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Essentials of Anatomy and Physiology Fifth edition Seeley, Stephens and Tate Slide 2.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 7: Muscular System
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Contraction of a Skeletal Muscle Slide 6.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Individual muscle fiber contraction is “all or none” Within a skeletal muscle, not all fibers may be stimulated Different combinations of muscle fiber contraction give variations in response “Strength” of response
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Types of Graded Responses Slide 6.20a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Twitch Involves a single muscle fiber Single, brief contraction Not a normal muscle function Figure 6.9a, b Phases of a Muscle Twitch
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Types of Graded Responses Slide 6.20a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Twitch has three phases Lag phase Contraction Relaxation Figure 6.9a, b Phases of a Muscle Twitch
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Types of Graded Responses Slide 6.20b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Summation Increasing force of contraction of muscle fiber Recruitment Increasing the number of muscle fibers contracting Figure 6.9a, b
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Types of Graded Responses Slide 6.20b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Tetanus (sustained contraction) One contraction is immediately followed by another The muscle does not return to a resting state Due to increased frequency of stimuli The effects are added Figure 6.9a, b
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Types of Graded Responses Slide 6.20b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fatigue: Muscle eventually runs out of ATP Fibers cannot contract Figure 6.9a, b Types of Graded Responses: Tetanus and Fatigue
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Types of Graded Responses Slide 6.21a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Unfused (incomplete) tetanus Some relaxation occurs between contractions The result is summation Figure 6.9a, b Figure 6.9c,d Summation
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Muscle Response to Strong Stimuli Slide 6.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Muscle force depends upon number of fibers stimulated More fibers contracting results in greater muscle tension Muscles continue to contract until they run out of energy
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Energy for Muscle Contraction Slide 6.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Initially, muscles used stored ATP for energy Bonds of ATP are broken to release energy Only 4-6 seconds worth of ATP is stored After this, other pathways must be used
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Energy for Muscle Contraction Slide 6.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Aerobic Respiration Metabolic pathways in the mitochondria Glucose is broken down, releasing energy This is a slow reaction requiring oxygen Figure 6.10c
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Energy for Muscle Contraction Slide 6.26a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Anaerobic respiration Breaks down glucose without oxygen Glucose is broken down to pyruvic acid produces some ATP Pyruvic acid is converted to lactic acid Figure 6.10b
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Energy for Muscle Contraction Slide 6.26b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Anaerobic respiration ( continued ) This reaction is not as efficient, but is fast Huge amounts of glucose are needed Lactic acid produces muscle fatigue Figure 6.10b
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Muscle Fatigue and Oxygen Debt Slide 6.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings When a muscle is fatigued, it is unable to contract The common reason for muscle fatigue is oxygen debt Oxygen must be “repaid” Oxygen is required to get rid of lactic acid
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Types of Muscle Contractions Slide 6.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Isotonic (equal tension) contractions Myofilaments slide past each other during contractions The muscle shortens Isometric (equal weight) contractions Tension in the muscles increases The muscle is unable to shorten
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Muscle Tone (tonus) Slide 6.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Some fibers are contracted even in a “relaxed” muscle Different fibers contract at different times to provide muscle tone Maintains posture The process is involuntary
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Muscles and Body Movements Slide 6.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Movement is produced when a muscle moves an attached bone Figure 6.12
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Muscles and Body Movements Slide 6.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Bones serve as levers Lever: a rigid rod Fulcrum: point of rotation Figure 6.12
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Muscles and Body Movements Slide 6.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Movement requires force or energy Object to be moved provides resistance “System” consists of a fulcrum, resistance, and energy for movement
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Muscles and Body Movements Slide 6.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Joints serve as fulcra Classes of levers: First class Second class Third class Figure 6.12
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Muscles and Body Movements Slide 6.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings First class lever: fulcrum lies between resistance and energy Example: hyperextending neck tilt face upward, look at the ceiling Trapezius and splenius muscles
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Muscles and Body Movements Slide 6.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Second class lever: resistance lies between “energy” and fulcrum Example: standing on “tip toes” Gastrocnemius muscle
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Muscles and Body Movements Slide 6.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Third class: “energy’ is applied between resistance and fulcrum flexing elbow Biceps brachii Figure 6.12
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Muscles and Body Movements Slide 6.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Third class lever: most common in a human body Figure 6.12
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Muscles and Body Movements Slide 6.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Muscles are attached at two points Origin – fixed attachment Insertion – movable attachment Figure 6.12
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Muscles and Body Movements Slide 6.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Muscle attachments must cross a joint (fulcrum) If it doesn’t, no movement! Figure 6.12
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Effects of Exercise on Muscle Slide 6.31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Results of increased muscle use Increase in size of muscle fibers (hypertrophy), NOT in number of fibers Increase in actin and myosin Increase in blood supply, mitochondria Muscle becomes resistant to fatigue
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Types of Ordinary Body Movements Slide 6.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Flexion Extension Rotation Abduction Circumduction
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Body Movements Slide 6.33 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.13
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Special Movements Slide 6.34 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Dorsiflexion: toes point “up” Plantar flexion: toes point “down” Inversion: soles of feet “in” Eversion: soles of feet “out” Supination: face or palm “up” Pronation: face or palm “down”
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Functions of Muscles Slide 6.35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Prime mover – muscle with the major responsibility for a certain movement Antagonist – muscle that opposes or reverses a prime mover
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Functions of Muscles Slide 6.35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Synergist – muscle that aids a prime mover in a movement and helps prevent rotation Fixator – stabilizes the origin of a prime mover
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Naming of Skeletal Muscles Slide 6.36a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Direction of muscle fibers Example: rectus (straight) Relative size of the muscle Example: maximus (largest)
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Naming of Skeletal Muscles Slide 6.36b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Location of the muscle Example: many muscles are named for bones (e.g., temporalis) Number of origins Example: triceps (three heads)
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Naming of Skeletal Muscles Slide 6.37 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Attachments of muscle Example: sterno (origin on the sternum) Shape of the muscle Example: deltoid (triangular) Action of the muscle Example: flexor and extensor (flexes or extends a bone)
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