ELAINE N. MARIEB EIGHTH EDITION 6 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY PART A The Muscular System

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Muscular System Function of Muscles:  Produce movement  Maintain posture  Stabilize joints  Generate heat Three basic muscle types are found in the body  Skeletal muscle  Cardiac muscle  Smooth muscle

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Characteristics of Muscles  Muscle cells are elongated, and are called muscle fibers (muscle cell = muscle fiber)  Contraction of muscles is due to the movement of microfilaments  All muscles share some terminology  Prefix myo refers to muscle  Prefix mys refers to muscle  Prefix sarco refers to flesh

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Characteristics Skeletal Muscle:  Most are attached by tendons to bones  Multinucleate – more than 1 nucleus  Striated – have visible banding  Voluntary – subject to conscious control  Cells are surrounded and bundled by connective tissue

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Connective Tissue Wrappings of Skeletal Muscle  Endomysium – around single muscle fiber  Perimysium – around a fascicle (bundle) of fibers  Epimysium – covers the entire skeletal muscle  Fascia – on the outside of the epimysium Figure 6.1

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Attachments  Muscles attach to bones by:  Tendons – cord-like structure  Aponeuroses – sheet-like structure  Sites of muscle attachment  Bones  Cartilages  Connective tissue coverings

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle Characteristics Smooth Muscle:  Has no striations  Spindle-shaped cells  Single nucleus  Involuntary – no conscious control  Found mainly in the walls of hollow organs Figure 6.2a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Characteristics Cardiac Muscle:  Has striations  Usually has a single nucleus  Joined to another muscle cell at an intercalated disc  Involuntary  Found only in the heart Figure 6.2b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle  Sarcolemma – specialized plasma membrane  Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum  Sarcomere – contractile unit of a muscle fiber Figure 6.3a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.3b Microscopic Anatomy of Skeletal Muscle  Myofibril  Bundles of myofilaments – actin & myosin  Myofibrils are aligned to give distinct bands  I band = light band  A band = dark band

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle  Organization of the sarcomere  Thick filaments = myosin filaments  Made of the protein myosin  Thin filaments = actin filaments  Composed of the protein actin Figure 6.3c

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle  Myosin filaments have heads (extensions, or cross bridges)  At rest, there is a bare zone that lacks actin filaments  Sarcoplasmic reticulum (SR) – stores calcium used in contractions - During contraction myosin & actin slide past eachother Figure 6.3d

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Stimulus to Muscles  Irritability –receive and respond to stimulus  Contractility – shorten when stimulated  Skeletal muscles must be stimulated by a nerve to contract  Motor unit  One neuron  Muscle cells stimulated by that neuron Figure 6.4a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Stimulus to Muscles  Neuromuscular junctions – association site of nerve and muscle (where they meet) Figure 6.5b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Stimulus to Muscles  Synaptic cleft – gap between nerve and muscle  Nerve and muscle do not touch  Area between nerve and muscle filled with interstitial fluid  Neurotransmitters travel across space Figure 6.5b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Nerve Impulse to Muscle  Neurotransmitter acetylcholine – chemical released by nerve upon arrival of impulse  Acetylcholine attaches to receptors on the sarcolemma of muscle  Sarcolemma becomes permeable to sodium (Na + )  Sodium rushes into the cell and generates an action potential (stimulus) for contraction  Once started, muscle contraction cannot be stopped

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Sliding Filament Theory of Muscle Contraction  Activation by nerve causes myosin heads (crossbridges) to attach to binding sites on actin  Myosin heads then bind to the next site actin  This continued action slides myosin along actin  The result is that the muscle is shortened (contracted) Figure 6.7

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Sliding Filament Theory Figure 6.8

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Contraction of a Skeletal Muscle Skeletal Muscle Contraction:  Muscle fiber contraction is “all or none”  Within a skeletal muscle, not all fibers may be stimulated during the same interval  Different combinations of muscle fiber contractions may give differing responses  Graded responses – different degrees of skeletal muscle shortening

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses  Twitch  Single, brief contraction  Not a normal muscle function Figure 6.9a–b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses  Tetanus (summing of contractions)  One contraction is immediately followed by another  Contraction is smooth and sustained Figure 6.9a–b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Response to Strong Stimuli  Muscle force depends upon the number of fibers stimulated  More fibers contracting results in greater muscle tension  Muscles can continue to contract unless they run out of energy

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction Energy for Muscle Contraction:  First, muscles used stored ATP for energy  Bonds of ATP are broken to release energy (lasts only few seconds)  After this initial time, cells need to undergo aerobic or anaerobic respiration to produce energy for contraction

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction  Aerobic Respiration  Occurs in the mitochondria  Glucose is broken down to carbon dioxide, water and ATP (energy)  This is a slower reaction that requires continuous oxygen Figure 6.10b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction  Anaerobic glycolysis  Breaks down glucose without oxygen  Glucose is broken down to pyruvic acid, then lactic acid, to produce some ATP  Not as efficient as aerobic respiration Build up of lactic acid Produces muscle fatigue Figure 6.10c

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Muscle Contractions  Isotonic contractions  Myofilaments are able to slide past each other during contractions  The muscle shortens  Isometric contractions  Tension in the muscles increases  The muscle is unable to shorten Different fibers contract at different times to provide muscle tone

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscles and Body Movements  Movement is attained due to a muscle moving an attached bone  Muscles are attached to at least two points  Origin – attachment to an immoveable bone  Insertion – attachment to a movable bone Figure 6.12

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Effects of Exercise on Muscle  Results of increased muscle use  Increase in muscle size  Increase in muscle strength  Increase in muscle efficiency  Muscle becomes more fatigue resistant

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Ordinary Body Movements Types of body movements due to muscles  Flexion: brings bones closer together  Extension: opposite of flex, increases distance between bones  Rotation: movement around longitudinal axis (shaking head no)  Abduction: moving limb away from body  Adduction: opposite, move limb toward body  Circumduction: proximal end is stationary and distal end moves in a circle

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Body Movements Figure 6.13a–c

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Body Movements Figure 6.13d

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Special Movements  Dorsifelxion: toes up, walking on heels  Plantar flexion: toes down, walking on toes  Inversion: turn sole medially (in toward body)  Eversion: turn sole laterally (away from body)  Supination: turn palm up (facing anteriorly)  Pronation: turn palm down (facing posteriorly)  Opposition: ability to move thumb to touch other fingers

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Muscles  Prime mover (Agonist) – muscle with the major responsibility for a certain movement  Antagonist – muscle that opposes or reverses a prime mover  Synergist – muscle that aids a prime mover in a movement and helps prevent rotation  Fixator – stabilizes the origin of a prime mover

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Naming of Skeletal Muscles  Direction of muscle fibers:  Example: rectus (straight)  Relative size of the muscle:  Example: maximus (largest)  Location of the muscle:  Example: temporalis (temporal bone)  Number of origins:  Example: triceps (three heads)  Shape of the muscle  Example: deltoid (triangular)  Action of the muscle  Example: flexor and extensor

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Head and Neck Muscles Figure 6.15

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Trunk Muscles Figure 6.16

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Deep Trunk and Arm Muscles Figure 6.17

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscles of the Pelvis, Hip, and Thigh Figure 6.19c

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscles of the Lower Leg Figure 6.20

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Superficial Muscles: Anterior Figure 6.21

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Superficial Muscles: Posterior Figure 6.22