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2 Chapter 9 The Muscular System

3 Introduction Skeletal muscles: movement in environment Smooth muscles: intestines, ureters, veins and arteries Cardiac muscle: pumps blood through heart and blood vessels 40–50% of body weight

4 The Types of Muscle

5 The Types of Muscle (cont’d.) Skeletal: voluntary, striated, and multinucleated Smooth: involuntary, nonstriated, and uninucleated Cardiac: involuntary, striated, and uninucleated

6 The Anatomy of Skeletal or Striated Muscle

7 The Anatomy of Skeletal or Striated Muscle (cont’d.) Skeletal muscle cell surrounded by sarcolemma Fasciculi: bundles of fascicles Fascicles: individual bundles of muscle fibers

8 The Anatomy of Skeletal or Striated Muscle (cont’d.) Perimysium: surrounds each fascicle Epimysium: covers the perimysium Fascia: covers the epimysium Myosin: A bands Actin: I bands Z lines H zone

9 The Anatomy of Skeletal or Striated Muscle (cont’d.) Sarcomere: between two adjacent Z lines –Actual contraction process occurs here Sarcotubular system –T system and sarcoplasmic reticulum

10 The Physiology of Muscle Contraction

11 Introduction Motor unit: all muscle cells innervated by one motor neuron Muscle cell properties –Excitability –Conductivity –Contractility –Elasticity

12 Neuroelectrical Factors Na + higher concentration outside muscle cell K + higher concentration inside muscle cell Resting potential: charge outside positive and inside negative Electrical potential: rush of Na + inside cell K + moves outside cell attempting to balance

13 Neuroelectrical Factors (cont’d.)

14 Neuroelectrical Factors (cont’d.) Action potential –Calcium released –Troponin and tropomyosin action inhibited –Activated myosin links to actin filaments

15 Chemical Interactions Myosin heads contain ATP ATP releases energy upon myosin/action link Energy released used to pull action Sodium: potassium pump pumps out sodium Resting potential restored

16 Chemical Interactions

17 Energy Sources ATP: energy source for muscle contraction ATP production –Glycolysis –Krebs citric acid cycle –Electron transport Alternate sources: fatty acids and phosphocreatine

18 The Muscle Twitch

19 The Muscle Twitch (cont’d.) Stimulus > latent period > contraction > relaxation Contraction strength depends on –Strength, speed, and duration of stimulus –Weight of load –Temperature All-or-none law

20 The Muscle Twitch (cont’d.)

21 Muscle Tone

22 Muscle Tone (cont’d.) State of partial contraction throughout whole muscle Maintains pressure on abdominal contents Helps maintain blood pressure Aids digestion Types –Isotonic, isometric

23 The Anatomy of Smooth Muscle

24 The Anatomy of Smooth Muscle (cont’d.) Found in hollow structures Involuntary, uninucleated, nonstriated Arrangement (two layers) –Longitudinal (outer) –Circular (inner)

25 The Anatomy of Cardiac Muscle

26 The Anatomy of Cardiac Muscle (cont’d.) Autonomic nervous system control Involuntary, uninucleated, striated Intercalated disks: coordinate contraction Cardiac muscles: contract, relax, and contract 75 times/minute

27 The Naming and Actions of Skeletal Muscles

28 The Naming and Actions of Skeletal Muscles (cont’d.) Action Shape Origin and insertion Location Direction of fibers

29 The Naming and Actions of Skeletal Muscles (cont’d.) Origin: more fixed attachment of muscle Insertion: movable attachment of muscle Tendons: attach muscle to bone Aponeurosis: wide flat tendon

30 The Naming and Actions of Skeletal Muscles (cont’d.) Flexors: bend limb at a joint Extensor: straighten limb at a joint Abductors: move limb away from midline Adductors: bring limb toward midline Rotators: revolve limb around axis

31 The Naming and Actions of Skeletal Muscles (cont’d.) Dorsiflexors: raise the foot Plantar flexors: lower the foot Supinators: turn palm upward Pronators: turn palm downward

32 The Naming and Actions of Skeletal Muscles (cont’d.) Levators: raise a part of the body Depressors: lower a part of the body Prime movers or agonists: bring about an action Antagonists: oppose agonists Synergists: assist prime movers

33 The Function and Location of Selected Skeletal Muscles

34 Superficial muscles of the body, anterior view Superficial Muscles

35 Superficial muscles of the body, posterior view Superficial Muscles (cont’d.)

36 Muscles of Facial Expression Occipitalis Frontalis Zygomaticus Levator labii superioris Orbicularis oris and buccinator

37 Some muscles of the head and neck, anterior view Muscles of Facial Expression (cont’d.)

38 Some muscles of the head and neck, lateral view Muscles of Facial Expression (cont’d.)

39 Muscles of Mastication Masseter Temporalis Pterygoid

40 Muscles of the Eye Superior rectus Inferior rectus Medial rectus Lateral rectus Superior and inferior oblique

41 Muscles Moving the Head Sternocleidomastoid –Contraction of both causes flexion of neck –Contraction of one causes rotation to left or right

42 Muscles Moving the Head

43 Muscles Moving the Shoulder Girdle Levator scapulae Rhomboids Pectoralis minor Trapezius Serratus anterior

44 Muscles Moving the Humerus Pectoralis major Latissimus dorsi Teres minor Deltoid Supraspinatus Infraspinatus

45 Muscles Moving the Humerus

46 Muscles Moving the Elbow Brachialis Biceps brachii Brachioradialis Triceps brachii Anconeus

47 Muscles Moving the Wrist Flexor carpi Extensor carpi

48 Muscles Moving the Hand Supinator Pronator teres Pronator quadratus

49 Muscles Moving the Thumb Flexor pollicis Extensor pollicis Adductor pollicis Abductor pollicis Opponens pollicis

50 Muscles Moving the Fingers Flexor digitorum Extensor digitorum Interossei

51 Muscles of the Abdominal Wall External oblique Internal oblique Transversus abdominis Rectus abdominis

52 Muscles of the Abdominal Wall (cont’d.)

53 Muscles of Respiration or Breathing Diaphragm –Main muscle External and internal intercostals –Expand the ribs

54 Muscles Moving the Femur Psoas Iliacus Gluteus maximus Gluteus medius Gluteus minimus Tensor fascia lata

55 Muscles Moving the Knee Joint Biceps femoris Semitendinosus Semimembranosus Popliteus Gracilis Sartorius Quadriceps femoris

56 Muscles Moving the Knee Joint

57 Muscles Moving the Foot Gastrocnemius Tibialis posterior Soleus Peroneus longus Plantaris Tibialis anterior Peroneus tertius

58 Muscles Moving the Toes Flexor hallucis Extensor hallucis Flexor digitorum Extensor digitorum Abductor hallucis Abductor digiti minimi

59 Summary Described the gross and microscopic anatomy of skeletal muscle Contrasted skeletal, smooth, and cardiac muscle anatomy Described muscle contraction and the role of neuroelectrical and chemical factors and energy sources Named major muscles of the body