Transcript Muscular System

Anatomy & Physiology 2
Unit 3
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Skeletal muscles:
 Muscles that move bones of
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the skeleton
These allow you to move,
walk, dance, run, etc
These muscles are all
voluntary, meaning you can
move them on your own,
when you want to
The cells are very long and
cylindrical (can be up to 1ft
long), have obvious striation
and are multinucleate
Skeletal muscles attach to
bones by tendons
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Cardiac Muscles:
 Found only in the heart
 These muscles have
their own “beat”
 They are involuntary,
meaning you don’t
control your heart beat,
it controls itself
 The cells branch into
chains, have striations
and are uninucleate
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Smooth Muscles:
 Makes up your
intestines, arteries and
many other body organs
 Most of these are
involuntary, but some
are voluntary to some
degree
 The cells are long and
thin, have no striations
and are uninucleate
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Provides movement
Maintains posture
Stabilizes joints
Generates heat
A muscle fiber is
composed of many
myofibrils surrounded
by the sarcolemma
 The myofibril is a
unique organelle
composed of a thin
filament (actin) and a
thick filament (myosin)
 These are what cause
muscle contraction
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Muscles work by
contracting and relaxing
Skeletal muscles work by
contracting against the
bone and pulling bone
All muscles work in pairs,
meaning when one
contracts the other
relaxes and vice versa
When the muscle
contracts the actin and
myosin “catch” on one
another
 When the muscle is
relaxed the actin and
myosin “release” each
other
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Isotonic Contractions
 Typical shortening and
lengthening contractions
 Examples: squats, curls,
smiling, picking up a child
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Isometric Contractions
 Occurs when the muscles
do not shorten and
lengthening but still
contracting
▪ Examples: moving or
holding furniture, holding a
child
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When muscles are used
for a long period of time
they fatigue and oxygen
debt (can’t take oxygen
in fast enough for the
muscles) occurs
However, they will
continue to function, but
under a different system
This system has a “pay
back” period and lactic
acid accumulates in the
cells
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Flexion – bending knees
or elbows
Extension –
straightening the knee
or elbow
Rotation – shaking your
head “no”
Abduction – fanning
fingers or toes apart
Adduction – opposite of
abduction
Circumduction – moving
a limb in a circle
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Direction – rectus
(straight), oblique (slant)
Relative size – maximus
(largest), minimus
(smallest)
Location – temporalis
(temporal bone),
frontalis (frontal bone)
Number of origins –
biceps (two origins),
triceps (three origins),
quadriceps (four origins)
Location of origin and
insertion –
sternocleidomastoid
(attaches to the
sternum, clavicle and
mastoid bones)
 Shape of muscle –
deltoid (triangular)
 Action of muscle –
flexor, extensor and
adductor
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Muscular Dystrophy
 Disease that causes the
slow wasting away of
skeletal muscle
 Can be inherited
 Mostly common in males
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Strained Muscles
 Caused by weak muscles
that are not used to
exercise
 Usually not a problem and
takes a few days to heal