Complications can arise if positive and negative feedback loops are
affected or altered in any way, leading to homeostatic imbalance.
LEARNING OBJECTIVE [ edit ]
Analyze disease as a result of homeostatic imbalance
KEY POINTS [ edit ]
Many diseases are a result of homeostatic imbalance or an inability of the body to restore a
functional and stable internal environment.
Aging is a source of homeostatic imbalance as the control mechanisms of the feedback loops lose
their efficiency.
Diseases that result from a homeostatic imbalance includediabetes, dehydration, hypoglycemia,
hyperglycemia, gout, and any disease resulting from bloodstream toxins.
Diabetes occurs when the control mechanism for insulinbecomes imbalanced either because
insulin is deficient or the cells have become resistant to insulin.
Homeostasis is the property of a system that regulates its internal environment, maintaining a
stable, relatively constant set of properties such as temperature or pH, in which the body's
internal environment is kept stable and functional.
TERMS [ edit ]
homeostasis
The ability of a system or living organism to adjust its internal environment to maintain a stable
equilibrium; such as the ability of warm-blooded animals to maintain a constant temperature.
blood sugar regulation
Insulin is a hormone, produced by the pancreas, which is central to regulating carbohydrate and
fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up
glucose from the blood, storing it as glycogen inside these tissues. Glucagon, a peptide hormone
secreted by the pancreas, raises blood glucose levels. Its effect is opposite that of insulin, which
lowers blood glucose levels. The pancreas releases glucagon when blood sugar (glucose) levels fall
too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released into
the bloodstream.
diabetes
A group of metabolic diseases whereby a person (or other animal) has high blood sugar due to an
inability to produce, metabolize, or respond to the hormone insulin.
EXAMPLE [ edit ]
Paula Deen, host of a Food Network cooking show, disclosed that she has type 2 diabetes. Deen is
famous for cooking rich, high-calorie food, which can lead to obesity. Obesity upsets homeostatic
controls and is a risk factor in type 2 diabetes. In order to try to bring her metabolism back into
balance, Deen began exercising and reduced her portion sizes.
Give us feedback on this content: FULL TEXT [edit ]
The ability of a system or
livingorganism to adjust its internal
environment and maintain a stable
equilibrium such as the ability of warmblooded animals to maintain a constant
internal temperature are examples
of homeostasis. Positive and negative
feedbacks are equally important for the
healthy functioning of one's body and to
restore and maintain the body's
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physiological systems within a normal functional range. Complications can arise if any of the
two feedbacks are affected or altered in any way leading to homeostatic imbalance.
Many diseases are a result of homeostatic imbalance. As it ages, every organism will lose
efficiency in its control systems. The inefficiencies gradually result in an unstable internal
environment that increases the risk for illness. In addition, homeostatic imbalance is also
responsible for the physical changes associated with aging. Even more serious than illness
and other characteristics of aging is death. Heart failure has been seen where nominal
negative feedback mechanisms become overwhelmed and destructive positive
feedbackmechanisms then take over.
Diseases that result from a homeostatic imbalance include diabetes, dehydration,
hypoglycemia, hyperglycemia, gout, and any disease caused by a toxin present in the
bloodstream. All of these conditions result from the presence of an increased amount of a
particular substance. In ideal circumstances, homeostatic control mechanisms should
prevent this imbalance from occurring. However, in some people, the mechanisms do not
work efficiently enough or the quantity of the substance exceeds the levels at which it can be
managed. In these cases, medical intervention is necessary to restore the balance or
permanent damage to the organs may result. Most homeostatic regulation is controlled by
the release of hormones into the bloodstream. The human body performs blood sugar
regulationby maintaining constant levels of glucose throughout the day, even after a 24-hour
fast . During long periods of fasting, glucose levels are reduced only very slightly. Insulin,
secreted by the beta cells of the pancreas, effectively transports glucose to the body's cells by
instructing the cells to keep the glucose for their own use. If the glucose inside the cells is
high, the cells will convert it to the insoluble glycogen to prevent the soluble glucose from
interfering with cellular metabolism. Ultimately, this lowers blood glucose levels; insulin
helps to prevent hyperglycemia. When insulin is deficient or cells become resistant to it,
diabetes occurs. Glucagon, secreted by the alpha cells of the pancreas, encourages cells to
break down stored glycogen or convert non-carbohydrate carbon sources to glucose via
gluconeogenesis, thus preventing hypoglycemia. The kidneysare used to remove excess water
and ions from the blood. These are then expelled as urine. The kidneys perform a vital role in
homeostatic regulation in mammals, removing the body's waste products such as excess
water, salt, and urea from the blood.
Serum Insulin
pmol/L
Blood glucose
8.0
glucose blood levels
7.5
126
sucrose*­rich foods (*glucose­fructose)
7.0
6.5
108
6.0
5.5
90
5.0
4.5
72
4.0
3.5
mg/dL
3.0
7:00
9:00 11:00
Breakfast
1:00
3:00
Lunch
5:00
7:00
Dinner
9:00
11:00 1:00
3:00
5:00
7:00
based on [Daly98]
Homeostasis of Glucose Metabolism
This image illustrates glucose metabolism over the course of a day. Homeostasis may become
imbalanced if the pancreas is over­stressed, making it unable to balance glucose metabolism. This
could lead to diabetes.