Download Muscle Tissues

Muscular System
Muscle Tissues
The muscular system is the biological system that allows humans to move. The muscular system, in vertebrates, is controlled through
the nervous system. Much of your muscle movement occurs without your conscious control and is necessary for your survival. The
contractions of your heart and the intestinal movements, called peristalis, that push food through your digestive system are examples
of involuntary muscle movements. Involuntary muscle movement is controlled by the autonomic nervous system. Voluntary muscle
contractions are used to move the body and can be finely controlled, such as the pincer-type movements of the fingers that are needed
to pick up chess pieces or the gross movements of legs, arms, and the torso that are needed in skating. Voluntary muscle movement is
controlled by the somatic nervous system.
Each muscle in the body is composed of specialized structures called muscle fibers. Muscle fibers are long, thin cells that have a
special talent that other cells do not have—they are able to contract. 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 contractions. Exceptions to this are the
actions of cilia, the flagellum on sperm cells, and the amoeboid movements of some white blood cells.
There are three types of muscle tissue in the body: skeletal, smooth, and cardiac.
 Skeletal muscle is usually attached to the skeleton. Skeletal muscles are used to move the body. They generally contract
voluntarily (controlled by the somatic nervous system), although they can also contract involuntarily through reflexes.
 Smooth muscle is found within the walls of organs and structures such as the esophagus, stomach, intestines, bronchi, uterus,
urethra, bladder, and blood vessels. Unlike skeletal muscle, smooth muscle is involuntary muscle, which means it is not
under your conscious control.
 Cardiac muscle is also an involuntary muscle, but it is a specialized kind of muscle found only within the heart.
Cardiac and skeletal muscles are striated (they have striations), meaning they contain highly-regular arrangements of bundles of
protein fibers that give them a “striped” appearance. Smooth muscle does not have such bundles of fibers and is non-striated. While
skeletal muscles are arranged in regular, parallel bundles, cardiac muscle fibers connect at branching, irregular angles. Skeletal muscle
contracts and relaxes in short, intense bursts, whereas cardiac muscle contracts constantly for 70 to 80 years (an average life span) or
even longer.
Skeletal Muscle
Skeletal muscle, which is attached to bone, is responsible for body movements and body posture.
There are approximately 639 skeletal muscles in the human body, all under voluntary control.. The
basic units of skeletal muscles are muscle cells that have many nuclei. Each cell acts independently
of its neighboring muscle cells. These cells also contain light and dark stripes called striations,
which are shown in Figure below. The striations are a result of the orientation of the contractile
proteins inside the cells. On average, adult males are made up of 40 to 50 percent skeletal muscle tissue, and an adult female is made
up of 30 to 40 percent skeletal muscle tissue.
A micrograph of skeletal muscle. The stripy appearance of skeletal muscle tissue is due to long protein filaments that run the length of
the fibers.[Figure4]
When skeletal muscles contract, bones move. But how do muscles make your bones move? A voluntary
muscles usually works across a joint. It is attached to both the bones on either side of the joint by strong cords
called tendons. A tendon is a tough band of connective tissue that connects a muscle to a bone. Tendons are
similar to ligaments, except that ligaments join bones to each other. Muscles move the body by contracting
against the skeleton. When muscles contract, they get shorter. By contracting, muscles pull on bones and
allow the body to move.
Muscles can only contract. They cannot actively extend, though they can move or relax back into the noncontracted neutral position. Therefore, to move bones in opposite directions, pairs of muscles must work in
opposition. Each muscle in the pair works against the other to move bones at the joints of the body. The
muscle that contracts to cause a joint to bend is called the flexor. The muscle that contracts to cause the joint to straighten is called the
extensor. When one muscle is contracted, the other muscle from the pair is always elongated.
For example, the biceps and triceps muscles work together to allow you to bend and straighten your elbow. When you want to bend
your elbow, your biceps muscle contracts (and, at the same time, the triceps muscle relaxes. The biceps is the flexor, and the triceps is
the extensor of your elbow joint. Other muscles that work together are the quadriceps and hamstrings used to bend and straighten the
knee, and the pectorals and trapezius used to move the arms and shoulders forward and backward. During daily routines we do not use
muscles equally. For example, we use our biceps more than our triceps due to lifting against gravity.
The biceps and triceps act against one another to bend and straighten the elbow joint. To bend the elbow, the biceps contracts and the
triceps relaxes. To straighten the elbow, the triceps contract and the biceps relax.
Smooth Muscle
Smooth muscle is found in the walls of the hollow internal organs such as blood vessels, the intestinal tract, the urinary bladder, and
the uterus. It is under the control of the autonomic nervous system. Unlike skeletal muscle, smooth muscle cells do not have striations
(smooth muscle is called non-striated muscle). Smooth muscle cells are spindle-shaped, have one central nucleus, and are generally
arranged in sheets or bundles rather than the regular grouping that skeletal muscle cells form. Smooth muscle cells are connected by
gap junctions, which are little pores or gaps in the cell membrane that link adjoining cells, allowing for quick passage of chemical
messages between cells. Smooth muscle is very different from skeletal muscle and cardiac muscle in terms of structure and function,
as shown in Figure below. Smooth muscle contracts slowly and rhythmically.
Smooth muscle. The appearance of smooth muscle is very different from skeletal and cardiac muscle. The muscle protein fibers within
smooth muscles are arranged very differently than the protein fibers of
skeletal or cardiac muscles, shown in (a). The spindly shape of smooth
muscle cells can be seen in (b).[Figure5]
Cardiac Muscle
Cardiac muscle, which is found in the walls of the heart, is also under the
control of the autonomic nervous system. A cardiac muscle cell has
characteristics of both a smooth muscle and a skeletal muscle cell. It has one
central nucleus, similar to smooth muscle, but is
striated like skeletal muscle. The cardiac muscle
cell is rectangular in shape, as can been seen in Figure below. The contraction of cardiac muscle is
involuntary, strong, and rhythmical. Cardiac muscle has many adaptations that makes it highly resistant to
fatigue. For example, it has the largest number of mitochondria per cell of any muscle type. The
mitochondria supply the cardiac cells with energy for constant movement. Cardiac cells also contain
myoglobins (oxygen-storing pigments) and are provided with a large amount of nutrients and oxygen by a
rich blood supply.
Cardiac muscle is similar to skeletal muscle in chemical composition and action. However, the structure
of cardiac muscle is different in that the muscle fibers are typically branched, like a tree branch, and
connect to other cardiac muscle fibers through intercalated discs, which are a type of gap junction. A
close-up of an intercalated disc is shown
Compare and Contrast The 3 types of muscle tissue
Injuries of the Muscular System
There are several types of possible injuries to the muscular system: sprains, strains, cramps, spasms, splints, and tendinitis.
Sprains and strains both involve a stretch and/or tear of part of the muscular system. A sprain is a stretch or tear of a ligament, and a
strain is a stretch or tear a muscle or tendon. Treatment involves the rice method: rest, ice, compression, and elevation. Strains can be
especially slow to heal.
A cramp or spasm is a sudden involuntary muscle contraction after over-activity or due to dehydration. It's treated through rest,
drinking water, stretching, and electrolyte replacement.
Splints (most commonly shin splints) are an injury involving inflammation of the muscles due to repetitive stress or over activity, like
running. Treatment includes rest, ice, anti-inflammatory medication, and changes to footwear and activity intensity.
Tendinitis is the inflammation of the tendon often because of chronic damage, though we now know most cases have no such
inflammation and are purely muscle damage. This can happen when an injury is made worse by not resting or an action is done
repeatedly to the point that multiple injuries occur. Treatments involve pain management and physical therapy to strengthen muscles.
2. Look at the above injuries what might have help prevented these injuries
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Diseases & Disorders of the Muscular System
Diseases and disorders of the muscular system include dystrophy, tendinosis, FMS, mitochondrial myopathy, myasthenia gravis, and
tetanus.
Muscular dystrophy is a group of diseases that weaken the muscular system and make it harder to move. The diseases are usually
progressive - they get worse over time - and effect proteins causing the death of muscle cells.
Tendinosis is a degenerative disease that causes tendons to break down and form scar tissue when the tendons are no longer able to
repair themselves after an injury. There are many commonly used treatments, but they're not very effective.
Fibromyalgia syndrome (or FMS) is basically widespread chronic pain. It is often resistant to treatment and so the focus is usually
on learning how to live with the issue.
Mitochondrial myopathy is a defect in how ATP is produced in mitochondria. It makes it hard for the mitochondria to produce
energy from your food, which causes muscle cells to become damaged and feel weak. Again, we can only treat symptoms and not stop
the progression of the disorder itself.
Myasthenia gravis is where the immune system attacks the junction between the nerves and muscles, making it hard for your brain to
communicate with the muscles. This also makes muscles feel weak. Treatments include plasma exchange and various drugs.
Tetanus is a bacterial infection of the muscular system and causes anything from stiffness and pain to paralysis. It's treated with
antitoxins, antibiotics and pain management.
3. Which one of the disorders is probably the worst _____________________________________________________________
Which one of the disorders can be managed and has the least affect _________________________________________________
Importance of Exercise
While many injuries and disorders of the muscular system are caused by exercise - exercising too much, exercising with not enough
variation, or falling or straining a muscle - exercise is also the key to keeping the muscular system healthy. Often part of treating a
muscular problem is gradually reintroducing exercise to strengthen the muscles. The key is exercise should be done regularly, in a
variety of ways, but without pushing yourself too hard.
4. How often and how long should a person exercise ______________________________________________________________