endocrine system overview

*all the hormones have their own set*

endocrine communication

hormones diffuse into blood and alter function of target organs

paracrine communication

hormones diffuse into local extracellular fluid to alter function of neighboring cells

autocrine communication

hormones diffuse into local extracellular fluid and alters function of the cell that released it

receptor

membrane bound or intracellular protein with a specific shape to bind a hormone

specificity

only specific hormones bind to specific receptors

affinity

bond strength between the hormone and receptor

hormonal stimuli

a hormone stimulates/inhibits the release of another hormone

neural stimuli

a nervous system structure stimulates release

humoral stimuli

something dissolved into the blood (that is not a hormone) stimulates release

steroid hormones

• hydrophobic

• cannot float in blood without aid

• can enter a cell

• require an intracellular receptor

• long lasting

• degraded by intracellular enzymes

amino acid based hormones

• can dissolve in blood

• cannot enter a cell

• use a membrane bound receptor

• short duration

• degraded by liver/ kidneys

chaperone molecules

must surround steroid hormones in order to allos transport through blood

hypophyseal portal tract

capillary bed shared by the hypothalamus and anterior pituitary

anterior pituitary

stimulated by hormones

posterior pituitary

stimulated by neurons

synergism

two hormones work together and have an additive effect

antagonism

two hormones perform the opposite function

permissiveness

one hormone gives another permission to operate