Glossary

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False-Negative

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

False-Positive

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

Febrile

Characterized by fever; feverish

Feedback System

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.

Feedback System

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.

Fibroid

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

Fibrosis

Abnormal formation of tissue that is tough, sinewy, resembling fibers

Fluorescent Microscope
A fluorescence microscope is an optical microscope that uses fluorescence and phosphorescence instead of or in addition to reflection and absorption to study properties of organic or inorganic substances. The 'fluorescence microscope' refers to any microscope that uses fluorescence to generate an image whether it is a more simple set up like an epifluorescence microscope or a more complicated design such as a confocal microscope which uses optical sectioning to get better resolution of the fluorescent image.
Folliculitis

Infected hair follicles

Fragile X Syndrome

The most common inherited cause of mental retardation; takes its name from the appearance of the stained X chromosome under a microscope – there is a site near the end of this chromosome that does not stain, indicating its fragility. The gene in the fragile region is important in making a special protein needed by developing brain cells.

Functional Testing

Also known as: Activity testing


Functional testing is used to determine whether or not a specific substance is properly performing its biological role in the body and to what extent. This testing can determine how well a specific coagulation factor is performing its role in the coagulation cascade; for example, normal amounts of fibrinogen can be present, but if not working properly, abnormal coagulation results. Functional testing can also determine the correct level of activity of other substances such as hormones and enzymes.

Fungus

Plural: Fungi


One of the four major groups of microorganisms (bacteria, viruses, parasites and fungi) that occurs in nature as a yeast (small unicellular structure similar to bacteria) or a mold (large filamentous forms that may be seen with the naked eye)

Furuncle

Also known as: Boil


A painful, inflamed area of skin with a defined border, collection of pus and a hard central core usually caused by a bacterial infection of a hair follicle and surrounding tissue

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