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Muscles and Levers
Chapter 15, section 3
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Kinds of Muscle
• Skeletal muscle = muscles attached to bone
• Smooth muscle = involuntary muscles inside
many internal organs (found in your digestive
tract and walls of blood vessels)
• Cardiac muscle =heart muscle, involuntary
3
Kinds of Muscle
• Involuntary = muscle not under your control
▫ Example: smooth and cardiac (digestion and
pumping your blood)
• Voluntary = muscle you control
▫ Example: skeletal (jumping up and down)
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Movement
• Tendons are strands of connective tissue that
attach muscles to bones.
• When a muscle gets shorter or contracts, the
two bones it is connected to move closer.
• Muscles often work in pairs to produce
controlled motions.
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Movement
• The muscle that bends part of your body is a
flexor.
• The muscle that straightens part of your
body is an extensor.
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Levers in the Body
• Read Page 478 and write down a definition
for the following words:
• Lever
• Fulcrum
• Effort Force
• Load
• Mechanical Advantage
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Levers in the Body
• Lever = rigid bar that pivots around a fixed point
• Fulcrum = fixed point
• Effort Force = force applied to the lever
• Load = force that resists the motion of the lever
• Mechanical Advantage = an increase in the amount
of work that can be done with a lever.
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Match the Body Parts
• Bone is the….
• LEVER!
• Joint is the…
• FULCRUM!
• Muscle is the…
• Effort Force!
• Now give an example of a lever system in your
body, be sure to label what is the lever, fulcrum,
etc.
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Three Classes of Levers
• The type of lever is determined by the
location of the fulcrum, in relation to the load
and the effort force.
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Class
Picture
Example
1st
Tilting the neck
2nd
Raising up on the
balls of your feet
3rd
Lifting a book
with your arm
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Use it or Lose it
• Exercised muscles are stronger and longer
than those that are not used.
• Strong muscles can also help squeeze blood to
the heart.
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Use it or Lose it
• Resistance Exercise strengthens skeletal
muscles by working against a weight.
• Aerobic Exercise increases the muscle
strength of the heart and increases
endurance.
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Muscle Injury
• Read page 481 and explain the terms
• Strain = when a muscle or tendon is over
stretched or torn.
▫ Usually happens because of an inadequate warm-up
• Tendonitis = an inflammation of the tendon that
did not heal after a strain.
• Anabolic Steroids = drugs that make muscles
stronger and damage the heart, liver, kidneys,
and can stop bone growth.