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MUSCULAR SYSTEM OVERVEIW
“the power system”
Nearly half our weight comes from
muscle tissue.
There are 650 different muscles in the
human body.
Muscles give us form and shape.
Muscles produce most of our body heat.
MUSCLE TYPES
SKELETAL
TYPES OF MUSCLES
SMOOTH
CARDIAC
Skeletal Muscle
• Attached to bone
• Striated (striped) appearance
• VOLUNTARY
• Multinucleated muscle cell bundles
(muscle cells = muscle fibers)
• SARCOLEMMA = cell membrane
• Contract quickly, fatigue easily, can’t
maintain contraction for long period of
time
Smooth Muscle
• Visceral (organ) muscle
• Found in walls of digestive system, uterus
and blood vessels
• Cells small and spindle-shaped
• INVOLUNTARY
• Controlled by autonomic nervous system
• Act slowly, do not tire easily, can remain
contracted for long time
Cardiac Muscle
• Found only in the heart
• Striated and branched
• Involuntary
• Cells are fused – when one contracts, they
all contract
• Involuntary
MAIN FUNCTIONS
Four important roles in body:
1. Responsible for all body movement.
2. Responsible for body form and shape
(posture)
3. Stabilize joints
4. Responsible for body heat and maintaining
body temperature.
SKELETAL MUSCLE ACTIVITY
Stimulation and Contraction of Skeletal Muscle
Cells
• EXCITEABILITY (IRRITABILITY) – the ability to
respond to certain stimuli by producing impulses.
• CONTRACTIBILITY – the ability of a muscle to
reduce the distance between the parts of its
contents or the space it surrounds.
SKELETAL MUSCLE ACTIVITY
• MOTOR UNIT – a motor neuron plus all the muscle
fibers it stimulates.
• NEUROMUSCULAR JUNCTION – the junction
between the motor neuron’s fiber which transmits
the impulse – and the muscle cell membrane.
• ACETYLCHOLINE – chemical neurotransmitter,
diffuses across the synaptic cleft (carries impulse
across synaptic cleft)
• MUSCLE FATIGUE – caused by the accumulation of
lactic acid in the muscles.
• OXYGEN DEBT – after exercise, the amount of
oxygen needed by the muscle to change lactic acid
back to glucose.
• MUSCLE TONE - When muscles are slightly
contracted and ready to pull.
• DIAPHRAGM – Dome-shaped muscle that separates
the abdominal and thoracic cavities, aids in
breathing
MUSCLE CONTRACTIONS
Muscle Tone
In order to function, muscles should always be slightly contracted and
ready to pull.
Muscle contractions may be isotonic or isometric.
ISOTONIC CONTRACTION
When muscles contract and shorten. (Walk, talk, etc.)
ISOMETRIC CONTRACTION
When the tension in a muscle increases
but the muscle does not shorten.
(exercises such as tensing the abdominal muscles.)
MUSCULAR SYSTEM
“the power system”
MUSCLE MOVEMENT
1. Muscles move bones by pulling on them.
As a muscle contracts, it pulls the insertion bone closer to the
origin bone. Movement occurs at the joint between the origin and
the insertion.
2. Groups of muscles usually contract to produce a single
movement.
3. When the antagonist muscles contract, they produce a movement
opposite to that of the prime movers.
Gross Anatomy of Skeletal Muscles
Anterior Surface of Body
Frontalis
Orbicularis oris
Sternocleidomastoids
Deltoid
Pectoralis major
Biceps brachii
Intercostals muscles
Rectus abdominus
External oblique
Sartorius
Quadriceps group
Gross Anatomy of Skeletal Muscles
Posterior Surface of Body
Occipitallis
Trapezius
Deltoid
triceps brachii
Latissimus dorsi
Gluteus medius
Gluteus maximus
Hamstrings
Gastrocnemius
Soleus
Achilles tendon
Disorders and Related Terminology
• ATROPHY – wasting away of muscle due to
lack of use.
• HYPERTROPHY – an increase in the size of
the muscle cell.
• STRAIN – tear in the muscle resulting from
excessive use. Bleeding inside the muscle
can result in pain and swelling. Ice packs will
help stop bleeding and reduce swelling.
• MUSCLE SPASM (cramp) – sustained
contraction of the muscle, usually because
of overuse.
• MYALGIA – muscle pain
• TENDONITIS – inflammation of a tendon