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28 Cards in this Set

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derived from greek words "endo" and "crino", meaning to separate within
Endocrine System
body's communication organ system; composed of glands that secrete chemical signals into the circulatory system
secretory products of endocrine glands; means "to set into motion"; a chemical signal that
1)is produced in minute amounts by collections of cells
2)is secreted into the interstitial places
3)enters the circulatory system, where it is transported some distance, and
4)acts on specific tissues at another site in the body to influence the activity of those tissues in a specific fashion
Amplitude-modulated signals
signals that impact target tissues mainly by increases or decreases in the conc. of hormones in the body fluid; most endocrine hormones are this
Frequency-modulated signals
signals that vary in frequency but not in amplitude; exert their effect based on frequency of stimulus; common among neuronal signals
chemical signals that are secreted into the circulatory system by neurons;
function like hormones
Intercellular chemical signals
allow one cell to communicate with other cells
Autocrine chemical signals
type of intercellular chemical signal released by cells and have a local effect on the same cell type from which the chemical signals are released
Paracrine chemical signals
type of intercellular chemical signal released by cells and affect other cell types locally without being transported in the blood
specialized chemical signals that are secreted into the environment and modify the behavior and the physiology of other individuals
Biological half-life
the length of time it takes for half a dose of a substance to be eliminated from the circulatory system
Factors by which the half-life of hormones is shortened
3)Active Transport
Factors by which the half-life of hormones is lengthened
1)bind reversibly with plasma proteins
2)some hormones are protected by their structure (i.e., carbohydrate complexes of glycoprotein hormones
accomplished when cells in the liver attach water-soluble molecules to the hormone, usually sulfate or glucuronic acid; "mark" molecules for excretion by the kidney and liver at a greater rate
Receptor site
the portion of each protein or glycoprotein molecule where a chemical signal binds on a receptor molecule
the tendency for each type of chemical signal to bind to a specific type of receptor site, and not to others
a phenomenon in which the number of receptors on a cell surface can rapidly decrease after exposure to certain chemical signals;
in general, tissues that exhibit this are adapted to respond to short-term increases in hormone conc. and tissues that respond to hormones maintained at constant levels normally do not exhibit this
periodic increases in the sensitivity of some cells to certain hormones;
results from an increase in the rate of receptor molecule synthesis
Membrane-bound receptors
hormone molecule receptors that extend across the plasma membrane and have their receptor sites exposed to the outer surface of the plasma membrane;
initiates a response inside the cell
Intracellular receptors
receptors in the cytoplasm or in the nucleus of the cell; usually interact with lipid-soluble hormones
complex receptor proteins of the plasma membrane that produce intracellular response through the action of a second-messenger; consists of three subunits: alpha, beta, and gamma
Intracellular mediators
ions or molecules that either enter the cell, or are synthesized in the cell, and regulate enzyme activities inside of the cell
Adenylate cyclase
an enzyme activated by G proteins; converts ATP to cAMP
Protein kinases
enzymes that regulate the activity of other enzymes by attaching phosphates to them; activated by cAMP
regulation of cellular activity by the attachment of phosphate ions;
increases or decreases the activity of the enzyme, depending on the specifc enzyme
Cyclic guanine monophosphate (cGMP)
an intracellular mediator molecule that is synthesized in response to a chemical signal binding with a membrane-bound receptor;
combine with specific enzymes in the cytoplasm of the cell and activates them, producing a response
Guanylate cyclase
an enzyme located at the inner surface of the plasma membrane that converts GTP to cGMP and two phosphates
Cascade effect
an amplification system that facilitates rapid hormonal response within a cell; results when a few mediator molecules activate several enzymes and each of the activated enzymes in turn activates several other enzymes that produce the final response