Three types of muscles

Transcription

1 The Muscular System

2 Three types of muscles Smooth Cardiac Skeletal This chapter focuses on skeletal muscle

3 walls of the viscera (organs), blood vessels, bronchioles Smooth muscle

4 INVOLUNTARY muscle NONSTRIATED (no stripes) The contraction of smooth muscle enables the viscera to perform their functions

5 Smooth muscle

6 Cardiac muscle Found only in the HEART Striated involuntary Cardiac muscle cells are long branching cells that fit together tightly at junctions called INTERCALATED DISCS

7 Intercalated discs promote rapid conduction of electrical signals throughout the heart

8 Cardiac muscle

9 Skeletal muscle Generally attached to bone VOLUNTARY muscle Cells are long cylinders

10 Composed of proteins arranged to make the muscle appear striped, or STRIATED

11 Skeletal muscles: produce movement maintain body posture stabilize joints produce HEAT to maintain body temperature

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13 Skeletal Muscle Precursor cell: Myoblast Fuses together with other myoblasts to form one large cell with many nuclei called a muscle fiber(myotube)

14 Skeletal muscle Many muscle fibers make a muscle Have the ability to shorten or contract

15 Skeletal Muscle Cells Sarcolemma: plasma membrane in muscles Myofibrils: long ribbon-like organelles Sarcomeres: chains of contractile units

16 Sarcomere: functional unit of muscle

17 Sarcomere

18 Sliding Filament Model of Muscle Contraction Thin and thick filaments slide past each other to shorten sarcomere. Actin: thin filaments Myosin: thick filaments

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20 How muscles contract When muscles contract, they shorten Muscles shorten because the sarcomeres shorten The sarcomeres shorten because the actin and myosin filaments slide past each other

21 How does the sarcomere shorten? When stimulated, the myosin heads make contact with the actin, forming temporary connections called CROSSBRIDGES The crossbridges pull the actin to the center of the sarcomere The actin slides past the myosin

22 Crossbridges in action

23 The sarcomeres shorten not because the actin and myosin proteins shrink or shrivel up, but because the proteins slide past one another Remember.

24 The role of calcium and ATP ATP and CALCIUM play important roles in the contraction and relaxation of muscle ATP helps the myosin heads form and break the crossbridges with the actin However, ATP can only perform its role if calcium is present

25 Calcium is stored in the sarcoplasmic reticulum (ER of muscle cells) When the muscle is stimulated, calcium is released from the sarcoplasmic reticulum and causes the actin, myosin, and ATP to interact

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27 Muscle Contraction controlled by the Nervous system Skeletal muscle contraction can take place only if the muscle is first stimulated by a nerve This type of nerve is called a MOTOR or SOMATIC NERVE The area where the motor nerve meets the muscle is called the NEUROMUSCULAR JUNCTION (NMJ)

28 The NMJ

29 What happens at the NMJ? The stimulated nerve causes an electrical signal, or nerve impulse, to move along the nerve toward the nerve ending Stored in pouches at the nerve ending is a NEUROTRANSMITTER called ACETYLCHOLINE (ACh)

30 The ACh is released into the NMJ space The ACh diffuses across the space and binds to receptor sites on the muscle membrane The ACh stimulates the receptors and causes an electrical signal to develop along the muscle membrane

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32 The electrical signal stimulates the sarcoplasmic reticulum to release calcium The calcium allows for the interaction of actin, myosin, and ATP the muscle contracts

33 Energy Sources Creatine phosphate phosphorylates ADP ADP! ATP (no oxygen used)

34 Aerobic respiration: constant oxygen and glucose supply

35 Anaerobic glycolysis and lactic acid fermentation No oxygen used Not much energy produced this way but much faster than aerobic respiration

36 Lactic acid buildup: muscle fatigue and soreness

37 Muscle Fatigue and Oxygen Debt Fatigue: muscle unable to contract even though it is being stimulated. ph denatures ATPase and excess H+ ions interfere with Ca2+ ions

38 Muscle Fatigue and Oxygen Debt Oxygen debt occurs during prolonged muscle activity Amount of work and length of workout depends on a muscle s blood supply

39 Muscle Fatigue and Oxygen Debt Oxygen debt from vigorous activity must be paid back Rapid deep breathing

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41 Responses of a whole muscle.. The sliding filament hypothesis explains the contraction and relaxation of a single muscle fiber A whole skeletal muscle, however, is composed of thousands of muscle fibers The contraction of a whole muscle differs from that of a single muscle fiber

42 A single muscle fiber contracts in an ALL-OR-NOTHING response the fiber contracts as strongly as possible It never partially contracts A whole muscle, however, is capable of contracting partially It can contract weakly or very strongly

43 Lifting a pencil may require the contraction of several hundred muscle fibers, in an all-or-nothing manner But only a few fibers are contracting Lifting a 100 lb weight, however, requires contraction of thousands of fibers, all contracting in an all-or-nothing manner

44 The greater muscle force is achieved by using, or recruiting, additional fibers This process is called RECRUITMENT The strength of skeletal muscle contraction can be varied by RECRUITMENT of additional muscle fibers

45 Classification of Muscles Slow twitch More mitochondria, more blood supply (dark meat) Slower contraction for endurance

46 Classification of Muscles Fast twitch Specialized for rapid, forceful contractions Short term contractions Less blood supply (white meat)

47 Most muscles are a mixture of both Genetically determined Rigorous training can alter the ratio

48 Types of Muscle Contraction Isotonic: actin and myosin filaments slide past each other and the muscle shortens

49 Types of Muscle Contraction Isometric: filaments try to slide but muscle is pitted against an immovable object

50 Muscle tone: continuous partial contraction

51 If nerve supply to muscle is destroyed, muscle is no longer stimulated, loses tone & becomes paralyzed, flaccid and atrophied.

52 Muscle attachment Muscles form attachments to other structures: a tendon attaches muscle to bone a flat, sheet-like fascia, called APONEUROSIS connects muscle to muscle, or muscle to bone

53 Tendon Ligament

54 aponeurosis

55 Origin and insertion. These terms refer to the sites of muscle attachment: ORIGIN of the muscle attaches to the stationary (immovable) bone INSERTION attaches to the moveable bone

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57 Although most movement is accomplished through the cooperation of groups of muscles, a single muscle is generally responsible for most of the movement The chief muscle is called the PRIME MOVER

58 Assisting the prime mover are helper muscles called SYNERGISTS Synergists cooperate with other muscles In contrast, ANTAGONISTS are muscles that oppose the action of another muscle

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60 Movement occurs from the contraction and relaxation of alternating muscles When one contracts (prime mover), the other must relax (antagonist)

61 Concentric movement: contraction Eccentric movement: relaxation Muscle exert force even as they lengthen

62 Naming skeletal muscles There are 656 muscles in the human body!!

63 The names of various muscles are generally based on one or more of the following characteristics: Size Shape Direction of fibers Location Number of origins Origin and insertion Muscle action

64 Size Vastus huge Maximus large Longus long Minimus small Brevis - short

65 Shape Deltoid triangular Latissimus wide Trapezius trapezoid Rhomboideus rhomboid Teres round

66 Fiber direction Fibers are lined up in several directions: Rectus straight Oblique diagonal Transverse across Circularis - circular

67 location The names of muscles often reflect their location: Pectoralis chest Gluteus buttock Brachii arm Supra above Infra below Sub underneath Lateralis - lateral

68 Number of origins Muscle may be named according to the number of sites to which it is anchored: Biceps 2 sites Triceps 3 sites Quadriceps 4 sites

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70 Muscle action Abductor muscle moves the limb away from the midline of the body Adductor muscle moves the limb toward the midline

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75 Common Body Movements Flexion: movement in (generally) sagittal plane that decreases the angle of the joint and brings bones closer together Extension: opposite of flexion; creates distance between bones or parts of body Hyperextension: greater than 180 degrees

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77 Common Body Movements Rotation: movement of a bone around its longitudinal axis

78 Common Body Movements Abduction: moving a limb away (usually on the frontal plane) from the midline Fanning of fingers or toes also Adduction: opposite of abduction

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80 Common Body Movements Circumduction: combination of flexion, extension, abduction, and adduction (circular movement)

81 Special Movements (occur only at certain joints Dorsiflexion: lifting the foot so that superior surface approaches the shin (standing on heels)

82 Special Movements (occur only at certain joints Plantar flexion: pointing the toes

83 Special Movements (occur only at certain joints Inversion: turn sole medially Eversion: turn sole laterally

84 Special Movements (occur only at certain joints Supination: forearm rotates laterally so that palms face forward Pronation: forearm rotates medially so palms face posteriorly

85 Special Movements (occur only at certain joints Opposition: move thumb to touch the tips of the other fingers on the same hand

86 Five Golden Rules on Muscle Activity All muscles cross at least one joint. The bulk of the muscle lies proximal to the joint crossed. All muscles have at least two attachments: origin and insertion. Muscles can only pull, they never push. During contraction, the muscle insertion moves toward the origin.

87 Exercise Inactivity: muscle weakness and wasting. Use it or lose it!

88 Exercise Aerobic or endurance exercise Stronger, flexible muscles with greater resistance to fatigue Increased blood supply Increased number of mitochondria Improved digestion and elimination, neuromuscular coordination, stronger skeleton, increased heart stroke volume, increased lung capacity No increase in muscle size

89 Exercise Resistance (isometric) Increased muscle size and strength

90 What is wrong with bulking up? Nothing, as long as it is done through weight lifting and exercise Increase in muscle size is due to increase in actomyosin within the cell Bulking up with the use of steroids is dangerous!

91 Steroids are believed to cause liver cancer, atrophy (shrinking) of the testicles in males, hypertension, and severe psychotic mood swings

92 American College of Sports Medicine advises resistance training with non-maximal weights for adolescents Optimal bone mass Reduce obesity Decrease sports injuries

93 Homeostatic Imbalances Sprain: Ligament stretches or tears

94 Homeostatic Imbalances Strain: injury to muscle or tendon

95 RICE Rest Ice Compression elevation

96 Homeostatic Imbalances Muscular dystrophy: muscles enlarge due to fat and connective tissue deposit, but muscle fibers degenerate and atrophy Sex-linked, more common in males

97 Homeostatic Imbalances Amyotrophic lateral sclerosis (ALS) Lou Gehrig s disease Loss of control of voluntary muscles due to destruction of nerves that innervate them.