Glossary

Incorrect but commonly used name for leiomyoma, a frequent benign smooth muscle tumor of the uterus

Also known as: Feedback Mechanism, Feedback Loop

The body uses feedback systems to control certain functions. A feedback system uses one of the products of a pathway, usually the end product, to control the activity of the pathway and to regulate the amount of that product. Feedback control may be positive or negative.

To understand negative feedback, think of how the thermostat in your house controls the temperature. Lets say that the thermostat is set at 70 degrees F (the end product concentration). When the temperature falls below 70 degrees F, the feedback system is triggered and the furnace lights and starts to pump warm air into the house. When the air in the house reaches 70 degrees F, the thermostat shuts off the furnace (no more product made; no more hot air generated). A negative feedback system maintains a steady state or equilibrium and is the one most commonly found in the body.

Positive feedback systems increase the rate of formation of the product. This tends to cause change in the system rather than maintain a steady state. Think of how when a person works hard and is praised for their efforts (given positive feedback), they work harder still, expecting more praise. There are very few positive feedback systems in the body. One example, however, is lactation. The suckling action of an infant produces prolactin, which leads to milk production; more suckling leads to more prolactin, which in turn leads to more lactation. This is a positive feedback system as the product (milk) produces more suckling and more hormone. When the child is no longer breast feeding, the prolactin drops off and milk production goes down.

Also known as: Feedback Mechanism, Feedback Loop

The body uses feedback systems to control certain functions. A feedback system uses one of the products of a pathway, usually the end product, to control the activity of the pathway and to regulate the amount of that product. Feedback control may be positive or negative.

To understand negative feedback, think of how the thermostat in your house controls the temperature. Lets say that the thermostat is set at 70 degrees F (the end product concentration). When the temperature falls below 70 degrees F, the feedback system is triggered and the furnace lights and starts to pump warm air into the house. When the air in the house reaches 70 degrees F, the thermostat shuts off the furnace (no more product made; no more hot air generated). A negative feedback system maintains a steady state or equilibrium and is the one most commonly found in the body.

Positive feedback systems increase the rate of formation of the product. This tends to cause change in the system rather than maintain a steady state. Think of how when a person works hard and is praised for their efforts (given positive feedback), they work harder still, expecting more praise. There are very few positive feedback systems in the body. One example, however, is lactation. The suckling action of an infant produces prolactin, which leads to milk production; more suckling leads to more prolactin, which in turn leads to more lactation. This is a positive feedback system as the product (milk) produces more suckling and more hormone. When the child is no longer breast feeding, the prolactin drops off and milk production goes down.

Characterized by fever; feverish

Test or procedure result inappropriately indicating a positive or abnormal result when, in fact, no abnormal condition is actually present.

Test or procedure result inappropriately indicating a normal or negative result when, in fact, an abnormal condition is actually present.

Fluid that has leaked into a body cavity as a result of injury or inflammation; it has a higher than normal protein content and may be cloudy due to increased numbers of white blood cells.

External, originating outside of an organ, tissue, cell or the body. It may refer to a substance that is administered to the body, such as exogenous insulin or testosterone.

Cells or tissue that produce substances that are released through a duct and into another organ; for example, the pancreas releases digestive juices into the intestine.

Removal of some of a person's blood and its replacement with equal amounts of donor blood

Repeated inability to achieve or sustain an erection

Outbreak of an infectious disease that spreads rapidly among a population in a defined geographic area

Leukocyte (white blood cell) with granules that are stained by the dye, eosin. Eosinophils, normally about 1-3% of the total white blood cell count, are believed to function in allergic responses and in resisting some infections.

Protein produced in cells that speeds up the rate of biological reactions; the names of many enzymes end in "-ase" (e.g., lipase, amylase).