9.0 Endocrine Flashcards
what are the 3 classes for hormones?
hormone = chemical released by a cell in one part of the body that affects cells in antoher part
endocrine: hormones secreted directly into blodo stream
Neuroendocrine: hormones produced by neurons secreted into blodostream
exocrine: hormones are secreted directly into a duct (can enter blood stream)
qutocrine vs paracrine
autocrine: chemicals that exert effects on same cells
ex: cytokine interleukin-1 from monocytes
Paracrine: locally acting chemicals that affect nearby cells
-> responses to allergens, tissue repair, formation of scar tissue and blood clotting
*peptides are not considered hormones, hormones are long distnaced chemical signals
two mechanisms of hormones
- *Second messengers -** Regulatory G proteins tend to be amino acid-based hormones
- *Direct gene activation** - Tend to be steroid hormones
what are the actions of hormones (cellular changes to target cells)?
Alter plasma membrane permeability
Stimulate protein synthesis
Activate or deactivate enzyme systems
Induce secretory activity
Stimulate mitosis (growth)
hwo does target specificity relate to hormone activity
- target cells must ahve specific receptors to which the hormone binds
ACTH receptors: found on certain cells of adrenal cortex
Thyroxin receptors found on nearly all cells of body
what factors influence target cell activation
- Blood levels of the hormone
- Relative number of receptors on the target cell
- The affinity of those receptors for the hormone
how do hormones circulate in the blood? what are their concentrations influenced by?
- circulate as free or bound
- > sterior and thyroid bound to plasma proteins
- > most of rest are free
Concentration of circulation hormoens dep on: rate of release, speed of inactivation, removal from body
hormones are removed by …
Degrading enzymes
The kidneys and liver enzymes
half lives of hormoens
thyori longers (days)
steriods some of shortest (4-120 min)
what are the 3 types of interactions of hormones at target cells
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permissiveness
- one hormone cant act without another hormone being present
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Synergism
- more than one hormone produces the same effects on a target cell
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Antagonism
- one or more hormones oposes the action of another hormone (insulin and glucagon, dopamine and prolactin)
how is hormone release controlled
- by blood levels: negative feedbck, vary only in a narrow desirable range
- Synthesized and released in response to: Hormonal stimuli, neural stimuli, humoral stim
How does humoral stimuli influence hormone release
- secretions of hormones in direct response to changing blood levels of ions and nutrients
ex: concentration of calcium ions in blood (reg release of parathyroid formone)
How does neural stimuli influence hormone release
- nerve fibers stim hormone release
- innervation thoruhg spinal chord
ex: preganglioninc SNS fibers stimulate adrenal medulla cells to release catecholamines
How does hormonal stimuli influence hormone release
- from tropic hormones: one hormone that alters the release of another
- tropic hormones secreted by hypothalamus to stim anterior pituitary galnd to secrete hormones that stimulate other endocrine glands
What are teh 3 types of hormones
- Eicosanoids: leukotrienes and prstaglandind (not a true hormone, more autocrine and paracrine function)
- Amino acid based; amines, thyroxine, peptides and protein hormones
- Steroids: gonadal and adrenocortical
why are eicosanoids relevant for therapeutics
- form thomboxanes in platelets and prostaglandins in cells
- > pathway of NSAIDs
describe the eicosanoid pathway
- formation of prostaglandins: induce labour, vasodilation, pain, pyretic
- formation of prostacylcins: inhibit platelet aggregation, vasodilation
- free arachidonic acid converted to PGG via COX-1 and COX-2
- can inhibt COX2 w/ VIOXX
describe the leukotriene pathway
conversation of arachidonic acid to LTE (involves in asthma inflammation) and LTB (extravascularization
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