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THIRD EDITION
HUMAN PHYSIOLOGY
AN INTEGRATED APPROACH
Dee Unglaub Silverthorn, Ph.D.
Chapter 12
Muscles
PowerPoint® Lecture Slide Presentation by
Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
About this Chapter
• Muscle types
• What muscles do
• How muscles contract
• Contraction to locomotion
• Roles of smooth muscles
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Muscles
• Contract!
• Generate motion
• Generate force
• Generate heat
• Support
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Muscular System Functions
• Body movement (Locomotion)
• Maintenance of posture
• Respiration
• Diaphragm and intercostal contractions
• Communication (Verbal and Facial)
• Constriction of organs and vessels
• Peristalsis of intestinal tract
• Vasoconstriction of b.v. and other structures (pupils)
• Heart beat
• Production of body heat (Thermogenesis)
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Properties of Muscle
• Excitability: capacity of muscle to respond
to a stimulus
• Contractility: ability of a muscle to shorten
and generate pulling force
• Extensibility: muscle can be stretched back
to its original length
• Elasticity: ability of muscle to recoil to
original resting length after stretched
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Muscle Types
• Cardiac – heart
• Smooth – internal organs
• Skeletal – "voluntary"
• Attach to bone
• Move appendages
• Support body
• Antagonistic pairs
• Flexors
• Extensors
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Types of Muscle
• Skeletal
• Attached to bones
• Makes up 40% of body weight
• Responsible for locomotion, facial expressions, posture, respiratory
movements, other types of body movement
• Voluntary in action; controlled by somatic motor neurons
• Smooth
• In the walls of hollow organs, blood vessels, eye, glands, uterus, skin
• Some functions: propel urine, mix food in digestive tract,
dilating/constricting pupils, regulating blood flow,
• In some locations, autorhythmic
• Controlled involuntarily by endocrine and autonomic nervous systems
• Cardiac
• Heart: major source of movement of blood
• Autorhythmic
• Controlled involuntarily by endocrine and autonomic nervous systems
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Categories of skeletal muscle actions
• Categories Actions
• Extensor
Increases the angle at a joint
• Flexor
Decreases the angle at a joint
• Abductor Moves limb away from midline of body
• Adductor Moves limb toward midline of body
• Levator
Moves insertion upward
• Depressor Moves insertion downward
• Rotator
Rotates a bone along its axis
• Sphincter Constricts an opening
S12-8
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Connective Tissue Sheaths
• Connective Tissue of a Muscle
• Epimysium. Dense regular c.t. surrounding entire muscle
• Separates muscle from surrounding tissues and organs
• Connected to the deep fascia
• Perimysium. Collagen and elastic fibers surrounding a
group of muscle fibers called a fascicle
• Contains b.v and nerves
• Endomysium. Loose connective tissue that surrounds
individual muscle fibers
• Also contains b.v., nerves, and satellite cells (embryonic stem cells
function in repair of muscle tissue
• Collagen fibers of all 3 layers come together at each
end of muscle to form a tendon or aponeurosis.
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Muscle Types
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Figure 12-1: Three types of muscles
Muscle Tissue Types
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Skeletal Muscle Anatomy
• About 40% body mass
• Muscle fibers – cells
• Fascicle – bundle
• Motor unit
• Muscle
• sheath
• Attach to tendons (which attach to bone)
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Nerve and Blood Vessel Supply
• Motor neurons
• stimulate muscle fibers to contract
• Neuron axons branch so that each muscle fiber (muscle cell) is
innervated
• Form a neuromuscular junction (= myoneural junction)
• Capillary beds surround muscle fibers
• Muscles require large amounts of energy
• Extensive vascular network delivers necessary oxygen
and nutrients and carries away metabolic waste produced
by muscle fibers
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Skeletal Muscle Anatomy
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Figure 12-3a-1: ANATOMY SUMMARY: Skeletal Muscle
Skeletal Muscle Anatomy
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Figure 12-3a-2: ANATOMY SUMMARY: Skeletal Muscle
Muscle Fiber Structure
• Multiple nuclei
• Sarcolemma
• T-tubules
• Sarcoplasmic reticulum
• Sarcoplasm
• Mitochondria
• Glycogen & ions
• Myofibrils
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Muscle Fiber Structure
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Figure 12-3b: ANATOMY SUMMARY: Skeletal Muscle
Muscle Fiber Structure
Figure 12-4: T-tubules and the sarcoplasmic reticulum
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Myofibrils: Site of Contraction
• Actin – "thin fibers"
• Tropomysin
• Troponin
• Myosin – "thick fibers"
• Titin – elastic anchor
• Nebulin – non-elastic
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Myofibrils: Site of Contraction
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Figure 12-3c-f: ANATOMY SUMMARY: Skeletal Muscle
Sarcomere: Organization of Fibers
• Z disks
• I band
• A band
• H Zone
• M line
• Titin
• Nebulin
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Figure 12-5: The two- and three-dimensional organization of a sarcomere
Sarcomere: Organization of Fibers
Figure 12-6: Titin and nebulin
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Contraction Sequence: Sliding Filament Theory
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Figure 12-9 (steps 1 & 2): The molecular basis of contraction
Contraction Sequence: Sliding Filament Theory
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Figure 12-9 (steps 3 & 4): The molecular basis of contraction
Contraction Sequence: Sliding Filament Theory
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Figure 12-9 (steps 5 & 6): The molecular basis of contraction
Skeletal Muscle Contraction: Mechanism
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Figure 12-11a: Excitation-contraction coupling
Skeletal Muscle Contraction: Mechanism
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Figure 12-11b: Excitation-contraction coupling
One Postulated Cause of Muscle Fatigue
• Stress responses in skeletal muscle during
E-C coupling. Stress-induced RyR1 dysfunction
can result in SR Ca2+ leak, which potentially
activates numerous Ca2+-dependent cellular
damage mechanisms. AC, adenylate cyclase.
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Energy for Contraction: ATP & Phosphocreatine
• Aerobic Respiration
• Oxygen
• Glucose
• Fatty acids
• 30-32 ATPs
• Anaerobic Respiration
• Fast but
• 2 ATP/glucose
• Phosphocreatine ATPs
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Energy for Contraction: ATP & Phosphocreatine
Figure 12-13: Phosphocreatine
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Muscle Fatigue: Causes not well known
• Central
• "Feeling"
• Lactic acid
• Peripheral
• Glycogen depletion
• Ca2+ interference
• High Pi levels
• ECF high K+
• ACh depletion
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Figure 12-14: Locations and possible causes of muscle fatigue
Fiber Contraction Speed: Fast Twitch
• Rate
• 2-3 times faster
• SR uptake of Ca2+
• ATP splitting
• Anaerobic/Fatigue easily
• Power lifting
• Fast/delicate
• Sprint
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Fiber Contraction Speed: Fast Twitch
Figure 12-15: Fast-twitch glycolytic and slow-twitch muscle fibers
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Fiber Contraction Speed: Oxidative Fast & Slow
• Oxidative Fast Twitch
• Intermediate speed
• Anaerobic & aerobic
• Slow Twitch: Aerobic, less fatigue
• More mitochondria
• More capillaries
• Myoglobin
• Endurance activities
• Postural muscles
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Coordinating the Fibers: Force of Contraction
• Excitation and Twitch
• Length–Tension: more crossbridges: more
tension
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Figure 12-16: Length-tension relationships in contracting skeletal muscle
Coordinating the Fibers: Summation to Tetanus
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Figure 12-17: Summation of contractions
Smooth Muscle
• Fusiform cells
• One nucleus per cell
• Nonstriated
• Involuntary
• Slow, wave-like
contractions
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Smooth Muscle
• Cells are not striated
• Fibers smaller than those in skeletal
muscle
• Spindle-shaped; single, central nucleus
• More actin than myosin
• No sarcomeres
• Not arranged as symmetrically as
in skeletal muscle, thus NO
striations.
• Caveolae: indentations in sarcolemma;
• May act like T tubules
• Dense bodies instead of Z disks
• Have noncontractile intermediate
filaments
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Smooth Muscle
• Grouped into sheets in walls of hollow organs
• Longitudinal layer – muscle fibers run parallel to organ’s long axis
• Circular layer – muscle fibers run around circumference of the organ
• Both layers participate in peristalsis
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Smooth Muscle
• Is innervated by autonomic nervous system (ANS)
• Visceral or unitary smooth muscle
• Only a few muscle fibers innervated in each group
• Impulse spreads through gap junctions
• Whole sheet contracts as a unit
• Often autorhythmic
• Multiunit:
• Cells or groups of cells act as independent units
• Arrector pili of skin and iris of eye
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Smooth Muscle Cell
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Smooth Muscle Contraction: Mechanism
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Smooth Muscle Relaxation: Mechanism
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Contractile fibers are arranged in oblique bundles
rather than in parallel sarcomeres
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Myosin of Smooth Muscle
• Different isoform than that found in skeletal
muscle
• Smooth muscle myosin ATPase activity is
much slower, contraction is longer
• Myosin light chain in the myosin head
regulates contraction and relaxation
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Smooth Muscle
• Relatively little sarcoplasmic reticulum
• Lacks T-tubules
• Chemically linked to the cell membrane, rather
than mechanically linked
• Ca +2 storage is supplemented by caveolae , small
vesicles that cluster close to the cell membrane.
Voltage/ligand gated Ca +2 channels
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Single-Unit Muscle
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Properties of Single-Unit Smooth Muscle
• Gap junctions
• Pacemaker cells
with spontaneous
depolarizations
• Innervation to few
cells
• Tone = level of
contraction without
stimulation
• Increases/decreases
in tension
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• Graded Contractions
• No recruitment
• Vary intracellular
calcium
• Stretch Reflex
• Relaxation in
response to sudden
or prolonged stretch
Multi-Unit Muscle
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Comparisons Among Skeletal, Smooth, and
Cardiac Muscle
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