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The Muscular
System
Chapter 6
Muscle Functions
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Producing movement – complex movement
such as walking, or simple facial movement
Maintain Posture – tiny adjustments
happen constantly to keep balance
Stabilizing Joints – muscles and tendons
keep bones of various joints together.
Generating Heat – Muscle activity produces
heat
Smooth Muscle
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No Striation
Involuntary.
Walls of hollow organs
Uninucleated
Slow moving but
tireless
Cardiac Muscle
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Only in Heart
Striated
Involuntary
Branching cells
Skeletal Muscle
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Aka striated muscle
Multinucleated cells
Voluntary
Soft and fragile, but
can exert tremendous
power.
Skeletal Muscle
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Muscle cells need to be wrapped and
supported by connective tissue to make
sure they do not rip apart.
A pulled muscle can sometimes be a
breaking of this connective tissue sheet.
Muscles are bundled multiple times for
added strength.
Tendons
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The connective tissue that surround muscle cells
will gather at the ends of muscles to form
tendons.
Tendons are slender and strong, attaching the
muscle to bones and other muscles.
They are more durable then muscle cells and can
wrap over bone without breaking, they are also
thinner allowing for more to cross over joints.
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Micro Lab
Skeletal Muscle Anatomy
Muscle Cell Anatomy
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The muscle cell is full
of myofibrils.
The striation or stripes
of a skeletal muscle
cell come from
Sarcomeres – active
section of the
myofibrils that line up
end to end like cars in
a train.
Sarcomere Anatomy
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The sarcomere is
made up of two main
parts. Actin and
Myosin.
Myosin (red)
Actin (blue)
Notice the space
between the actin –
important for
contractions
Mechanism of Muscle Contraction
sliding filament
Sarcomere Anatomy
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When each individual
sarcomere shortens
the entire muscle
shortens. This is a
contraction.
Contractions are
started by nerve
impulses, more on that
next chapter.
Exercise
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Aerobic/Endurance – Increases blood flow
to muscles, more mitochondria in cells.
Muscle cells do not increase in size.
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Helps in digestion, strengthens skeleton, heart
Resistance/Isometric – muscles are pitted
against immovable objects. Actin and
myosin filaments get thicker to be able to
hold better. Makes the cells thicker. No
new cells for the most part.
Isometric Contractions
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Muscles do not always contract when
nerves signal them too.
When pushing against an immovable
object, myosin tries to grab and pull actin,
however, their grip slips and actin doesn’t
move. Think about a car spinning its
wheels, gas is being used, but the car isn’t
moving.
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s
Muscle Energy
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Millions of molecules or ATP are used just to
contract one muscle once. Where does it come
from?
Aerobic Respiration – making ATP from breaking
down food. 36 ATP : 1 Glucose
Anerobic Respiration – lactic acid fermentation.
Without oxygen, the muscle will make ATP and
lactic acid through a type of fermentation. 2 ATP :
1 Glucose
Muscle Energy
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Direct phosphorylation by Creatine
phosphate – Creatine phosphate found in
the muscles can artificially add a phosphate
to ADP to make ATP, giving it more energy
again. Can only occur for about 20
seconds before the creatine is depleted.
Muscle Fatigue
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Usually due to oxygen debt.
Muscles with good blood supply will fatigue
less.
Oxygen debt must be paid back, even after
activity stops. We will breathe heavily and
deeply after a run until our muscles receive
the oxygen they lack.
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Hand Dynamometer Activity
Muscle Attachment
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Origin – attachment to
the immovable bone.
Insertion – attachment
to the movable bone
Five Golden Rules of Muscles
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Most muscles cross at least one joint
Most of the muscle lies proximal to the joint
crossed
All muscles have at least two attachments.
Muscles can only pull, never push
During contraction, the insertion always
moves toward the origin.
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Finish Lab
Types of body movements
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Flexion – generally
makes decreases the
angle of the joint. Hinge
joints
Extension – opposite of
flexion, increases the
angle of the joint.
Hyperextension – when
the joint bends in a way
that it normally wouldn’t
Types of body movements
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Rotation – movement
of bones back and
forth around an axis.
Shaking your head no
is a rotation.
Types of boy movements
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Abduction – moving a
limb away from the
midline of the body
Adduction – moving a
limb toward the
midline of the body.
Types of body movements
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Circumduction –
Combination of
flexion, extension,
abduction, and
adduction. Seen in
ball and socket joints.
Muscle interactions
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Muscles can only pull, never push.
Because of this, muscles usually work in
pairs, when one contracts, the other
relaxes.
Prime Mover vs. Antogonist.
Synergists – muscles that help prime
movers.
Face and Neck
Shoulder and Chest
Abdominal Muscles
Back