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Slide 0 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Chapter 7 The Muscular System.

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1 Slide 0 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Chapter 7 The Muscular System

2 Slide 1 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Chapter 7 Lesson 7.1 Chapter 7 Lesson 7.1

3 Slide 2 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Introduction Muscular tissue enables the body and its parts to move Movement is caused by ability of muscle cells (called fibers) to shorten or contract Muscle cells shorten by converting chemical energy (obtained from food) into mechanical energy, which causes movement Three types of muscle tissue exist in the body

4 Slide 3 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Muscle Tissue Types of muscle tissue Skeletal musclealso called striated or voluntary muscle Is 40% to 50% of body weight; attached to bones Microscope reveals crosswise stripes or striations Contractions can be voluntarily controlled (Contd…)

5 Slide 4 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Muscle Tissue Types of muscle tissue (contd) Cardiac musclecomposes bulk of heart Cardiac muscle cells branch frequently Characterized by unique dark bands called intercalated disks Interconnected nature of cardiac muscle cells allows heart to contract efficiently as a unit (Contd…)

6 Slide 5 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Muscle Tissue (…Contd) Types of muscle tissue (contd) Nonstriated muscle or involuntary musclealso called smooth or visceral muscle Lacks cross stripes or striation when seen under a microscope; appears smooth Found in walls of hollow visceral structures such as digestive tract, blood vessels, and ureters Contractions not under voluntary control; movement caused by contractions is involuntary Functionall muscle cells specialize in contraction (shortening)

7 Slide 6 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Muscle Tissue (…Contd) Muscle tissue

8 Slide 7 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Structure of Skeletal Muscle Structure Skeletal muscle: an organ composed mainly of skeletal muscle cells and connective tissue Extend from one bone across a joint to another bone (Contd…)

9 Slide 8 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Structure of Skeletal Muscle (…Contd) Structure Parts of a skeletal muscle: Originattachment to the bone that remains relatively fixed when movement at the joint occurs Insertionpoint of attachment to the bone that moves when a muscle contracts Bodymain part of the muscle (Contd…)

10 Slide 9 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Structure of Skeletal Muscle (…Contd) Muscles attach to the bone by tendonsstrong cords of fibrous connective tissue Some tendons: enclosed in synovial-lined tubes and lubricated by synovial fluid Bursaesmall synovial-lined sacs containing a small amount of synovial fluid (Contd…)

11 Slide 10 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Structure of Skeletal Muscle (…Contd) Attachments of a skeletal muscle

12 Slide 11 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Structure of Skeletal Muscle (…Contd) Microscopic structure Muscle tissue consists of specialized contractile cells called fibers Each fiber contains two kinds of very fine, threadlike structures: Thick myofilaments =Myosin Thin myofilaments =Actin (Contd…)

13 Slide 12 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Structure of Skeletal Muscle (…Contd) Sarcomere: basic functional (contractile) unit Separated from each other by dark bands called Z lines Sliding filament model explains mechanism of contraction o Thick and thin myofilaments slide past each other as a muscle contracts

14 Slide 13 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Functions of Skeletal Muscle Movement Muscles produce movement As muscle contracts, it pulls the insertion bone closer to the origin bone Movement occurs at the joint between the origin and the insertion (Contd…)

15 Slide 14 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Functions of Skeletal Muscle (Contd…) Movement Groups of muscles usually contract to produce a single movement o Prime movercontraction is mainly responsible for producing a movement o Synergistcontractions help the prime mover produce a movement o Antagonistactions oppose the action of a prime mover in a movement (Contd…)

16 Slide 15 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Functions of Skeletal Muscle (…Contd) Posture Tonic contraction: specialized muscle contraction that enables us to maintain body position Only a few of a muscles fibers shorten at one time Tonic contractions produce no movement Tonic contractions maintain muscle tone called posture (Contd…)

17 Slide 16 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Functions of Skeletal Muscle (…Contd) Heat production Survival depends on the ability to maintain constant body temperature Feveran elevated body temperature; often a sign of illness Hypothermiaa reduced body temperature Contraction of muscle fibers produces most of the heat required to maintain normal body temperature

18 Slide 17 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Fatigue Reduced strength of muscle contraction Caused by repeated muscle stimulation Repeated muscular contraction depletes cellular ATP store and outstrips the ability of the blood supply to replenish oxygen and nutrients (Contd…)

19 Slide 18 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Fatigue (…Contd) Contraction in the absence of adequate oxygen produces lactic acid, which contributes to muscle soreness Oxygen debtthe continued metabolic effort required to burn excess lactic acid that may accumulate during prolonged periods of exercise

20 Slide 19 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Role of Other Body Systems in Movement Muscle functioning depends on the functioning of many other parts of the body Respiratory, circulatory, nervous, muscular, and skeletal systems play essential roles in producing normal movements

21 Slide 20 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Motor Unit Stimulation of a muscle by a nerve impulse is required to produce movement Motor neuron: specialized nerve that transmits an impulse to a muscle, causing contraction Neuromuscular junction: specialized point of contact between a nerve ending and the muscle fiber it innervates Motor unit: the combination of a motor neuron with the muscle cell(s) it innervates

22 Slide 21 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Muscle Stimulus A muscle will contract only if an applied stimulus reaches a certain level of intensity Threshold stimulus: minimal level of stimulation required to cause a muscle fiber to contract Once stimulated by a threshold stimulus, a muscle fiber will contract completely, a response called all or none (Contd…)

23 Slide 22 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Muscle Stimulus (…Contd) Different muscle fibers in a muscle are controlled by different motor units having different threshold-stimulus levels Although individual muscle fibers always respond all or none to a threshold stimulus, the muscle as a whole does not

24 Slide 23 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Types of Skeletal Muscle Contraction Twitch and tetanic contractions Twitch contractionsa quick, jerky response to stimulus Single contraction of muscle fibers caused by a single threshold stimulus Tetanic contractionssustained, steady muscular contractions Caused by a series of stimuli bombarding a muscle in rapid succession (Contd…)

25 Slide 24 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Types of Skeletal Muscle Contraction (…Contd) Isotonic contractions Contraction of a muscle that produces movement at a joint The muscle changes length, causing the insertion end of the muscle to move relative to the point of origin Most types of body movements such as walking and running are isotonic contractions (Contd…)

26 Slide 25 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Types of Skeletal Muscle Contraction (…Contd) Isometric contractions Muscle contractions that do not produce movement The muscle as a whole does not shorten No movement occurs during isometric contractions, but tension within the muscle increases

27 Slide 26 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Types of Skeletal Muscle Contraction (…Contd) Types of Muscle Contraction

28 Slide 27 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Effects of Exercise on Skeletal Muscles Regular, properly practiced exercise improves muscle tone and posture, Results in more efficient heart and lung functioning Reduces fatigue (Contd…)

29 Slide 28 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Effects of Exercise on Skeletal Muscles Prolonged inactivity causes disuse atrophy Regular exercise increases muscle size, called hypertrophy (Contd…)

30 Slide 29 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Effects of Exercise on Skeletal Muscles (…Contd) Strength training: exercise involving contractions of muscles against heavy resistance Increases number of myofilaments in each muscle fiber Total mass of the muscle increases Does not increase the number of muscle fibers (Contd…)

31 Slide 30 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Effects of Exercise on Skeletal Muscles (…Contd) Endurance training: exercise that increases a muscles ability to sustain moderate exercise over long periods Sometimes called aerobic training Allows more efficient delivery of oxygen and nutrients to a muscle via increased blood flow Increases the number of blood vessels in a muscle Does not usually result in muscle hypertrophy

32 Slide 31 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Chapter 7 Lesson 7.2 Chapter 7 Lesson 7.2

33 Slide 32 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Skeletal Muscle Groups Muscles of the head and neck Facial muscles Orbicularis oculi, orbicularis oris, zygomaticus Muscles of mastication Masseter, temporal Sternocleidomastoidflexes head Trapeziuselevates shoulders and extends head (Contd…)

34 Slide 33 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Skeletal Muscle Groups (…Contd) Muscles of the head and neck (Contd…)

35 Slide 34 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Skeletal Muscle Groups (…Contd) Muscles that move the upper extremities Pectoralis majorflexes upper arm Latissimus dorsiextends upper arm Deltoidabducts upper arm Biceps brachiiflexes forearm Triceps brachiiextends forearm (Contd…)

36 Slide 35 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Skeletal Muscle Groups (…Contd) Muscles of the trunk Abdominal muscles Rectus abdominis External oblique Internal oblique Transversus abdominis Respiratory muscles Intercostal muscles Diaphragm (Contd…)

37 Slide 36 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Skeletal Muscle Groups (…Contd) Muscles of the trunk (Contd…)

38 Slide 37 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Skeletal Muscle Groups (…Contd) Muscles that move the lower extremities Iliopsoasflexes thigh Gluteus maximusextends thigh Adductor musclesadduct thighs Hamstring musclesflex lower leg Semimembranosus Semitendinosus Biceps femoris (Contd…)

39 Slide 38 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Skeletal Muscle Groups (…Contd) Muscles that move the lower extremities Quadriceps femoris groupextend lower leg Rectus femoris Vastus muscles Tibialis anteriordorsiflexes foot Gastrocnemiusplantar flexes foot Peroneus groupflex foot

40 Slide 39 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Types of Movements Produced by Skeletal Muscle Contractions Flexiondecreases the angle between two bones at their joint: bending Extensionincreases the angle between two bones at their joint: straightening Abductionmovement of a part away from the midline of the body Adductionmovement of a part toward the midline of the body Rotationmovement around a longitudinal axis (Contd…)

41 Slide 40 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Types of Movements Produced by Skeletal Muscle Contractions (…Contd) Flexion and extension of the elbow (Contd…)

42 Slide 41 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Types of Movements Produced by Skeletal Muscle Contractions (…Contd) Supination and pronationhand positions from rotation of the forearm Supination: palm turned to the anterior position Pronation: palm faces posteriorly Dorsiflexion and plantar flexionfoot movements Dorsiflexion: elevation of the dorsum or top of the foot Plantar flexion: bottom of the foot is directed downward (Contd…)

43 Slide 42 Copyright © 2005, Elsevier, Inc. All Rights Reserved. Types of Movements Produced by Skeletal Muscle Contractions (…Contd) Examples of body movements


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