Homeostatic ImbalancesBy Dwi Notosusanto

(Faculty of Medicine University of Indonesia)

Homeostasis is so important that most disease can be regarded as a result of its disturbance, a condition called homeostatic imbalances. As we age, our body’s control systems become less efficient, and our internal environment becomes less and less stable. These events increase our risk for illness and produce the changes we associate with aging. Another important source of hemostatic imbalance occurs when the usual negative feedback mechanisms are overwhelmed and destructive positive feedback mechanisms take over. Some instances of heart failure reflect this phenomenon

When body is subjected to physical trauma (as often happens in an automobile accident), the abdominopelvic organs are most vulnerable. This is because the walls of the abdominal cavity are formed only by trunk muscles and are not reinforced by bone. The pelvic organs receive a somewhat greater degree of protection from the bony pelvis.

When serous membrane are inflamed, their normally smooth surfaces become roughened. This leads to excruciating pain as the organs stick together and drag across one another, as anyone who has experienced pleurisy (inflammation of the pleurae) or peritonitis (inflammation of the peritoneal) knows.

Maintaining proper ionic balance in our body fluids is one of the most crucial homeostatic roles of the kidneys. When this balance is severely disturbed, virtually nothing in the body works.

Definite changes in glycocalyx occur in a cell that is becoming cancerous. In fact, a cancer cell’s glycocalyx may change almost continuously, allowing it to keep ahead of immune system recognition mechanisms and avoid destruction.

Selective permeability is a characteristic of healthy. Intact cells. When a cell (or its plasma membrane) is severely damaged, the membrane becomes permeable to virtually everything, and substances flow into and out of the cell freely. This phenomenon is evident when someone has been severely burned. Precious fluids, proteins, and ions ‘weep’ from the dead and damaged cells.

Hypertonic solutions are sometimes infused intravenously into the blood stream of edematous patients (those swollen because water is retained in their tissues) to draw excess water put of the extracellular space and move it into the bloodstream so that it can be eliminated by the kidneys). Hypotonic solutions may be used (with care) to rehydrate the tissues of extremely dehydrated patients. In less extreme cases of dehydration, drinking hypotonic fluids (colas, apple juice, and sports drinks) usually doses trick.

Glycogen and certain lipids in the brain are degraded by lysosomes at a relatively constant rate. In Tay-Sach disease, an inherited condition seen mostly in Jews from Central Europe, the lysosomes lack an enzyme needed to break down a glycolipid abundant in nerve cell membranes. As a result, the nerve cell lysosomes swell with the undigested lipids, which interfere with nervous system functioning. Affected infants typically have doll-like features and pink translucent skin. At 3 to 6 months of age, the first signs of disease appear (listlessness, motor

weakness). These progress to mental retardation, seizures, blindness, and ultimately death within 18 months.

An important characteristic of cancerous epithelial cells is their failure to respect this boundary (basement membrane), which they penetrate to invade the tissues beneath.

Because cartilage is avascular and aging cartilage cells lose their ability to divide, cartilage heals slowly when injured. This phenomenon is excruciatingly familiar to those who have experienced sports injuries. During later life, cartilage tend to calcify or even ossify (become bony). In such cases, the chondrocyte are poorly nourished and die.

Scar tissue that forms in the wall of urinary bladder, heart, or other muscular organ may severely hamper the function of that organ. The normal shrinking of the scar reduces the internal volume of an organ and may hinder or even block movement of substances through a hollow organ. Scar tissue hampers muscle’s ability to contract and may interfere with its normal excitation by nervous system. In the heart, these problem may lead to progressive heart failure. In irritated visceral organ, particularly following abdominal surgery, adhesions may form as the newly forming scar tissue connects adjacent organs together. Such adhesions can prevent the normal shifting about (churning) of loops of the intestine, dangerously obstructing the flow of foodstuffs through it. Adhesions can also restrict heart movements and immobilize joints.

Extreme stretching of the skin, such as occurs during pregnancy, can tear the dermis. Dermal tearing is indicated by silver white scars called striae, commonly called ‘stretch marks’. Short term but acute trauma (as from a burn or wielding a hoe) can cause a blister, the separation of the epidermal and dermal layers by a fluid-filled pocket.

Despite melanin’s protective effects, excessive sun exposure eventually damages skin. It causes clumping of elastin fibers, which results in leathery skin; temporarily depresses the immune system; and can alter the DNA of skin cells and this way lead to skin cancer. The fact that dark-skinned people get skin cancer less often than fair-skinned people and get it in areas with less pigment-the soles of the feet and nail beds-attests to melanin’s effectiveness as a natural sunscreen. Ultraviolet radiation has other consequences as well. It destroys the body’s folate stores necessary for DNA synthesis, which can have serious consequences, particularly in pregnant women because deficit may impair the development of the embryo’s nervous system. Many chemicals induce photosensitivity; that is. they heighten the skin sensitivity to UV radiation, setting sun worshippers up for an unsightly skin rash. Such substances include some antibiotic and antihistamine drugs, and many chemicals in perfumes and detergents. Small, itchy, blisterlike lesions erupt all over the body; then the peeling begins, in sheets.

When hemoglobin is poorly oxygenated, both the blood and the skin of Caucasians appear blue, a condition called cyanosis. Skin often becomes cyanotic during heart failure and severe respiratory disorders. In dark-skinned individuals, the skin does not appear cyanotic because of the masking effects of melanin, but cyanosis is apparent in their mucous membranes and nail beds (the same sites where the red cast of normally oxygenated blood is visible)

Many alterations in skin color signal certain disease states, and in many people emostional states:

o Redness, or erythema: Reddened skin may indicate embarrassment (bluishing), fever, hypertension, inflammation, or allergy

o Pallor, or blanching: During fear, anger, and certain other types of emotional stress, some people become pale. Pale skin may also signify anemia or low blood pressure.

o Jaundice, or yellow cast: An abnormal yellow skin tone usually signifies a liver disorder, in which yellow bile pigments accumulate in the blood and are deposited in body tissues. [Normally, the liver cells secrete the bile pigments (bilirubin) as a component of bile.]

o Bronzing: A bronze, almost metallic appearance of the skin is a sign of Addison’s disease, hypofunction of the adrenal cortex.

o Black-and-blue marks, or bruises: Black-and-blue marks reveal where blood escaped from the circulation and clotted beneath the skin. Such clotted blood masses are calles hematomss

If sebaceous gland duct is blocked by accumulated sebum, a whitehead appears on the skin surface. If the material oxidizes and dries, it darkens to form a blackhead. Acne is an active inflammation of sebaceous glads accompanied by ‘pimples’ (pustule or cyst) on the skin. It is usually caused by bacterial infection, particularly staphylococcus, and can be mild or extremely severe, leading to permanent scarring. Seborrhea, known as ‘cradle cap’ in infants, is caused by overactive sebaceous glands. It begins on the scalp as pink, raised lesions that gradually become yellow to brown and begin to slough off oily scales.

In women, small amounts of androgens are normally produced by both the ovaries and the adrenal glands. Excessive hairiness, or hirsutism, as well as other signs of masculinization, may result from an adrenal gland or ovarian tumor that secretes abnormally large amounts of androgens. Since few women want a beard or hairy chest, such tumors are surgically removed as soon as possible.

Hair thinning can be induced by a number of factors that upset the normal balance between hair loss and replacement. Outstanding examples are acutely high fever, surgery, severe emotional trauma, and certain drugs (excessive vitamin A, some antidepressants and blood thinners, anabolic steroids, and most chemoteraphy drugs). Protein-deficient diets and lactation lead to hair thinning because new hair growth stops when protein needed for keratin synthesis is not available or is being used for milk production. In all of these cases, hair regrows if the cause of thinning is removed or corrected. In the rare condition called alopecia areata the follicles are attacked by the immune system and the hair falls out in patches. But again, the follicles survive. However, hair loss due to severe burn, excessive radiation, or other factors that eliminate the follicles is permanent.

Organic solvents and heavy metals are devastating to the body and can be lethal. Passage of organic solvents through the skin into the blood can cause the kidneys to shut down and can also cause brain damage. Absorption of lead results in anemia and neurological defects. These substances should never be handled with bare hands.

The mastoid process is full of air cavities, the mastoid sinuses, or air cells. Its position adjacent to the middle ear cavity (a high-risk area for infections spreading from the throat) puts it at risk for infection itself. A mastoid sinus infection, or mastoiditis, is notoriously difficult to treat. Since the mastoid air cells are separated from the brain by only a very thin bony plate, mastoid infections may spread to brain as well. Surgical removal of the mastoid process was once the best way to prevent life threatening brain inflammations in people susceptible to repeated bouts of mastoiditis. Today, antibiotic therapy is the treatment of choice.

There are several types of abnormal spinal curvatures. Some are congenital (present at birth); others result from disease, poor posture, or unequal muscle pull on the spine. Scoliosis, literally, twisted disease, is an abnormal lateral curvature that occurs most often in the thoracic region. It is quite common during late childhood, particularly in girls, for some unknown reason. Other, more severe cases result from abnormal vertebral structure, lower limbs of unequal length, or muscle paralysis. If muscles on one side of the body are nonfunctional, those of the opposite side exert an unopposed pull on the spine and force it out of alignment. Scoliosis is treated (with body braces or surgically) before growth ends to prevent permanent deformity and breathing difficulties due to a compressed lung.Kyphosis, or hunchback, is a dorsally exaggerated thoracic curvature. It is particularly common in elderly people because of osteoporosis, but may also reflect tuberculosis of the spine, rickets, or osteomalacia. Lordosis, or swayback, is an accentuated lumbar curvature. It, too

Severe or sudden physical trauma to the spine-for example from bending forward while lifting a heavy object-may result in herniation of one or more discs. A herniated (prolapsed) disc (commonly called a slipped disc) usually involves rupture of the annulus fibrosus followed by protrusion of the spongy nucleus pulposus through the annulus. If protrusion presses on the spinal cord or on spinal nerves exiting from the chord, numbness or excruciating pain may result. Herniated discs are generally treated with moderate exercise, massage, heat therapy, and pain killers. If this fails, the protruding disc may have to be removed surgically and a bone graft done to fuse the adjoining vertebrae. For those preferring to avoid general anesthesia, the disc can be partially vaporized with a laser in an out patient procedure called percutaneous laser disc decompression that takes only 30 to 40 minutes. The patient leaves with only an adhesive bandage to mark the spot.

Colle’s fracture is a break in the distal end of the radius. It is a common fracture when a failing person attempts to break his or her fall with outstretched hands.

The arrangement of its bones is such that the carpus is concave anteriorly and a ligament roofs over this concavity, forming the notoriously carpal tunnel. Besides the median nerve (which supplies the lateral side of the hand), several long muscle tendons, crowd into this tunnel. Overuse and inflammation of the tendons cause them to swell, compressing the median nerve, which causes tingling and numbness of the areas served. Pain is greatest at night. Those who repeatedly flex their wrists and fingers, such as those who work at computer keyboards all day,

are particularly susceptible to this nerve impairment, called carpal tunnel syndrome. This condition is treated by splinting the wrist during sleep or by surgery.

A Pott’s fracture occurs at the distal end of the fibula, the tibia, or both. It is a common spots injury.

Standing immobile for extended periods places excessive strain on the tendons and ligaments of the feet (because the muscles are inactive) and can result in fallen arches, or ‘flat feet,’ particularly if one is overweight. Running on hard surfaces can also cause arches to fall unless one wears shoes that give proper arch support.

Of all body joints, the knees are most susceptible to sports injuries because of their high reliance on non articular factors for stability and the fact that they carry the body’s weight. The knee can absorb a vertical force equal to nearly seven times body weight. However, it’s very vulnerable to horizontal blows, such as those that occur during blocking and tackling in football. When thinking of common knee injuries, remember the 3 Cs: collateral ligaments, cruciate ligaments, and cartilages (menisci). Most dangerous are lateral blows to the extended knees.