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Muscular System
The Muscular System
•Muscles are responsible for all
types of body movement
•Three basic muscle types are
found in the body
•Skeletal muscle
•Cardiac muscle
•Smooth muscle
Characteristics of Muscles
• Muscle cells are elongated
(muscle cell = muscle fiber)
• Contraction of muscles is due to
the movement of microfilaments
• All muscles share some
terminology
• Prefix myo refers to muscle
• Prefix mys refers to muscle
• Prefix sarco refers to flesh
Muscular System Functions
• The main function of the muscular
system is to move your bones.
Voluntary Muscle
• Voluntary muscles are under your
conscious control for things like
running, grabbing, and other activities.
Video Notes Anatomy Muscular System Voluntary
Skeletal Muscle
• Skeletal muscles are voluntary,
connected to bones, and are
responsible for your movement.
Skeletal Muscle Characteristics
• Most are
attached by
tendons to
bones
Skeletal Muscle Characteristics
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•
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Cells are multinucleate
Striated – have visible banding
Voluntary – subject to conscious control
Cells are surrounded and bundled by connective
tissue
Function of Muscles
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Produce movement
Maintain posture
Stabilize joints
Generate heat
Nerve Stimulus to Muscles
• Skeletal muscles must
be stimulated by a
nerve to contract
• Motor unit
• One neuron
• Muscle cells stimulated
by that neuron
Muscles and Body Movements
• Movement is attained
due to a muscle moving
an attached bone
Muscles and Body Movements
• Muscles are attached to at
least two points
• Origin – attachment to a
moveable bone
• Insertion – attachment to an
immovable bone
Muscles work in pairs.
• Muscles can only contract or pull, not
push and are controlled by electrical
impulses from the brain.
Muscles work in pairs.
• Because muscle cells can only
contract, not extend, skeletal muscles
must work in pairs.
Muscles work in pairs.
• While one muscle contracts, the other
muscle in the pair returns to its original
length.
Muscles work in pairs.
• Flexors bend
parts of your
body.
• Extensors
straighten parts
of your body.
Levers In Your Body
• Bones and muscles make levers which
are machines that make it easier to lift
and move things.
Lever Systems and Leverage
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bones act as levers
joints are the fulcrums
levers can operate
•
at a mechanical advantage
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mechanical disadvantage
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when a smaller effort can move a heavier load
when a larger effort moves lighter load
position of effort, load, and fulcrum on lever
determine mechanical advantage or
disadvantage
Levers In Your Body
• Levers achieve mechanical advantage:
a measure of how much easier it is to
lift or move something.
Naming Skeletal Muscles
•
Most skeletal muscle names contain
combinations of word roots for their features
1.
2.
3.
4.
5.
6.
size
shape
action
number of origins
location of muscle
sites of origin and insertion
Involuntary Muscle
• Involuntary muscles are not under your
conscious control and are responsible
for things like breathing and digesting
food.
Video Notes Anatomy Muscular System Involuntary
Muscular System Functions
• The muscular system is responsible for
the beating of your heart.
Cardiac Muscle
• Cardiac muscle is involuntary and only
found in the heart.
Video Notes Anatomy Muscular System Smooth and Cardiac Muscle
Cardiac Muscle Characteristics
• Has striations
• Usually has a single
nucleus
• Joined to another
muscle cell at an
intercalated disc
• Involuntary
• Found only in the
heart
Muscular System Functions
• The muscular system pushes food and
other materials through your body.
Smooth Muscle
• Smooth muscle is involuntary, found in
the digestive tract, and helps to move
food and materials through your body.
Smooth Muscle Characteristics
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•
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Has no striations
Spindle-shaped cells
Single nucleus
Involuntary – no
conscious control
• Found mainly in the
walls of hollow organs
Effects of Exercise on Muscle
Aerobics result in stronger muscles
due to increase blood supply
Muscle fibers increase mitochondria
and oxygen storage
Muscle becomes more fatigue
resistant
Heart enlarges to pump
more blood to body
Does not increase skeletal
muscle size
Effects of Exercise on Muscle
• Results of increased muscle
use from resistance training
• Individual muscle cells
make more contractile
filaments & connective
tissue increases
• Increase in muscle size
• Increase in muscle strength
Types of Ordinary Body Movements
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Flexion
Extension
Rotation
Abduction
Circumduction
Body Movements
Body Movements
Muscular Dystrophy
• Congenital muscle-destroying disease affect
specific muscle groups
• Muscle fibers degenerate & atrophy due to an
absence of dystrophin, a protein that helps keep
muscle cells intact
• Most common & serious—Duchenne’s M.D.
• Mostly in males (diagnosed between2-6 yrs)
• Survival is rare beyond early 30’s
• X-linked recessive
Myasthenia gravis
• Rare adult disease caused by antibodies
to acetylcholine receptors at the
neuromuscular junction which prevents
the muscle contraction from occurring
• Drooping upper eyelids, difficulty
swallowing & talking, muscle
weakness & fatigue
• Death occurs when respiratory muscles
cease to function
Aging
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Connective Tissue increases
Amount of Muscle tissue decreases
Muscles become stringier (sinewy)
Body weight declines due to loss of
muscle mass
• By age 80, muscle strength usually
decrease by 50% without weight
training exercises