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Human Homeostasis

Updated on May 4, 2012

What is Homeostasis

Homeostasis is the process by which the body attempts to maintain a state of stable physiological balance. The word homeostasis is derived from the Greek, homeo or "same", and stasis or "stable" and means remaining stable or remaining the same.

The body needs to maintain homeostasis in order to stay alive. Working as a fine-tuned machine, the human body has a way of keeping its inner environment constant no matter what the outside environment is like. Homeostasis uses hormones to control body conditions. This is vital for the body's survival, because the chemical reactions taking place are easily imbalanced so it is necessary to both monitor and control the conditions. The liver, the kidneys, and the brain (hypothalamus, the autonomic nervous system and the endocrine system) help maintain homeostasis. The liver is responsible for metabolizing toxic substances and maintaining carbohydrate metabolism. The kidneys are responsible for regulating blood water levels, re-absorption of substances into the blood, maintenance of salt and ion levels in the blood, regulation of blood pH, and excretion of urea and other wastes.

Physical health depends on properly functioning homeostatic mechanism-that is, regulatory controls in the body that help maintain homeostasis. When these controls function improperly or break down completely, illness results. Persistent stress, for example, can disrupt several of the body's homeostatic mechanisms, leading to disease.

homeostasis and stress
homeostasis and stress

Stress Results in Disease by Disrupting Homeostatic Mechanisms

Stress is prevalent in many of our lives. Most people cope with infrequent or short-term stress fairly well. Stress causes little harm when it occurs infrequently. If it is prolonged, however, stress can increase the risk of cardiovascular disease (diseases of the heart and arteries). Persistent stress may also increase the risk of ulcers and weaken the immune system. In addition, it may increase the likelihood of developing mental disorders. Fortunately for us, stress can be alleviated by exercise, relaxation training, massage, acupuncture, and

other measures. This doesn't imply that all diseases result from homeostatic imbalance. Some are produced by genetic defects; others are caused by bacteria or viruses. But even in these instances, diseases often result from an upset in regulatory mechanisms of the body that disrupt homeostasis. An excellent example is acquired immune deficiency syndrome, or AIDS. AIDS is caused by a virus that attacks certain cells of the immune system. This, in turn, results in a reduction in a key protective mechanism of the body, which is vital to bomeostasis. In other diseases, temporary upsets in homeostasis may make us more susceptible to infectious agents.

The Body Balance and Stress

According to a recent study, people under stress are twice as likely to suffer from colds and the flu as those who are not.

Energy Balance
Energy Balance

Energy Balance

Some people eat to live, but many others seem to live to eat. No matter what your orientation, food probably occupies a central part of your life. If you're like many others, you may often plan your daytime activities around meals. In addition, you spend a good part of your life shopping for, preparing, and eating meals. Depending on your income, 10-20% of the money you earn goes to buy food. Thus, 1.5-3 hours of each workday goes to providing money for food. (The rest goes to paying income tax!)

If you live to be 65, you will consume over 70,000 meals. Because foods affect your body in many ways, what you eat will determine how you feel in your later years. That's how important nutrition is to your health. Despite the increased emphasis on nutrition today, studies suggest that most Americans pay little attention to their diet. To perform and feel our very best, though, we must eat a balanced diet to acquire the energy and nutrients needed by our cells, tissues, and organs.

A balanced diet is attained by eating a variety of foods. The nutrients we need to survive and prosper physically and mentally can be divided into two broad categories: macronutrients and micronutrients.

Macronutrients are required in relatively large quantities and include four substances: water, carbohydrates, lipids, and proteins. Micronutrients are substances needed in small quantities and include two broad groups: vitamins and minerals.

Homeostasis Basic Iron Metabolism
Homeostasis Basic Iron Metabolism

Basic Iron Metabolism

It must be a law of human nature. Ask almost any couple, and they will tell you: She lies shivering under the covers on a cold winter night while he bakes. Out on a hike in winter, he stays warm in a light jacket while she bundles up in stocking cap, down coat, and gloves. What causes this difference between many men and women? Part of the answer may lie in iron-not pumping iron, but dietary iron. Quite simply, many American women do not consume enough iron to offset losses that occur during menstruation, the monthly discharge of blood and tissue from the lining of the uterus. Iron deficiencies in women may reduce internal heat production.

John Beard, a researcher at Pennsylvania State University, published a study that supports this conclusion. Beard compared two groups of women, one with low levels of iron in the blood and another with normal levels. Beard found that body temperature dropped more quickly in iron-deficient women exposed to cold than in those with normal iron levels. He also found that iron-deficient women generated 13% less body heat. Adding credence to the hypothesis that iron deficiency reduces body heat and makes women colder, Beard gave the iron-deficient women iron supplements for 12 weeks, after which they responded normally to cold. These findings illustrate how important proper nutrition is to normal physiological function, especially homeostasis.

PH level of the body
PH level of the body

PH Level of the Body

Another widely important factor in maintaining homeostasis is the PH level of the body. Requiring a higher alkaline content of water helps keep the machine in working order and produces an overall better state of health. Many of the waste management organs such as the kidney and liver filter out the acidic properties of the food and water we ingest in order to properly hydrate the body and purge it of unwanted acidic properties. Although these functions are carried out by the body naturally, there are ways to help the natural process and keep the body at an elevated state of homeostasis. By limiting the amount of acidic materials ingested, it becomes easier for the body to regulate itself and keep in working order.

Various areas of the body serve different purposes and create a perfect balance within. Another important system of the body is the nervous system. Basic bodily functions such as heart rate and breathing are regulated by the nervous system as is the urinary and digestive systems. A gland within the brain known as the pituitary gland releases hormones and enzymes based on specific materials introduced within the body. Also helping to adjust the body's balance of fluids and electrolytes, these processes become much easier to regulate when ingesting food and water higher in alkalinity.

One of the ways to help maintain a higher level of homeostasis is the use of alkaline water. Created with the use of a water ionizer, this water is easier for the body to process and aids in natural regulation of the body's inner environment. With a constant challenge for the body to maintain balance, diet that lacks the right nutrients and PH can be more detrimental than one might think.

Ref: "Human biology" Daniel D. Ckiras

homeostasis of sleep
homeostasis of sleep

Homeostasis and Sleep

Not All Physiological Processes Remain Constant Over Time, But Those That Fluctuate Do So in Predictable Ways

Body temperature varies during a 24-hour period by as much as 0.5"C. Blood pressure may change by as much as 20%, and the number of white blood cells, which fight infection, can vary by 50% during the day. Alertness also varies considerably. About 1:00 P.M. each day, for instance, most people go through a slump. For most of us, activity and alertness peak early in the evening, making this an excellent time to study. Daily cycles, such as these, are called circadian rhythms (sir-kade-ee-an; "about a day"). Circadian rhythms are natural body rhythms linked to the 24-hour day-night cycle. Many hormones follow daily rhythmic cycles. The male sex hormone testosterone, for example, follows a 24-hour cycle. The highest levels occur in the night, particularly during dream sleep. Dream sleep occurs primarily in the early morning hours-the later the hour, the longer the periods of dream sleep.

Not all cycles occur over 24 hours, however. Some can he much longer. The menstrual cycle, for instance, is a recurring series of events in the reproductive functions of women that lasts, on average, 28 days. During the menstrual cycle, levels of the female sex hormone estrogen undergo dramatic shifts. Estrogen concentrations in the blood are low at the beginning of each cycle and peak on day 14, when ovulation normally occurs. Throughout the remaining 14 days, estrogen levels are rather high. Then they drop off again when a new cycle begins. Estrogen levels follow this cycle month after month in women of reproductive age. The important point here is that the body is not static. Although many chemical substances are held within a fairly narrow range by homeostatic mechanisms, others fluctuate widely in normal and quite essential cycles. Over the long run, these changes are quite predictable. They also occur within prescribed physiological limits; they do not run out of control. They are part of the body's dynamic balance, just as yearly weather changes are part of the dynamic balance of the planet's climate.

Thermoregulation in Humans

temperature homeostasis
temperature homeostasis

Humans are warm-blooded, maintaining a near-constant body temperature. Thermoregulation is an important aspect of human homeostasis. Heat is mainly produced by the liver and muscle contractions. Humans have been able to adapt to a great diversity of climates, including hot humid and hot arid. High temperatures pose serious stresses for the human body, placing it in great danger of injury or even death. In order to deal with these climatic conditions, humans have developed physiologic and cultural modes of adaptation.

Temperature may enter a circle of positive feedback, when temperature reaches extremes of 45°C (113°F), at which cellular proteins denature, causing the active site in proteins to change, thus causing metabolism stop and ultimately death.

The ideal internal body temperature for humans is 98.6 degrees F. In a state of homeostasis this temperature will fluctuate slightly depending on the level of activity in which a person is engaged. For instance, a person's body temperature may be slightly lower than the ideal temperature at rest and slightly higher during periods of exercise.

Temperature Detection and Reaction

When met with environments that threaten the internal temperature of the body, such as cold or hot conditions, the human body is triggered into response. For example, nerve endings in the skin detect temperature changes in the environment outside the body and signal the brain to either increase or decrease the heat inside the body.

When the body senses warm temperatures any number of reactions may occur. Sweating is one method for reducing body temperature. The sweat glands in the skin excrete sweat, which contains water and some nutrients. The process of evaporation then works to cool the body. The drawback to perspiration is the loss of water. Maintaining water within the body is especially important in high temperatures.

In cold conditions the brain may signal blood vessels to constrict, reducing blood flow and preventing heat loss. If necessary the body will shiver involuntarily. This action releases heat through the consumption of energy. Long-term cold conditions cause metabolic changes to occur in the body. For example, the breakdown of glucose and other molecules increases during periods of cold weather, releasing heat in the process.

Humans can thrive in conditions ranging from the arctic to the equator, and with a variety of diets and lifestyles.

Part of the reason for this adaptability is the body's ability to maintain homeostasis.

Find Your Balance

Here you can find books that will help you understand how to maintain your body balance and remain healthy

pancreatic islets
pancreatic islets

Homeostasis of sugar

Sugar is an essential constituent of the blood. It is also called "blood glucose." In the fasting state, as in the morning before breakfast, the blood sugar concentration is between 80 and 90 mg. per 100 cc. of blood. Even after several days of fasting the blood sugar will be maintained around this level in a well-nourished individual. It is essential to normal health that the blood sugar be maintained at this level, and that it should not fall below this level for periods longer than an hour. After a meal containing sugar the blood sugar rises at once, usually reaches a concentration of 120 to 140 mg. after 11/2 to 2 hours, and then gradually falls during the third and fourth hours to the previous fasting level. (Fig. 1.) In some individuals the blood sugar may reach 180 mg. and higher after a meal containing sugar, and, accompanying this high level, sugar may be found in the urine.

This abnormally high concentration of blood sugar is called in medicine Hyperglycemia (Hyper--excessive; Glycemia—blood sugar). The opposite state, an abnormally low blood sugar concentration, is called Hypoglycemia (Hypo—less; Glycemia— blood sugar). Fig. 2 shows the hypoglycemic type of curve, and Fig. 3 shows the hyperglycemic type of curve.

The maintenance of the blood sugar at normal levels is brought about by an efficient regulatory mechanism. The main organs in this mechanism are the liver, the autonomic nervous system,pancreas and other glands of internal secretion called endocrine glands.

The pancreatic Islets of Langerhans are the sites of production of insulin, glucagon and somatostatin.

Most cells in the human body use the sugar called glucose as their major source of energy. Glucose molecules are broken down within cells in order to produce adenosine triphosphate (ATP) molecules, energy-rich molecules that power numerous cellular processes. Glucose molecules are delivered to cells by the circulating blood and therefore, to ensure a constant supply of glucose to cells, it is essential that blood glucose levels be maintained at relatively constant levels. Level constancy is accomplished primarily through negative feedback systems, which ensure that blood glucose concentration is maintained within the normal range of 70 to 110 milligrams (0.0024 to 0.0038 ounces) of glucose per deciliter (approximately one-fifth of a pint) of blood.

Negative feedback systems are processes that sense changes in the body and activate mechanisms that reverse the changes in order to restore conditions to their normal levels. Negative feedback systems are critically important in homeostasis, the maintenance of relatively constant internal conditions. Disruptions in homeostasis lead to potentially life-threatening situations. The maintenance of relatively constant blood glucose levels is essential for the health of cells and thus the health of the entire body.

Read more: Blood Sugar Regulation - Biology Encyclopedia

The Nervous and Endocrine System

Two of the most important systems for maintaining homeostasis are the nervous and endocrine systems. Basic bodily functions such as heart rate and breathing may be stimulated or slowed under neural control. The nervous system helps regulate breathing and the urinary and digestive systems, and it interacts with the endocrine system.

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      okpaowaa@gmail.com 7 weeks ago

      to learn more about homeostasis

    • profile image

      Echo Phoenix 4 years ago

      Brilliant! I was looking for a refresher course on homeostasis and found it here:) I'd say, everything I learned about it in college all in a wee nutshell! Thanks.

    • profile image

      JoshK47 4 years ago

      Quite an interesting read, indeed - thanks for sharing! Blessed by a SquidAngel!

    • profile image

      dream1983 5 years ago

      Great lens, nice info! Thumbs up!

    • DuncanBoud profile image

      DuncanBoud 5 years ago

      Very informative, I learned a lot reading this. Plenty to think about!

    • profile image

      anonymous 5 years ago

      nice lens

      good information

    • Ram Ramakrishnan profile image

      Ram Ramakrishnan 5 years ago

      Very well presented.

    • Diana Wenzel profile image

      Renaissance Woman 5 years ago from Colorado

      It seems all of life is about balance. I know my systems are much more balanced since I changed lifestyles (green living). This is a very interesting article about a crucial topic. Thank you for building awareness so others may live healthier lives. Appreciated!

    • Northbright profile image

      Norbert Isles 5 years ago from Philippines

      Very important and useful information. I enjoyed it.

    • VeseliDan profile image

      VeseliDan 5 years ago

      Really useful information on human homeostasis! I enjoyed reading it.

    • profile image

      anonymous 5 years ago

      Great information.

    • Daphsam LM profile image

      Daphsam LM 5 years ago

      Very interesting and informative lens. I never knew that about the water! Thanks for sharing and pay closer attention to what I eat:)

    • Thrinsdream profile image

      Thrinsdream 5 years ago

      Interesting lens. Took some getting through as there is so much information (in a good way!). I am so glad I eat mainly raw food! With thanks and appreciation. Cathi x

    • Linda Pogue profile image

      Linda Pogue 5 years ago from Missouri

      Great information. What we eat makes a bit difference!

    • Countryluthier profile image

      E L Seaton 5 years ago from Virginia

      Body balance, I never gave it much thought until recently. This lens is immensely helpful.

    • sousababy profile image

      sousababy 5 years ago

      Excellent . . I like the emphasis on water. We really do require such a delicate balance (esp. of blood pH) for homeostasis. Too often, we (I'm so guilty of this) will forego getting the proper amount of sleep to get some work done. It catches up with us eventually - esp. when we hit our 40's.