Download The Muscular System - Marshall Middle

(Students: Bolded, italicized, and underlined sections will be on the exam)
The Muscular System:
I. Function of the System:
A. The primary functions of this system are to support the skeleton, provide
skeletal movement, control the digestive system, pump blood, regulate body
heat, and to protect soft tissue.
II. The Main Parts of the System:
Overview of the System and Parts:
There are more than 640 muscles in the body, which together account for about 40
percent of a person's weight.. They are the part of our body that allow us to move.
They are made up of special tissues that can contract, or shorten, when they receive a
signal from the brain. The muscles are attached to bones by stretchy tissue called
tendons. When the muscles contract, they pull on the tendons which pull on the
bones and cause our limbs to move.
Muscles hardly ever work alone. Muscles can get shorter and pull, but they cannot
push. So most muscles are arranged in opposing teams. One team pulls the body part
one way, then the other team pulls it back again. As each team pulls, the other team
relaxes and gets stretched. Muscles band together to form muscle groups which
work together.
Voluntary muscles, such as your arms and legs can be controlled by your thoughts.
All this muscle action is controlled by your brain, which sends and receives signals
through your nervous system.
!
Muscle actions can be voluntary or involuntary. Involuntary muscles, such as the
heart, diaphragm and intestines, are automatically controlled by the brain. You don't
have to think about making them work. For example the heart beats between 60 and
80 beats every minute without you having to think about it.
The 3 Main Types of Muscle Tissue: In the body, there are three types of muscle:
skeletal (striated), smooth, and cardiac.
A. Skeletal Muscle: Skeletal muscles provide skeletal movement, controls the
entrances and exits of the digestive tract (sphincter muscles), produce heat,
and protects bones and soft tissue. They are attached to bones by tendons,
and work in flexor/extensor pairs that either contract or relax to create bone
movement. Skeletal muscles regulate body temperature by small contractions
of the muscle tissue; the friction of the cells within the tissue help to create
warmth. Skeletal muscle tissues help to protect the bones and internal
organs, such as the digestive organs in the abdomen. The peripheral portion
of the central nervous system (CNS) controls the skeletal muscles. Thus, these
muscles are under conscious, or voluntary, control. Within the skeletal muscle
system there are two types of muscles, axial muscles support and position the
axial skeleton. The appendicular muscles support, move and brace limbs. The
basic unit is the muscle fiber with many nuclei. These muscle fibers are striated
(having transverse streaks) and each acts independently of neighboring muscle
fibers.
B. Smooth Muscle: Smooth muscle, found in the walls of the hollow internal
organs such as blood vessels, the digestive tract, bladder, and uterus, is under
control of the autonomic nervous system. This means that it cannot be
controlled consciously and thus acts involuntarily. The non-striated (smooth)
muscle cell is spindle-shaped and has one central nucleus. Smooth muscle
contracts slowly and rhythmically.
C. Cardiac Muscle: Cardiac muscle, found in the walls of the heart that pumps
blood throughout the body, is also under control of the autonomic nervous
system. The cardiac muscle cell has one central nucleus, like smooth muscle, but
it also is striated, like skeletal muscle. The cardiac muscle cell is rectangular in
shape. The contraction of cardiac muscle is involuntary, strong, and rhythmical.
Some Major Groups of Skeletal Muscles:
Muscle Fibers:
The muscular system is composed of specialized cells called muscle fibers. Their
predominant function is contractibility. Muscles, where attached to bones or internal
organs and blood vessels, are responsible for movement. Nearly all movement in the
body is the result of muscle contraction. Exceptions to this are the action of cilia, the
flagellum on sperm cells, and amoeboid movement of some white blood cells.
Additional Information About Skeletal Muscles:
The integrated action of joints, bones, and skeletal muscles produces obvious
movements such as walking and running. Skeletal muscles also produce more subtle
movements that result in various facial expressions, eye movements, and respiration.
Almost all skeletal muscles either originate or insert on the skeleton producing
various forms of movement: flexion, extension, adduction, abduction, protraction,
retraction, elevation, depression, rotation, circumduction, pronation, supination,
inversion, or eversion.
In addition to movement, muscle contraction also fulfills some other important
functions in the body, such as posture, joint stability, and heat production. Posture,
such as sitting and standing, is maintained as a result of muscle contraction. The
skeletal muscles are continually making fine adjustments that hold the body in
stationary positions. The tendons of many muscles extend over joints and in this way
contribute to joint stability. This is particularly evident in the knee and shoulder
joints, where muscle tendons are a major factor in stabilizing the joint. Heat
production, to maintain body temperature, is an important by-product of muscle
metabolism. Nearly 85 percent of the heat produced in the body is the result of
muscle contraction.
A whole skeletal muscle is considered an organ of the muscular system. Each organ
or muscle consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood
or vascular tissue.
Skeletal muscles vary considerably in size, shape, and arrangement of fibers. They
range from extremely tiny strands such as the stapedium muscle of the middle ear
to largest mass of muscle tissue, the Gluteous Maximus in the buttocks and thigh.
Some skeletal muscles are broad in shape and some narrow. In some muscles the
fibers are parallel to the long axis of the muscle, in some they converge to a narrow
attachment, and in some they are oblique.
Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal
muscle may be made up of hundreds, or even thousands, of muscle fibers bundled
together and wrapped in a connective tissue covering. Each muscle is surrounded by
a connective tissue sheath called the epimysium. Fascia, connective tissue outside the
epimysium, surrounds and separates the muscles. Portions of the epimysium project
inward to divide the muscle into compartments. Each compartment contains a bundle
of muscle fibers. Each bundle of muscle fiber is called a fasciculus and is surrounded
by a layer of connective tissue called the perimysium. Within the fasciculus, each
individual muscle cell, called a muscle fiber, is surrounded by connective tissue called
the endomysium.
Skeletal muscle cells (fibers), like other body cells, are soft and fragile. The connective
tissue covering furnish support and protection for the delicate cells and allow them
to withstand the forces of contraction. The coverings also provide pathways for the
passage of blood vessels and nerves.
Commonly, the epimysium, perimysium, and endomysium extend beyond the fleshy
part of the muscle, the belly or gaster, to form a thick ropelike tendon or a broad, flat
sheet-like aponeurosis. The tendon and aponeurosis form indirect attachments from
muscles to the periosteum of bones or to the connective tissue of other muscles.
Typically a muscle spans a joint and is attached to bones by tendons at both ends.
One of the bones remains relatively fixed or stable while the other end moves as a
result of muscle contraction.
Skeletal muscles have an abundant supply of blood vessels and nerves. This is
directly related to the primary function of skeletal muscle, contraction. Before a
skeletal muscle fiber can contract, it has to receive an impulse from a nerve cell.
Generally, an artery and at least one vein accompany each nerve that penetrates the
epimysium of a skeletal muscle. Branches of the nerve and blood vessels follow the
connective tissue components of the muscle of a nerve cell and with one or more
minute blood vessels called capillaries.
Most skeletal muscles have names that describe some feature of the muscle. Often
several criteria are combined into one name. Associating the muscle's characteristics
with its name will help you learn and remember them. The following are some terms
relating to muscle features that are used in naming muscles.
*Size: vastus (huge); maximus (large); longus (long); minimus (small); brevis (short).
*Shape: deltoid (triangular); rhomboid (like a rhombus with equal and parallel sides);
latissimus (wide); teres (round); trapezius (like a trapezoid, a four-sided figure with
two sides parallel).
*Direction of fibers: rectus (straight); transverse (across); oblique (diagonally);
orbicularis (circular).
*Location: pectoralis (chest); gluteus (buttock or rump); brachii (arm); supra(above); infra- (below); sub- (under or beneath); lateralis (lateral).
*Number of origins: biceps (two heads); triceps (three heads); quadriceps (four
heads).
*Origin and insertion: sternocleidomastoideus (origin on the sternum and clavicle,
insertion on the mastoid process); brachioradialis (origin on the brachium or arm,
insertion on the radius).
*Action: abductor (to abduct a structure); adductor (to adduct a structure); flexor (to
flex a structure); extensor (to extend a structure); levator (to lift or elevate a
structure); masseter (a chewer).
III. Interactions With Other Systems:
The muscle system interacts with every system, since it helps to protect all of the
intermal organs. Also, it helps to regulate body temperate throughout the body.
Some examples of systems that directly interact with the system include:
• The Nervous System: The nervous system controls the muscles.
• The Circulatory System: The heart is made of cardiac muscle tissue.
• The Digestive System: The hollow tract of the digestive system is made of
smooth muscle tissue. Also, skeletal muscle tissue controls the entrances and
exits of the major organs (sphincter muscles).
• The Lymphatic System: Lymph is moved throughout the body tissue by
movement of the muscle tissue.
IV. Some Disease and Disorders:
• Arthritis: Arthritis is not a single disease. Over 170 types of arthritis exist. The
name which means "inflammation of the joint" is a misnomer since the joint is
not inflamed in all types of arthritis. Arthritis is a disease which can greatly
impact quality of life and is potentially disabling. It is often caused by ‘old age’
and ‘not moving around’. Arthritis sufferers can take inflammatory drugs to
help alleviate the pain, however, there is no cure.
• Muscle Strains: Muscle strains or ruptures can occur in the back just like they
can anywhere else in the body. A muscle strain (or tear) in the back is usually
caused by a sudden movement or trying to lift something that is too heavy. The
injury however is often a long time coming on as the muscles in the back gradually
tighten up due to bad posture and overuse. These muscles go into spasm and do
not get enough blood through them resulting in weakness. So when someone
complains they bent down to pick up a piece of paper and tore a muscle in the
back, it is not just the piece of paper that caused it but a gradual build up of tension
over weeks and months.
• Muscle Contusion: If you have suffered a direct blow to a muscle, particularly one
near a bone then you must treat it as a contusion. Symptoms include:
• A sudden sharp pain in the back.
• Possibly swelling or bruising over the area of the rupture.
• Difficulty in moving - bending forwards, sideways or straightening.
• Muscle Tears: Muscle tears are graded 1, 2 or 3 depending on how bad the tear is.
Grade 1: Symptoms: Tightness in the back; may be able to walk properly;
probably won't have much swelling. Treatment: See a sports injury
professional or therapist who specialises in back problems; use a heat
retainer until you feel no pain; ease down training for a week or two
but no need to stop unless there is getting pain; use sports massage
techniques to speed up recovery (very important); use joint
manipulation techniques; use ultrasound and electrical stimulation;
rehabilitation and strengthening program; use a lumbar heat retainer.
Grade 2: Symptoms: Probably cannot walk properly; may get occasional sudden
twinges of pain during activity; may notice swelling; pressing in
causes pain. Treatment: Rest; see a sports injury professional for
rehabilitation advice; use sports massage techniques to speed up
recovery (very important); use ultrasound and electrical stimulation;
prescribe a rehabilitation programme of mobility, stretching
and strengthening exercises.
Grade 3: Symptoms: Unable to walk properly; severe pain; bad swelling
appearing immediately; static muscle contraction will be painful and
might produce a bulge in the muscle; expect to recovery of 3 to twelve
weeks or more. Treatment: Seek medical attention immediately;
R.I.C.E. (Rest, Ice, Compress, Elevate.); use crutches; follow a
rehabilitation plan as directed by the sports therapist; use sports
massage techniques to speed up recovery (very important); apply joint
manipulation techniques; use ultrasound and electrical stimulation; go
on a rehabilitation program.
If the victim suspects a grade two or three injury it is recommend they should see a
Sports Injury or back Specialist immediately.
Muscular Dystrophy: Muscular dystrophy is the name given to a large number of
medical conditions where there is a progressive weakening and wasting of
muscles.
Cause: The main cause is genetic. They are usually inherited from a parent or
parents through their genes, but sometimes appear out of the blue. They affect
babies, children, young people and adults of any race. About one in every 2,000
people in the US will have an nmd, but the effects are much wider than that.
Relatives may be carrying the faulty genes while not showing any symptoms.
That is why so much research has already gone into finding which genes are at
fault and how they might be repaired. The genetic risks vary. In some types of
nmd both the father and mother must have a faulty gene to pass it on. This is
called recessive inheritance. In other types, it only needs one parent to pass on a
faulty gene. This is called dominant inheritance. In Duchenne md the mother
usually passes the faulty gene on to her son. This is called x-linked inheritance.
Progress in research means that once one member of a family is diagnosed it may
be possible to test other relatives to detect carriers, or to carry out a "family
study". Not all conditions are inherited however. Some conditions are
autoimmune. That means the immune system turns inwards to attack targets
within the body rather than fighting off external dangers. And there can be a
new mutation (or change) in the genes that causes types of nmd to appear for no
apparent reason.
Symptoms: Some nmds are life-threatening. Others may be very disabling or
merely cause a mild disability. Symptoms do not always appear straight away.
Muscular dystrophy is mainly progressive. The signs may become more obvious
over time. Some symptoms will not show until adulthood. Progress in genetic
counselling and diagnosis however is making it much easier to predict which
family members may develop the condition over time. The main characteristic of
md is a progressive weakening of muscles. Other parts of the body can also be
affected however. Cataracts (a clouding in the eye's lens) are common in
myotonic dystrophy for example. The heart can be affected in several types of
md, whether the individual has the condition or is a carrier. Linked symptoms like
this provide another reason for ensuring accurate diagnosis by specialists.
Cure: There is, as yet, no cure, but there are ways of treating the symptoms of
some conditions (like myotonia congenita) and there is much that can be done
practically to improve life for those affected.
Muscular dystrophy and other neuromuscular conditions
Conditions now classed as muscular dystrophy
¥ Duchenne md
¥ Becker md
¥ Emery-Dreifuss dystrophy
¥ congenital md
¥ limb girdle md (several types)
¥ facioscapulohumeral dystrophy (FSH)
¥ scapulohumeral dystrophy
¥ autosomal recessive childhood dystrophy (like Duchenne md and Becker md)
¥ ocular md
¥ oculopharyngeal md
¥ myotonic dystrophy
Related neuromuscular conditions include
¥ spinal muscular atrophy (more than one type)
¥ Charcot Marie Tooth disease
also known as hereditary motor sensory neuropathy (HMSN)
¥ autoimmune myopathies
¥ myotonic disorders
¥ myasthenia gravis