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Muscular System
Allied Health Sciences I
Melissa Lewis, RN
Muscles
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½ of our body weight comes from our
muscles
Human body has 656 different muscles
Muscles give body form and shape
Muscles are also responsible for movement
3 Types of Muscles
1. Skeletal
 2. Smooth
 3. Cardiac
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These muscles can be described as striated
(striped) , spindle-shaped, and non-striated.
Skeletal Muscles
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Attach to bones of skeleton
Striped or striated
Voluntary muscles
Each muscle cell is multi-nucleated and
known as a muscle fiber
The cell membrane of a muscle cell =
sarcolemma
Cytoplasm of muscle cell = sarcoplasm
Smooth (visceral) Muscle
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Small and spindle-shaped
Only have one nucleus
Non-striated
They are not attached to bones
They act slowly and do not tire easily
They remain contracted for a long time
Involuntary
They are controlled by the autonomic (automatic)
nervous system
Smooth (visceral) Muscle cont…
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They are found in the walls of
stomach, intestines, uterus, & blood
vessels
Their actions = helping food pass
along uterine contractions, control of
diameter of blood vessels
Cardiac Muscle
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Found only in the heart
Striated
Involuntary
Cardiac cells are joined in a continuous network
So, when one cell receives a signal to contract
they all contract together to cause a heart beat
Normal heart rate is 72 beats/minute
Cardiac cells have to have continuous oxygen to
function (no oxygen for 30 seconds = death)
Sphincter/dilator Muscles
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Special circular muscles in the openings
between the esophagus and stomach, and
stomach and small intestine
Also found in anus, urethra, mouth
They open and close to control passage of
substances
Principle Skeletal Muscles
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Skeletal muscles are voluntary
Made up of all muscles that attach to and help the
skeleton move
Make up lining of walls of oral, abdominal, and
pelvic cavities
Control movement of eyeballs, eyelids, lips,
tongue, and skin
Muscles are named by their location, size,
direction, # of origins, location of origin &
insertion, and action
Examples:
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Location: Frontalis – forehead
Size: Gluteous maximus – largest muscle
in buttock
Number of origins – Biceps – 2-headed
muscle on humerus
Location of origin/insertion –
sternocleidomastoid – originates in sternum
Misc. Muscle Information
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656 muscles in human body
327 antagonistic pairs
2 unpaired muscles
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Orbicularis oris
Diaphragm
Muscular Regions
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Head, neck, trunk & extremity
All Muscles have 4 things in common:
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Contractibility – When a muscle contracts, it
shortens causing a decrease in distance b/w parts
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Excitability – To respond to certain stimuli by
producing impulses
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No other cell can do this
Both muscle and nervous cells can do this
Extensibility – Ability to be stretched
Elasticity – Ability to return to its original length
when relaxed
Muscle Attachments &
Functions:
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Muscles have to be attached to
bones to cause movement
Muscles only pull, they never push
Muscle Attachments & Functions
cont…
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1. Origin – part of the skeletal muscle that is
attached to a fixed structure or bone (it moves the
least during contraction)
2. Insertion – the other end of attachment , that
is attached to movable part (it moves the most
during contraction)
3. Belly – central body of muscle
4. Prime mover – muscles work in pairs,
produces movement in a single direction
Muscle Attachments & Functions
cont…
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5. Antagonist – this is the second muscle
that has an opposite pull from the prime
mover
6. Synergists – group of muscles, which
help steady a movement or stabilize joint
activity
***Example of antagonist pair would be the
biceps and the triceps (when the biceps is
contracted, the triceps is relaxed)***
Sources of Energy and Heat
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Muscles not only move our bodies, but
they also produce heat.
Our body temp must be between 98.6
degrees F and 99.8 degrees F.
Muscle cells make adenosine triphosphate
(ATP)
ATP is necessary for muscles to contract
and make heat that body needs
Contraction of Skeletal Muscle
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Two things that cause movement by muscles
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1. Myoneural stimulation
2. Contraction of muscle proteins
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***A nerve impulse initiates movement
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5 steps to muscles movement (look in book 4 this)
 1. Nerve Impulse
 2. Axon
 3. Acetylcholine
 4. Synaptic cleft
 5. Sarcolemma
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For cell to return to a resting state, potassium and
sodium ions diffuse back to their initial positions
outside the cell
Muscle Tone and Fatigue
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Muscle tone – muscles are always slightly
contracted. Gives muscle tone. Muscle tone
maintained through adequate nutrition and regular
exercise.
Atrophy – disuse of muscles thus they shrink or
atrophy
Hypertrophy – over-exercise, muscles become
enlarged or hypertrophied
Muscle fatigue – caused by build-up of lactic
acid in muscles. Lactic acid is a waste product of
muscle cells.
Exercise and Training
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Exercise and training changes the size, structure
and strength of a muscle.
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Proper training can improve:
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Atrophy – muscles goes away
Hypertrophy – muscles get bigger
Coordination
Respiratory and circulatory system
Rids excess fat
Joint movement
Strength can improve
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Muscle size
Muscle coordination
Functioning of cortical brain region
Injury and overuse
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Sprain –
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Strain –
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Ligaments either torn from attachments to bones or
torn across. Rapid swelling and acute pain
Treatment = anti-inflammatory drugs
Tear in muscle result of excessive use (tx = ice)
Bursitis –
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these bursa sacs contain synovial fluid that serves as
lube to prevent friction b/w tendon and bone. If sac is
injured it can cause bursitis.
Injury and overuse cont…
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Muscle spasm – a cramp (sustained
contraction of the muscle)
Myalgia – muscle pain
Muscular dystrophy – group of diseases
in which the muscle cells deteriorate
Myasthenia gravis – leads to progressive
muscular weakness and paralysis,
sometimes death (unknown cause)
Tendons
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Cords of connective tissue that attach the
muscles to bone
Sometimes they are excessively stretched
through exercise
They become unable to contract & return to
their original place
Therefore, they are more susceptible to
straining and tearing
Recreational Injuries
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Tennis Elbow – also called lateral
epicondylitis
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Inflammed tendon that connects arm muscle
to elbow
Treatment = pain relief, ice packs, surgery
last resort
Recreational Injuries cont…
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Shin splints – occur when there is injury to
muscle tendon in front of shin
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Usually occurs during jogging
One should wear supportive shoes
Rotator cuff disease – inflammation of
group of tendons that fuse together and
surround shoulder joint
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Treatment = rest & physical therapy
Treatment
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Massage – occasionally a HC professional
may need to give a total body massage or a
massage to specific body area
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One must know which skeletal muscles are
involved and proper way to massage area
Physiotherapy – treatment of disease/injury
by physical means using light, heat, cold,
water, electricity, massage, & exercise
Intramuscular Injections
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Injections (shots) given directly into
the muscle
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Most common sites for intramuscular
injections:
 Deltoid
muscle of upper arm
 Vastus Lateralis (anterior thigh)
 Gluteus medius (buttocks)
Major Muscles of Body
MUSCLE
LOCATION
FUNCTION
Sternocleidomastoid
Side of neck
Turns & flexes
head
Trapezius
Upper back &
neck
Turns head,
moves shoulder
Deltoid
Shoulder
Abducts arm
Major Muscles of Body
MUSCLE
LOCATION
FUNCTION
Biceps brachii
Upper arm
Flexes lower
arm
Triceps brachii
Upper arm
Extends lower
arm
Pectoralis major Upper chest
Adducts upper
arm
Major Muscles of Body
MUSCLE
LOCATION
FUNCTION
Intercostals
Between ribs
Moves ribs for
breathing
Rectus
abdominus
Ribs to pubis
Compresses
abdomen
Latissimus dorsi Spine around to Extends &
chest
adducts upper
arm
Major Muscles of Body
MUSCLE
LOCATION
FUNCTION
Gluteus
maximus
Buttocks
Extends thigh
Sartorius
Front of thigh
Abducts
Quadriceps
femoris
Front of thigh
Extends leg
Major Muscles of Body
MUSCLE
LOCATION
FUNCTION
Tibialis anterior Front of lower
leg
Flexes & inverts
foot
Gastrocnemius
Back of lower
leg
Flexes sole of
foot
Diaphragm
Dome-shaped muscle
separating thoracic &
abdominal cavities
Helps control
breathing
Major Muscles of Body
MUSCLE
Hamstring
LOCATION
FUNCTION
Posterior thigh
Extends hip and
flexes knee
Posterior thigh
Extends hip and
flexes knee
Hamstring is
actually the 3
muscles below
1. Semitendinosus
2. Semimembranosus
3. Bicepts femoris
The End!!!
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