Biological Functions: processes and structures by which organisms adjust to short-term or long-term changes in their environment. (Brooker, 4)

Biology rarely rests with a single solution. Instead, it tends to ceaselessly reinvent solutions. (Eagleman, 127) The primary function of “circulatory systems” is to transport necessary materials to all the cells of an animal’s body, and to transport waste products away from the cells where they can be released into the environment. (Brooker, 995) Oxygen is taken into the body by … “respiratory” structures. (Brooker, 1017) If the nutrients in food are in a form that cannot be directly used by cells, they must be broken down into smaller molecules, a process known as “digestion.” (Brooker, 865) “Homeostasis” is critical in the regulation of salt and water levels in body fluid. (Brooker, 1039) ”Communication” takes several forms in nature and involves all of the major sensory systems. It may occur over long distances, as (with) “sound waves,” or (via) “endocrine glands” that secrete “hormones” into the bloodstream. (Brooker, 1061) Medicine’s knowledge base has always involved understanding how the body works and how this is communicated in “disease.” (Bynum, 11)

Absorption: the process in which small molecules are transported from the digestive cavity into (the) circulatory system. (Brooker, 865) The uptake of fluids and other substances by the tissues of the body. (OxfordMed)

Adaptation: processes and structures by which organisms adjust to short-term or long-term changes in their environment. (Brooker, 4) Changes in biological features that help an organism cope with its “environment.” These changes include physiological, “phenotypic” and “genetic” changes. (MeSH)

Cellular Communication: process through which cells can detect and respond to “signals” in the extracellular space. (Norman, 6/10/09) Involves not only sending and receiving signals but also their interpretation. For this to occur, a signal must affect the “conformation,” or shape, of a “receptor.” When a signal and receptor interact, a "conformational change" occurs in the receptor, eventually leading to some type of response in the cell. (Brooker, 171-172)

Signaling: a vital function of the membrane that involves cells sensing changes in their environment and interacting with each other. (Brooker, G-6) (Process in which an) activated receptor stimulates a series of "proteins" forming a “signaling pathway.” Via “calcium channels” in animals, (signaling) occurs in ("synaptic transmission"), "muscle" contraction, and “enzyme” secretion. (Norman, 6/10/09) (Includes) the intracellular transfer of information through a signaling pathway. An “activation” (or “inhibition”) signal from a hormone or "neurotransmitter" is mediated via the coupling of an enzyme to a “second messenger system” or to an “ion channel.” Plays an important role in activating cellular functions, "cell differentiation," and cell proliferation. Some (signaling) pathways may be part of larger (signaling) pathways (MeSH) Also referred to as ‘cell signaling’ and ‘signal transduction.’

Autocrine Signaling: mode of communication wherein a bound hormone affects the function of the cell type that produced the hormone. (MeSH) Cells release signals that affect themselves and nearby target cells. (Norman, 6/10/09)

Direct Intercellular Signaling: contact between adjacent cells. Used to coordinate tissue activity. For example, cardiac muscle contraction, "cilia" movement. (Norman, 6/10/09)

Endocrine Signaling: cells release hormones that travel relatively long distances to affect target cells. (Norman, 6/10/09)

Paracrine Signaling: cellular signaling in which a (ligand) secreted by a cell affects other cells in the local environment. This term is often used to denote the action of intercellular signaling “peptides” and proteins on surrounding cells. (MeSH) Involves neurotransmitter cells and numerous local target cells. (Norman, 6/10/09) Does not affect the cell secreting the signal, but it does influence the behavior of target cells in close proximity. (Brooker, 173)

Signaling Pathway: a group of proteins that convert an initial signal to a different signal inside the cell. (Brooker, G-34) Also referred to as ‘signal transduction pathway.’

Sorting Signals: short stretches of amino acid sequences that direct proteins to their correct cellular location. (Brooker, 117)

Homeostasis: internal balance of key life functions such as "temperature" stability, "energy" usage, and "nutrient" intake. Homeostatic self regulation is the body’s ability to achieve and maintain homeostasis. (Blakeslee, 213) Living cells and organisms regulate their (own) cells and bodies to maintain relatively stable internal conditions. (Booker, 4) The body monitors and maintains internal states at relatively constant levels. The tendency to reach or maintain equilibrium. (Hockenbury, 301) Homeostatic mechanisms maintain the levels of a wide range of features such as temperature, "pH," water potential, and blood "glucose" "concentration." Through homeostatic (processes) behavior is directed which initiates drinking, feeding and temperature regulation. For example, a drop in body temperature initiates a variety of processes (such as shivering) which restore the temperature of the body. (Cardwell, 121) Many of these mechanisms rely on "negative feedback." (Indge, 137) Key structure responsible is the “hypothalamus.” (Blumenfeld, 821) Adjective - ‘homeostatic.’ 

Feedback Inhibition: a form of regulation in which the product of a "metabolic" pathway "inhibits" an enzyme that acts early in the pathway, thus preventing the over accumulation of the production. (Brooker, G-14)

Negative Feedback: mechanism that counters an initial change in homeostasis. (Norman, 6/11/09) Process in which a departure from the set level is detected by receptors. These convey information to ‘effectors’ which bring about a return to the original value. (Indge, 137) A change in the variable being regulated brings about responses that move the variable in the opposite direction. Thus, a decrease in body temperature leads to responses that increase body temperature - that is, move it back toward its original value. (Brooker, 858)

Positive Feedback: a mechanism that enhances an initial change in homeostasis. (Norman, 6/11/09) Communication within a system in that the "input" signal generates an "output" response which returns to influence the continued activity or productivity of that system. (MeSH) (Used to) accelerate a process, leading to what is sometimes called an ‘explosive system.’ This is contrary to the principle of homeostasis, because positive feedback has no obvious means of being stopped. (Brooker, 859) 

Secretion: to form and release a substance. In the body, cells secrete substances, such as sweat that cools the body or hormones that act in other parts of the body. (NCIt) The release of a substance from a cell. Begins when the body sends a biochemical "message" to a cell to begin producing a particular substance. (Lewis, 20) The "golgi apparatus" packages different types of materials into secretory "vesicles" that later fuse with the "plasma membrane," thereby releasing their contents outside the (cell). (Brooker, 78) Verb - ‘secrete.' Adverb 'secretory.'

Endocrine Glands: make hormones that are released directly into the blood and travel to tissues and organs all over the body. The endocrine system controls growth, sexual development, sleep, hunger, and the way the body uses food. (NCIt) Produce "testosterone," "estrogen," "growth hormones," "adrenaline," "thyroid" hormone, and many others. (Lynch, 76) Secrete hormones which always go directly from the cells into the “blood.” (Indge, 123)

Adrenal Glands: pair of endocrine glands that are involved in the human “stress” response. (Hockenbury, 56) A small gland that makes "steroid" hormones, “adrenaline,” and “noradrenaline.” These hormones help control “heart rate,” “blood pressure,” and other important body functions. There are two adrenal glands, one on top of each kidney. (NCIt)

Adrenal Cortex: the outer portion of the adrenal glands. (Hockenbury, 56) The adrenal cortex makes ‘androgen’ and “corticosteroid” hormones. (NCIt)

Adrenal Medulla: the inner portion of the adrenal glands. (Hockenbury, 56) Makes chemicals such as epinephrine (adrenaline) and norepinephrine (noradrenaline) which are involved in sending nerve signals. (NCIt)

Pineal Gland: a pea-sized mass of nerve tissue attached by a stalk to the posterior wall of the “third ventricle” of the brain, deep between the “cerebral hemispheres” at the back of the skull. (OxfordMed) A tiny organ in the cerebrum that produces “melatonin.” (NCIt) Also referred to as ‘pineal body.’

Pituitary Gland: the main endocrine gland. It produces hormones that control other glands and many body functions, especially growth. (NCIt) A small body attached to the base of the brain that is important in controlling growth and development and the functioning of the other endocrine glands. (Oxford) Consists of two lobes, the anterior and posterior lobes. Also referred to as the ‘hypophysis.’

Adenohypophysis: the glandular or anterior lobe of the pituitary gland. (MeSH) Has glandular properties. (Patestas, 376) Secretes several hormones. (NCIt) Also referred to as ‘anterior lobe of pituitary gland.’

Neurohypophysis: posterior lobe of the pituitary gland. The neural lobe of the pituitary gland which stores and releases “vasopressin” and “oxytocin.” (NCIt) Has neural properties. (Patestas, 376) Also referred to as ‘posterior lobe of pituitary gland.’

Thyroid: a large endocrine gland which secretes hormones regulating growth and development through control of the rate of metabolism. (Oxford) Gland located at the base of the neck that produces and secretes “thyroxine” and other hormones. Thyroxine is important for metabolic control. (NCIt) Also referred to as ‘thyroid gland.’

Exocrine Glands: glands that pass their secretions into a duct. (Indge, 123) A gland from which secretions reach a free surface of the body by ducts. Found in the skin, breast, eyelid, and ear. In the breast, secrete fat droplets into breast milk. In the ear, help form earwax. In the skin and eyelid are sweat glands. (NCIt)