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PowerPoint Lecture Outlines
to accompany
Hole’s Human
Anatomy and Physiology
Eleventh Edition
Shier w Butler w Lewis
Chapter
9
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
Chapter 9
Muscular System
Three Types of Muscle Tissues
Skeletal Muscle
• usually attached
to bones
• under conscious
control
• striated
Cardiac Muscle
• wall of heart
• not under
conscious control
• striated
Smooth Muscle
• walls of most viscera,
blood vessels, skin
• not under conscious
control
• not striated
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Structure of a Skeletal Muscle
Skeletal Muscle
• organ of the muscular
system
- skeletal muscle tissue
- nervous tissue
- blood
- connective tissues
• fascia
• tendons
• aponeuroses
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Connective Tissue Coverings
• epimysium
• perimysium
• fascicles
• endomysium
• muscle
• fascicles
• muscle fibers
• myofibrils
• thick and thin filaments
4
Skeletal Muscle Fibers
• sarcolemma
• sacroplasm
• sarcoplasmic reticulum
• transverse tubule
• triad
• cisternae of sarcoplasmic
reticulum
• transverse tubule
• myofibril
• actin filaments
• myosin filaments
• sarcomere
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Sarcomere
• I bands
• A bands
• H zone
• Z lines
• M line
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Myofilaments
Thick Filaments
• composed of myosin
• cross-bridges
Thin Filaments
• composed of actin
• associated with troponin
and tropomyosin
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Neuromuscular Junction
• also known as
myoneural junction
• site where an axon and
muscle fiber meet
• motor neuron
• motor end plate
• synapse
• synaptic cleft
• synaptic vesicles
• neurotransmitters
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Motor Unit
• single motor neuron
• all muscle fibers controlled by motor neuron
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Stimulus for Contraction
• acetylcholine (ACh)
• nerve impulse causes release
of ACh from synaptic vesicles
• ACh binds to ACh receptors
on motor end plate
• generates a muscle impulse
• muscle impulse eventually
reaches sarcoplasmic reticulum
and the cisternae
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Excitation Contraction
Coupling
• muscle impulses cause
sarcoplasmic reticulum to
release calcium ions into
cytosol
• calcium binds to troponin to
change its shape
• position of tropomyosin is
altered
• binding sites on actin are
exposed
• actin and myosin molecules
bind
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Sliding Filament Model of Muscle
Contraction
• When sarcromeres
shorten, thick and thin
filaments slide past one
another
• H zones and I bands
narrow
• Z lines move closer
together
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Cross-bridge Cycling
• myosin cross-bridge attaches
to actin binding site
• myosin cross-bridge pulls
thin filament
•ADP and phosphate
released from myosin
• new ATP binds to
myosin
• linkage between actin
and myosin cross-bridge
break
•ATP splits
•myosin cross-bridge goes back
to original position
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Relaxation
• acetylcholinesterase – rapidly decomposes Ach
remaining in the synapse
• muscle impulse stops
• stimulus to sarcolemma and muscle fiber membrane
ceases
• calcium moves back into sarcoplasmic reticulum
• myosin and actin binding prevented
• muscle fiber relaxes
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Major Events of Muscle
Contraction and Relaxation
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Energy Sources for
Contraction
1) Creatine phosphate
2) Cellular respiration
• creatine phosphate – stores energy that quickly converts
ADP to ATP
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Oxygen Supply and
Cellular Respiration
• Anaerobic Phase
• glycolysis
• occurs in cytoplasm
• produces little ATP
• Aerobic Phase
• citric acid cycle
• electron transport chain
• occurs in the mitochondria
• produces most ATP
• myoglobin stores extra
oxygen
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Oxygen Debt
Oxygen debt – amount of oxygen needed by liver cells to
use the accumulated lactic acid to produce glucose
• oxygen not available
• glycolysis continues
• pyruvic acid
converted to lactic acid
• liver converts lactic
acid to glucose
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Muscle Fatigue
• inability to contract
• commonly caused from
• decreased blood flow
• ion imbalances across the sarcolemma
• accumulation of lactic acid
• cramp – sustained, involuntary muscle contraction
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Heat Production
• by-product of cellular respiration
• muscle cells are major source of body heat
• blood transports heat throughout body
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Muscular Responses
Threshold Stimulus
• minimal strength required to cause contraction
Recording a Muscle
Contraction
• twitch
• latent period
• period of contraction
• period of relaxation
• refractory period
• all-or-none response
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Length-Tension Relationship
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Summation
• process by which individual twitches combine
• produces sustained contractions
• can lead to tetanic contractions
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Recruitment of Motor Units
• recruitment - increase in the number of motor units
activated
• whole muscle composed of many motor units
• more precise movements are produced with fewer
muscle fibers within a motor unit
• as intensity of stimulation increases, recruitment of
motor units continues until all motor units are
activated
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Sustained Contractions
• smaller motor units (smaller diameter axons)
- recruited first
• larger motor units (larger diameter axons)
- recruited later
• produce smooth movements
• muscle tone – continuous state of partial contraction
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Types of Contractions
• isotonic – muscle contracts and
changes length
• eccentric – lengthening
contraction
• concentric – shortening contraction
• isometric – muscle contracts but
does not change length
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Fast and Slow Twitch
Muscle Fibers
Slow-twitch fibers (type I)
• always oxidative
• resistant to fatigue
• red fibers
• most myoglobin
• good blood supply
Fast-twitch glycolytic fibers (type IIa)
• white fibers (less myoglobin)
• poorer blood supply
• susceptible to fatigue
Fast-twitch fatigueresistant fibers (type IIb)
• intermediate fibers
• oxidative
• intermediate
amount of
myoglobin
• pink to red in color
•resistant to fatigue
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Smooth Muscle Fibers
Compared to skeletal muscle fibers
• shorter
• single, centrally located nucleus
• elongated with tapering ends
• myofilaments randomly organized
• lack striations
• lack transverse tubules
• sarcoplasmic reticula not well developed
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Types of Smooth Muscle
Visceral Smooth Muscle
• single-unit smooth muscle
• sheets of muscle fibers
• fibers held together by gap
junctions
• exhibit rhythmicity
• exhibit peristalsis
• walls of most hollow organs
Multiunit Smooth Muscle
• less organized
• function as separate units
• fibers function separately
• irises of eye
• walls of blood vessels
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Smooth Muscle Contraction
• Resembles skeletal muscle contraction
• interaction between actin and myosin
• both use calcium and ATP
• both are triggered by membrane impulses
• Different from skeletal muscle contraction
• smooth muscle lacks troponin
• smooth muscle uses calmodulin
• two neurotransmitters affect smooth muscle
• acetlycholine and norepinephrine
• hormones affect smooth muscle
• stretching can trigger smooth muscle contraction
• smooth muscle slower to contract and relax
• smooth muscle more resistant to fatigue
• smooth muscle can change length without changing
tautness
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Cardiac Muscle
• located only in the heart
• muscle fibers joined together by intercalated discs
• fibers branch
• network of fibers contracts as a unit
• self-exciting and rhythmic
• longer refractory period than skeletal muscle
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Characteristics of Muscle Tissue
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Skeletal Muscle Actions
• origin – immovable end
• insertion – movable end
• prime mover (agonist) –
primarily responsible for
movement
• synergists – assist prime mover
• antagonist – resist prime
mover’s action and cause
movement in the opposite
direction
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Body Movement
Four Basic Components of Lever
1. rigid bar – bones
2. fulcrum – point on which bar moves; joint
3. object - moved against resistance; weight
4. force – supplies energy for movement; muscles
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Levers and Movement
35
Major Skeletal Muscles
36
Major Skeletal Muscles
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Muscles of Facial Expression
38
Muscles of Mastication
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Muscles of Facial Expression
and Mastication
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Muscles That Move the Head
and Vertebral Column
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Muscles That Move the Head
and Vertebral Column
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Muscles That Move the
Pectoral Girdle
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Muscles That Move the
Pectoral Girdle
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Muscles That Move the Arm
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Muscles That Move the Arm
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Muscles That Move the Arm
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Muscles That Move the
Forearm
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Muscles That Move the
Forearm
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Muscles That Move the
Forearm
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Cross Section of the Forearm
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Muscles That Move the Hand
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Muscles That Move the Hand
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Muscles of the Abdominal Wall
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Muscles of the Abdominal Wall
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Muscles of the Pelvic Outlet
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Muscles of Pelvic Outlet
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Muscles That Move the Thigh
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Muscles That Move the Thigh
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Muscles That Move the Thigh
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Muscles That Move the Leg
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Muscles That Move the Leg
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Muscles That Move the Leg
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Muscles That Move the Leg
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Muscles That Move the Foot
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Muscles That Move the Foot
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Muscles That Move the Foot
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Life-Span Changes
• myoglobin, ATP, and creatine phosphate
decline
• by age 80, half of muscle mass has
atrophied
• adipose cells and connective tissues replace
muscle tissue
• exercise helps to maintain muscle mass and
function
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Clinical Application
Myasthenia Gravis
• autoimmune disorder
• receptors for ACh on muscle cells are attacked
• weak and easily fatigued muscles result
• difficulty swallowing and chewing
• ventilator needed if respiratory muscles are affected
• treatments include
• drugs that boost ACh
• removing thymus gland
• immunosuppressant drugs
• antibodies
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