Muscular system -

The function of the muscular
system is to create
movement, protect organs,
aid digestion, and ensure
blood flow
Smooth muscle provides
structure for the walls of
hollow organs like the
bladder, stomach, and
blood vessels with uninucleated muscle cells that
contract involuntarily.
• Smooth muscle has the
ability to stretch and
maintain tension for long
periods of time, such as
uterine contractions
during childbirth
Skeletal muscles attach to
the skeleton and come in
pairs. They are responsible
for motion, and usually
contract voluntarily. A
short single contraction is
a twitch, and a sustained
contraction is tetanus.
Skeletal muscle cells are
Cardiac muscle is found
only in the heart, and it is
characterized by endurance
and consistency. It can
stretch in a limited way,
like smooth muscle, and
contract with the force of a
skeletal muscle. It is a
twitch muscle only and
contracts involuntarily.
molecules of acetylcholine diffuse
across the neuromuscular cleft and
trigger a muscle contraction.
1. the impulse is transferred from a neuron to the sarcolemma of a
muscle cell.
2 - The impulse travels along the sarcolemma and passes to the
sarcoplasmic reticulum.
3 - Ca2+ diffuses out of the SR and among the myofilaments.
4 -Calcium fills the binding sites in the troponin molecules. the shape
and position of the tropinin changes which in turn causes movement of
the attached tropomysin molecule.
5 - Movement of tropomysin allows the myosin head to contact actin.
6 - Contact with actin causes the myosin head to swivel.
The most common type of inherited muscular
disorder is muscular dystrophy. This disease
causes muscles to progressively waste away.
There are six forms of muscular dystrophy.
The most frequent form appears in boys aged
three to seven, because it’s a sex-linked
Approx. 1 in 544,00 live births will have MD.
The first manifestation of the disease is
clumsiness when walking. This occurs because
the muscles of the pelvis and the thighs are
first affected. The disease spreads to muscles
in other areas of the body, and by the age of
ten, a child is usually confined to a wheelchair
or a bed. Death usually occurs before
Treatment usually focuses on delaying or
alleviating symptoms, with corticosteroids and
physical therapy.
Fibromyalgia causes widespread chronic musculoskeletal pain, accompanied by fatigue.
Researchers believe that fibromyalgia amplifies painful sensations by affecting the way
the brain processes pain signals.
The disorder affects an estimated 10 million people in the U.S. and an estimated 3-6% of
the world population. Symptoms sometimes begin after a physical trauma, surgery,
infection or significant psychological stress. In other cases, symptoms gradually
accumulate over time with no single triggering event.
Women are much more likely to develop fibromyalgia than are men.
While there is no cure for fibromyalgia, a variety of medications can help control
symptoms. Exercise, relaxation and stress-reduction measures also may help.