Download Ch. 39 - Locomotion and Support Systems

Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 39
Locomotion and
Support Systems
Lecture Outline
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Outline
• 39.1 Diversity of Skeletons
• 39.2 The Human Skeletal System
• 39.3 The Muscular System
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Diversity of Skeletons
• Exoskeletons and Endoskeletons
 Exoskeleton – external skeleton
• Molluscs – composed of calcium carbonate
• Arthropods – composed of chitin
– Animal must molt (shed their exoskeleton) in
order to grow
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Diversity of Skeletons
• Exoskeletons and Endoskeletons
 Endoskeleton – internal skeleton
• Echinoderms
– Composed of spicules and plates of calcium carbonate
embedded in the living tissue of the body wall
• Sharks and Rays
– Composed of cartilage
• Bony fishes, amphibians, reptiles, birds, and mammals
– Composed of bone and cartilage
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Diversity of Skeletons
• Exoskeletons and Endoskeletons
 Endoskeleton (continued)
• Advantages:
–
–
–
–
–
Grows with the animal
Supports the weight of large animals
Protects vital internal organs
Protected by outer tissues
Allows flexible movements
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Exoskeleton
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Michael Fogden/OSF/Animals Animals/Earth Scenes
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The Vertebrate Endoskeleton
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Advantages of Jointed Endoskeleton
Can grow with the animal
Supports the weight of large animal
Protects vital internal organs
Is protected by outer tissues
Allows flexible movements
© E. R. Degginger/Photo Researchers, Inc.
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39.2 The Human Skeletal
System
• Functions
 Support of the body
 Protection of vital internal organs
 Sites for muscle attachment
 Storage reservoir for ions
 Production of blood cells
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The Human Skeletal System
• Bone Growth and Removal
 Cartilaginous structures in early development act as
models for future bones
• Models are eventually converted to bones as calcium salts are
deposited in the matrix by bone forming cells
• Endochondral ossification
– The conversion of cartilaginous models to bones
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The Human Skeletal System
• Bone Growth and Removal
 Osteoblasts - bone-forming cells
• Synthesize new matrix
 Osteoclasts
• Break down bone, remove worn cells, deposit
calcium in the blood
 Osteocytes - mature bone cells
• Osteoblasts that become caught in the matrix
• Live within the lacunae of osteons
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The Human Skeletal System
• Anatomy of a Long Bone
 Gross anatomy
• Medullary cavity in center bounded by
– Compact bone at the sides
– Spongy bone at the ends
 Details
• Compact bone
– Unit of structure called osteon (Haversian systems)
– Concentric lacunae arranged around a central canal
– Lacunae separated by a matrix of collagen fibers and mineral deposits
• Spongy bone
– Numerous bars and plates separated by irregular spaces
– Spaces filled with red bone marrow, which produces blood cells
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The Muscular System
• Microscopic Anatomy and Physiology
 Sarcolemma
• Plasma membrane
 Sarcoplasmic Reticulum
• Modified endoplasmic reticulum
• Stores calcium ions
 Myofibrils
• Contractile structures in the sarcoplasm
 Sarcomeres
• Units of contraction within myofibrils
• Consist primarily of two types of protein filaments
– Thick filaments made of myosin
– Thin filaments made of actin
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The Muscular System
• Sliding Filament Model
 Actin filaments are found at both ends of sarcomere
• One end of each filament is attached to a Z line at
one end of the sarcomere
• The other end suspended in sarcoplasm
 Myosin filaments are suspended between Z lines
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The Muscular System
• Sliding Filament Model (continued)
 When a muscle fiber contracts,
• Actin filaments slide past the myosin filaments and
approach one another
• Causes the Z lines to move toward each other
• The sarcomeres shorten
• The filaments remain the same length
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The Muscular System
• Sliding Filament Model (continued)
 When a muscle fiber contracts,
• Actin filaments slide past the myosin filaments and approach
one another
• Causes the Z lines to move toward each other
• The sarcomeres shorten
• The filaments remain the same length
 Working muscles require ATP
• Myosin filaments break down ATP and form crossbridges
that pull actin filaments toward the center of the sarcomere
• Sustained exercise requires cellular respiration to regenerate
ATP
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The Muscular System
• Use of ATP in Contraction
 Cellular respiration does not immediately supply all of the ATP
that is needed within a cell
 Muscle fibers rely on creatine phosphate
• Regenerates ATP through the following process:
Creatine-P + ADP
ATP + creatine
 When creatine phosphate is depleted and the cell still needs
more ATP for muscle contraction to occur, it undergoes
fermentation
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Skeletal Muscle Fiber Structure and
Function
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A muscle contains
bundles of muscle
fibers, and a muscle
fiber has many
myofibrils.
bundle of
muscle
fibers
myofibril
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(gymnast): © Corbis RF
Skeletal Muscle Fiber Structure and
Function
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A muscle contains
bundles of muscle
fibers, and a muscle
fiber has many
myofibrils.
bundle of
muscle
fibers
myofibril
(gymnast): © Corbis RF
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Skeletal Muscle Fiber Structure and
Function
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A muscle contains
bundles of muscle
fibers, and a muscle
fiber has many
myofibrils.
bundle of
muscle
fibers
myofibril
sarcolemma
mitochondrion
one myofibril
sarcoplasm
skeletal
muscle
fiber
Z line
T tubule sarcoplasmic
reticulum
crossbridge
one sarcomere
Z line
nucleus
myosin
actin
H zone
Z line
Sarcomeres are contracted.
A band
6,000X
I band
Sarcomeres are relaxed.
(gymnast): © Corbis RF; (myofi bril): © Biology Media/Photo Researchers,Inc.
A myofibril has many sarcomeres.
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Accidental Discovery of Botox
• The botulism toxin is produced by the
bacterium Clostridium botulinum
 One of the most lethal substances known
 By the 1920’s the toxin had been isolated in
pure form
• The pure form allowed scientists to determine that
the toxin acted by preventing nerves from
communicating with muscles
• Scientists soon began using the toxin to treat
conditions in which the muscles contract too much
– Eye conditions and spasms of facial muscles
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Accidental Discovery of Botox
• Canadian ophthalmologist Jean Carruthers used
the toxin to treat her patients’ eye conditions
 She soon noticed that the treatment caused the facial
wrinkles on her patient to subside
 She convinced her husband, a dermatologist, to use
the toxin to reduce wrinkles in his patients
• The treatment was successful and the toxin is now FDA
approved and used throughout the country
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The Muscular System
• Muscle Innervation
 Neuromuscular junction
• The synaptic contact between a nerve fiber and a
muscle fiber
• Nerve impulses bring about the release of a
neurotransmitter called acetylcholine (ACh) that
crosses the synaptic cleft
• Acetylcholine signals the muscle fiber to contract
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Neuromuscular Junction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
skeletal muscle fiber
axon branch
axon terminal
myofibril
neuromuscular
junction
synaptic
vesicle
a. One motor axon causes
several muscle fibers to
contract.
synaptic
cleft
acetylcholine
(ACh)
muscle fiber
axon branch
plasma
membrane
of axon
axon terminal
acetylcholinesterase
(AChE)
Na+
synaptic vesicle
folded
sarcolemma
synaptic cleft
sarcolemma
ACh receptor
mitochondrion
myofibril
nucleus
b. A neuromuscular junction is the juxtaposition of an axon
terminal and the sarcolemma of a muscle fiber.
c. The release of a neurotransmitter (ACh) causes receptors
to open and Na+ to enter a muscle fiber.
© Victor B. Eichler, Ph.D.
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The Muscular System
• Role of Calcium in Muscle Contraction
 Acetylcholine binds to receptors in the sarcolemma
 The sarcolemma generates impulses that spread down
T tubules to the sarcoplasmic reticulum
 Calcium is released from the sarcoplasmic reticulum
 Calcium ions bind with troponin
 Troponin regulates the position of tropomyosin, which
can block myosin binding sites on actin filaments
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The Role of Calcium and Myosin in
Muscle Contraction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
actin filament
troponin
myosin binding sites
Ca2+
Ca2+
Troponin-Ca2+ complex pulls tropomyosin
away, exposing myosin binding sites.
tropomyosin
a. Function of Ca2+
actin filament
P
ADP
myosin
filament
cross-bridge myosin head
1
ATP is hydrolyzed when
myosin head is unattached.
ATP
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2 ADP + P are bound to
myosin as myosin head
attaches to actin.
Binding of ATP causes
myosin head to assume
resting position.
3 Upon ADP + P release,
power stroke occurs:
head bends and pulls actin.
b. Function of myosin
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