Download MUSCULAR SYSTEM AHI

MUSCULAR SYSTEM
“the power system”
• Muscle is an organ that contracts to move,
support, or stabilize part of the body
MUSCLE CONTRACTIONS
Muscle
Tone
In order to function, muscles should
always be slightly contracted and ready to
pull.
Whatever a person is doing – moving,
standing, or sitting – the brain makes tiny
adjustments to the tone of individual
muscles so posture is always preserved.
Only during sleep does muscle tone
diminish and the body relax completely.
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
• 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.
1.Responsible for all body movement.
2.Responsible for body form and shape
(posture)
3.Responsible for body heat and
maintaining body temperature.
TYPES OF MUSCLES
• SMOOTH
• CARDIAC
• SKELETAL
Skeletal Muscle
Attached to bone
Striated (striped) appearance
VOLUNTARY – caused by a person’s
conscious decision to do something
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
= special circular muscles in openings of
esophagus and stomach, stomach and
small intestine, anus, urethra and mouth.
CHARACTERISTICS OF
MUSCLES
• CONTRACTIBILITY – the ability of a
muscle to reduce the distance between
the parts of its contents or the space it
surrounds.
• EXCITEABILITY (IRRITABILITY) – the
ability to respond to certain stimuli by
producing impulses.
EXTENSIBILITY – the ability to be
stretched.
ELASTICITY – ability of muscle to
return to its original length when
relaxing.
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.
MOVEMENT
• Muscles pull the bones, to which they are
attached by tendon, across a joint
• When a muscle contracts, one of the
bones to which it is attached – the
insertion – moves, while the other
attachment point – the origin – remains
fixed.
• Since they can only pull and not push,
muscles work in antagonistic pairs to
produce opposing movements.
• Ex: flexor muscles in the forearm, bend
fingers, while their antagonists, the
extensor muscles, straighten them.
• Ex: The biceps muscle pulls the forearm
upward toward the shoulder to bend the
arm. Its antagonist, the triceps, pulls the
forearm downward to straighten the arm.
The brachioradialis acts as a synergist to
the biceps, helping it bend the arm.
• Muscles that work together to produce the
same movement are called synergists
• Rule: A muscle’s insertion bone moves
toward its origin bone.
• 2. Groups of muscles usually contract
to produce a single movement.
MUSCLE TERMS
• MOTOR UNIT – a motor neuron plus all
the muscle fibers it stimulates.
The nerve impulses that stimulate contraction
are carried in nerves by bundles of wire-like
motor neurons. As a motor neuron nears a
muscle, it divides into several branches
called axon terminals, each serving a
different muscle fiber. TOGETHER, each
motor neuron and the muscle fibers it
stimulates are called a MOTOR UNIT
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.
• If too little O2 reaches the muscles during
strenuous exercise, waste lactic acid
builds up, causing the muscles to ache.
OXYGEN DEBT
– after exercise, the amount of oxygen
needed by the muscle to change lactic
acid back to glucose.
An athlete pants after a race because his
body needs to get extra oxygen to its cells
– over & above their resting oxygen
consumption- In order to “pay off” an
“oxygen debt.”
This “debt” is generated during hard
exercise by anaerobic respiration, when
muscle fibers obtain energy without using
oxygen. The waste product of this process
– lactic acid – must be disposed of by
aerobic respiration, a process that requires
extra oxygen, before muscles can work
normally again
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
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
NAMING MUSCLES
• Every skeletal muscle is given a Latin
name according to one or more of its
features and some cover several features.
MUSCLE FEATURES &
DESCRIPTIONS
LOCATION: Example: the frontalis runs
over the frontal bone of the skull
RELATIVE SIZE: using terms such as
maximus (largest), minimus (smallest),
longus (long), and brevis (short).
Example: the gluteus maximus is the
biggest gluteal
• SHAPE- Example: the two trapezius
muscles form a trapezoid (four sided)
shape
• ACTION – using terms such as flexor
(bends a joint) and extensor (straightens a
joint). Example: the flexor carpi ulnaris
bends the hand at the wrist.
• ORIGIN & INSERTION
• Ex.: the sternocleidomastoid has origins
(where bones do not move) on the breast
bone (sternum) and collar bone (clavicle –
cleido) and insertions (where bones do
move) on the mastoid process of the
skull’s temporal bone.
• NUMBER OF ORIGINS
Using terms such as biceps (two heads)
Ex: the biceps brachii (arm) has two origins
on the scapula (shoulder blade)
• Deltoid – mean triangular – which is
named after its shape
• Gastrocnemius - fleshy calf muscle whose
name means “belly of the leg”
• Orbicularis oculi – forms a ring around the
eye (means “circular” and “of the eye”