Download MS I MUSCULAR SYSTEM

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.
THREE MAIN FUNCTIONS
•
•
•
Responsible for all body movement.
Responsible for body form and shape
(posture)
Responsible for body heat and
maintaining body temperature.
TYPES OF MUSCLES
• SMOOTH
• SKELETAL
• CARDIAC
Skeletal Muscle
• Attached to bone
• Striated (striped) appearance
• VOLUNTARYcaused 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
SPHINCTER
= 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
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
• HERNIA – organs can protrude through
this weak muscle.
• FLAT FEET (TALIPES) – weakening of
leg muscles that support the arch,
downward pressure on the foot
eventually flattens out the arches.
Condition can be helped by exercise,
massage and corrective shoes.
• TETANUS (lockjaw) – Infectious
disease, continuous spasms of
voluntary muscles, caused by a toxin
from the bacillus clostridium tetani,
enters the body through puncture
wound. Prevented by an anti-toxoid
vaccine.
• TORTICOLLIS (wry neck) – may be due
to an inflammation of the trapezius
and/or sternocleidomastoid muscle.
• MUSCULAR DYSTROPHY – group of
diseases in which muscle cells
deteriorate. Most common is
Duchenne Muscular Dystrophy, caused
by a genetic defect.
• MYASTHENIA GRAVIS – progressive
muscular weakness and paralysis,
sometimes death. Cause unknown.
Fatal when respiratory muscles are
paralyzed.
• TENDONITIS – inflammation of a
tendon
• CONTRACTURE – tightening or
shortening of a muscle.
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”