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