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Chapter 6: Muscular System Anatomy & Physiology Kasprowicz.

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1 Chapter 6: Muscular System Anatomy & Physiology Kasprowicz

2 The essential function of muscle is contraction – making it responsible for almost all body movement.

3 Types of Muscle 1)Skeletal 2)Cardiac 3)Smooth

4 General Muscle Characteristics muscle cells are elongated = muscle fibers (smooth, skeletal) contain myofilaments (ability to contract) terminology: myo-, mys- = muscle sarco- = flesh

5 Skeletal Muscle 1) Very large, multinucleated cells 2) Striated (visible stripes or banding pattern) 3) Voluntary (conscious) control; can be reflexive too 4) muscle fibers (cells) are bundled together by strong connective tissues  exert great force, but tire easily

6 Connective Tissues in Skeletal Muscle Deep fascia

7 Connective Tissues in Skeletal Muscles  Endomysium – around single muscle fiber  Perimysium – around a fascicle (bundle) of fibers  Epimysium – covers the entire skeletal muscle  Deep Fascia – on the outside of the epimysium

8 Connective Tissues in Skeletal Muscle

9 Connective Tissues in Skeletal Muscles  tendon – dense connective tissue attaching muscle to bone (cord-like)  aponeuroses – attach muscles indirectly to bone,cartilages or connective tissue coverings (sheet- like)  Epimysium blends into a connective tissue attachment

10 Connective Tissues in Skeletal Muscles

11 Aponeurosis of the external oblique

12 Connective Tissues in Skeletal Muscles Refer to pg. 272 in your textbook

13 Smooth Muscle 1) Spindle-shaped cells with one nucleus 2) no striations 3) Involuntary (no conscious control) 4) Found in hollow visceral organs 5) Have small amount of endomysium

14 Smooth Muscle 6) slow, sustained, tireless movement 7) often layers in opposite directions

15 Smooth Muscle: Stomach Wall

16 Cardiac Muscle 1) Branching cells with one nucleus connected by intercalated discs 2) Striated 3) Involuntary (no conscious control) 4) small amounts of endomysium

17 Cardiac Muscle 5) Cardiac fibers are arranged in spiral or 8- shaped bundles

18 Muscle Functions 1) Producing movement 2) Maintaining posture 3) Stabilizing joints 4) Support soft tissues 5) Generating heat 6) Guard entrances and exits

19 Muscle Functions

20 Skeletal Muscle Fiber (Cell) Formation

21

22 Microscopic Anatomy of Muscle  Cells are multinucleate  Nuclei are just beneath the sarcolemma (1) sarcolemma - specialized plasma membrane of muscle cells

23 Microscopic Anatomy of Muscle (2) Cytoplasm filled with myofibrils myofibrils – perfectly aligned, ribbon- like organelles; give muscle fiber its striped appearance

24 Microscopic Anatomy of Muscle (2) Cytoplasm filled with myofibrils A closer look at the myofibril Light (I) bands Dark (A) bands

25 Microscopic Anatomy of Muscle (2) Cytoplasm filled with myofibrils Banding Pattern: Light (I) bands contain the Z disc Dark (A) bands contain the H zone M line - holds adjacent filaments together; center of H zone

26 Microscopic Anatomy of Muscle An even closer look at the myofibril… (3) Sarcomere - contractile unit of the myofibril - Z disc to Z disc

27 Microscopic Anatomy of Muscle An even closer look at the myofibril… (3) Sarcomere

28 Microscopic Anatomy of Muscle Zooming in on the sarcomere… (4) Myofilaments - special proteins that cause muscle to contract Two Types: a) myosin (thick filament) b) actin (thin filament)

29 Microscopic Anatomy of Muscle Two Types: a) myosin (thick filament)  protein with heads that form cross bridges b/t thick & thin filaments during muscle contraction  Contain ATPase enzymes

30 Microscopic Anatomy of Muscle Two Types: b) actin (thin filament)  Made of the contractile protein actin & some other regulatory proteins

31 Microscopic Anatomy of Muscle Zooming in around the H zone….

32 Microscopic Anatomy of Muscle (5) Sarcoplasmic reticulum (SR) specialized smooth ER surrounding each myofibril stores calcium which is released when muscle is stimulated to contract

33 Microscopic Anatomy of Muscle Sarcoplasmic reticulum (SR)

34 Microscopic Anatomy of Muscle Sarcoplasmic reticulum (SR)

35 Let’s put this all together…. Microscopic Organization of Muscle: Level 1 (refer to Fig. 10-6, pg. 278)

36 Let’s put this all together…. Microscopic Organization of Muscle: Level 2

37 Let’s put this all together…. Microscopic Organization of Muscle: Level 3

38 Let’s put this all together…. Microscopic Organization of Muscle: Level 4

39 Let’s put this all together…. Microscopic Organization of Muscle: Level 5

40 Skeletal Muscle Activity: Initiating the Contraction

41 Special Functional Properties of Muscle  Irritability – ability to receive and respond to a stimulus (a property shared with neurons)  Contractility – ability to shorten when an adequate stimulus is received

42 Skeletal muscles must be stimulated by a nerve to contract (motor neuron).

43 Quick Review of Neurons & Synapses

44

45

46 Nerve Stimulus to Muscle Motor unit: One neuron & the muscle cells stimulated by that neuron

47 Nerve Stimulus to Muscle Neuromuscular junctions the neuron & muscle fibers do NOT touch separated by a gap called the synaptic cleft which is filled w/ interstitial fluid

48 Nerve Stimulus to Muscle Neuromuscular junctions

49 Transmission of Nerve Impulse to Muscle Neurotransmitters chemical released by neurons used to “carry” the impulse across the synaptic cleft Acetylcholine (ACh) is the neurotransmitter used at the neuromuscular junction of skeletal muscle

50 Transmission of Nerve Impulse to Muscle Steps in Impulse Transmission  ACh is released by the pre-synaptic axon terminal of the motor neuron  ACh crosses the synaptic cleft & attaches to receptors on the sarcolemma  Sarcolemma becomes permeable to sodium (Na + )

51 Transmission of Nerve Impulse to Muscle Steps in Impulse Transmission Sodium floods into the cell generating an action potential (electrical current)  Once started, muscle contraction cannot be stopped !!  ACh is broken down by the enzyme acetylcholinesterase This prevents continued contraction of the muscle cell in the absence of additional nerve impulses.

52 Transmission of Nerve Impulse to Muscle Steps in Impulse Transmission When an action potential sweeps along the sarcolemma and a muscle cell is excited, calcium ions are released from the sarcoplasmic reticulum

53 Transmission of Nerve Impulse to Muscle Steps in Impulse Transmission The flood of Ca + ions is the final trigger for the contraction of the muscle

54 Skeletal Muscle Activity: Sliding Filament Theory of Muscle Contraction

55 Mechanism of Muscle Contraction Sliding Filament Theory: Overview  Myosin heads form cross bridges with binding sites on actin  Myosin heads detach & then bind to the next site on actin Resting Sarcomere Sarcomere Contracts

56 Mechanism of Muscle Contraction Sliding Filament Theory: Overview  This action continues, causing the myosin & actin to slide past each other Sarcomere Contracts Resting Sarcomere

57 Mechanism of Muscle Contraction Sliding Filament Theory: Overview Collective shortening of the muscle cell sarcomeres = muscle contraction Sarcomere Contracts Resting Sarcomere

58 The Contraction Cycle : The Nitty Gritty Step 1: Ca + ions released from the SR attach to the troponin- tropomyosin complex Binding sites on the actin filament are exposed

59 The Contraction Cycle : The Nitty Gritty Step 1:

60 The Contraction Cycle : The Nitty Gritty Step 2: myosin heads attach to actin binding sites, forming cross bridges ATP was required to prep the myosin head (ATP  ADP + P)

61 The Contraction Cycle : The Nitty Gritty Step 2:

62 The Contraction Cycle : The Nitty Gritty Step 3: ADP + P released from myosin head myosin head flexes/pivots = “power stroke”

63 The Contraction Cycle : The Nitty Gritty Step 3:

64 The Contraction Cycle : The Nitty Gritty Step 4: ATP binds to myosin head, causing it to detach from the actin filament

65 The Contraction Cycle : The Nitty Gritty Step 5: myosin head re-energized (ATP  ADP + P) Step 6: Ca + ions pumped back into the SR troponin-tropomyosin complex moves back to its original position

66 The Contraction Cycle : The Nitty Gritty

67

68 Muscle Contraction Animations Muscle Contraction 3-D Animation Action Potentials & Muscle Contraction https://highered.mcgraw- hill.com/sites/ /student_view0/chapter10/animation__breakdown_of_atp_and_crossbridge_movement_during_muscle_contraction.html Break Down of ATP & Cross Bridge Attachment https://highered.mcgraw-hill.com/sites/ /student_view0/chapter10/animation__sarcomere_contraction.html Sarcomere Contraction

69 Contraction of the Whole Muscle The “all-or-none” response of muscle contraction refers to the muscle cell, NOT the whole muscle Whole muscle reacts with a graded response (different degrees of shortening)

70 Contraction of the Whole Muscle Graded responses are produced in 2 ways: 1) Change the frequency of stimulation 2) Change the # of muscle cells stimulated/time - more activated muscle cells stronger FORCE of contraction

71 Contraction of the Whole Muscle Muscle Twitch – 1 stimulus; single, brief, jerky contraction 1 Changing Stimulation Frequency

72 Contraction of the Whole Muscle Wave Summation– frequency of stimulus increases; less time to relax; contraction strength “summed” 2 Changing Stimulation Frequency

73 Contraction of the Whole Muscle Incomplete Tetanus – frequency of stimulation increases even more 3 Changing Stimulation Frequency

74 Contraction of the Whole Muscle Tetanus – frequency of stimulation very rapid; no evidence of relaxation; smooth, sustained contraction 4 Changing Stimulation Frequency

75 Energy for Muscle Contraction  Initially, muscles used stored ATP for energy  ATP is hydrolyzed into ADP + P  Only 4-6 seconds worth of ATP is stored by muscles  After this, other metabolic pathways must be used to produce ATP

76 Energy for Muscle Contraction Pathway 1: Direct Phosphorylation  Muscle cells contain creatine phosphate (CP)  CP is a high-energy molecule that transfers energy to ADP, regenerating ATP  CP supplies are exhausted in about 20 seconds

77 Energy for Muscle Contraction Pathway 1: Direct Phosphorylation

78 Energy for Muscle Contraction Pathway 2: Anaerobic Respiration (a.k.a. lactic acid fermentation)  breaks down glucose without oxygen  Glucose is broken down to pyruvic acid; 2 ATP are produced  Pyruvic acid  lactic acid

79 Energy for Muscle Contraction Pathway 2: Anaerobic Respiration (lactic acid fermentation)

80 Energy for Muscle Contraction Pathway 2: Anaerobic Respiration  This reaction is not as efficient, but it is fast  Huge amounts of glucose are needed  Lactic acid produces muscle fatigue  Duration: seconds

81 Energy for Muscle Contraction Pathway 3: Aerobic Respiration  Series of metabolic pathways that occur in the mitochondria & require oxygen  Glucose is broken down to carbon dioxide and water releasing energy  This is a slower reaction that requires continuous oxygen  High energy pay-off: 36 ATP

82 Energy for Muscle Contraction Pathway 3: Aerobic Respiration

83 Muscle Fatigue & Oxygen Debt  When a muscle is fatigued, it is unable to contract  The common reason for muscle fatigue is oxygen debt  Oxygen must be “repaid” to tissue to remove oxygen debt  Oxygen is required to get rid of accumulated lactic acid  Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less

84 Types of Muscle Contraction Isotonic Muscle Contraction  The myofilaments slide past each other  muscle shortens  movement occurs Examples: bending knee, rotating the arms, smiling

85 Types of Muscle Contraction Isometric Muscle Contraction muscle is not able to shorten muscle tension keeps increasing Examples: lifting a 1000 lb. object alone; pushing against an object that doesn‘t move

86

87 Muscle Tone state of continuous partial contractions  Different fibers contract at different times to provide muscle tone muscle remains firm, healthy & ready for action Increasing muscle tone increases metabolic energy used, even at rest

88 Muscle Tone

89 If the nerve supply to a muscle is destroyed, the muscle is no longer stimulated in this manner, and it loses tone and becomes paralyzed. Soon after, it becomes flaccid (soft and flabby) and begins to atrophy (waste away).

90 Muscle Tone

91 Effects of Exercise “use it or lose it” Aerobic (Endurance) Exercise Examples: jogging, biking, swimming stronger, more flexible muscles w/ greater resistance to fatigue

92 Effects of Exercise Aerobic (Endurance) Exercise Physiological Effects 1) increased blood supply to muscles 2) more mitochondria 3) increased metabolism 4) keeps bones strong 5) improves neuromuscular coordination

93 Effects of Exercise “use it or lose it” Resistance (Isometric) Exercise Examples: weight training increased muscle size and strength

94 Effects of Exercise Aerobic (Endurance) Exercise Physiological Effects 1) increased # of myofilaments  increased size of muscle fibers 2) more connective tissue 3) keeps bone strong

95 “Golden Rules” of Skeletal Muscle Activity 1) All (almost ) skeletal muscle cross a least one joint 2) Most of a skeletal muscle lies proximal to the joint crossed 3) All skeletal muscles have at least 2 attachments: the origin and the insertion 4) Skeletal muscles can only PULL (create tension) 5) When a muscle contracts, the insertion moves toward the origin

96 Types of Body Movements  Movement occurs when a muscle contracts and moves an attached bone  Muscles are attached to at least two points  Origin – attachment to a immoveable bone  Insertion – attachment to an movable bone

97 Types of Body Movements When a skeletal muscle contracts, its insertion moves toward its origin

98 Body Movements: Muscle Interactions  prime mover – muscle primarily responsible for a certain movement Example: biceps, hamstrings (a.k.a. agonist)  Antagonist – muscle that opposes or reverses a prime mover  Triceps when biceps flexes; quads when hamstrings flex

99 Prime Mover – biceps Antagonist – triceps Prime Mover – triceps Antagonist – biceps

100 Body Movements: Muscle Interactions  Synergist – muscle that aids a prime mover in a movement and helps prevent rotation Example: finger flexor muscles brachioradiulus & brachialis in the forelimb

101

102 Types of Body Movements 1)Flexion decreases angle of joint, bringing 2 bones closer together common in hinge, ball & socket joints 2)Extension increases the angle of a joint, moving the bones apart hyperextension >180° angle

103 Flexion & Extension Hyperextension

104 Flexion & Extension

105 Types of Body Movements 3) Rotation movement of a bone around its longitudinal axis common in ball & socket joints atlas (C1) around the axis (C2)

106 Rotation

107 Types of Body Movements 4) Abduction movement of a limb away from the medial plane also used to refer to fanning of finger or toes 5) Adduction movement of a limb toward the midline

108 Abduction & Adduction

109

110 Types of Body Movements 6) Circumduction proximal end is stationary; distal end moves in a circle limb moves in a cone shape common in ball & socket joint combo of flexion, extension, abduction & adduction

111 Circumduction

112 Special Body Movements 1) Dorsiflexion (point toes up towards shin) & Plantar Flexion (pointing the toes)

113 Special Body Movements 2) Inversion (turn sole of foot medially) & Eversion (turn sole of foot laterally)

114 Special Body Movements 3)Supination & Pronation movements of the radius around the ulna supination: palm forward; radius & ulna are parallel (anatomical position); thumb lateral pronation: palm facing back; radius crosses ulna; thumb medial

115 Special Body Movements 3)Supination & Pronation

116 Special Body Movements 4)Opposition movement of thumb across palm to touch fingertips

117 Elevation & Depression

118 Protraction & Retraction

119 Naming Skeletal Muscles 1)Direction of muscle fibers in reference to an imaginary line (midline of body, long axis of limb) ie. Rectus (fibers parallel to line) Oblique (fibers at a slant to line)

120 Naming Skeletal Muscles 2) Relative Size Longus = long Longissimus = longest Teres = long and round Brevis = short Magnus = large Major = larger Maximus = largest Minor = small Minimus = smallest

121 Naming Skeletal Muscles 3) Location of the Muscle in reference to the associated bone ie. temporalis (temporal bone) frontalis (frontal bone)

122 Naming Skeletal Muscles 4) Number of origins ie. biceps, triceps, quadriceps 5)Location of the muscle’s origin and insertion ie. Sternocleidomastoid muscle

123 Naming Skeletal Muscles 6) Shape of the muscle ie. Deltoid (triangular) 7) Action of the muscle ie. adductor muscle, extensor muscle

124 Head & Neck Muscles

125 Head and Neck Muscles Facial Muscles Frontalis raises eyebrows and wrinkles the forehead Orbicularis Oculi close, squint, blink and wink the eyes Orbicularis Oris closes the mouth and protrudes the lips; the “kissing” muscle

126 Head and Neck Muscles Buccinator flattens the cheek (whistling or playing a trumpet); also a chewing muscle Zygomaticus “smiling” muscle; raises the corners of the mouth upward

127 Head and Neck Muscles Chewing Muscles Buccinator Masseter closes the jaw by elevating the mandible (prime mover) Temporalis helps masseter close the jaw (synergist)

128 Frontalis Orbicularis oculi Zygomaticus Orbicularis oris Buccinator Masseter Temporalis

129 Frontalis Orbicularis oculi Orbicularis oris Zygomaticus Buccinator Temporalis Masseter

130 Frontalis Zygomaticus Orbicularis oris Orbicularis oculi Buccinator Temporalis Masseter

131 Head and Neck Muscles Neck Muscles Platysma pulls down corners of the mouth, downward sag of the mouth Sternocleidomastoid two-headed muscle; flex your neck (bowing of head); tilt head to side

132 Frontalis Orbicularis oculi Zygomaticus Orbicularis oris Buccinator Masseter Temporalis Platysma Sternocleido- mastoid

133 Frontalis Orbicularis oculi Orbicularis oris Zygomaticus Buccinator Temporalis Masseter Sternocleidomastoid Plastysma

134 Frontalis Zygomaticus Orbicularis oris Orbicularis oculi Buccinator Temporalis Masseter Sternocleido- mastoid platysma

135 Trunk Muscles move the vertebral column (mostly posterior, anti-gravity muscles) anterior thorax muscles (move ribs, head & arms) muscles of the abdominal wall (help move vertebral column & form the “girdle” holding internal organs in place)

136 Trunk Muscles Anterior Muscles: Thorax Pectoralis Major - fan-shaped muscle - origin: sternum, pectoral girdle, ribs - insertion: humerus - adduct & flex the arm

137 Pectoralis major Pectoralis minor

138 Trunk Muscles Anterior Muscles: Thorax Intercostal Muscles - deep muscles between the ribs - aid in breathing (external – inhale, internal – forcible exhale)

139 External intercostals Internal intercostals

140 Trunk Muscles Anterior Muscles: Abdominal Girdle Rectus abdominus - pubis to rib cage - flex the vertebral column - compression of abdominal contents

141 Trunk Muscles Anterior Muscles: Abdominal Girdle External Oblique - lateral walls of abdomen - origin: ribs insertion: illium - flex the vertebral column, rotate/bend trunk

142 Trunk Muscles Anterior Muscles: Abdominal Girdle Internal Oblique - origin: iliac crest insertion: ribs - function same as external oblique Transversus abdominis - deepest muscle in abdomen - fibers run horizontally - compresses the abdominal contents

143

144 Trunk Muscles Posterior Muscles Trapezius - kite-shaped muscle - origin: occipital bone to last thoracic vertebrae insertion: scapula & clavicle - head extension & movement of scapula

145 Trunk Muscles Posterior Muscles Latissimus Dorsi - 2 large, flat muscles in the lower back - origin: lower spine & ilium insertion: proximal end of humerus - arm extension & adduction (“power stroke”)

146 Trunk Muscles Posterior Muscles Erector Spinae - prime mover of back extension (keep your body “erect”); control bending at the waist - paired; deep in the back - span vertebral column

147 Trunk Muscles Posterior Muscles Qudratus lumborum - posterior abdominal wall - flex spine laterally, extend vertebral column - origin: iliac crest insertion: upper lumbar vertebrae

148 Trunk Muscles Posterior Muscles Deltoids - triangular muscle forming shoulder - origin: spine of scapula to clavicle insertion: proximal humerus - prime mover of arm abduction

149

150

151 Muscles of the Upper Limb Muscles of the Upper Limb The anterior arm muscles cause elbow flexion strongest: brachialis biceps brachii “weakest”: brachioradialis posterior arm: triceps brachii

152 Muscles of the Upper Limb Anterior Arm Muscles Biceps brachii - origin: 2 heads in pectoral girdle insertion: radius - prime mover of forearm flexion & supination

153 Muscles of the Upper Limb Anterior Arm Muscles Brachialis - origin: humerus insertion: ulna - forearm flexion Brachioradialis - origin: humerus insertion: distal forearm

154 Muscles of the Upper Limb Posterior Arm Muscles Triceps brachii - origin: 3 heads in pectoral girdle insertion: olecranon process of ulna - prime mover of elbow extension - biceps brachii antagonist

155

156 Muscles of the Lower Limb cause movement of hip, knee & foot joints some of the largest, strongest muscles in the body specialized for walking & balance many of the muscles cross 2 joints and can cause movement at both

157 Muscles of the Lower Limb Muscles that Move the Hip Joint Gluteus Maximus - forms most of the flesh of the buttock - origin: sacrum & illiac insertion: femur & iliotibial tract - hip extensor (important when climbing and jumping)

158 Muscles of the Lower Limb Muscles that Move the Hip Joint Gluteus Medius - beneath gluteus maximus - hip abductor; steadies pelvis when walking Iliopsoas (two, fused muscles) - prime mover of hip flexion; keeps upper body from falling backward when standing

159 Muscles of the Lower Limb Muscles that Move the Hip Joint Adductor Muscles - group of muscles; medial thigh - adduct, or press, thighs together - origin: pelvis insertion: femur - tend to get flabby

160 Iliopsoas Adductor muscles Anterior View

161 Posterior View Gluteus medius Gluteus maximus Adductor magnus Iliotibial tract

162 Muscles of the Lower Limb Muscles that Move the Knee Joint Hamstring Group - group of muscles; posterior thigh - biceps femoris, semimembranosus, semitendinosus - origin: ischium insertion: tibia - prime movers of thigh extension & knee flexion

163 Muscles of the Lower Limb Muscles that Move the Knee Joint Sartorius - thin, strap-like, relatively weak flexor - most superficial thigh muscle - synergist in sitting “criss cross applesauce”

164 Muscles of the Lower Limb Muscles that Move the Knee Joint Quadriceps Group - group of muscles; anterior thigh - rectus femoris & 3 vastus muscles - origin: pelvis & thigh insertion: tibia via patellar ligament - prime movers of knee extension; hip flexion

165 Iliopsoa s Adductor muscles Anterior View Sartorius Rectus femoris Vastus lateralis Vastus medialis

166 Posterior View

167 Muscles of the Lower Limb Muscles that Move the Ankle & Foot Tibialis Anterior - superficial muscle of anterior leg (shin) - origin: tibia insertion: tarsals - dorsiflex & invert the foot Fibularis Muscles - plantar flexion and eversion - origin: fibula insertion: metatarsals

168 Muscles of the Lower Limb Muscles that Move the Ankle & Foot Gastrocnemius - forms curved calf; 2 parts - origin: femur insertion: heel using Achille’s tendon - prime mover of plantar flexion

169 Muscles of the Lower Limb Muscles that Move the Ankle & Foot Soleus - deep to gastrocnemius - origin: tibia & fibula (no effect on knee) insertion: heel using Achille’s tendon - plantar flexion

170 Anterior View Posterior View

171


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