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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint.

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Presentation on theme: "Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint."— Presentation transcript:

1 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint ® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community College C H A P T E R 9 Muscles and Muscle Tissue P A R T A

2 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Overview  The three types of muscle tissue are skeletal, cardiac, and smooth  These types differ in structure, location, function, and means of activation PLAY InterActive Physiology ®: Anatomy Review: Skeletal Muscle Tissue, page 3

3 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Similarities  Skeletal and smooth muscle cells are elongated and are called muscle fibers  Muscle contraction depends on two kinds of myofilaments – actin and myosin  Muscle terminology is similar  Sarcolemma – muscle plasma membrane  Sarcoplasm – cytoplasm of a muscle cell  Prefixes – myo, mys, and sarco all refer to muscle

4 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Tissue  Packaged in skeletal muscles that attach to and cover the bony skeleton  Has obvious stripes called striations  Is controlled voluntarily (i.e., by conscious control)  Contracts rapidly but tires easily  Is responsible for overall body motility  Is extremely adaptable and can exert forces ranging from a fraction of an ounce to over 70 pounds

5 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functional Characteristics of Muscle Tissue  Excitability, or irritability – the ability to receive and respond to stimuli  Contractility – the ability to shorten forcibly  Extensibility – the ability to be stretched or extended  Elasticity – the ability to recoil and resume the original resting length

6 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Function  Skeletal muscles are responsible for all locomotion  Cardiac muscle is responsible for coursing the blood through the body  Smooth muscle helps maintain blood pressure, and squeezes or propels substances (i.e., food, feces) through organs  Muscles also maintain posture, stabilize joints, and generate heat

7 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Figure 9.2a PLAY InterActive Physiology ®: Anatomy Review: Skeletal Muscle Tissue, pages 4-6

8 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Structure and Organization of Skeletal Muscle Table 9.1b

9 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle: Nerve and Blood Supply  Each muscle is served by one nerve, an artery, and one or more veins  Each skeletal muscle fiber is supplied with a nerve ending that controls contraction  Contracting fibers require continuous delivery of oxygen and nutrients via arteries  Wastes must be removed via veins

10 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of a Skeletal Muscle Fiber  Each fiber is a long, cylindrical cell with multiple nuclei just beneath the sarcolemma  Fibers are 10 to 100  m in diameter, and up to hundreds of centimeters long  Each cell is a syncytium produced by fusion of embryonic cells

11 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of a Skeletal Muscle Fiber  Sarcoplasm has numerous glycosomes and a unique oxygen-binding protein called myoglobin  Fibers contain the usual organelles, myofibrils, sarcoplasmic reticulum, and T tubules

12 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Myofibrils Figure 9.3b PLAY InterActive Physiology ®: Anatomy Review: Skeletal Muscle Tissue, pages 7-8

13 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sarcomeres Figure 9.3c PLAY InterActive Physiology ®: Anatomy Review: Skeletal Muscle Tissue, page 9

14 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Myofilaments: Banding Pattern Figure 9.3c,d

15 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Ultrastructure of Myofilaments: Thick Filaments Figure 9.4a,b

16 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Ultrastructure of Myofilaments: Thin Filaments Figure 9.4c

17 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Arrangement of the Filaments in a Sarcomere  Longitudinal section within one sarcomere Figure 9.4d

18 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sarcoplasmic Reticulum (SR) Figure 9.5

19 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sliding Filament Theory of Contraction (continued)

20 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Excitation-Contraction Coupling (continued)  Ca 2+ attaches to troponin.  Tropomyosin- troponin complex configuration change occurs.  Cross bridges attach to actin.

21 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Contraction (continued)

22 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Neuromuscular Junction  The neuromuscular junction is formed from:  Axonal endings, which have small membranous sacs (synaptic vesicles) that contain the neurotransmitter acetylcholine (ACh)  The motor end plate of a muscle, which is a specific part of the sarcolemma that contains ACh receptors and helps form the neuromuscular junction

23 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Motor Unit: The Nerve-Muscle Functional Unit  Large weight-bearing muscles (thighs, hips) have large motor units  Muscle fibers from a motor unit are spread throughout the muscle; therefore, contraction of a single motor unit causes weak contraction of the entire muscle

24 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Motor Unit: The Nerve-Muscle Functional Unit PLAY InterActive Physiology ®: Contraction of Motor Units, pages 3-9 Figure 9.13a

25 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Motor Unit (continued)  Each somatic neuron together with all the muscle fibers it innervates.  Each muscle fiber receives a single axon terminal from a somatic neuron.  Each axon can have collateral branches to innervate an equal # of fibers.

26 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Synaptic vesicles containing neurotransmitter molecules Axon of presynaptic neuron Synaptic cleft Ion channel (closed) Ion channel (open) Axon terminal of presynaptic neuron Postsynaptic membrane Mitochondrion Ion channel closed Ion channel open Neurotransmitter Receptor Postsynaptic membrane Degraded neurotransmitter Na + Ca 2+ 1 2 3 4 5 Action potential Figure 11.18 Synaptic Cleft: Information Transfer

27 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Neuromuscular Junction Figure 9.7 (a-c)

28 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Excitation-Contraction Coupling  Na + diffusion produces end-plate potential (depolarization).  + ions are attracted to negative plasma membrane.  If depolarization sufficient, threshold occurs, producing APs.

29 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Excitation-Contraction (EC) Coupling 1.Action potential generated and propagated along sarcomere to T-tubules 2.Action potential triggers Ca2+ release 3.Ca++ bind to troponin; blocking action of tropomyosin released 4.Contraction via crossbridge formation; ATP hyrdolysis 5.Removal of Ca+2 by active transport 6.Tropomyosin blockage restored; contraction ends Figure 9.10

30 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 9.10 ADP PiPi Net entry of Na + Initiates an action potential which is propagated along the sarcolemma and down the T tubules. T tubule Sarcolemma SR tubules (cut) Synaptic cleft Synaptic vesicle Axon terminal ACh Neurotransmitter released diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma. Action potential in T tubule activates voltage-sensitive receptors, which in turn trigger Ca 2+ release from terminal cisternae of SR into cytosol. Calcium ions bind to troponin; troponin changes shape, removing the blocking action of tropomyosin; actin active sites exposed. Contraction; myosin heads alternately attach to actin and detach, pulling the actin filaments toward the center of the sarcomere; release of energy by ATP hydrolysis powers the cycling process. Removal of Ca 2+ by active transport into the SR after the action potential ends. SR Tropomyosin blockage restored, blocking myosin binding sites on actin; contraction ends and muscle fiber relaxes. Ca 2+ 1 2 3 4 5 6

31 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Contraction of Skeletal Muscle (Organ Level)  Contraction of muscle fibers (cells) and muscles (organs) is similar  The two types of muscle contractions are:  Isometric contraction – increasing muscle tension (muscle does not shorten during contraction)  Isotonic contraction – decreasing muscle length (muscle shortens during contraction)

32 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Isotonic Contractions Figure 9.19a

33 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Isometric Contractions Figure 9.19b

34 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Twitch  A muscle twitch is the response of a muscle to a single, brief threshold stimulus  There are three phases to a muscle twitch  Latent period  Period of contraction  Period of relaxation

35 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Phases of a Muscle Twitch  Latent period – first few msec after stimulus; EC coupling taking place  Period of contraction – cross bridges from; muscle shortens  Period of relaxation – Ca 2+ reabsorbed; muscle tension goes to zero Figure 9.14a

36 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Twitch Comparisons Figure 9.14b

37 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Graded Muscle Responses  Graded muscle responses are:  Variations in the degree of muscle contraction  Required for proper control of skeletal movement  Responses are graded by:  Changing the frequency of stimulation  Changing the strength of the stimulus

38 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Response to Varying Stimuli  More rapidly delivered stimuli result in incomplete tetanus  If stimuli are given quickly enough, complete tetanus results Figure 9.15

39 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Twitch, Summation, and Tetanus (continued)

40 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Response: Stimulation Strength  Threshold stimulus – the stimulus strength at which the first observable muscle contraction occurs  Beyond threshold, muscle contracts more vigorously as stimulus strength is increased  Force of contraction is precisely controlled by multiple motor unit summation  This phenomenon, called recruitment, brings more and more muscle fibers into play

41 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stimulus Intensity and Muscle Tension Figure 9.16

42 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Size Principle Figure 9.17

43 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Treppe: The Staircase Effect  Staircase – increased contraction in response to multiple stimuli of the same strength  Contractions increase because:  There is increasing availability of Ca 2+ in the sarcoplasm  Muscle enzyme systems become more efficient because heat is increased as muscle contracts

44 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Treppe: The Staircase Effect Figure 9.18

45 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Tone  Muscle tone:  Is the constant, slightly contracted state of all muscles, which does not produce active movements  Keeps the muscles firm, healthy, and ready to respond to stimulus  Spinal reflexes account for muscle tone by:  Activating one motor unit and then another  Responding to activation of stretch receptors in muscles and tendons

46 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Isotonic Contractions  In isotonic contractions, the muscle changes in length (decreasing the angle of the joint) and moves the load  The two types of isotonic contractions are concentric and eccentric  Concentric contractions – the muscle shortens and does work  Eccentric contractions – the muscle contracts as it lengthens

47 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Isotonic Contractions Figure 9.19a

48 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Isometric Contractions  Tension increases to the muscle’s capacity, but the muscle neither shortens nor lengthens  Occurs if the load is greater than the tension the muscle is able to develop

49 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Isometric Contractions Figure 9.19b

50 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Metabolism: Energy for Contraction  ATP is the only source used directly for contractile activity  As soon as available stores of ATP are hydrolyzed (4-6 seconds), they are regenerated by:  The interaction of ADP with creatine phosphate (CP)  Anaerobic glycolysis  Aerobic respiration PLAY InterActive Physiology ®: Muscle Metabolism, pages 3-15

51 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Metabolism: Energy for Contraction Figure 9.20

52 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Metabolism of Skeletal Muscles (continued)  Phosphocreatine (creatine phosphate):  Rapid source of renewal of ATP.  ADP combines with creatine phosphate.  [Phosphocreatine] is 3 times [ATP].  Ready source of high-energy phosphate.

53 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Fatigue  Muscle fatigue – the muscle is in a state of physiological inability to contract  Muscle fatigue occurs when:  ATP production fails to keep pace with ATP use  There is a relative deficit of ATP, causing contractures  Lactic acid accumulates in the muscle  Ionic imbalances are present

54 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Fatigue  Intense exercise produces rapid muscle fatigue (with rapid recovery)  Na + -K + pumps cannot restore ionic balances quickly enough  Low-intensity exercise produces slow-developing fatigue  SR is damaged and Ca 2+ regulation is disrupted

55 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Heat Production During Muscle Activity  Only 40% of the energy released in muscle activity is useful as work  The remaining 60% is given off as heat  Dangerous heat levels are prevented by radiation of heat from the skin and sweating

56 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Force of Muscle Contraction  The force of contraction is affected by:  The number of muscle fibers contracting – the more motor fibers in a muscle, the stronger the contraction  The relative size of the muscle – the bulkier the muscle, the greater its strength  Degree of muscle stretch – muscles contract strongest when muscle fibers are 80-120% of their normal resting length

57 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Force of Muscle Contraction Figure 9.21a–c

58 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Length Tension Relationships Figure 9.22

59 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Fiber Type: Functional Characteristics  Speed of contraction – determined by speed in which ATPases split ATP  The two types of fibers are slow and fast  ATP-forming pathways  Oxidative fibers – use aerobic pathways  Glycolytic fibers – use anaerobic glycolysis  These two criteria define three categories – slow oxidative fibers, fast oxidative fibers, and fast glycolytic fibers PLAY InterActive Physiology ®: Muscle Metabolism, pages 16-22

60 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Twitch Comparisons Figure 9.14b

61 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 9.2

62 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Fiber Type: Speed of Contraction  Slow oxidative fibers contract slowly, have slow acting myosin ATPases, and are fatigue resistant  Fast oxidative fibers contract quickly, have fast myosin ATPases, and have moderate resistance to fatigue  Fast glycolytic fibers contract quickly, have fast myosin ATPases, and are easily fatigued PLAY InterActive Physiology ®: Muscle Metabolism, pages 24-29

63 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Effects of Aerobic Exercise  Aerobic exercise results in an increase of:  Muscle capillaries  Number of mitochondria  Myoglobin synthesis

64 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Effects of Resistance Exercise  Resistance exercise (typically anaerobic) results in:  Muscle hypertrophy  Increased mitochondria, myofilaments, and glycogen stores

65 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Overload Principle  Forcing a muscle to work promotes increased muscular strength  Muscles adapt to increased demands  Muscles must be overloaded to produce further gains

66 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Proportion and Organization of Myofilaments in Smooth Muscle Figure 9.26

67 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle  Composed of spindle-shaped fibers with a diameter of 2-10  m and lengths of several hundred  m  Lack the coarse connective tissue sheaths of skeletal muscle, but have fine endomysium  Organized into two layers (longitudinal and circular) of closely apposed fibers

68 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle  Found in walls of hollow organs (except the heart)  Have essentially the same contractile mechanisms as skeletal muscle

69 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Smooth Muscle  SR is less developed than in skeletal muscle and lacks a specific pattern  T tubules are absent  Plasma membranes have pouchlike infoldings called caveoli

70 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Smooth Muscle  Ca2+ is sequestered in the extracellular space near the caveoli, allowing rapid influx when channels are opened  There are no visible striations and no sarcomeres  Thin and thick filaments are present

71 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Proportion and Organization of Myofilaments in Smooth Muscle  Ratio of thick to thin filaments is much lower than in skeletal muscle  Thick filaments have heads along their entire length  There is no troponin complex

72 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Proportion and Organization of Myofilaments in Smooth Muscle  Thick and thin filaments are arranged diagonally, causing smooth muscle to contract in a corkscrew manner  Noncontractile intermediate filament bundles attach to dense bodies (analogous to Z discs) at regular intervals

73 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Smooth Muscle  Smooth muscle lacks neuromuscular junctions  Innervating nerves have bulbous swellings called varicosities  Varicosities release neurotransmitters into wide synaptic clefts called diffuse junctions

74 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Smooth Muscle Figure 9.25

75 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Contraction of Smooth Muscle  Whole sheets of smooth muscle exhibit slow, synchronized contraction  They contract in unison, reflecting their electrical coupling with gap junctions  Action potentials are transmitted from cell to cell

76 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Contraction of Smooth Muscle  Some smooth muscle cells:  Act as pacemakers and set the contractile pace for whole sheets of muscle  Are self-excitatory and depolarize without external stimuli

77 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Contraction Mechanism  Actin and myosin interact according to the sliding filament mechanism  The final trigger for contractions is a rise in intracellular Ca 2+  Ca 2+ is released from the SR and from the extracellular space  Ca 2+ interacts with calmodulin and myosin light chain kinase to activate myosin

78 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Role of Calcium Ion  Ca 2+ binds to calmodulin and activates it  Activated calmodulin activates the kinase enzyme  Activated kinase transfers phosphate from ATP to myosin cross bridges  Phosphorylated cross bridges interact with actin to produce shortening  Smooth muscle relaxes when intracellular Ca 2+ levels drop

79 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Smooth Muscle: Single Unit  The cells of single-unit smooth muscle, commonly called visceral muscle:  Contract rhythmically as a unit  Are electrically coupled to one another via gap junctions  Often exhibit spontaneous action potentials  Are arranged in opposing sheets and exhibit stress- relaxation response

80 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Smooth Muscle: Multiunit  Multiunit smooth muscles are found:  In large airways to the lungs  In large arteries  In arrector pili muscles  Attached to hair follicles  In the internal eye muscles

81 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Smooth Muscle: Multiunit  Their characteristics include:  Rare gap junctions  Infrequent spontaneous depolarizations  Structurally independent muscle fibers  A rich nerve supply, which, with a number of muscle fibers, forms motor units  Graded contractions in response to neural stimuli

82 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscular Dystrophy  Muscular dystrophy – group of inherited muscle- destroying diseases where muscles enlarge due to fat and connective tissue deposits, but muscle fibers atrophy

83 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscular Dystrophy  Duchenne muscular dystrophy (DMD)  Inherited, sex-linked disease carried by females and expressed in males (1/3500)  Diagnosed between the ages of 2-10  Victims become clumsy and fall frequently as their muscles fail

84 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscular Dystrophy  Progresses from the extremities upward, and victims die of respiratory failure in their 20s  Caused by a lack of the cytoplasmic protein dystrophin  There is no cure, but myoblast transfer therapy shows promise


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