 Copyright © 2010 Pearson Education, Inc. Contraction & Relaxation of Skeletal Muscle The contraction cycle consists of 4 steps 1) ATP hydrolysis Hydrolysis of ATP reorients and energizes the myosin head 2) Formation of cross-bridges Myosin head attaches to the myosin-binding site on actin 3) Power stroke During the power stroke the crossbridge rotates, sliding the filaments 4) Detachment of myosin from actin As the next ATP binds to the myosin head, the myosin head detaches from actin The contraction cycle repeats as long as ATP is available and the Ca ++ level is sufficiently high Continuing cycles applies the force that shortens the sarcomere

34 Copyright © 2010 Pearson Education, Inc. Cross Bridge Cycle Continues as long as the Ca2+ signal and adequate ATP are present Cross bridge formation—high-energy myosin head attaches to thin filament Working (power) stroke—myosin head pivots and pulls thin filament toward M line Cross bridge detachment—ATP attaches to myosin head and the cross bridge detaches “Cocking” of the myosin head—energy from hydrolysis of ATP cocks the myosin head into the high-energy state

35 Copyright © 2010 Pearson Education, Inc. Contraction & Relaxation of Skeletal Muscle

36 Copyright © 2010 Pearson Education, Inc. 1 Myosin heads hydrolyze ATP and become reoriented and energized ADP P = Ca 2+ Key: Contraction cycle continues if ATP is available and Ca 2+ level in the sarcoplasm is high 1 Myosin heads hydrolyze ATP and become reoriented and energized Myosin heads bind to actin, forming crossbridges ADP P P = Ca 2+ Key: 2 Contraction cycle continues if ATP is available and Ca 2+ level in the sarcoplasm is high 1 Myosin heads hydrolyze ATP and become reoriented and energized Myosin heads bind to actin, forming crossbridges Myosin crossbridges rotate toward center of the sarcomere (power stroke) Contraction cycle continues if ATP is available and Ca 2+ level in the sarcoplasm is high ADP P P = Ca 2+ Key: Myosin heads hydrolyze ATP and become reoriented and energized Myosin heads bind to actin, forming crossbridges Myosin crossbridges rotate toward center of the sarcomere (power stroke) As myosin heads bind ATP, the crossbridges detach from actin Contraction cycle continues if ATP is available and Ca 2+ level in the sarcoplasm is high ADP ATP P P = Ca 2+ Key: ATP 2 3 4

37 Copyright © 2010 Pearson Education, Inc. Figure Actin Cross bridge formation. Cocking of myosin head. The power (working) stroke. Cross bridge detachment. Ca 2+ Myosin cross bridge Thick filament Thin filament ADP Myosin PiPi ATP hydrolysis ATP 24 3 ADP PiPi PiPi

38 Copyright © 2010 Pearson Education, Inc. Contraction & Relaxation of Skeletal Muscle

39 Copyright © 2010 Pearson Education, Inc. Role of Calcium (Ca 2+ ) in Contraction At low intracellular Ca 2+ concentration: Tropomyosin blocks the active sites on actin Myosin heads cannot attach to actin Muscle fiber relaxes

40 Copyright © 2010 Pearson Education, Inc. Role of Calcium (Ca 2+ ) in Contraction At higher intracellular Ca 2+ concentrations: Ca 2+ binds to troponin Troponin changes shape and moves tropomyosin away from active sites Events of the cross bridge cycle occur When nervous stimulation ceases, Ca 2+ is pumped back into the SR and contraction ends

41 Copyright © 2010 Pearson Education, Inc. Contraction & Relaxation of Skeletal Muscle

42 Copyright © 2010 Pearson Education, Inc. Muscle Contraction The generation of force Does not necessarily cause shortening of the fiber Shortening occurs when tension generated by cross bridges on the thin filaments exceeds forces opposing shortening

43 Copyright © 2010 Pearson Education, Inc. Requirements for Skeletal Muscle Contraction 1.Activation: neural stimulation at a neuromuscular junction 2.Excitation-contraction coupling: ( not heavily discussed 2015) Generation and propagation of an action potential along the sarcolemma Final trigger: a brief rise in intracellular Ca 2+ levels

44 Copyright © 2010 Pearson Education, Inc. Skeletal Muscle Contraction ? How does a muscle contract?

45 Copyright © 2010 Pearson Education, Inc. Sequence of a Muscle Contraction (Summary) Brain Spinal Cord Nerve (Action potential) Motor Unit Neuromuscular Junction (Calcium is released) Acetylcholine (Neurotransmitter) Contraction

46 Copyright © 2010 Pearson Education, Inc. Motor Unit single motor neuron (a single nerve) one motor neuron and many skeletal muscle fibers 9-9

47 Copyright © 2010 Pearson Education, Inc. Contraction & Relaxation of Skeletal Muscle The Neuromuscular Junction Motor neurons have a threadlike axon that extends from the brain or spinal cord to a group of muscle fibers Neuromuscular junction (NMJ) Action potentials arise at the interface of the motor neuron and muscle fiber Synapse Where communication occurs between a somatic motor neuron and a muscle fiber Synaptic cleft Gap that separates the two cells Neurotransmitter Chemical released by the initial cell communicating with the second cell Synaptic vesicles Sacs suspended within the synaptic end bulb containing molecules of the neurotransmitter acetylcholine (Ach) Motor end plate The region of the muscle cell membrane opposite the synaptic end bulbs Contain acetylcholine receptors

48 Copyright © 2010 Pearson Education, Inc. Neuromuscular Junction 9-8 site where a motor nerve fiber and a skeletal muscle fiber meet

49 Copyright © 2010 Pearson Education, Inc. Muscle Contraction 9-10 Action potential causes the release of Ca ++ at the NMJ. a neurotransmitter releases a chemical substance from the motor end fiber, causing stimulation of the muscle fiber That substance is called acetylcholine (ACh) ACh causes the muscle fibers to become stimulated and contract (shorten).

50 Copyright © 2010 Pearson Education, Inc. Contraction & Relaxation of Skeletal Muscle Nerve impulses elicit a muscle action potential in the following way 1) Release of acetylcholine Nerve impulse arriving at the synaptic end bulbs causes many synaptic vesicles to release ACh into the synaptic cleft 2) Activation of ACh receptors Binding of ACh to the receptor on the motor end plate opens an ion channel Allows flow of Na + to the inside of the muscle cell 3) Production of muscle action potential The inflow of Na + makes the inside of the muscle fiber more positively charged triggering a muscle action potential The muscle action potential then propagates to the SR to release its stored Ca ++ 4) Termination of ACh activity (Relaxation) Ach effects last only briefly because it is rapidly broken down by acetylcholinesterase (AChE)

51 Copyright © 2010 Pearson Education, Inc. 1 Axon terminal Axon collateral of somatic motor neuron Sarcolemma Myofibril ACh is released from synaptic vesicle Junctional fold Synaptic vesicle containing acetylcholine (ACh) Sarcolemma Synaptic cleft (space) Motor end plate Synaptic cleft (space) (a) Neuromuscular junction (b) Enlarged view of the neuromuscular junction (c) Binding of acetylcholine to ACh receptors in the motor end plate Synaptic end bulb Synaptic end bulb Neuromuscular junction (NMJ) Synaptic end bulb Motor end plate Nerve impulse 1 1 Axon terminal Axon collateral of somatic motor neuron Sarcolemma Myofibril ACh is released from synaptic vesicle ACh binds to Ach receptor Junctional fold Synaptic vesicle containing acetylcholine (ACh) Sarcolemma Synaptic cleft (space) Motor end plate Synaptic cleft (space) (a) Neuromuscular junction (b) Enlarged view of the neuromuscular junction (c) Binding of acetylcholine to ACh receptors in the motor end plate Synaptic end bulb Synaptic end bulb Neuromuscular junction (NMJ) Synaptic end bulb Motor end plate Nerve impulse Na Axon terminal Axon collateral of somatic motor neuron Sarcolemma Myofibril ACh is released from synaptic vesicle ACh binds to Ach receptor Junctional fold Synaptic vesicle containing acetylcholine (ACh) Sarcolemma Synaptic cleft (space) Motor end plate Synaptic cleft (space) (a) Neuromuscular junction (b) Enlarged view of the neuromuscular junction (c) Binding of acetylcholine to ACh receptors in the motor end plate Synaptic end bulb Synaptic end bulb Neuromuscular junction (NMJ) Synaptic end bulb Motor end plate Nerve impulse Muscle action potential is produced Na Axon terminal Axon collateral of somatic motor neuron Sarcolemma Myofibril ACh is released from synaptic vesicle ACh binds to Ach receptor Junctional fold Synaptic vesicle containing acetylcholine (ACh) Sarcolemma Synaptic cleft (space) Motor end plate Synaptic cleft (space) (a) Neuromuscular junction (b) Enlarged view of the neuromuscular junction (c) Binding of acetylcholine to ACh receptors in the motor end plate Synaptic end bulb Synaptic end bulb Neuromuscular junction (NMJ) Synaptic end bulb Motor end plate Nerve impulse Muscle action potential is produced ACh is broken down Na

52 Copyright © 2010 Pearson Education, Inc. Pearson NMJ

53 Copyright © 2010 Pearson Education, Inc. Relaxation of a Muscle- Review acetylcholinesterase – an enzyme that breaks down acetylcholine. NMJ muscle impulse stops calcium moves back into sarcoplasmic reticulum myosin and actin action prevented muscle fiber relaxes Cd 9-14

54 Copyright © 2010 Pearson Education, Inc. Recruitment of Motor Units 9-22 Recruitment - increase in the number of motor units activated whole muscle composed of many motor units all or none principle as intensity of stimulation or contraction increases, recruitment of motor units continues until all motor units are activated = all or none principle

55 Copyright © 2010 Pearson Education, Inc. Applications for M. Contraction/Relaxation Botulinum toxin Blocks release of ACh from synaptic vesicles May be found in improperly canned foods A tiny amount can cause death by paralyzing respiratory muscles Used as a medicine (Botox®) Strabismus (crossed eyes) Blepharospasm (uncontrollable blinking) Spasms of the vocal cords that interfere with speech Cosmetic treatment to relax muscles that cause facial wrinkles Alleviate chronic back pain due to muscle spasms in the lumbar region

56 Copyright © 2010 Pearson Education, Inc. Applications for Muscle Contraction/Relaxation Curare A plant poison used by South American Indians on arrows and blowgun darts Causes muscle paralysis by blocking ACh receptors inhibiting Na + ion channels Derivatives of curare are used during surgery to relax skeletal muscles Anticholinesterase Slow actions of acetylcholinesterase and removal of ACh Can strengthen weak muscle contractions Ex: Neostigmine Treatment for myasthenia gravis Antidote for curare poisoning Terminate the effects of curare after surgery Myasthenia Gravis Common symptoms can include: A drooping eyelid Blurred or double vision Slurred speech Difficulty chewing and swallowing Weakness in the arms and legs Chronic muscle fatigue Difficulty breathing

57 Copyright © 2010 Pearson Education, Inc. Question ???? We now know how a muscle contracts and relaxes, so is energy needed for that to happen? NOorYES?

58 Copyright © 2010 Pearson Education, Inc. How is energy that is stored in food released? Cellular Respiration Oxygen Glucose Energy ATP H 2 O + CO 2

59 Copyright © 2010 Pearson Education, Inc. ENERGY The energy used to power the interaction between actin and myosin filaments comes from ATP (useable chemical energy) produced by cellular respiration. ATP stored in skeletal muscle last only about six seconds. ATP must be regenerated continuously if contraction is to continue

60 Copyright © 2010 Pearson Education, Inc. Ways to Make Energy Sources for Contraction Creatine phosphate – stores energy that quickly converts unusable energy (ADP) to usable energy (ATP) 6 Seconds!! Cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. 1) Creatine phosphate (ADP)2) Cellular respiration (Aerobic or Anaerobic)

61 Copyright © 2010 Pearson Education, Inc. Muscle Metabolism

62 Copyright © 2010 Pearson Education, Inc. Muscle Metabolism Creatine Phosphate Excess ATP is used to synthesize creatine phosphate Energy-rich molecule Creatine phosphate transfers its high energy phosphate group to ADP regenerating new ATP Creatine phosphate and ATP provide enough energy for contraction for about 15 seconds

63 Copyright © 2010 Pearson Education, Inc. Ways to Make Energy Sources for Contraction Creatine phosphate – stores energy that quickly converts unusable energy (ADP) to usable energy (ATP) 6 Seconds!! Cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. 1) Creatine phosphate (ADP)2) Cellular respiration (Aerobic or Anaerobic)

64 Copyright © 2010 Pearson Education, Inc. Cellular Respiration (CR) THREE SERIES OF REACTIONS in CR 1.Glycolysis 2.Citric acid cycle 3.Electron transport chain Produces carbon dioxide water ATP (chemical energy) heat Two Types of Reactions Anaerobic Respiration Anaerobic Respiration (without O 2 ) - produce little ATP Aerobic Respiration Aerobic Respiration (requires O 2 ) - produce most ATP 4-11

65 Copyright © 2010 Pearson Education, Inc. Anaerobic Reaction (Glycolysis) Recall that glycolysis results in pyruvate acid. If O 2 is not present, pyruvate can be fermented into LACTIC ACID. Lactic Acid It is a waste product of pyruvate acid. Occurs in many muscle cells. Accumulation causes muscle soreness and fatigue.

66 Copyright © 2010 Pearson Education, Inc. Muscle Metabolism Anaerobic Respiration Series of ATP producing reactions that do not require oxygen Glucose is used to generate ATP when the supply of creatine phosphate is depleted Glucose is derived from the blood and from glycogen stored in muscle fibers Glycolysis breaks down glucose into molecules of pyruvic acid and produces two molecules of ATP If sufficient oxygen is present, pyruvic acid formed by glycolysis enters aerobic respiration pathways producing a large amount of ATP If oxygen levels are low, anaerobic reactions convert pyruvic acid to lactic acid which is carried away by the blood Anaerobic respiration can provide enough energy for about 30 to 40 seconds of muscle activity

67 Copyright © 2010 Pearson Education, Inc. Ways to Make Energy Sources for Contraction Creatine phosphate – stores energy that quickly converts unusable energy (ADP) to usable energy (ATP) 6 Seconds!! Cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. 1) Creatine phosphate (ADP)2) Cellular respiration (Aerobic or Anaerobic)

68 Copyright © 2010 Pearson Education, Inc. Oxygen Supply & Cellular Respiration Anaerobic Phase Steps are called glycolysis. occur in the cytoplasm no oxygen produces pyruvic acid and produces lactic acid little ATP Aerobic Phase Steps are called citric acid cycle and electron transport chain. occur in the mitochondrion oxygen produces most ATP / CO2/ H2O

69 Copyright © 2010 Pearson Education, Inc.

70 Muscle Metabolism Aerobic Respiration Activity that lasts longer than half a minute depends on aerobic respiration Pyruvic acid entering the mitochondria is completely oxidized generating ATP carbon dioxide Water Heat Each molecule of glucose yields about 36 molecules of ATP Muscle tissue has two sources of oxygen 1) Oxygen from hemoglobin in the blood 2) Oxygen released by myoglobin in the muscle cell Myoglobin and hemoglobin are oxygen-binding proteins Aerobic respiration supplies ATP for prolonged activity Aerobic respiration provides more than 90% of the needed ATP in activities lasting more than 10 minutes

71 Copyright © 2010 Pearson Education, Inc. Ways to Make Energy Sources for Contraction Creatine phosphate – stores energy that quickly converts unusable energy (ADP) to usable energy (ATP) 6 Seconds!! Cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. 1) Creatine phosphate (ADP)2) Cellular respiration (Aerobic or Anaerobic)

72 Copyright © 2010 Pearson Education, Inc. Summary of Cellular Respiration Total ATP Production 2 ATP – Glycolysis 2 ATP – Citrus Acid Cycle 34 ATP – Electron Transport Chain 38 ATP – Total energy released from one molecule of glucose.

73 Copyright © 2010 Pearson Education, Inc. Oxygen Debt oxygen not available glycolysis continues pyruvic acid converted to lactic acid Oxygen debt – amount of oxygen needed by liver to convert lactic acid to glucose

74 Copyright © 2010 Pearson Education, Inc. Muscle Metabolism Oxygen Consumption After Exercise After exercise, heavy breathing continues and oxygen consumption remains above the resting level Oxygen debt The added oxygen that is taken into the body after exercise This added oxygen is used to restore muscle cells to the resting level in three ways 1) to convert lactic acid into glycogen 2) to synthesize creatine phosphate and ATP 3) to replace the oxygen removed from myoglobin

75 Copyright © 2010 Pearson Education, Inc. What happens to the lactic acid once it has accumulated? The liver filters the blood and rids the body of toxins. Lactic acid is a toxin. liver converts lactic acid to glucose

76 Copyright © 2010 Pearson Education, Inc. Muscle Fatigue Muscle fatigue- Muscle fatigue- is a state of physiological inability to contract commonly caused from – decreased blood flow – ion imbalances – accumulation of lactic acid cramp – sustained, involuntary contraction 9-18

77 Copyright © 2010 Pearson Education, Inc. Muscle Metabolism Muscle Fatigue Inability of muscle to maintain force of contraction after prolonged activity Factors that contribute to muscle fatigue: Inadequate release of calcium ions from the SR Depletion of creatine phosphate Insufficient oxygen Depletion of glycogen and other nutrients Buildup of lactic acid and ADP Failure of the motor neuron to release enough acetylcholine

78 Copyright © 2010 Pearson Education, Inc. Control of Muscle Tension

79 Copyright © 2010 Pearson Education, Inc. Contraction and Relaxation of Skeletal Muscle Length–Tension Relationship The forcefulness of muscle contraction depends on the length of the sarcomeres When a muscle fiber is stretched there is less overlap between the thick and thin filaments and tension (forcefulness) is diminished When a muscle fiber is shortened the filaments are compressed and fewer myosin heads make contact with thin filaments and tension is diminished

80 Copyright © 2010 Pearson Education, Inc. Types of Contractions Isotonic – muscle contracts and changes length 2. Concentric – shortening contraction 1. Eccentric – lengthening contraction 1. Isometric – muscle contracts but does not change length Two Types Two Types of Isotonic Contractions

81 Copyright © 2010 Pearson Education, Inc. Muscle Tone 9-23 Muscle tone Muscle tone – continuous state of partial contraction -Even when a muscle appears to be at rest, a certain amount of sustained contraction is occurring in its fibers. Atrophy Atrophy – a wasting away or decrease in size of an organ or tissue. Hypertrophy Hypertrophy – Enlargement of an organ or tissue.

82 Copyright © 2010 Pearson Education, Inc. Types of Contractions

83 Copyright © 2010 Pearson Education, Inc. Smooth and Cardiac Muscle

84 Copyright © 2010 Pearson Education, Inc. Smooth Muscle Fibers 9-26 Compared to skeletal muscle fibers shorter single nucleus elongated with tapering ends myofilaments randomly organized no striations

85 Copyright © 2010 Pearson Education, Inc. Two Types of Smooth Muscle Visceral Smooth Muscle Location - walls of most hollow organs (intestine) contractions are slow and sustained rhythmicityexhibit rhythmicity – pattern of repeated contractions peristalsis exhibit peristalsis – wave-like motion that helps substances through passageways. Multiunit Smooth Muscle irises of eye walls of blood vessels contractions are rapid and vigorous similar to skeletal muscle tissue SEM: Arteriole SEM: Stomach

86 Copyright © 2010 Pearson Education, Inc. Smooth Muscle Tissue Microscopic Anatomy of Smooth Muscle Contains both thick filaments and thin filaments Not arranged in orderly sarcomeres No regular pattern of overlap thus not striated Contain only a small amount of stored Ca ++ Filaments attach to dense bodies and stretch from one dense body to another Dense bodies Function in the same way as Z discs During contraction the filaments pull on the dense bodies causing a shortening of the muscle fiber

87 Copyright © 2010 Pearson Education, Inc. Smooth Muscle Tissue Physiology of Smooth Muscle Most smooth muscle fibers contract or relax in response to: Action potentials from the autonomic nervous system Pupil constriction due to increased light energy In response to stretching Food in digestive tract stretches intestinal walls initiating peristalsis Hormones Epinephrine causes relaxation of smooth muscle in the air-ways and in some blood vessel walls Changes in pH, oxygen and carbon dioxide levels

88 Copyright © 2010 Pearson Education, Inc. Smooth Muscle Contraction Resembles skeletal muscle contraction interaction between actin and myosin both use calcium and ATP both depend on impulses Different from skeletal muscle contraction hormones affect smooth muscle stretching can trigger smooth muscle contraction smooth muscle slower to contract and relax smooth muscle more resistant to fatigue 9-28

89 Copyright © 2010 Pearson Education, Inc. Cardiac Muscle Anatomy only in the heart striated uninuclear cells join end-to-end forming a network arrangement of actin and myosin are not as organized as skeletal musclePhysiology self-exciting tissue (Pacemaker) rhythmic contractions involuntary, all or nothing contractions Pumps blood to: 1. lungs for oxygenation 2. body for distribution of O2 and nutrients 9-29

90 Copyright © 2010 Pearson Education, Inc. Cardiac Muscle Tissue Principal tissue in the heart wall Intercalated discs Allow muscle action potentials to spread from one cardiac muscle fiber to another autorhythmic muscle fibers Continuous, rhythmic activity Have the same arrangement of actin and myosin as skeletal muscle fibers Mitochondria are large and numerous Depends on aerobic respiration to generate ATP Requires a constant supply of oxygen Able to use lactic acid produced by skeletal muscle fibers to make ATP

91 Copyright © 2010 Pearson Education, Inc. Aging and Muscular Tissue Aging Brings a progressive loss of skeletal muscle mass A decrease in maximal strength A slowing of muscle reflexes A loss of flexibility With aging, the relative number of slow oxidative fibers appears to increase Aerobic activities and strength training can slow the decline in muscular performance

92 Copyright © 2010 Pearson Education, Inc. Of Note: Types of Skeletal Muscle Fibers Muscle fibers vary in their content of myoglobin Red muscle fibers Have a high myoglobin content Appear darker (dark meat in chicken legs and thighs) Contain more mitochondria Supplied by more blood capillaries White muscle fibers Have a low content of myoglobin Appear lighter (white meat in chicken breasts)


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