UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM

Transcription

1 LEARNING OUTCOMES: 9.1 Introduction UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM 1. List various outcomes of muscle actions. 9.2 Structure of a Skeletal Muscle 2. Describe the structure of a skeletal muscle. 3. Name the major parts of a skeletal muscle fiber and describe the functions of each. 9.3 Skeletal Muscle Contraction 4. Describe the neural control of skeletal muscle contraction. 5. Identify the major events of skeletal muscle fiber contraction. 6. List the energy sources for the skeletal muscle fiber contraction. 7. Describe oxygen debt. 8. Describe how a muscle may become fatigued. 9.4 Muscular Responses 9. Distinguish between a twitch and sustained contraction. 10. Explain how various types of muscular contractions produce body movements and help maintain posture. 11. Distinguish between fast and slow twitch muscle fibers. 9.5 Smooth Muscles 12. Distinguish between the structures and functions of multiunit smooth muscle and visceral smooth muscle. 13. Compare the contraction mechanisms of skeletal and smooth muscle fibers. 9-1

2 LEARNING OUTCOMES: 9.6 Cardiac Muscle UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM 14. Compare the contraction mechanisms of skeletal and cardiac muscle fibers. 9.7 Skeletal Muscle Actions 15. Explain how the attachments, locations, and interactions of skeletal muscles make possible certain movements. 9.8 Major Skeletal Muscles 16. Identify and locate the skeletal muscles of each body region and describe the action(s) of each muscle. 9.9 Life-Span Changes 17. Describe aging-related changes in the muscular system. 18. Discuss how exercise can help maintain a healthy muscular system as the body ages. 9-2

3 9.1 INTRODUCTION UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM A. All body movements require muscles. B. Muscles are organs composed of specialized cells that use the chemical energy stored in nutrients to exert a pulling force on structures to which they are attached. C. Muscle actions also: 1. provide muscle tone 2. propel body fluids and food 3. generate the heartbeat 4. distribute heat D. Three Muscle Types (Review Chapter 5, Muscle Tissues) 1. Skeletal 2. Smooth 3. Cardiac * See Table 9.2, page 310: Characteristics of Muscles Tissues. E. This chapter focuses primarily on skeletal muscle. 9.2 STRUCTURE OF SKELETAL MUSCLE Each skeletal muscle is an organ made up of skeletal muscle fibers, connective tissue coverings, blood vessels, and nerve fibers. A. Connective Tissue (CT) Coverings: See Fig 9.2, page 294 & Fig 9.3, page Each muscle fiber (cell) is wrapped in a thin, delicate layer of CT called endomysium. 2. Many muscle fibers are bundled together into groups called fascicles. See Fig 9.3, page 295. a. Each fascicle is wrapped in a second layer of CT made of collagen called perimysium. 3. Many fascicles are bundled together to form a skeletal muscle. a. Each skeletal muscle is covered by a third layer of dense, fibrous CT called epimysium. 4. Each skeletal muscle is then covered by a fourth, very tough fibrous layer of CT called deep fascia. a. The deep fascia may extend past the length of the muscle (tendon or aponeurosis), and attach that muscle to a bone, cartilage or muscle. b. See Fig 9.1, page 293 to compare these two extensions. 9-3

4 9.2 STRUCTURE OF SKELETAL MUSCLE B. Skeletal Muscle Fibers Recall from Chapter 5 that skeletal muscle fibers possess striations: 1. A muscle fiber is a long, thin cell. a. Each muscle fiber is composed of myofibrils. o Each myofibril is composed of two types of protein filaments (cytoskeletal elements): 1. Thick filaments composed of the protein myosin. 2. Thin filaments primarily composed of the protein actin. o Striations are caused by the arrangement of thick and thin filaments within the myofibrils: See Fig 9.5, page A-Band = dark area = overlapping of thick and thin filaments. 2. I-Band = light area = thin filaments alone. o The length of each myofibril is divided into sarcomeres: 1. Sarcomeres meet one another at an area called the Z-line. o See Fig 9.4, page Thick filaments = protein myosin. See Fig 9.6, page 296. a. rod-like tail (axis) that terminates in two globular heads (or cross bridges). b. The myosin heads (cross bridges) interact with active sites on thin filaments making linkages between the thick and thin filament. 3. Thin filaments = protein actin. See Fig 9.6, page 296. a. coiled helical structure (resembles twisted strands of pearls) b. Tropomyosin = rod-shaped protein spiraling around actin backbone to stabilize it. c. Troponin = complex of polypeptides: o one binds to actin o one binds to tropomyosin o one binds to calcium ions d. Both tropomyosin and troponin help control actin's interaction with myosin during contraction. 9-4

5 9.2 STRUCTURE OF SKELETAL MUSCLE B. Skeletal Muscle Fibers 4. Within the sarcoplasm of a muscle fiber, there are two specialized membranous organelles: See Fig 9.7, page 297. a. Sarcoplasmic reticulum (SR) o o o o network of membranous channels that surrounds each myofibril and runs parallel to it same as endoplasmic reticulum in other cells SR has high concentrations of calcium ions compared to the sarcoplasm (maintained by active transport calcium pump). When stimulated by muscle impulse, membranes become more permeable to calcium ions and calcium diffuses out of SR and into sarcoplasm. b. Transverse tubules (TT) set of membranous channels that extend into the sarcoplasm as invaginations continuous with muscle cell membrane (sarcolemma) TTs are filled with extracellular fluid and extend deep into the muscle cell. Each TT runs between two enlarged portions of SR called cisternae. These structures form a triad near the region where actin and myosin overlap. c. SR and TT are involved in activating the muscle contraction mechanism (discussed in greater detail later). d. Because one TT is associated with two SR they are termed the triad. 9-5

6 9.3 SKELETAL MUSCLE CONTR A. Neuromuscular Junction (NMJ) Stimulation of Skeletal Muscle Cell 1. NMJ = the site where a motor nerve ending (fiber) and a skeletal muscle fiber meet (also called a synapse or synaptic cleft). a. In order for a skeletal muscle to contract, its fibers must first be stimulated by a motor neuron. b. See Figure 9.8, page Other important features: a. Motor neuron = the nerve cell that stimulates the muscle cell. b. Neurotransmitter = chemical substance released from a motor ending (fiber), causing stimulation of the sarcolemma of muscle fiber; acetylcholine (ACh). c. Motor Unit = one motor neuron and many skeletal muscle fibers. See Fig 9.17, page 306. d. Motor End Plate = the specific part of a skeletal muscle fiber's sarcolemma directly beneath the NMJ. B. Stimulus for Contraction See Table 9.1, page Introduction: The function of skeletal muscle is to move bones of the skeleton under voluntary control. Contraction of a skeletal muscle fiber is a complex interaction of several cellular and chemical constituents. The final result is a movement whereby actin and myosin filaments slide past one another. Accordingly, the muscle fiber shortens and pulls on its attachments. 2. The process begins when a motor impulse is initiated by the brain. It travels down the spinal cord, into a motor neuron, which branches into many motor nerve fibers/endings. a. Each motor nerve fiber extends to the motor end-plate of a skeletal muscle fiber forming a neuromuscular junction (NMJ). b. When the motor impulse reaches the end of the motor nerve fiber/ending, the membrane is depolarized (-70mV to -55mV). o o Calcium ions rush into motor nerve fiber, and neurotransmitter (Acetylcholine) is released into the NMJ (via exocytosis). 3. Acetylcholine diffuses across the NMJ & stimulates/depolarizes the motor end-plate (sarcolemma) of a skeletal muscle fiber from -100mV to 70mV. 4. The muscle impulse begins and travels over the surface of the skeletal muscle fiber and deep into the muscle fiber by means of the TTs. 9-6

7 9.3 SKELETAL MUSCLE CONTR C. Excitation Contraction Coupling 1. The muscle impulse reaches the sarcoplasmic reticulum, which releases calcium ions into the sarcoplasm of the muscle fiber. 2. Calcium binds to troponin, moving tropomyosin and exposing myosin binding sites on actin filament. 3. Linkages (cross-bridges) form between actin and myosin. 4. Actin filaments are pulled inward by myosin cross-bridges. 5. The muscle fiber shortens as contraction occurs. D. The Sliding Filament Model of Muscle Contraction 1. a most popular theory concerning muscle contraction 2. first proposed by Hugh Huxley in states that muscle contraction involves the sliding movement of the thin filaments (actin) past the thick filaments (myosin) 4. sliding continues until the overlapping between the thin and thick filaments is complete. * Remember that in a relaxed muscle cell, overlapping of thick and thin filaments is only slight (i.e. striations). 5. Changes in muscle during contraction: See Fig 9.10, page 301. a. The distance between the Z-lines of the sarcomeres decreases. b. The I-Bands (light bands) shorten and disappear. c. The A-Bands move closer together, but do not diminish in length. 6. The Role of Calcium in Contraction Mechanism: a. In a resting muscle cell (i.e. in the absence of calcium ions): Tropomyosin blocks or inhibits the myosin binding sites on actin. See Fig 9.9(1), page 300. b. When calcium ions (Ca 2+ ) are present: Ca 2+ binds to troponin causing a conformational change in the troponin-complex, which causes: 1. tropomyosin to move 2. which "opens" or exposes the myosin binding sites on actin 3. This results in interaction between the active sites on actin and the heads (or cross bridges) of myosin. See Fig 9.9(2), page

8 9.3 SKELETAL MUSCLE CONTR E. Cross-Bridge Cycling See Fig 9.9, page 300. When calcium ions are present, the myosin binding sites on actin are exposed: 1. Cross-bridge attaches. a. ATP breakdown provides energy to cock myosin head. b. Cocked myosin attaches to exposed actin binding site. 2. Cross-bridge (myosin head) springs from cocked position and pulls on actin filament. 3. Cross bridges break. a. ATP binds to cross-bridge (but is not yet broken down) b. Myosin heads are released from actin. * As long as calcium ions and ATP are present, this step-wise walking continues until the muscle fiber is fully contracted. F. Relaxation See right side of Table 9.1, page Acetylcholinesterase is an enzyme present in the NMJ. 2. It immediately destroys acetylcholine, so the motor end-plate is no longer stimulated (i.e. so it cannot cause continuous muscle contraction). 3. Calcium ions are transported from sarcoplasm back into sarcoplasmic reticulum. 4. Linkages between actin and myosin are broken. 5. The muscle fiber relaxes. G. Energy Sources for Contraction 1. Introduction: The energy used to power the interaction between actin and myosin comes from ATP. 2. ATP stored in skeletal muscle lasts only about six seconds. a. ATP must be regenerated continuously if contraction is to continue. b. There are three pathways in which ATP is regenerated: Coupled Reaction with Creatine Phosphate (CP) Anaerobic Cellular Respiration Aerobic Cellular Respiration 3. Coupled Reaction with Creatine Phosphate (CP) See Fig 9.11, page 302. o o o CP + ADP creatine + ATP Muscle stores a lot of CP. This coupling reaction allows for about 10 seconds worth of ATP. 9-8

9 9.3 SKELETAL MUSCLE CONTR H. Oxygen Supply and Cellular Respiration: See Fig 9.12, page 303. Review from Chapter Anaerobic Respiration a. Steps are called glycolysis. b. Steps occur in the cytoplasm of the cell. c. results in production of pyruvic acid and 2 ATP. 2. Aerobic Respiration a. Steps are called citric acid cycle and electron transport chain. b. Oxygen is required. c. Steps occur in the mitochondrion of the cell. d. results in CO 2, water and 36 ATP. * See box on page 304, which illustrates how a runner utilizes the sources discussed above. I. Oxygen Debt: See Fig 9.13, page The oxygen debt is the amount of oxygen necessary to support a. the conversion of lactic acid (see below) to glucose. b. the resynthesis of ATP and CP. c. the return of tissue and blood O 2 levels back to pre-exercise levels. J. Muscle Fatigue 1. Muscle fatigue is a state of physiological inability to contract. 2. If no oxygen is available in muscle cells to complete aerobic respiration, pyruvic acid is converted to lactic acid, which in animals causes muscle fatigue and soreness. See Fig 9.13, page 303 and text on page results from a relative deficit of ATP and/or accumulation of lactic acid (which decreases ph). K. Heat Production 1. Almost half of the energy released during muscle contraction is lost to heat, which helps maintain our body temperature at 37 o C. a. Excessive heat is lost through many negative feedback mechanisms (discussed in chapter 1) including sweating, dilation of superficial blood vessels, increased breathing rate, and increased heart rate. 9-9

10 9.4 MUSCULAR RESPONSES A. Threshold Stimulus UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM 1. is the minimal strength of stimulation required to cause contraction. 2. A skeletal muscle fiber s resting membrane potential must be depolarized from 100mV to 70mV, before an impulse begins. Therefore the threshold stimulus is +30mV. B. Recording a Muscle Contraction: See Fig 9.14, page A myogram is a recording of a muscle contraction. 2. A twitch is a single contraction that lasts a fraction of a second, followed by relaxation. See Fig 9.16a, page The delay between stimulation and contraction is called the latent period. 4. The force a muscle fiber can generate depends on the length to which it is stretched when stimulated. See Fig 9.15, page A muscle fiber must return to its resting state (-100mV) before it can be stimulated again. This is called the refractory period. 6 All-or-None Response a. If a muscle fiber is brought to threshold or above, it responds with a complete twitch. b. If the stimulus is subthreshold, the muscle fiber will not respond. 7. Staircase Effect (treppe): a. Most muscle fiber contraction is all-or-none. b. However a muscle fiber that has been inactive can be subjected to a series of stimuli and: The fiber undergoes a series of twitches with relaxation between. The strength of each successive contraction increases slightly. This phenomenon is small and brief and involves excess calcium in the sarcoplasm and muscle warming. C. Summation: See Fig 9.16b, page When several stimuli are delivered in succession to a muscle fiber, it cannot completely relax between contractions. 2. The individual twitches begin to combine and the muscle contraction becomes sustained. a. In a sustained contraction, the force of individual twitches combines in a process called summation. Also See 9.4 E below. b. When the resulting sustained contraction lacks even slight relaxation, it is called tetanic contraction. Fig 9.16c, page

11 9.4 MUSCULAR RESPONSES UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM D. Recruitment of Motor Units 1. Recall that a motor unit is a motor neuron and the many skeletal muscle fibers it stimulates. See Fig 9.17, page Because the motor neuron branches into several motor nerve endings, it can stimulate many skeletal muscles fibers at the same time, which then contract simultaneously. a. The number of muscle fibers in a motor unit varies from ten-hundreds. 3. Because a whole muscle is composed of many motor units, controlled by many different motor neurons, simultaneous contraction of all units does not necessarily occur. 4. As the intensity of stimulation increases, recruitment of motor units increases, until all contract simultaneously. E. Sustained Contractions 1. Even when a muscle is at rest, a certain amount of sustained contraction is occurring in its fibers. This is called muscle tone. a. Muscle tone is very important in maintaining posture. F. Types of Contractions: See Fig 9.18, page Isotonic contractions a. The muscle shortens and its attachment(s) move(s). 2. Isometric contraction, a. The muscle becomes taut, but the attachment(s) do not move; tensing a muscle. 3. Most muscular movements involve both isotonic and isometric contractions. 4. See Clinical Application 9.2, page 308: Use and Disuse of Skeletal Muscles. G. Fast- and Slow-Twitch Muscle Fibers 1. Muscle fibers vary in contraction speed (i.e. slow or fast twitch). 2. Slow-Twitch Fibers are also called red fibers. a. They contain oxygen carrying pigment, myoglobin, receive a rich blood supply, and contain many mitochondria. b. can generate ATP fast enough to keep up with breakdown c. These fibers contract for long periods without fatiguing. 3. Fast-twitch fibers are also called white fibers. a. They contain less myoglobin, blood, and fewer mitochondria. b. contain extensive sarcoplasmic reticulum to store and reabsorb calcium. c. These fibers contract rapidly, but fatigue easily due to lactic acid accumulation. b. See box on page 308 re: dark and white meat. 9-11

12 9.5 SMOOTH MUSCLES: UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM A. Introduction: The contraction mechanism of smooth muscle is similar to that of skeletal muscle in that interaction occurs between actin and myosin. However the transverse tubules and sarcoplasmic reticula are greatly reduced, and troponin is absent. B. Smooth Muscle Fibers - Two types: See pages in text. 1. Multiunit smooth muscle a. location: o irises of eyes o walls of blood vessels b. Contraction is rapid and vigorous (similar to skeletal muscle tissue). 2. Visceral smooth muscle a. Location = the walls of hollow organs. b. Contraction is slow and sustained. o Rhythmicity = pattern of repeated contractions. o Peristalsis = wave-like motion that helps push substances through passageways. c. Structure: o random arrangement of actin and myosin filaments o Two layers of muscle surround the passageway. 1. inner circular layer 2. outer longitudinal layer d. See Fig 5.29, page 172. C. Smooth Muscle Contraction: 1. A protein, calmodulin binds to calcium ions (no troponin), and activates the contraction mechanism. 2. Most calcium diffuses into smooth muscle cells from the extracellular fluid (reduced SR). 3. Norepinephrine and acetylcholine are smooth muscle neurotransmitters. 4. Contraction is slow and sustained. 9-12

13 9.6 CARDIAC MUSCLE: See text pages , Fig 9.19, page 310 and Fig 5.30, page 173. Will be studied in greater detail in Chapter 15. A. Location: 1. only in heart B. Anatomy: 1. Striated uninuclear cells joined end-to-end forming a network a. Cell junctions are called intercalated discs. o gap junctions o See Fig 5.1, page Arrangement of actin and myosin is not as organized as in skeletal muscle. 3. contains sarcoplasmic reticula, transverse tubules, and numerous mitochondria: a. Sarcoplasmic reticulum is less developed than SR in skeletal muscle and stores much less calcium. * See box on page 309 re: Calcium channel blockers. C. Physiology 1. Self-exciting tissue (i.e. Pacemaker ) 2. Rhythmic contractions ( beats/minute) 3. Involuntary, all-or-nothing contractions a. function as a syncytium (all-or-nothing) 4. Pumps blood to: a. lungs for oxygenation b. body for distribution of oxygen and nutrients. * See Table 9.2, page 310: Characteristics of Muscles Tissues. 9-13

14 9.7 SKELETAL MUSCLE S UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM A. Introduction: Skeletal muscles generate a great variety of body movements. The action of a muscle primarily depends upon the joint associated with it and the manner in which the muscle is attached on either side of that joint. B. Body Movement 1. Skeletal muscles are attached to bones by tendons. a. serve as levers to move bones b. See Fig 9.20 page 311 for examples of levers. c. See Fig 9.21 page 312 for examples of how muscles pull on bones. C. Origin and Insertion: See Fig 9.22, page 312. Recall that skeletal muscles are usually attached to a fixed body part and a moveable body part: 1. The origin of a muscle is its immovable (anchored) end. 2. The insertion of a muscle is the movable end of a muscle. * When a muscle contracts and shortens, its insertion is pulled toward its origin. D. Review of Skeletal Muscle Actions (from Chapter 8) 1. Flexion = decreasing the angle between 2 bones (i.e. head toward chest). 2. Extension = increasing the angle between 2 bones (i.e. straightening the knee). 3. Hyperextension = increasing the angle greater than at anatomical position (i.e. bending the head back). 4. Dorsiflexion = bringing toes toward shin. 5. Plantar flexion = pointing one's toe (flexion toward the sole). 6. Abduction = moving a limb away from the midline (i.e. raising arm or thigh laterally). 7. Adduction = moving a limb toward the midline. 8. Rotation = turning movement of a bone along its longitudinal axis. 9. Circumduction = moving a limb in a circular (cone-shaped) manner. 10. Supination = thumbs up. 11. Pronation = thumb down. 12. Eversion = sole outward. 13. Inversion = sole inward. 14. Protraction = moving a part forward (i.e. chin thrust forward). 15. Retraction = moving a part backward (i.e. pulling the head back). 16. Elevation = raising a part (i.e. shoulder shrug). 17. Depression = lowering a part (i.e. depressing the mandible). 9-14

15 9.7 SKELETAL MUSCLE S UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM E. Interactions of Skeletal Muscles See page Prime Mover (agonist) = the primary muscle responsible for a movement. o The biceps brachii is the prime mover in flexing the arm at the Elbow. 2. Synergist(s) = muscles that assist the prime mover. The brachialis helps the biceps brachii during elbow flexion. 3. Antagonist(s) = the muscle(s) in opposition to the action of the prime mover. The antagonist relaxes (or stretches) during the prime movement. o The triceps brachii is the antagonist of the biceps brachii during elbow flexion. 4. Fixators = muscle groups that stabilize the origin of the prime mover (i.e. hold it in place) so that the prime mover can act more efficiently. o The scapula is the origin for many arm muscles, but it must be held in place by fixator muscles in order to function in this way. a. serratus anterior b. pectoralis minor 9.8 MAJOR SKELETAL MUSCLES NAMING OF SKELETAL MUSCLES CHARACTERISTIC EXAMPLES EXAMPLES IN HUMANS Direction of fascicles relative to midline Location (i.e. the bone or body part that a muscle covers) Relative Size Number of Origins (Heads) Shape Location of Origin and/or Insertion rectus = parallel transverse = perpendicular oblique = at 45 o angle frontal bone tibia maximus = largest longus = longest brevis = shortest biceps = 2 origins triceps = 3 origins deltoid = triangle trapezius = trapezoid serratus = saw-toothed orbicularis = circular origin = sternum insertion = mastoid process Rectus abdominis Transversus abdominis External Oblique Frontalis Tibialis Anterior Gluteus maximus Palmaris longus Peroneus longus Biceps brachii Triceps brachii Deltoid Trapezius Serratus anterior Orbicularis oris Sternocleidomastoid Action of Muscle flexion extension adduction Flexor carpi radialis Extensor digitorum Adductor longus 9-15

16 9.8 MAJOR SKELETAL MUSCLES (Keyed at the end of this outline) ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE. Use the figures and tables on pages to complete the following information. If a muscle is starred (*), please include its origin and insertion. Also see Human and Cadaver Reference Plates Fifty-Five Seventy-Five, pages A. Muscles of Facial Expression: See Fig 9.25 and Table 9.3 on page 315. Epicranius Frontalis Occipitalis Orbicularis oris Zygomaticus (*) Major Minor Buccinator Platysma Orbicularis oculi B. Muscles of Mastication: See Fig 9.25 on page 315 and Table 9.4 on page 316. Masseter(*) Temporalis 9-16

17 9.8 MAJOR SKELETAL MUSCLES ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE. C. Muscles that Move the Head and Vertebral Column: See Fig 9.25 on page 315, Fig 9.26, page 317, and Table 9.5 on page 318. Sternocleidomastoid (*) Erector Spinae D. Muscles that Move (or fixate) the Pectoral Girdle: See Fig 9.27 on page 319, Fig 9.28 on page 320, and Table 9.6 on page 321. Trapezius (*) Pectoralis minor Serratus anterior E. Muscles that Move the Arm (Humerus): See Fig 9.27, page 319, Fig 9.28, page 320, and Table 9.7, page 322. Pectoralis major (*) Latissimus dorsi Deltoid 9-17

18 9.8 MAJOR SKELETAL MUSCLES UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE. F. Muscles that Move the Forearm (radius & ulna): See Fig 9.30, page 322, Fig 9.31, page 323, and Table 9.8, page 324. Biceps Brachii (*) Brachialis Brachioradialis Triceps brachii G. Muscles that Move the Hand See Fig 9.32, page 325, Fig 9.33, page 326, and Table 9.9, page 327. Flexor carpi radialis Flexor carpi ulnaris Palmaris longus Extensor digitorum 9-18

19 9.8 MAJOR SKELETAL MUSCLES ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE. H. Muscles of the Abdominal Wall: See Fig 9.35, page 329, and Table 9.10, page 330. Rectus abdominis (*) External Oblique Internal Oblique Transversus abdominis I. Muscles of the Pelvic Outlet See Fig 9.36 page 330 and Table 9.11 page 331. Levator ani Coccygeus Superficial transversus perinea Bulbospongiosus Ischiocavernosus Sphincter urethrae 9-19

20 9.8 MAJOR SKELETAL MUSCLES ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE. J. Muscles that Move the Thigh (Femur): See Fig 9.37, page 332, Fig 9.38, page 333, and Table 9.12, page 335. Gluteus Maximus (*) Gluteus Medius Adductor Longus Gracilis * See box on page 331 re: Gluteal Gait. K. Muscles that Move the Leg (Tibia & Fibula): See Fig 9.37, page 322, Fig 9.39, page 334, and Table 9.13, page 336. Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius Sartorius (*) Biceps femoris Semitendinosus Semimembranosus 9-20

21 9.8 MAJOR SKELETAL MUSCLES UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE. L. Muscles that Move the Foot See Fig 9.41, page 337, Fig 9.42, page 338, Fig 9.43, page 339, and Table 9.14, page 340. Tibialis anterior Fibularis longus Gastrocnemius (*) Soleus * Note the location of the Calcaneal Tendon in Fig 9.43, page 339. * See box on page 340 re: Torn Achilles (Calcaneal) Tendon 9.9 LIFE-SPAN CHANGES A. Supplies of ATP, myoglobin, and creatine phosphate in muscle fibers begin to decline in one s forties. B. Half of one s muscle mass has been replaced by connective and adipose tissue by age 80, and reflexes are reduced. C. Exercise is the best way to maintain muscle function. Both strength training and aerobic exercise, with stretching before and after, is recommended. A side benefit of regular exercising, especially among older individuals is fewer bouts of depression. 9-21

22 OTHER INTERESTING TOPICS: UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM A. The Muscular Movements Behind Texting. See Introduction on page 293. B. Tendinitis and Tenosynovitis, See box on page 294. C. Compartment Syndrome. See box on page 294. D. Muscle Strain. See box on page 297. E. Dystrophin in skeletal muscle. See box on page 297. F. Poliomyelitis. See box on page 298. G. Myasthenia Gravis. See Clinical Application 9.1, page 299. H. Botulism and Botox. See box on page 299. I. Rigor Mortis. See box on page 301. J. TMJ Syndrome. See Clinical Application 9.3, page 316. K. Triangle of Auscultation. See box on page 332. L. Parkinson Disease. See box on page 327. M. Gluteal Gait. See box on page 331. N. Pulled Hamstring. See box on page 334. O. Myositis Ossificans. See box on page 336. INNERCONNECTIONS of the Muscular System - see page 342. CHAPTER SUMMARY see pages 341, CHAPTER ASSESSMENTS see pages INTEGRATIVE ASSESSMENTS/CRITICAL THINKING see page

23 SKELETAL MUSCLE SUMMARY TABLES A. Muscles of Facial Expression Epicranius Frontalis Occipitalis Orbicularis oris Zygomaticus Major and Minor (*) Origin: zygomatic bone Insertion: corners of orbicularis oris Covers cranium over forehead over occipital circular muscle around the mouth muscle that connects zygomatic arch to corner of mouth elevates eyebrow closes lips ( kissing muscle ) elevates corners of mouth ( smiling muscle ) Buccinator hollow of cheek compresses cheeks trumpeter s muscle Platysma lower border of mandible pouting muscle Orbicularis oculi circular muscle around eye closes eye B. Muscles of Mastication Masseter(*) Origin: Zygomatic Arch Insertion: Lateral Mandible Temporalis over lateral mandible convergent muscle over temporal bone elevates mandible elevates mandible 9-23

24 SKELETAL MUSCLE SUMMARY TABLES C. Muscles that Move the Head and Vertebral Column: Sternocleidomastoid(*) Origin: sternoclavicular region Insertion: mastoid process of temporal Erector Spinae Major neck muscle Group of midline dorsum muscles flexion of head toward chest (as synergists) rotation/abduction of head (as antagonists) Maintain posture D. Muscles that Move the Pectoral Girdle Trapezius (*) Origin: occipital bone & spines of C7-T12 Insertion: clavicle, spine and acromion process of scapulae Pectoralis minor Serratus anterior Trapezoid shaped muscle in posterior neck and upper back Muscle deep to Pectoralis major Saw-toothed lateral thoracic muscle elevates pectoral girdle ( shoulder shrug ) scapula fixator scapula fixator E. Muscles that Move the Arm (Humerus) Pectoralis major (*) Origin: clavicle, sternum, & costal cartilages of ribs 1-6 Insertion: between tubercles of humerus Large, convergent chest muscle flexes arm medially (pull arms forward and together) Latissimus dorsi Large, back muscle adduction of humerus Deltoid Triangular shaped shoulder muscle abduction of humerus 9-24

25 SKELETAL MUSCLE SUMMARY TABLES F. Muscles that Move the Forearm (radius & ulna) Biceps Brachii (*) Origin: Coracoid process Insertion: Radial tuberosity Brachialis Brachioradialis Triceps brachii fusiform, parallel, anterior upper arm muscle (two origins) muscle beneath biceps brachii lateral muscle between upper and forearm posterior upper arm muscle (three heads) flexion of arm at elbow (prime mover) flexion of arm at elbow (synergist) flexion of arm at elbow (synergist) extension of arm at elbow G. Muscles that Move the Hand Flexor carpi Radialis Flexor carpi Ulnaris Palmaris longus anterior, lateral forearm muscle anterior, medial forearm muscle anterior forearm muscle located between two above flexion of wrist flexion of wrist flexion of wrist Extensor digitorum posterior forearm muscle extension of wrist/fingers 9-25

26 SKELETAL MUSCLE SUMMARY TABLES H. Muscles of the Abdominal Wall Rectus abdominis (*) Origin: pubic crest & symphysis Insertion: xiphoid process & costal cartilages of 5-7 th ribs External Oblique Internal Oblique Transversus abdominis strap like muscle from costal cartilages to ilium superficial/lateral oblique abdominal muscle deep oblique abdominal muscle deep abdominal muscle that runs perpendicular to rectus abdominis tenses abdominal wall tenses abdominal wall tenses abdominal wall tenses abdominal wall I. Muscles of the Pelvic Outlet Levator ani Coccygeus Superficial transversus perinea Bulbospongiosus Ischiocavernosus Thin sheet surrounding anus, urethra and vagina Fan shaped, posterior to levator ani Band of muscle anterior to levator ani Surrounds base of penis or vagina Band of muscle lateral to bulbospongiosus Supports viscera and aids sphincters Same as above Supports viscera Male assists ejaculation Female constricts vaginal orifice Same as above Sphincter urethrae Surround urethra Opens and closes urethral orifice 9-26

27 SKELETAL MUSCLE SUMMARY TABLES J. Muscles that Move the Thigh (Femur) Gluteus Maximus (*) Origin: dorsal ilium, sacrum, coccyx Insertion: posterior femur buttocks, largest muscle in body extension of hip at thigh (as in walking or climbing stairs) Gluteus Medius lateral hip muscle abduction of femur Adductor Longus medial thigh muscle adduction of femur Gracilis medial thigh muscle adduction of femur K. Muscles that Move the Tibia & Fibula Rectus femoris anterior thigh quadriceps extension of leg at knee Vastus lateralis Vastus Medialis Vastus intermedius Sartorius (*) Origin: iliac spine Insertion: medial tibia lateral anterior thigh quadriceps medial anterior thigh quadriceps deep anterior thigh quadriceps parallel strap-like muscle that crosses thigh extension of leg at knee extension of leg at knee extension of leg at knee flexion of knee forward Biceps femoris posterior thigh hamstring flexion of leg at knee Semitendinosus posterior thigh hamstring flexion of leg at knee Semimembranosus posterior thigh hamstring flexion of leg at knee 9-27

28 SKELETAL MUSCLE SUMMARY TABLES L. Muscles that Move the Foot Tibialis anterior anterior to tibia dorsiflexion Peroneus longus lateral to fibula eversion Gastrocnemius (*) Origin: condyles of femur Insertion: calcaneus posterior lower leg (i.e. calf muscle) two origins plantar flexion (prime mover) Soleus deep to gastrocnemius plantar flexion (synergist) 9-28