Endocrine Flashcards
(43 cards)
Hormone
chem released by cell in one part of body that affects cells in other parts of organism
endocrine hormone
hormones secreted directly into BS
neuroendocrine hormone
hormones produced by neurons secreted into BS
exocrine hormone
hormones secreted directly into a duct rather than BS
Autocrine and paracrine
autocrine
-chems that excert effects on same cells
paracrine
-locally acting chems affect nearby cells
NOT HORMONES - hormones are long dist chem sigs
2 mechs hormones affect cell activity
1) second messengers
- regulatory G-proteins tend to be AA based hormones
2) Direct gene activation
- tend be steroid hormones
Hormones action
one or more of:
- alter PM perm
- stim protein synth
- activate/deac enz systems
- induce secretory activity
- stimulate mitosis
target cell specificity
target cells must have specific receptors to which hormone binds
ACTH receptors only on certain cells of adrenal cortex
thyroxin receptors on nearly all cells in body
Target cell activation (3 factors)
-upreg v downreg
1) blood levels of hormone
2) relative number of receptors on target cell
3) affinity of receptors for hormone
upregulation - target cells make more receptors in response to hormone
downregulation - target cells lose receptors in response to hormone
forms of hormones circulating in blood
free or bound
- steroids and thyroid hormones are bound to plasma proteins
- most of rest are unencumbered (hydrophillic)
Concentrations of hormone in blood reflect (3)
rate of release
speed of inactivation
removal from body
how are hormones removed
degrading enzymes
kidney and liver enzymes
length last thyroid>polypeptides>proteins>steroids
3 types of hormone interaction
permissiveness
synergism
antagonism
permissiveness
hormone cant exert its effect without another hormone being present
synergism
more than one type of hormone produces same effect on target cell
antagonism
one or more hormones oppose the action of another
blood levels of hormones
-control and vary
controlled by negative feedback system
vary only within narrow desirable range
hormones
synthesized and released in response to
humoral stimuli
neural stimuli
hormonal stimuli
humoral stimuli
secretion of hormones in response to changing blood levels of ions and nutrients (parathyroid glands)
neural stimuli
nerve stimuli trigger hormone release (adrenal medulla)
hormonal stimuli
release hormones in response to hormones released by other endocrine organs
-tropic hormones = hormones that alter secretion of other hormones
Nervous system modulation
NS modifies stimulation of endocrine glands and their neg feedback systems
-can override normal endocrine controls
ex. blood glucose maintained by endocrine
-hypothalamus and SNS activation ramp up blood glucose levels
+override control by insulin and glucagon
three types of hormones
1) Eicosanoids - leukotrienes and prostaglandins (not ture hormones)
2) AA based - Amines, thyroxine, peptides and protein hormones
3) steroids - gonadal and adrenocortical hormones
Eicosanoids
short lived biologically active lipids with autocrine and paracrine activity
derived from arachadonic acid
aa produced by alpha-linolenic acid (omega 3 FA) acid and linoleic acid (omega 6 FA)
