autocrine
chemical messenger that, when secreted, works only within the cell that produces it
calmodulin
intercellular protein that binds calcium
circadian rhythm
fluctuations that repeat multiple times due to a set change in time, such as the change from light to dark
down regulation
cellular reduction in the number of hormone receptors to a molecule, which lessens the cell's reaction to the molecule
exocytosis
the bulk transport of large molecules across the cell membrane
G-protein
intermediate molecule that, when activated during the binding of a receptor, turns on a secondary messenger system
half-life
amount of time it takes for half of a hormone concentration to be removed from the blood
hormonal stimulus
release of one hormone in response to another produced by a different organ
hormone
chemical secreted by an endocrine gland that targets a particular cell to produce a response
humoral stimulus
release of a hormone due to a change in the ion and nutrient composition of the blood
hydrophilic
able to tolerate being close to or in water
hypophyseal portal system
connection of capillaries that exists between the hypothalamus and the anterior pituitary gland that serves to deliver anterior pituitary hormones
lipophilic
able to tolerate being close to or in lipids
negative feedback
system used by the body to counteract a change
neural stimulus
signal sent by nerves to release hormones
paracrine
chemical messenger that affects the cells in its immediate area
synapse
space found between two nerve cells, across which neurotransmitters travel
target cell
cell that is impacted by a particular hormone