Chapter 8 The Muscular System

Transcription

1 Chapter 8 The Muscular System Copyright 2015 Wolters Kluwer Health Lippincott Williams & Wilkins

2 Overview

3 Key Terms acetylcholine membrane potential synapse actin motor unit synergist action potential myalgia tendon agonist myoglobin tonus antagonist myosin tropomyosin atrophy neuromuscular junction troponin contractility excitability fascicle glycogen insertion neurotransmitter origin prime mover sarcomere spasm

4 Types of Muscle Learning Objective 1. Compare the three types of muscle tissue.

5 The Muscular System Learning Objectives 2. Describe three functions of skeletal muscle. 3. Describe the structure of a skeletal muscle to the level of individual cells. 4. Outline the steps in skeletal muscle contraction.

6 The Muscular System (cont.) Learning Objectives 5. List compounds stored in muscle cells that are used to generate energy. 6. Explain what happens in muscle cells contracting anaerobically. 7. Cite the effects of exercise on muscles. 8. Compare isotonic and isometric contractions.

7 The Mechanics of Muscle Movement Learning Objectives 9. Explain how muscles work together to produce movement. 10.Compare the workings of muscles and bones to lever systems.

8 Skeletal Muscle Groups Learning Objectives 11. Explain how muscles are named. 12. Name some of the major muscles in each muscle group, and describe the locations and functions of each.

9 Effects of Aging on Muscles Learning Objective 13. Describe how muscles change with age.

10 Muscular Disorders Learning Objective 14. List the major disorders of muscles and their associated structures.

11 Case Study Learning Objective 15. Describe some of the diagnostic signs of muscular dystrophy based on the case study.

12 Word Anatomy Learning Objective 16. Show how word parts are used to build words related to the muscular system.

13 Types of Muscle

14 Types of Muscle (cont.) Checkpoint 8-1 What are the three types of muscle?

15 Types of Muscle (cont.) Pop Quiz 8.1 Which type of muscle tissue is striated and involuntary? A) Cardiac B) Intercalated C) Smooth D) Skeletal

16 Types of Muscle (cont.) Pop Quiz Answer 8.1 Which type of muscle tissue is striated and involuntary? A) Cardiac B) Intercalated C) Smooth D) Skeletal

17 The Muscular System Learning Objectives 2. Describe three functions of skeletal muscle. 3. Describe the structure of a skeletal muscle to the level of individual cells. 4. Outline the steps in skeletal muscle contraction

18 The Muscular System (cont.) Learning Objectives 5. List compounds stored in muscle cells that are used to generate energy. 6. Explain what happens in muscle cells contracting anaerobically. 7. Cite the effects of exercise on muscles. 8. Compare isotonic and isometric contractions.

19 The Muscular System (cont.) Skeletal Muscle Has Three Primary Functions: Skeletal movement Posture maintenance Heat generation

20 The Muscular System (cont.) Muscle Structure Fascicles Bundles of muscle cells (fibers) that make up a whole muscle Connective tissue Holds fascicles and whole muscle together Three layers Endomysium Perimysium Epimysium Tendons

21 The Muscular System (cont.) Figure 8-1 Structure of a skeletal muscle. What is the innermost layer of connective tissue in a muscle? What layer of connective tissue surrounds a fascicle of muscle fibers?

22 The Muscular System (cont.) Muscle Cells in Action Motor unit: A single neuron and all the muscle fibers it stimulates Small motor units used for fine movements Large motor units used for broad movements

23 The Muscular System (cont.) Muscle Cells in Action (cont.) Neuromuscular junction (NMJ): The point at which a nerve fiber contacts a muscle fiber A type of synapse NMJ anatomy Motor neuron Neurotransmitter (acetylcholine; ACh) Motor end plate (on muscle fiber) Contains acetylcholine receptors

24 The Muscular System (cont.) Muscle Cells in Action (cont.) The NMJ allows motor neuron to stimulate the muscle fiber to become electrically excited (action potential). Action potential stimulates muscle contraction. Events at the NMJ: ACh is released from motor neuron into synaptic cleft. ACh diffuses across synaptic cleft toward motor end plate. ACh binds to receptors on motor end plate and stimulates action potential.

25 The Muscular System (cont.) Figure 8-2 The neuromuscular junction (NMJ).

26 The Muscular System (cont.) Muscle Cells in Action (cont.) The sarcomere is the functional unit of contraction in the skeletal muscle fiber. Sarcomere anatomy: Thick filaments (myosin) Thin filaments (actin) Regulatory proteins Troponin Tropomyosin

27 The Muscular System (cont.) Figure 8-3 Detailed structure of a skeletal muscle cell.

28 The Muscular System (cont.) Muscle Cells in Action (cont.) Sarcomeres contract via the sliding filament mechanism: Myosin heads bind to actin, forming cross-bridges. Using stored energy, myosin heads pull actin filaments together within the sarcomeres, and the cell shortens. New ATP is used to detach myosin heads and move them back into position for another power stroke.

29 The Muscular System (cont.) Figure 8-4 Sliding filament mechanism of skeletal muscle contraction. Do the actin or myosin filaments change in length as contraction proceeds?

30 The Muscular System (cont.) Muscle Cells in Action (cont.) Calcium regulates sarcomeric contraction within the muscle cell: Action potential from the NMJ travels to the sarcoplasmic reticulum (SR). The SR releases calcium into cytoplasm. Calcium shifts troponin and tropomyosin off of thin filament so that binding sites on actin are exposed. Sliding filament mechanism now able to proceed. Muscle relaxes when stimulation ends and calcium is pumped back into the SR.

31 The Muscular System (cont.) Figure 8-5 Role of calcium in muscle contraction.

32 The Muscular System (cont.) Summary of Events in a Muscle Contraction 1. ACh is released from neuron ending into synaptic cleft at the NMJ. 2. ACh binds to motor end plate and produces an action potential. 3. The action potential travels to the SR. 4. SR releases calcium into cytoplasm. 5. Calcium shifts troponin and tropomyosin off of thin filaments so that binding sites on actin are exposed.

33 The Muscular System (cont.) Summary of Events in a Muscle Contraction (cont.) 6. Myosin heads bind to actin, forming cross-bridges. 7. Using stored energy, myosin heads pull actin filaments together within sarcomeres, and cell shortens. 8. New ATP is used to detach myosin heads and move them back to position for another power stroke. 9. Muscle relaxes when stimulation ends and calcium is pumped back into SR.

34 The Muscular System (cont.) Checkpoints 8-2 What are the three main functions of skeletal muscle? 8-3 What are bundles of muscle fibers called? 8-4 What is the term for the difference in electrical charge on the two sides of a plasma membrane? 8-5 What is the name of the special synapse where a nerve cell makes contact with a muscle cell? 8-6 What neurotransmitter is involved in the stimulation of skeletal muscle cells? 8-7 What filaments interact to produce muscle contraction? 8-8 What mineral is needed for interaction of the contractile filaments?

35 The Muscular System (cont.) Pop Quiz 8.2 A single neuron and all the muscle fibers it stimulates comprise a: A) Motor end plate B) Motor unit C) Neuromuscular junction D) Synapse

36 The Muscular System (cont.) Pop Quiz Answer 8.2 A single neuron and all the muscle fibers it stimulates comprise a: A) Motor end plate B) Motor unit C) Neuromuscular junction D) Synapse

37 The Muscular System (cont.) Pop Quiz 8.3 The two filaments that form cross-bridges are: A) Actin and troponin B) Tropomyosin and myosin C) Actin and myosin D) Troponin and tropomyosin

38 The Muscular System (cont.) Pop Quiz Answer 8.3 The two filaments that form cross-bridges are: A) Actin and troponin B) Tropomyosin and myosin C) Actin and myosin D) Troponin and tropomyosin

39 The Muscular System (cont.) Energy Sources Muscle contraction requires ATP. Skeletal muscle prefers to produce ATP via aerobic metabolism, which requires: Oxygen Glucose Storage compounds ensure an adequate supply of oxygen and glucose for aerobic ATP metabolism. Myoglobin Glycogen

40 The Muscular System (cont.) Energy Sources (cont.) Storage compounds: Myoglobin, glycogen, fatty acids During strenuous activity, muscle cells use anaerobic ATP metabolism, which does not require ATP. Breakdown of creatine phosphate Anaerobic glycolysis Lactic acid accumulation and oxygen debt Excess postexercise oxygen consumption: After strenuous exercise, the person takes in extra oxygen (via rapid breathing) to remove lactic acid and replenish energy stores.

41 The Muscular System (cont.) Effects of Exercise Improved balance, joint flexibility Increased muscle size (hypertrophy) Improved muscle tissue Vasodilation Strengthened heart muscle Improved breathing and respiratory efficiency Weight control Stronger bones

42 The Muscular System (cont.) Types of Muscle Contractions Partial (muscle tone or tonus) Isotonic No change in tension Muscle length shortens Movement Isometric Great increase in tension Muscle length unchanged No movement

43 The Muscular System (cont.) Checkpoints 8-9 What compound is formed in oxidation of nutrients that supplies the energy for muscle contraction? 8-10 What compound stores reserves of oxygen in muscle cells? 8-11 What are the two main types of muscle contraction?

44 The Muscular System (cont.) Pop Quiz 8.4 Which muscle cell compound stores oxygen? A) Creatine phosphate B) Glycogen C) Hemoglobin D) Myoglobin

45 The Muscular System (cont.) Pop Quiz Answer 8.4 Which muscle cell compound stores oxygen? A) Creatine phosphate B) Glycogen C) Hemoglobin D) Myoglobin

46 The Mechanics of Muscle Movement Learning Objectives 9. Explain how muscles work together to produce movement. 10. Compare the workings of muscles and bones to lever systems.

47 The Mechanics of Muscle Movement (cont.) Tendons attach muscles to bones. Origin: Attached to more fixed part of skeleton Insertion: Attached to more movable part of skeleton

48 The Mechanics of Muscle Movement (cont.) Figure 8-6 Muscle attachments to bones. Does contraction of the brachialis produce flexion or extension at the elbow?

49 The Mechanics of Muscle Movement (cont.) Muscles Work Together Many muscles function in pairs. Prime movers Antagonists Synergists

50 The Mechanics of Muscle Movement (cont.) Levers and Body Mechanics Musculoskeletal system as a lever system Lever bone Fulcrum joint Force applied by muscle Three classes of levers First class Second class Third class most body systems

51 The Mechanics of Muscle Movement(cont.) Figure 8-7 Levers. In a third-class lever system, where is the fulcrum with regard to the effort and the resistance?

52 The Mechanics of Muscle Movement (cont.) Checkpoints 8-12 What are the names of the two attachment points of a muscle, and how do they function? 8-13 What is the name of the muscle that produces a movement as compared with the muscle that produces an opposite movement? 8-14 Of the three classes of levers, which one represents the action of most muscles?

53 The Mechanics of Muscle Movement cont.) Pop Quiz 8.5 In anatomic lever systems, the fulcrum is the: A) Bone B) Bursa C) Insertion D) Joint

54 The Mechanics of Muscle Movement (cont.) Pop Quiz Answer 8.5 In anatomic lever systems, the fulcrum is the: A) Bone B) Bursa C) Insertion D) Joint

55 Skeletal Muscle Groups Learning Objectives 11. Explain how muscles are named. 12. Name some of the major muscles in each muscle group, and describe the locations and functions of each.

56 Skeletal Muscle Groups (cont.) Characteristics for Naming Muscles Characteristic Location Size Shape Direction Number of heads Action Example Temporalis; near the skull s temple Gluteus maximus; the largest Serratus anterior; serrated edge External oblique; runs obliquely Biceps brachii; two heads Flexor digitorum; flexes toes

57 Skeletal Muscle Groups (cont.) Figure 8-8 Superficial muscles, anterior view.

58 Skeletal Muscle Groups (cont.) Figure 8-9 Superficial muscles, posterior view.

59 Skeletal Muscle Groups (cont.) Muscles of the Head and Neck Name Location Function Orbicularis oculi Encircles eyelid Closes eye Levator palpebrae superioris Posterior orbit to upper eyelid Opens eye Orbicularis oris Encircles mouth Closes lips Buccinator Fleshy part of cheek Flattens cheek; helps in eating, whistling, and blowing wind instruments Zygomaticus major and minor Depressor anguli oris Cheekbone to mouth corners Mandible to mouth corners Temporalis Above and near ear Closes jaw Masseter At angle of jaw Closes jaw Raises mouth corners upward and laterally (smile) Lowers mouth corners (grimace) Sternocleidomastoid Along lateral neck, to mastoid process Flexes head; rotates head toward opposite side from muscle

60 Skeletal Muscle Groups (cont.) Figure 8-10 Muscles of the head. Which of the muscles in this illustration are named for a nearby bone?

61 Skeletal Muscle Groups (cont.) Muscles of the Upper Extremities Name Location Function Trapezius Latissimus dorsi Pectoralis major Serratus anterior Deltoid Posterior neck and upper back to clavicle and scapula Middle and lower back, to humerus Superior, anterior chest, to humerus Inferior to axilla on lateral chest Covers shoulder joint to lateral humerus Raises shoulder and pulls it back; superior portion extends and turns head Extends and adducts arm (prime mover) Flexes and adducts arm; medially rotates arm across chest; pulls shoulder forward and downward Moves shoulder forward; synergist in arm flexion and abduction Abducts arm; synergist in arm flexion rotation and extension

62 Skeletal Muscle Groups (cont.) Muscles of the Upper Extremities (cont.) Name Location Function Biceps brachii Brachialis Brachioradialis Anterior arm along humerus to radius Deep to biceps brachii; inserts at anterior elbow joint Lateral forearm from distal end of humerus to distal end of radius Supinates the forearm and hand; synergist in forearm flexion Primary flexor of forearm Synergist in forearm flexion Triceps brachii Posterior arm to ulna Extends forearm to straighten upper extremity

63 Skeletal Muscle Groups (cont.) Muscles of the Upper Extremities (cont.) Name Location Function Flexor carpi group Extensor carpi group Flexor digitorum group Extensor digitorum group Anterior forearm to hand Flexes hand Posterior forearm to hand Extends hand Anterior forearm to fingers Posterior forearm to fingers Flexes fingers Extends fingers

64 Skeletal Muscle Groups (cont.) Figure 8-11 Muscles that move the forearm and hand. What does carpi refer to in the names of muscles? Digitorum?

65 Skeletal Muscle Groups (cont.) Muscles of the Trunk Name Location Function Diaphragm Dome-shaped partition between thoracic and abdominal cavities Dome descends to enlarge the thoracic cavity from top to bottom during ventilation Intercostals Between ribs Alter thoracic cavity volume during ventilation Muscles of abdominal wall: External oblique Internal oblique Transversus abdominis Rectus abdominis Anterolateral abdominal wall Compress the abdominal cavity and expel substances from the body; flex the spinal column Levator ani Pelvic floor Aids in defecation Erector spinae Group of deep vertical muscles between the sacrum and skull Extends the vertebral column to produce erect posture

66 Skeletal Muscle Groups (cont.) Figure 8-12 Muscles of respiration.

67 Skeletal Muscle Groups (cont.) Figure 8-13 Muscles of the abdominal wall. What does rectus mean? Oblique?

68 Figure 8-14 Muscles of the female perineum (pelvic floor).

69 Skeletal Muscle Groups (cont.) Muscles That Move the Leg and Thigh Name Location Function Gluteus maximus Superficial buttock to femur Extends thigh Gluteus medius Deep buttock to femur Abducts thigh Iliopsoas Adductor group (e.g., adductor longus, adductor magnus) Sartorius Gracilis Crosses anterior hip joint to femur Medial thigh to femur Crosses anterior thigh from ilium to medial tibia Pubic bone to medial surface of tibia Flexes thigh when trunk is immobilized; flexes trunk when thighs are immobilized Adducts thigh Flexes thigh and leg (to sit cross-legged) Adducts thigh at hip; flexes leg at knee

70 Skeletal Muscle Groups (cont.) Muscles That Move the Leg and Thigh (cont.) Name Location Function Quadriceps femoris Rectus femoris Vastus medialis Vastus lateralis Vastus intermedius Anterior thigh to tibia Extends leg Hamstring group Biceps femoris Semimembranosus Semitendinosus Posterior thigh; ischium and femur to tibia and fibula Flexes leg at knee; extends and rotates thigh at hip

71 Skeletal Muscle Groups (cont.) Figure 8-15 Muscles of the thigh. How many muscles make up the quadriceps femoris?

72 Skeletal Muscle Groups (cont.) Muscles That Move the Foot Name Location Function Gastrocnemius Soleus Posterior leg to calcaneus, inserting by the Achilles tendon Posterior leg deep to gastrocnemius Plantar flexes foot (as in tiptoeing) Plantar flexes foot Tibialis anterior Anterior and lateral leg to foot Dorsiflexes and inverts foot at ankle (as in walking on heels); inverts foot (sole inward) Fibularis longus Lateral leg, to foot Everts foot (sole outward) Flexor digitorum group Extensor digitorum group Posterior leg and foot to inferior surface of phalanges Anterior surface of leg bones to superior surface of phalanges Flexes toes Extends toes

73 Skeletal Muscle Groups (cont.) Figure 8-16 Muscles that move the foot. On what bone does the Achilles tendon insert?

74 Skeletal Muscle Groups (cont.) Checkpoints 8-15 What muscle is most important in breathing? 8-16 What structural feature gives strength to the muscles of the abdominal wall?

75 Skeletal Muscle Groups (cont.) Pop Quiz 8.6 An antagonist to the gastrocnemius is the: A) Gracilis B) Sartorius C) Soleus D) Tibialis anterior

76 Skeletal Muscle Groups (cont.) Pop Quiz Answer 8.6 An antagonist to the gastrocnemius is the: A) Gracilis B) Sartorius C) Soleus D) Tibialis anterior

77 Effects of Aging on Muscles Learning Objectives 13. Describe how muscles change with age.

78 Effects of Aging on Muscles (cont.) Beginning at about age 40 Gradual loss of muscle cells Loss of power Tendency to flex hips and knees Decrease in height

79 Muscular Disorders Learning Objectives 14. List the major disorders of muscles and their associated structures.

80 Muscular Disorders (cont.) Common Terms Used When Describing Muscular Disorders Spasms Colic Seizure Convulsion Cramps Atrophy

81 Muscular Disorders (cont.) Muscle Injuries Strains Delayed-onset muscle soreness (DOMS) Rhabdomyolysis

82 Muscular Disorders (cont.) Diseases of Muscle Muscular dystrophy Myasthenia gravis Myalgia Myositis Fibrositis Fibromyositis Fibromyalgia syndrome (FMS)

83 Muscular Disorders (cont.) Disorders of Associated Structures Tendinitis Plantar fasciitis Tenosynovitis Shin-splints

84 Muscular Disorders (cont.) Figure 8-17 Muscular disorders.

85 Case Study Learning Objective 15. Describe some of the diagnostic signs of muscular dystrophy based on the case study.

86 Case Study (cont.) Diagnostic signs: Pseudohypertrophic calf muscles and thin thighs Weak thigh muscles Gower sign using the arms to walk up the body Low levels of dystrophin determined from a muscle biopsy

87 Word Anatomy Learning Objective 16. Show how word parts are used to build words related to the integumentary system.

88 Word Anatomy (cont.) Word Part Meaning The Muscular System Example aer/o air, gas An aerobic organism can grow in the presence of air (oxygen). an- not, without Anaerobic metabolism does not require oxygen. iso- same, equal In an isotonic contraction, muscle tone remains the same, but the muscle shortens. -lysis separation, Glycolysis is the breakdown of glucose. dissolving metr/o measure In an isometric contraction, muscle length remains the same, but muscle tension increases. my/o muscle The endomysium is the deepest layer of connective tissue around muscle cells. sarc/o flesh A sarcomere is a contracting subunit of skeletal muscle.

89 Word Anatomy (cont.) Word Part Meaning Example ton/o tone, tension See iso- example. troph/o nutrition, nurture Muscles undergo hypertrophy, an increase in size, under the effects of resistance training. vas/o vessel Vasodilation (widening) of the blood vessels in muscle tissue during exercise brings more blood into the tissue. The Mechanics of Muscle Movement erg/o work Synergists are muscles that work together. syn- with, together A synapse is a point of communication between a neuron and another cell. Skeletal Muscle Groups brachi/o arm The biceps brachii and triceps brachii are in the arm. quadr/i four The quadriceps muscle group consists of four muscles.

90 Word Anatomy (cont.) Word Part Meaning Example Muscular Disorders a- absent, lack Atrophy is a wasting of muscle as a result of of disuse (lack of nourishment). -algia pain Myalgia is muscular pain. dys- disordered, difficult In muscular dystrophy, there is deterioration of muscles. sthen/o strength Myasthenia gravis is characterized by muscular fatigue (lack of strength).