secreted by endocrine cells, chemical signal, circulates in bodily fluids, regulates behavior of other cells.
have a receptor that binds the specific hormone
enters blood vessels, circulated across entire body
limited distribution, stay in interstitial fluids or very localized blood vessels. Paracrine and autocrine.
endocrine and target cells are near each other
endocrine cells has receptors for its own hormone self regulatory
mechanisms of hormonal action
effect of hormone on target cell
open/close ion channel
changes membrane potential (relaxation or contraction of muscle)
change behavior of enzymes inside target cell
changes cell metabolism, changes secretion
change genetic expression of target cell
express or supress specific genes
secrete hormones into the interstitial fluid surrounding the secretory cells rather than into ducts.