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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Types of Ordinary Body Movements Slide 6.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Flexion  Extension  Rotation  Abduction  Circumduction

Body Movements Slide 6.33 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.13

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”

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

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

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)

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)

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)