The Muscular System
By Bryce Tappan
Functions of the Muscular System
One of the most important roles muscles play is
to give the body the ability to move. Muscles
contract and expand to move bones and
complete actions, and they are directed by the
central nervous system. Actions are divided
into voluntary and involuntary muscular
movements, and there are different types of
muscle that perform different functions.
http://www.unp.me/f150/muscular-system-functions-143366/
Skeletal Muscle
Skeletal muscles are joined to the bones by
tendons. Their purpose is to sustain posture and
stability, as well as control coordination. When
skeletal muscles contract or expand, they move
the bones that they are attached to. Skeletal
muscles are voluntary muscles, meaning that we
can consciously control them. Skeletal muscles
are also striated, which means that they are
divided into parallel fibers.
http://library.thinkquest.org/5777/mus3.htm
Cardiac Muscle
Cardiac muscles are the striated muscles within the
heart. They must contract and expand to sustain
blood flow, and so they must not become
fatigued. Cardiac cells have a high number of
mitochondria which allows for continuous
aerobic respiration to occur and the prevention
of fatigue. Cardiac muscle is involuntary muscle;
organisms do not consciously control its
functioning.
http://en.wikipedia.org/wiki/Cardiac_muscle
Smooth Muscle
Smooth muscle is involuntary and is not striated, and it is
found in the walls of blood vessels and within tracts of
the digestive and reproductive systems. In many
smooth muscles, called single-unit muscles, the entire
muscle contracts or expands at once. Smooth muscles
have the ability to stretch farther than striated
muscles, which makes them important in the digestion
process in the intestines. Smooth muscles are in
charge of regulating blood flow within the veins and
thus blood pressure.
http://en.wikipedia.org/wiki/Smooth_muscle_tissue
Sliding Filament Model
The sliding filament model is a theory that depicts how
muscles contract. Within muscle cells are sarcomeres.
Sarcomeres are the basic unit of muscles and are
composed of actin and myosin, two different types of
filaments. The movement of actin past myosin creates
tension within the muscle. ATP powers the movement
of fibers within the sarcmere. Actin is anchored to both
sides of the sarcomere, so when it slides, the
sarcomere shortens with the tension. As a result of
sarcomere shortening, muscles shorten as well. This is
the sliding filament model.
http://www.nature.com/scitable/topicpage/the-sliding-filament-theory-of-muscle-contraction14567666
Acetylcholine
Acetlycholine is a neurotransmitter found in both
the PNS and CNS. Its function in the PNS is to
activate muscles. It binds to acetlycholine
receptors in skeletal muscle fibers which then
opens sodium ion channels in the cell membrane
of the muscle cells. Sodium ions flood the cell
which induces the contraction of the muscle. In
cardiac muscle, acetlycholine actually stops the
contraction of muscle.
http://en.wikipedia.org/wiki/Acetylcholine
CA and Crossbridges
A crossbridge is the head of a myosin molecule
that is projected from a myosin filament. In
the sliding filament model, calcium ions are
released and they allow a bond to be formed
between myosin and actin filaments. While
attached, the myosin and actin pull on each
other, which contracts muscles.
http://www.merriam-webster.com/medical/crossbridge
http://en.wikipedia.org/wiki/Crossbridge
Actin & Myosin
Actin is a microfilament that gives support to cells
and gives myosin (another filament) a binding place
in order for muscle contraction to occur. It is a
protein that has many different functions within
different types of cells.
Myosin is known as a “motor protein” as it is
responsible for motility in conjunction with actin in
cells. It is also an important protein in muscular
contraction. (See Sliding Filament Model)
http://www.newworldencyclopedia.org/entry/Myosin
http://en.wikipedia.org/wiki/Actin#Functions
Disorders: Muscular Dystrophy
A) A disorder in which muscles strength and
deteriorate in time.
B) Loss of coordination, stiffness, immobility,
mental retardation
C) The most common type of muscular dystrophy,
Myotonic dystrophy, occurs for 1 out of every
20,000 people.
D) Physical therapy, surgery, mexiltine (medication)
http://www.livestrong.com/article/72452-disorders-muscular-system/
http://www.answers.com/topic/muscular-dystrophy
Disorders: Rhabdomyolysis
A) Breaking down of muscles, often as a result of
taking drugs such as cocaine and PCP.
B) Break down of muscles into myoglobin, which
then goes to the blood and kidneys, causing
kidney damage. Symptoms such as red urine,
muscle weakness and pain may occur
C) Rhabdomyolysis isn’t common, but is most
prevalent among drug users.
D) Hydration, diuretics, and bicarbonates can
alleviate the symptoms of Rhabdomyolysis
http://www.livestrong.com/article/72452-disorders-muscular-system/