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Protection, Support, and
Movement
Chapter 39
KEY CONCEPTS
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Many structures and processes have
evolved in animals for protection, support,
and movement
Learning Objective 1
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Compare the functions of the external
epithelium of invertebrates and vertebrates
Epithelial Tissue
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In both invertebrates and vertebrates
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protects underlying tissues
specialized sensory or respiratory functions
Outer epithelium specialized to secrete
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lubricants or adhesives
odorous or poisonous substances
Epithelial Tissue in Invertebrates
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Cuticle
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protective shell secreted by outer epithelium
Integumentary System of
Vertebrates
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Skin and structures that develop from it
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Mammalian skin includes
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hair, claws or nails, sweat glands, oil glands,
sensory receptors
Learning Objective 2
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Relate the structure of vertebrate skin to
its functions
Feathers and Hair
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Feathers of birds and hair of mammals
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form insulating layer
helps maintain constant body temperature
Epidermis 1
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Protects body from outer environment
Stratum corneum
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most superficial layer
consists of dead cells filled with keratin
Keratin
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insoluble protein
gives mechanical strength to skin
reduces water loss
Epidermis 2
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Stratum basale
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cells divide, are pushed up to skin surface
cells mature, flatten, produce keratin
eventually die and slough off
Dermis
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Consists of dense, fibrous connective tissue
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Rests on layer of subcutaneous tissue
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composed largely of insulating fat
Human Skin
Capillary
Epidermis
Nerve
endings
Openings of
sweat glands
Stratum
corneum
Stratum
basale
Melanocyte
(pigment cell)
Hair erector
muscle
Hair shaft
Sensory
receptor
(Pacinian
corpuscle)
Dermis
Subcutaneous
tissue
Artery
Hair follicle
Vein
Sweat gland
Sebaceous
gland
Fig. 39-1, p. 829
KEY CONCEPTS
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Epithelial coverings protect underlying
tissues and may be specialized for
sensory, respiratory, or other functions
Learning Objective 3
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Compare the structure and functions of
different types of skeletal systems,
including the hydrostatic skeleton,
exoskeleton, and endoskeleton
The Skeletal System
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Supports and protects the body
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Transmits mechanical forces generated by
muscles
Hydrostatic Skeleton
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Fluid in closed body compartment
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transmits forces generated by contractile cells
or muscle
Found in soft-bodied invertebrates
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cnidarians, flatworms, annelids
Hydrostatic Skeleton
Longitudinal
contractile fibers
of epidermal layer
Circular
contractile fibers
of gastrodermis
(a) Contraction of circular
contractile fibers elongates the body.
(b) Contraction of longitudinal
fibers shortens the body.
Fig. 39-2, p. 830
Longitudinal
contractile fibers
of epidermal layer
Circular
contractile fibers
of gastrodermis
(a) Contraction of circular
contractile fibers elongates the body.
(b) Contraction of longitudinal
fibers shortens the body. Stepped Art
Fig. 39-2, p. 830
Exoskeletons
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Nonliving skeleton
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characteristic of mollusks and arthropods
doesn’t grow, arthropods must molt periodically
Arthropod skeleton
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composed partly of chitin
jointed for flexibility
adapted for many lifestyles
Ecdysis
Endoskeletons
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Consist of living tissue
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can grow
Found in echinoderms and chordates
Learning Objective 4
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Describe the main divisions of the
vertebrate skeleton and the bones that
make up each division
The Vertebrate Skeleton 1
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Axial skeleton
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skull
vertebral column
rib cage
sternum
The Vertebrate Skeleton 2
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Appendicular
skeleton
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limbs
pectoral girdle
pelvic girdle
Fig. 39-5, p. 832
Skull
Sternum
Rib cage
Vertebrae
Axial skeleton (brown)
Fig. 39-5a, p. 832
Clavicle
Scapula
Humerus
Radius
Ulna
Pelvic
girdle
Carpals
Metacarpals
Phalanges
Femur
Patella
Fibula
Tibia
Tarsals
Metatarsals
Phalanges
Appendicular skeleton (brown)
Fig. 39-5b, p. 832
KEY CONCEPTS
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Skeletal systems, whether they are
hydrostatic skeletons, exoskeletons, or
endoskeletons, support and protect the
body and transmit mechanical forces
important in movement
Learning Objective 5
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Describe the structure of a typical long
bone
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Differentiate between endochondral and
intramembranous bone development
A Long Bone
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Consists of
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a thin outer shell of compact bone
surrounding inner spongy bone
a central cavity that contains bone marrow
A Long Bone
Articular surface
covered with
cartilage
Red
marrow
in
spongy
bone
Epiphysis
Metaphysis
Periosteum
Yellow
marrow
Blood
supply
Diaphysis
Compact
bone
Articular
cartilage
Epiphysis
Fig. 39-6, p. 833
Bone Development
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Long bones
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develop from cartilage templates during
endochondral bone development
Other bones (such as flat bones of skull)
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develop from noncartilage connective tissue
model by intramembranous bone
development
Bone Cells
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Osteoblasts
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Osteoclasts
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cells that produce bone
cells that break down bone
Osteoblasts and osteoclasts work together
to shape and remodel bone
Learn more about the human
skeletal system and a typical
long bone by clicking on the
figures in ThomsonNOW.
Learning Objective 6
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Compare the main types of vertebrate
joints
Joints
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Junctions of two or more bones
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Ligaments
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connective tissue bands
connect bones
limit movement in joint
Types of Joints
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Immovable joints
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Slightly movable joints
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sutures of the skull
joints between vertebrae
Freely movable joint
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enclosed by joint capsule lined with
membrane that secretes synovial fluid
Learning Objective 7
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Relate the structure and function of insect
flight muscles
Insect Flight Muscles
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Large numbers of mitochondria and
tracheae (air tubes)
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support high metabolic rate required for flight
Learning Objective 8
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Describe the structure of skeletal muscles
and their antagonistic actions
Muscular Systems
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In vertebrates and most invertebrates
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muscle tissue contracts (shortens)
moves body parts by pulling on them
Three types of muscle
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skeletal
smooth
cardiac muscle
The Muscular System
Muscles that
flex fingers
Platysma
Latissimus dorsi
Rectus abdominis
Linea alba
External oblique
Gluteus medius
Gracilis
Sartorius
Quadriceps femoris
Facial
muscles
Sternocleidomastoid
Trapezius
Clavicle
Deltoid
Pectoralis major
Biceps brachii
Brachialis
Wrist
and finger
flexors
Triceps brachii
Patella
Gastrocnemius
Soleus
Tibialis anterior
Tibia
Fig. 39-8a, p. 835
Sternocleidomastoid
Trapezius
Deltoid
Biceps brachii
Triceps brachii
Brachialis
Latissimus dorsi
Brachioradialis
External oblique
Muscles that
flex fingers
Gluteus maximus
Gracilis
Semitendinosus
Biceps femoris
Semi-membranosus
Hamstring
muscles
Gastrocnemius
Soleus
Achilles tendon
Calcaneus
Fig. 39-8b, p. 835
Vertebrate Skeletal Muscles
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Pull on tendons
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connective tissue, attaches muscles to bones
Muscle contraction
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pulls bone toward or away from the bone with
which it articulates
Muscle Actions
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Skeletal muscles act antagonistically to
one another
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Agonist
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muscle that produces a particular action
Antagonist
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produces the opposite movement
Muscle Actions
Biceps relaxes
Triceps contracts
Triceps relaxes
Biceps contracts
Flexion
Extension
Fig. 39-7, p. 834
Insert “Opposing muscle
action”
biceps_triceps.swf
Skeletal Muscle Structure 1
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Skeletal muscle (such as biceps)
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organ made up of hundreds of muscle fibers
Muscle fiber consists of
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threadlike myofibrils
composed of smaller myofilaments (filaments)
Muscle
Structure
Biceps
muscle
(a) A muscle such as the
biceps in the arm consists of
many fascicles (bundles) of
muscle fibers.
Fig. 39-9a, p. 836
Muscle fibers
(b) A fascicle wrapped in a
connective tissue covering.
Fig. 39-9b, p. 836
Sarcolemma
Sarcoplasmic reticulum
Myofibril
T tubule
Mitochondria
Nucleus
Z line
Myofilaments
Sarcomere
(c) Part of a muscle fiber showing
the structure of myofibrils. The Z
lines mark the ends of the
sarcomeres.
Fig. 39-9c, p. 836
1 µm
(d) TEM of a striated muscle.
Fig. 39-9d, p. 836
(e) LM showing striations.
25 µm
Fig. 39-9e, p. 836
Skeletal Muscle Structure 2
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Striations of skeletal muscle fibers
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overlapping actin and myosin filaments
Sarcomere
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contractile unit of actin (thin) and myosin
(thick) filaments
Sliding Filament Model
Cross
bridges
Actin (thin filament)
Myosin (thick filament)
Sarcomere
A band
I band
H zone
Actin (thin) filament
Cross bridges Myosin (thick) filament
Fig. 39-10a, p. 838
Insert “Sliding filament
model”
sliding_filament_v2.swf
Learning Objective 9
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List, in sequence, the events that take
place during muscle contraction
Muscle Contraction 1
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Acetylcholine released by motor neuron
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Causes depolarization of sarcolemma
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binds to receptors on muscle fiber surface
transmission of action potential
Action potential spreads through T tubules
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releasing Ca ions from sarcoplasmic reticulum
Muscle Contraction 2
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Ca ions bind to troponin in actin filaments
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causing troponin to change shape
Troponin pushes tropomyosin away from
binding sites on actin filaments
Muscle Contraction 3
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ATP binds to myosin
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ATP is split, putting myosin head in highenergy state (“cocked”)
Energized myosin heads attach to
exposed binding sites on actin filaments
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forming cross bridges that link myosin and
actin filaments
Muscle Contraction 4
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Cross bridge flexes as phosphate is
released
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power stroke pulls actin filament toward
center of sarcomere
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ADP released during power stroke
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Myosin head binds a new ATP
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lets myosin head detach from actin
Muscle Contraction 5
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As long as calcium ion concentration
remains elevated
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new ATP is split, sequence repeats
Myosin reattaches to new active sites
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filaments are pulled past one another
muscle continues to shorten
Actin and
Myosin
Interactions
1 Acetylcholine (released by motor neuron)
combines with receptors on muscle fiber,
causing depolarization and an action potential.
2 Impulse spreads through T tubules,
stimulating Ca2+ release from sarcoplasmic
reticulum.
Ca
ATP binding site
Myosin
filament
ATP
Ca2+
Tropomyosin
Ca2+
Actin
filament
Binding site
Ca2+
Ca2+
Ca2+
Ca2+
P ADP
Ca2+
Troponin
3 Ca2+ bind to troponin, causing change in
shape. Troponin pushes tropomyosin away,
exposing binding sites on actin filaments.
4 ATP is split. Myosin head, now
cocked, binds to exposed binding
site, forming cross bridge.
Fig. 39-11, p. 839
If Ca2+ is available
Ca2+
Ca2+
Ca2+
ATP
5
7 Actin-myosin complex binds ATP, and myosin
P
ADP
Pi is released.
detaches from actin.
ADP
6 Cross bridge flexes, and actin filament is pulled toward center of
sarcomere. This movement is the power stroke. ADP is released. Fig. 39-11, p. 839
Learning Objective 10
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Compare the roles of glycogen, creatine
phosphate, and ATP in providing energy
for muscle contraction
Energy for Muscle Contraction
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ATP
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immediate energy source for muscle contraction
ATP hydrolysis provides energy to “cock” myosin
Creatine phosphate
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intermediate energy storage compound
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Glycogen
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fuel stored in muscle fibers
KEY CONCEPTS
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During muscle contraction, energy from
ATP is used to slide muscle filaments so
that the muscle shortens
Learning Objective 11
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How do muscles work, including factors
that influence contraction?
Muscle Contraction
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Contraction of a whole muscle depends on
(1) number of muscle fibers contracting
(2) tension developed by each fiber
A Motor Unit
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All skeletal muscle fibers stimulated by a
single motor neuron
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Motor recruitment
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messages from brain activate motor neurons
The more motor units recruited,
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the stronger the contractions
A Motor Unit
Cross section of
spinal cord
Neuromuscular
junctions
(a) The motor unit
illustrated here shows
only a single motor
neuron fiber.
Spinal nerve
Muscle
Motor nerve fiber
Fig. 39-12a, p. 840
Motor nerve fiber
Neuromuscular
junction
Part of muscle fiber
10 µm
(b) SEM of some of the fibers in a motor unit. Note how neurons
branch to innervate all muscle fibers in the motor unit.
Fig. 39-12b, p. 840
Skeletal Muscle Responses
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Simple twitch
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Summation
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activated by brief electrical stimulus
2 twitches add together when 2nd stimulus is
received before 1st contraction is complete
Tetanus
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smooth, sustained contraction
series of separate stimuli timed close together
Summation and Tetanus
Muscle Tone
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State of partial contraction
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characteristic of muscles
Explore muscle action, structure,
and contraction as well as
summation and tetanus by
clicking on the figures in
ThomsonNOW.
KEY CONCEPTS
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Muscles contract; in most animals they
move body parts by pulling on them
Learning Objective 12
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Compare the structures and functions of
the three types of skeletal muscle fibers
Slow-Oxidative Fibers
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Specialized for endurance activities
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Contract slowly, fatigue slowly, rich in
mitochondria, obtain most of their ATP
from aerobic respiration
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Red color due to high myoglobin content
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red pigment that stores oxygen
Fast-Oxidative Fibers
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Specialized for rapid response
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Contract fast, have an intermediate rate of
fatigue, rich in mitochondria, obtain most
of their ATP from aerobic respiration
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Red color due to high myoglobin content
Fast-Glycolytic Fibers
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Generate high power for a brief period
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Contract fast, fatigue quickly, have few
mitochondria, use glycolysis as a major
pathway for ATP synthesis
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White fibers