hormones
have specific rates and rythms of secretion. 3 patternns:
diurnal
pusitile and cyclic
levels of a circulating substrate
feedback systems, eith positive or negative
affect only target cells
are excreted by kidneys or deactivate by liver or cellular mechani
regulation of hormone release
in response to altered cellular environment.
mechanisms
chemical factors
endocrine factors
neural control
structural categories of hormones
water vs lipid soluable
water soluable hormones
peptides GH, Insulin, Leptin, PTH Prolactin
Glycoproteins FHS LH
Polypeptides ACTH ADH calcitonin endorphins glucagon oxytocin
Amines epi, norepi
lipid soluable hormones
THyroxine, T3T4
steroids estrogens cortisol, mineralcorticoids, eg alsosterone progestins , testosterone
Arachadonic Acid derivitives eg leukotrienes prostaglandins prostcylclins thromboxanes
Hormones transport
circulatory system
peptides in free form
lipds are bound via a carrier molecule.
[ ] of binding proteins affect amount of free hormone. Only free hormones can signal a cell.
up regulation
caused by low # of receptors
down regulation
caused by high # of hormone to decrease the signal strength
hormone receptors
located in: (Water soluable) plasma membrane or (lipid )intracellular or nuclear compartment of target cell
first messenger
secreted into blodtream and takes it to target cell
second messenger
the signal then generates a second molecule eg cAMP cGMP calcium inositol triphosphate IP3
this takes the signal into the cell and mediates its effect on target cell eg. sysnthesis, transport or cellular growth
Steroid hormone receptors
synthesized from Cholesterol, eg androgens estrogens progestins glucocorticoids mineralocorticoids thryoid hormones vitamin D retinoid, small lipophilic hydrophobic and can cross the cellular membrane by simple diffusion.
HPA hypothalamic Pituitary System
neuroendocrine system
hypothalamus located at the base of the brain. connected to the pituitary by the pituitary stalk. the anterior pituitary is connected via hypophysial portal blood vessels
posterior connected via the hypothalamophypophysial tract.
pituitary gland
found in the sella turcica of the sphenoid
anterior adenohypophysis
posterior or neurohypophysis
differ in their embryonic origins cells types and functional relationship to the hypothalamus
anterior pituitary
75% of total pituitray. 3 regions:
pars distalis major: source of hormones
pars tuberalis think layer on ant and lat stalk
pars intermedialis disappears in the adult,
2 cell types of aAnt Pit.
chromophobes non secretory
chromophils: secretory
7 types of chromophils
regulated by :hypothalamic peptide hormones
feedback effects of hormones secreted by target glans
direct effects of pther mediating neurotransmitters
hypothalamic hormones
Thryotropin releasing hormone TRH
Gonadotropin Releasing Hormone GRH
Growth Hormone releaseing hormone GHRH
Corticotropin releasing hormone CRH
Substance P
prolactin-inhibiting factor PIF, dopamine
Prolactin releasing factor
Adrenocorticotropic hormone
corticotropic target: adrenal cortex
increased steroidgenesis cortisol and androgenic hormones
posterior pit.
Antidiuretic Hormone aka vasopressin, and Oxytocin
ADH
controls serum osmolality
increwases permeability of the renal tubules to water
vasoconstriction in high doses
regulation of some nervous system functions
oxytocin
uterine contraction and lactation in women
sperm motiility in men
also an antidiuretic effect
Thyroid gland
2 lobes contain follicles which secrete thyroid hormone,
C cells secrete calcitonin and somatostatin
regulation of thyroid hormone
complex, and involves the hypothalamus ant. pit, thyroid and biochemicals
Thyroid hormone TH
regulated by thyroid releasing hormone TRH through a negative feedback system that involves the ant pit and hypothalamus
TSH
thyroid stimulating hormone synthesized ans tored in the ant pit. stimulates secretion of TH by activating intracellular processes, including iodine uptake
TH acts on
thyroid, ant pit, and the median emmenence to regulate further TH production
synthesis of TH is dependent on
glycoprotein thyroglobulin TG which contains tyrosine. tyrosine combines with iodine to form T4 and T3.
T3 T4
T3 triiodothyronine
T4 thryoxine
bound by carrier molecules which store the hormones and provide a buffer for rapid changes in the hormone levels. free form is the active form
function of TH
alter protein synthesis, metabolic effects on proteins, carbs lipids and vitamins. TH also affects heat production and cardiac function
parathyroid glands
paired, behind upper and lower poles of the thyroid. PTH important calcium regulator
PTH secretion
regulated by levels of ionized ca+ in teh plasma and by cAMP within the cell
PTH effect
causes bone breakdown and resorption. in kidneyincr. reabsorption of calcium and decreases reabsorption of phosphorus and bicarbonate
islets of Langerhans)
carbohydrate metabolism
consist of alpha glucaogon. inverse to blood glucose levels
beta preproinsulin
delta somatostatin which inhibits glucagon and insulin secretion
F cells pancreatic polypeptide
insulin
regulates blood glucose [ ] abd iverall metabolism of fat protein and carbs
adrenal gland
above the kidneys.
adrenal medulla- catecholamines
cortex- steroid hormones from cholesterol: glucocorticoids mineralocorticoids adrenal androgens and estrogens
glucocorticoids
carbohydrate metabolism by increaseing blood glucose [ ] through gluconeogenesis in teh liver and by decreasing use of glucose.
inhibit immune and inflammatory responses.
cortisol
most potent glucocorticoid.
neede for the maintenence of life ad for protection from stress. regulation by the hypothalamus and ant pit
Cortisol secretion
relatd to ACTH which is stimulated by corticotropic releasing hormone CRH. ACTH binds with receptors of the adrenal cotrex which activates cAMP that leads to cortisol release
aldosterone
most potenet of the naturally orrucirn mineralocorticoids.
conserve sodium
regulated by the renin angiotensin system and by serum sodium [ ]
binds to site on nuclue altering protein production within cell. esp kidney to cause Na+ reabsoption and H+ excret
Adrenal Cortex
makes androgens and estrogens
adrenal medulla
secretes catecholamines epi and norepi.
epi is 10x stronger than norepi
release is stimulated by sympathetic nervous system ACTH and glucocorticoids
catecholamines
bind with varies targets and uptaken by neurons or excreted by kidneys
cause hyperglycemia, flight or fight and immune suppression
response to stressors
activation of the sympathetic dividion of the ANS
activation of the endocrine system
other hormones release in response to stress
GH prolactin testosterone ADH and insulin
sympathoadrenal axis
the link between the sympathetic nervous system and the adrenal medulla
geriatric consideration in endocrine and
atrophy and weight loss with vascular changes
decreased secretion and clearance of hormones
variable change in receptor binding and intracellular responses
pit.