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Ch. 39- Locomotion & Support Systems
I. Locomotion
A. Active travel from place to
place
B. Depends on the ability to
overcome two forces:
1. Friction
2. Gravity
C. These factors vary depending
upon the environment
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D. Swimming
1. Gravity not much of problem
a. Water supports weight
2. Friction is a problem
a. Water is dense; much
resistance
3. Modes of swimming:
a. Insects - use legs as oars
b. Squid - jet propelled
c. Fish - move bodies side to side
d. Marine mammals - move body
up and down
4. Streamlined shape is important
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E. Locomotion on Land
1. Little friction problem
a. Air offers little resistance
2. Gravity is a problem
a. Animal must support itself
b. Leg muscles expend energy:
 to propel forward
 to keep from falling down
c. Powerful muscles & strong
skeleton are important
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3. Types of Land Locomotion
a. Hopping - kangaroos
 Powerful leg muscles generate
power & then store energy
when animal lands
b. Walking - dogs, etc.
 4-legged creature keep 3 legs
on ground at one time
 2-legged ones have 1 leg on
ground at any time (less stable)
c. Running - all feet off ground at times
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Horse Running
d. Crawling
 Friction is a problem
 Snakes:
Crawl rapidly by undulating body
Move slowly using movable
scales on underside
 Earthworms
Use peristalsis:
 Circular & longitudinal muscles
alternate contractions & move
worm forward
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Locomotion in an Earthworm
4. Flying
a. Gravity is a problem
b. Key is shape of wings. All wings
must be airfoils. These are
structures whose shape alters air
currents in a way that creates lift
c. Air pressure under wing is greater
& this lifts the wing
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II. Skeletal Support
A. Functions of skeletons:
1. Help in movement
2. Support animal against gravity
3. Protect soft parts
B. Types of skeletons:
1. Hydrostatic
2. Exoskeletons
3. Endoskeletons
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C. Hydrostatic skeleton
1. Fluid held under pressure in a
closed body compartment
a. Gives body shape
b. Helps protect parts
c. Provides support for motion
2. Fluid inside coelom of earthworm
acts as a hydrostatic skeleton:
a. Muscles work against it
3. Works well for aquatic organisms
& those that crawl or burrow
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D. Exoskeleton
1. Rigid external skeleton
a. Mollusks - calcium carbonate
b. Arthropods - chitin
2. Muscles attach to inner surfaces
of exoskeleton to help move
jointed body parts
3. Provides protection, support &
flexibility
4. Must be molted & replaced by
large exoskeleton when animal
grows
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mmm
Exoskeletons
Molting
an Exoskeleton
mmm
Disadvantage: Must molt to grow. At this time they
are very vulnerable to predators.
E. Endoskeleton
1. Hard or leathery supporting
elements situated among soft
tissues of animal
a. Sponges - hard spicules
b. Echinoderms - hard plates
c. Vertebrates - cartilage or bone
 Sharks - ALL cartilage
 Other vertebrates retain
cartilage in areas where
flexibility is needed (joints)
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Shark Endoskeleton
Vertebrate Endoskeleton
Know these advantages
III. Human Skeleton
A. Skeleton is upright. Has 2 main
parts:
1. Axial skeleton
 Skull, vertebral column,
sternum, thoracic cage (ribs)
2. Appendicular skeleton
 Limbs (fore- & hind-)
 Girdles (pelvic & pectoral)
B. Skull balanced atop backbone
C. Backbone is S-shaped
D. Hands for grasping
E. Feet for walking on 2 legs
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The Human Skeleton
F. Bones
1. Bones are living, moist tissue
2. Consist of:
a. Connective tissue on outside
b. Cartilage at ends forms cushion
for joints
c. Matrix
 Material secreted by the living
cells.
 Consists of fibers of collagen
in calcium salts
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Anatomy of Long Bones
3. Structure of Long Bones
a. Shaft composed of compact bone
 Dense matrix
b. Central cavity contains:
 Yellow bone marrow (stores fat)
c. Ends composed of:
 Compact bone on outer layer
 Spongy bone in inner layer
 Little cavities with red bone
marrow (produces blood cells)
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Anatomy of Long Bones
G. Axial Skeleton
1. Skull:
a. Protects brain
b. Formed of cranium & facial
bones
• Membranous regions, called
fontanels, join cranial bones in
newborns
• Become sutures by age 2
c. Opening at base of skull for spinal
cord is called the foramen
magnum
d. Mandible = lower jaw
e. Maxilla = upper jaw
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Human Skull
2. Vertebral Column
a. Supports head & trunk
b. Protects spinal cord & roots of spinal
nerves
c. There are 24 vertebrae:
• 7 cervical (neck)
• 12 thoracic (chest)
• 5 lumbar (small of back)
• 5 sacral (fused into sacrum)
• coccyx (tailbone)
d. Intervertebral disks, composed of
fibrocartilage between vertebrae, act
as padding.
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3. Rib Cage
a. Contains thoracic vertebrae, ribs,
costal cartilages & sternum
(breastbone)
b. Ribs:
• 12 pairs
• Top 7 pairs are “true ribs” because
they attach to sternum
• Lower 5 are “false ribs”
c. Protects heart & lungs
d. Moves up & down during breathing
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The Rib Cage
H. Appendicular Skeleton
1. Pectoral girdle & arms
a. Linked loosely by ligaments
b. Scapula (shoulder blades) held
in place only by muscles
c. Humerus fits into socket of
scapula
●Very flexible; little stability
2. Pelvic girdle & legs
a. Coxal bones (hips) anchored to
sacrum
b. Pelvic cavity wider in females
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Pectoral Girdle &
arm
Pelvic Girdle & leg
Pelvic Girdles of Male & Females
I. Types of Joints
1. Bones are connected at joints
2. Three types of joints:
a. Fibrous
Immovable. Ex. = sutures
b. Cartilaginous
Slightly movable. Ex. = vertebrae
c. Synovial joints
Freely movable. Bones are
separated by a cavity.
Ligaments bind two bones to
each other
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3. Types of Synovial Joints
a. Ball-and-socket joint
♦ Allow rotation in several planes
♦ Humerus in pectoral girdle &
femur in pelvic girdle
b. Hinge joint
♦ Allows movement in single plane
♦ Knee & elbow
c. Pivot joint
♦ Allows one rotation
♦ Wrist; neck vertebrae joint
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Knee Joint
Human Musculature
III. Bone-Muscle Movements
A. Muscles connect to bones via
tendons
B. Muscles can ONLY contract
1. Contraction active process
2. Relaxation passive process
C. Antagonistic pairs
1. Muscles that attach to same
bone & move it in opposite
directions
a. biceps & triceps
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Antagonistic Pairs of Muscles
IV. Types of Muscles
A. Skeletal muscle
1. Striated in appearance
a. Have light & dark bands
2. Cells cylindrical & contain
many nuclei
3. Produces movement of body
a. Limbs, trunk, face, eyes
4. Innervated by somatic nervous
system
a. under conscious control
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Types of Muscle Tissue
B. Cardiac Muscle
1. Found in heart
2. Striated fibers; single nucleus
3. Innervated by autonomic N.S.
a. Not consciously controlled
C. Smooth Muscle
1. Found in walls of digestive tract;
blood vessels
2. Long, thin cells; single nucleus
3. Cells form sheets of muscle
4. Innervated by autonomic N.S.
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Types of Muscle Tissue
V. Muscle Contraction
A. Macroscopic Functioning
1. Simple Twitch
a. If you give one brief above-threshold
stimulus to a muscle it will respond
with one swift twitch
2. Summation
a. If the stimuli are given before complete
relaxation has occurred, a greater
contraction will occur.
3. Tetanus
a. If a rapid series of stimuli are given the
muscle will not relax between
contractions & you will get one smooth
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sustained contraction
Muscle Contraction
A = simple twitch, B = summation, C = tetanus
B. Microscopic Anatomy & Physiology
1. Whole muscles are composed of
individual muscle fibers. Each fiber is
a cell.
a. Sarcolemma – plasma membrane
●Forms a T-tubule system. This
penetrates down into the cell &
comes into close contact with
specialized ER called the
sarcoplasmic reticulum
♦Serve as storage site for Ca2+ ions
b. Sarcoplasmic reticulum encases
hundreds of myofibrils, the
contractile portions of the muscle fiber
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Skeletal Muscle Structure
Skeletal Muscle Fiber
2. Sarcomere structure
a. Myofibrils are cylindrical.
b. They are striated (banded)
♦Striations due to placement of protein
filaments within contractile units
called sarcomeres.
c. Sarcomere structure:
♦Extends between 2 dark Z lines.
♦Thick filaments, myosin.
♦Thin filaments, actin.
♦I band – lightest region (only actin)
♦H zone – medium (only myosin)
♦A
band
–
darkest
region
(both
a
&
m)
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Sarcomere Structure
3. Sliding Filament Model
a. As muscle fiber contracts, the
sarcomeres within the myofibrils
shorten
b. The actin filaments slide past the
myosin filaments.
♦The I band shortens
♦The H zone nearly disappears
c. The filaments do NOT change
length
d. This movement is called the
sliding filament model of muscle
contraction
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Sarcomere Functioning
4. Details of Sarcomere Structure
a. Molecules involved:
♦Creatine phosphate
♣High energy compound found in
muscles.
♣It passes a phosphate group to
ADP to form ATP in muscles
Creatine-P + ADP
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ATP + creatine
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♦Myosin filaments
Bundles of myosin molecules with
double globular heads (cross-bridges)
♦Actin filaments
1. Double row of twisted actin
molecules
2. Threads of tropomyosin wind about
actin filaments
3. Troponin occurs at intervals along
the threads
5. Neuromuscular Junction
a. Muscles stimulated by motor nerves.
b. Gap between neuron & muscle cell is
called the neuromuscular junction.
c. Motor neuron releases the transmitter
acetylcholine (ACh)
d. ACh binds to receptors in sarcolemma
of muscle fiber
e. This generates impulses that spread
down the T tubules to the
sarcoplasmic reticulum (SR)
f. The SR then releases calcium ions
g. This causes the contraction of the
myofibril units
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Neuromuscular Junction
Sliding Filaments – Actin & Myosin
6. How does Ca2+ cause contraction?
a. The released Ca2+ ions combine
with the troponin.
b. This causes a conformational
change which causes the
tropomyosin threads to shift their
position
c. This in turn exposes myosin binding
sites on the actin molecules
d. Myosin heads, which function as
ATPase enzymes, split ATP into
ADP + P.
e. This activates the heads so they
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can bind to actin
Sliding Filaments in Action
f. The ADP + P remain on myosin
heads until the heads attach to the
actin, forming cross bridges.
g. Then ADP + P are released which
causes cross-bridges to change their
positions. This is called the power
stroke.
h. When more ATP molecules bind to
myosin heads, the cross-bridges are
broken as the heads detach from the
actin.
i. Contraction continues until nerve
impulse ends and all calcium is
returned
to
storage
sites.
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