Download 2-1 Muscle-bone Sp12

Functions of the
skeletal system
Bone, Muscle and Moving
Separately neither bone
or muscle is able to
produce movement
Muscles contract (get
shorter)
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when the muscle
shortens, it pulls on the
bone
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Pulling on one bone
causes movement at
the accompanying joint
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Bone comes in 2 forms
Articular cartilage
growth plate
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Spongy bone
a tube of dense compact bone
spongy bone as the inner
support
Compact bone
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periosteum
growth plate
Spongy bone
Compact bone
Filled with yellow bone marrow
– stores fat
Bone tissue is served by
blood vessels and nerves
blood vessel
periosteum
blood vessel
prevents bone from grinding
against bone at a joint
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More detail on bone…
How do bones grow?
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Compact bone
osteocyte
in lacuna
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Osteocyte
100 µm
concentric
lamellae
Compact bone
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Red bone marrow – a
specialized tissue that makes
blood cells
Compact bone in the shaft
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Spongy bone at the ends
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Growth plate at the ends of
the bones
Articulating cartilage where
two bones meet
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Supports the body
Protects internal organs
Produces blood cells
Stores minerals (calcium
and phosphate)
Articular cartilage
A typical bone:
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working together with the
muscles
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Bones are alive!
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Moves the body
Concentric rings of
mineralized matrix
containing living bone cells
called osteocytes
These cells secrete the
surrounding material, or
matrix
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central canal
lacuna osteocyte nucleus
osteon
osteocytes
Bones first form as
cartilage. The
cartilage gradually
changes into bone
tissue - or ossifies
Spongy bone
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Made of plates with spaces
filled with red bone marrow
Spongy bone
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blood vessels
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How do bones grow?
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A "band" of cartilage
(called a growth
plate) remains as
long as the bone is
growing
Bones increase in
length as these
cartilage cells
continue to reproduce
and ossify
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A dynamic process – old bone is removed
from the skeleton and new bone is added.
Bones continue to change shape throughout
life in response to
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blood calcium levels
amount of stress placed on the bones
Usually, the removal and formation of bone
are in balance and maintain skeletal strength.
Bone remodeling
Large cells called osteoclasts
dissolve bone tissue
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Bone tissue is constantly
being replaced
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Bone is constantly being
replaced
Adds calcium and other minerals
to the bloodstream
Osteoblasts build the mineral
structure back up, pulling
calcium and minerals from the
bloodstream
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Bone resorption
Osteoclasts break down bone – erode the
bone surface
Adhere to the surface of bone and release
acids and enzymes
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© 2010 Pearson Education, Inc.
Bone remodeling
Why remodel bones?
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Growth and repair
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Bone formation
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Osteoblasts form new bone – repair the surface
They secrete bone matrix and promote calcium
deposition into the matrix
Bones able to respond to stress by
changing size, shape and strength
Allows the body to regulate the amount
of calcium in the blood
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Calcium is required for muscle contraction
and nerve impulse transmission
Bone remodeling 4:40
http://www.youtube.com/watch?v=BrI7Ra5FTus&feature=related
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© 2010 Pearson Education, Inc.
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Exercise plays an important
role in maintaining bone mass
Bone repair
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Treating a fracture
involves
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Putting the bone back
into its natural shape
Immobilizing it
Repair involves
remodeling – old
bone tissue is replaced
by new bone tissue
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© 2010 Pearson Education, Inc.
Osteoporosis:
Bone destruction > formation
What do you do to help your
bones?
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Bones are thinner,
more porous and
easily broken
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Do you exercise?
Drink milk or eat foods
high in calcium?
Get enough vitamin D?
Wear helmets and knee
pads when you ride a
bike or skateboard?
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What do we need calcium?
Skeletal Muscle
Transmits nerve impulses
Strengthens bone
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© 2010 Pearson Education, Inc.
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Skeletal muscle is
built like a cable
Muscle
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Nuclei
Bundle of
muscle fibers
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Single muscle fiber
(cell)
Bundle of muscle fibers
Each fiber is a single
cell with many nuclei
Striped
Myofibril
Muscle
Structure of
skeletal muscle
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Nuclei
Bundle of
muscle fibers
Single muscle fiber
(cell)
Myofibril
Light
Light
band Dark bandband
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Within each fiber (or
cell) are bundles of
protein fibers, or
myofibrils
Striped appearance
due to alternating light
and dark bands
Light
Light
band Dark bandband
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© 2010 Pearson Education, Inc.
Structure of
skeletal muscle
Myofibril
Light
band
Dark band
Light
band
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Sarcomere
Sliding filament model of
muscle contraction
Myofibrils are made of
two proteins
 Myosin: thick filaments
shaped like a golf club
Actin: thin filaments
These filaments slide
over one another during
muscle contraction
Sarcomere
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TEM
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Light
band
Thick
filaments
(myosin)
Dark band
Light
band
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Thin
filaments
(actin)
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Sarcomere
contractile units
region between 2 dark
lines (called Z lines)
Figure 27.31b
Contraction starts with a nerve
impulse
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Nerve
Motor
neuron
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Contraction shortens the sarcomere
But does not change the length of the thin
and thick filaments
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Contraction starts with a nerve
impulse
Nerve impulses
travel down motor
neurons to a
neuromuscular
junction
Muscle fibers (cells)
Muscle
Tendon
Bone
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Nerves send a contraction impulse across the
synapse via chemicals called neurotransmitters
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Contraction starts with a nerve
impulse
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A change in
electrical charge
(the action potential)
sweeps down the
membrane of the
muscle cell
What exactly happens when
signal is received?
End of Neuron
Muscle Nucleus
End of Neuron
ACh Released
Muscle contraction 0:42
http://www.youtube.com/watch?v=L2p73iuKJGY&NR=1
Myofibril
© 2010 Pearson Education, Inc.
© 2010 Pearson Education, Inc.
Muscle contraction
Sliding filament model of
muscle contraction
Myosin Pulls on Actin to Shorten Muscle
Actin
Calcium ion
Binding sites are
exposed
Thick filament (myosin)
1. Action Potential Arrives
Thin filament
(actin)
2. ER Releases Calcium
ATP
Myosin head
3. Calcium exposes
binding sites on Actin
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ATP
4. Myosin binds to actin
→ “power stroke”
Key events
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5. ATP Releases Myosin
for Another Round
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Heads of the myosin molecules bind to
Actin molecules in the thin filaments
Myosin head bends and pulls the thin filament
Contraction requires energy supplied by ATP.
Myosin
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© 2010 Pearson Education, Inc.
Thick filament (myosin)
Thin filament
(actin)
ATP
Myosin head
(low-energy
configuration)
The myosin head attaches to an actin filament.
ATP binds to a myosin head, which is then released
from an actin filament.
The power
stroke
ATP
ADP + P
Myosin head
(high-energy
position )
The myosin head bends back, pulling the actin
filament toward the center of the sarcomere.
As long as ATP is available, the process can be
repeated until the muscle is fully contracted.
The breakdown of ATP cocks the myosin head.
Need ATP to
detach myosin
head
Figure 27.33a
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Where does the energy for
contraction come from?
Sliding filament model
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Aerobic
glycogen or
fatty acids
2. Cock
ATP
ATP releases
energy to myosin
3. Attach
Myosin head binds
ATP, drops actin
Myosin attaches
to actin creating a
crossbridge
CO2 + H2 O
+
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Power stroke
Sliding filament 3:00 [show 1st part only]
c.
http://www.youtube.com/watch?v=0kFmbrRJq4w
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Anaerobic
glycogen
White fibers are suited for
bursts of activity
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fermentation
b.
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ATP
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Contain lots of mitochondria,
myoglobin (red, oxygen-carrying
molecule), and fat droplets
Endurance events
Most efficient way to make ATP
Requires oxygen
Aerobic respiration
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Where does the energy for
contraction come from?
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Red fibers are geared for
aerobic respiration
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1. Detach
4. Bend
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O2
Muscle fibers need ATP to
contract
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lactate
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+
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Weight lifting, sprinting
Make ATP energy faster and
without oxygen (anaerobic)
Use glucose as fuel
Fast-acting but results in
lactate build up
Does lactate buildup cause
muscle fatigue?
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Once thought that lactate
causes muscle fatigue
and “muscle burn”
Lactic acid isn’t the culprit
Muscle soreness is
caused by actual muscle
cell damage and
inflammation
ATP
Glycolysis
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What are the functions of
skeletal muscles?
Skeletal muscles work in pairs
Posture
Joint Stabilization
Making Heat
Triceps
relaxed
Tendon
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Biceps relaxed
Biceps
contracted
Movement
Triceps
contracted
Figure 27.30
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The skeletal and muscular
systems work together
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How Do Muscles Change When
Exercised???
Muscles Get:
Both are involved with movement
Both protect body organs
Bones store and release calcium
needed for muscle contraction and
nerve impulse conduction
Muscles help maintain body
temperature
Blood
Aerobic Exercise
Mitochondria
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© 2010 Pearson Education, Inc.
How Do Muscles Change When
Exercised???
Muscles Get:
Do athletes need more protein?
What fuel(s) are needed for athletic performance?
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Glucose
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Anaerobic Exercise
Fatty acids
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More Myosin & Actin Filaments
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Primary fuel for strengthand-power events
Glycolysis → rapid ATP syn.
Primary fuel for endurance
events
Aerobic metabolism
X
Protein
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Usually not metabolized to
fuel cell activity
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