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Muscular System
The Power System
Muscle Facts
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Nearly half our weight
comes from muscle
tissue.
There are 650 different
muscles in the human
body.
Video
Video
Three functions of muscle
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1. Responsible for all body movement.
Three functions of muscle
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2. Responsible for
body form/shape and
posture.
Three functions of muscle
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3. Responsible for
body heat and
maintaining body
temperature.
Types of muscles
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1. Skeletal = attached to bone. Video Naming
2. Smooth = present in organs.
3. Cardiac = found only in the heart.
Skeletal Muscle
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Attached to bone. (Tendons) p. 125
Striated (striped) appearance
Voluntary = you tell these muscles to move.
Multinucleated muscle cell bundles
Muscle cell = Muscle fiber
Sarcolemma = muscle cell membrane.
Contract quickly, fatigue easily, can’t
maintain contraction for long.
Microscopic view of Skeletal Muscle
Smooth Muscle
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Visceral (organ) muscle.
Found in walls of digestive system, uterus and blood
vessels.
Cells small and spindle-shaped.
Involuntary = these muscles move on their own.
Controlled by autonomic nervous system.
Act slowly, do not tire easily, can remain contracted
for a long time.
Microscopic view of Smooth Muscle
Cardiac Muscle
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Found only in the heart.
Cells look striated (striped) and branched.
Involuntary = muscle cells work on their own.
Cells are fused – when one contracts, they all
contract.
Does not get tired.
Microscopic view of Cardiac Muscle
Sphincter Muscles
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A sphincter is a
circular muscle that
normally maintains
constriction of a natural
body passage or orifice
and which relaxes as
required by normal
physiological
functioning.
Characteristics of Muscles (4)
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1. Contractibility – the
ability of a muscle to
reduce the distance
between the parts of its
contents or the space it
surrounds.
Muscle-Contraction
Contraction
Characteristics of Muscles
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2. Extensibility – the
ability of a muscle to
be stretched.
Characteristics of Muscles
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3. Exciteabillity –
(irritability) the ability
to respond to certain
stimuli by producing
impulses.
Characteristics of Muscle
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4. Elasticity – ability
of muscle to return to
its original length when
relaxing
How do muscles move?
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Muscles are attached to bones.
When a muscle moves it pulls on the bone
that it is attached to, causing the bone to
move.
Groups of muscles work together to create
movement.
Skeletal muscle movement
Motor Unit
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Motor unit = a motor neuron plus all the muscle
fibers it stimulates.
Motor unit
Neuromuscular junction
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Neuromuscular
junction = the space
between the neuron’s
fibers and the muscle
cells membrane.
The Neuromuscular
junction and the
Synaptic cleft are the
same thing.
Acetylcholine
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Acetylcholine = chemical neurotransmitter, it
diffuses from the end of the neuron across the
synaptic cleft/Neuromuscular junction.
Acetylcholine carries a message from a
neuron and delivers it to muscle cells.
This message is usually, “MOVE!”
Muscle Contraction
Muscle fatigue
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With movement of skeletal muscles you will
get muscle fatigue.
Muscle fatigue = inability of a muscle to
maintain its strength of contraction or tension.
When muscle activity is great, oxygen cannot
be supplied to the muscles fast enough and
lactic acid is produced.
Oxygen debt
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Oxygen is needed for muscle contraction.
When muscle activity is great, there is not enough
oxygen for things to happen normally.
After exercise has stopped, extra oxygen is needed to
get things back to normal.
The additional oxygen that must be taken into the
body after vigorous exercise to restore all systems
to normal is called oxygen debt.
Muscle tone
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A sustained partial contraction of portions of a
skeletal muscle in response to activation of
stretch receptors results in muscle tone.
Tone is essential for maintaining posture.
Common muscle disorders
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Atrophy = wasting
away of muscle due to
lack of use.
Hypertrophy
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Muscle hypertrophy = an increase in the size of the
muscle cells.
Muscle Strain
A muscle strain is a muscle tear.
Symptoms = pain and swelling
Remember the word RICE if you have an injury.
R = rest
I = ice
C = compress
E = elevate
Muscle spasm
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A muscle spasm is a sustained contraction of
a muscle.
These muscle contractions are involuntary.
Spasms/Cramps
Massage techniques
Myalgia
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Myalgia = muscle pain.
Tendonitis
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Tendons hold muscle
to bones.
Tendonitis is
inflammation of a
tendon.
Inflammation =
swelling and redness.
Muscular Dystrophies =
muscle destroying diseases
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Dystrophy = degeneration.
The most common form is Duchenne
muscular dystrophy (DMD).
Muscular dystrophies are due to genetic
defects.
This defect is usually X-linked recessive.
The End