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28 Cards in this Set

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What are paracrines?
secreted into ECF & diffuse to nearby cells in same tissue to exert effect
What is another name for paracrines?
local hormones
What are hormones?
chemical messengers secreted by endocrine glands that travel through blood to sstimulate distant target cells
What glands secrete hormones?
Endocrine Glands
Where do hormones bind?
only to target cells that possess the correct receptors
What is up-regulation?
increasing number of receptors to become more sensitive to hormones
What is down-regulation?
reducing number of receptors to become les sensitive to hormone
What is the pathway for hormones?
travel through blood vessels
How quickly do hormones travel?
much more slowly than nerve signals
How long do hormones effects last?
Much longer than nerve signals
What are steroid hormones?
derived from cholesterol with 4 ring structure
What are peptide hormones?
amino acid chains of varying lengths
What are monoamines
modified amino acids
What are eicosanoids?
local hormones derived from arachidonic fatty acid with prostaglandings
How do steroid & thyroid hormones enter the target cell?
they are lipid soluble, so diffuse through phospholipid plasma membrane
What results from the mechanism of steroid & thyroid hormones?
transcription produces new mRNA that directs synthesis of proteins that alter physiological activity of target cell
How do peptide hormones & catecholamines bind to target cells?
bind to extracellular receptors on surface of target cell
What is enzyme amplification?
cause hormones to bind to extracellular receptors & induce effects at low concentrations
What is activated by the receptor-hormone complex?
"second messenger" system
What happens when G protein activates adenylate cyclase?
ATP is converted into cAMP
What happens when G protein activates phospholipase?
breaks phospholipics in plasma membrake to diacylglycerol & IP3
What 3 things affect the responsiveness of a target cell to a hormone?
1)number of receptors
2)concentration of hormone
3)influences exerted by other hormones
what are synergistic effects?
involve 2 or more hormones together to produce greater effect than either can produce seperately
what are permissive effects?
occur when hormone acts on target cell to enhance cellss response to one or more additional hormones
What are antagonistic effects?
occur when hormone directly opposes effect that a different hormone has on the same target cell
What is negative feedback?
occurs when blood levels of a hormone increase & suppress further secretion of that hormone
What is positive feedback?
occurs when hormone-induced response intensifies initial stimulus causing release of additional hormones
What is an example of positive feedback?
childbirth