Basics of Endocrinology: PP 1 Flashcards
endocrine release mechanism
products released INTO the blood (ex: pancreas-insulin)
intracrine release mechanism
products released WITHIN OWN CELL
autocrine release mechanism
products released onto SECRETING CELL
paracrine release mechanism
products released onto ADJACENT CELL
exocrine release mechanism
products released via DUCTS (ex: sweat glands, salivary glands, mammary cells, pancreas w/ digestive juices)
ectocrine release mechanism
products released into the ENVIRONMENT (ex: pheromones)
chemical messenger
substance produced in a cell that affects the functions of other cells
hormone
a chemical messenger that’s released into the bloodstream/tissue fluid system that affects the function of target cells
neurotransmitter
a chemical messenger that acts on the neural synapse
peptide hormone
- a hormone composed of a sequences of amino acids
- polar and HYDROPHILIC (lipid phobic)
Steps to peptide protein synthesis–transcription
(occurs in nucleus)
- INITIATION: RNA polymerase binds to a promoter on DNA
a. this will signal the DNA to unwind - ELONGATION: addition of complementary RNA base pairs to unwound DNA
- TERMINATION: RNA polymerase crosses a “stop” (termination) sequence at DNA
a. mRNA detaches from the DNA - mRNA transported from nucleus–>cytoplasm–> ribosomes, where it will undergo translation
Steps to peptide protein synthesis–translation
(occurs in ribosomes)
- INITIATION: construction of initiation complex so translation can begin
a. tRNA attaches to small ribosomal unit
b. complex will bind to DNA and scan to find the start codon, bind to start codon
c. large ribosomal subunit joins to form initiation complex - ELONGATION: amino acids brought to ribosomes by tRNA’s–> linked to form a chain (this is the preprohormone)
- TERMINATION: stop codon–> release of preprohormone from complex
Preprohormone–> hormone steps
- signal peptide removed in the rough ER (preprohormone–> prohormone) by enzymes
- pro hormone passes from the ER to the Golgi via transport vesicles
- secretory vesicles containing enzymes and the pro hormone bud off the golgi
a. enzymes chop the pro hormone into into active peptides and fragments - vesicles release the contents via exocytosis
- hormone moves via the blood circulation: soluble in the blood b/c it is polar and hydrophilic
Peptide hormones: hypothalamus
- CRH
- GnRH
- GnIH
- GHRH
- GHIH
- TRH
Peptide hormones: Anterior Pituitary
- TSH
- FSH
- LH
- GH
- Prolactin
- ACTH
Peptide hormones: Posterior Pituitary
- Vasopressin
2. Oxytocin
hypophysiotropic hypogonadism
failure to reach sexual maturation; low/absent levels of LH
kisspeptin (kiss1) and hypophysiotropic hypogonadism
- mice without kiss1 gene failed to undergo sexual maturation and had immature sex organs, low gonadotropin levels, and low sex steroid concentrations, infertile
- gonadotropin release can be stimulated with GnRH injection–> suggesting that this problem^ is with GnRH release
Target: Peptide hormones
membrane receptors; affect their targets via secondary messengers
Monoamine Hormones
hormones derived from a single amino acid
- Catecholamines: derived from tyrosine, catechol with amine side group
a. epinephrine, norepinephrine, dopamine
- -^made in the adrenal medulla - Indolamines
a. serotonin, melatonin cycle - Thyroid hormones
a. T3 and T4
Catecholamines
tyrosine–> DOPA–> dopamine–> norepinephrine–> epinephrine
serotonin–> melatonin
tryptophan–(2-step enzymatic reaction to serotonin)–> in darkness, norepinephrine increases cAMP—> increased synthesis of N-acetyltransferase–> N-acetylserotonin–> melatonin
Steroid hormones
- structurally composed of a 4 ring base (3 6-carbon rings and 1-5 carbon ring)
- NONPOLAR and HYDROPHOBIC (aka lipidphilic)
- basic building block= cholesterol
- must bind to a carrier protein to move in the blood
Steroid hormones: adrenal cortex
- mineral corticoids
a. aldosterone - glucocorticoids
a. cortisol
b. corticosterone
c. DHEA - androgens (pregnenolone–> androgens)
- progesterone (progestins precursors to androgens^)
steroid hormones: ovary
- estrogens: estriol, estradiol, estrone
2. progesterone
steroid hormones: testes
- androgens
a. testosterone, dihydrotestosterone, androstenedione
Synthesis of mineral corticoids and glucocorticoids
cholesterol (mitochondria)–> pregnenolone (smooth ER)–> progesterone (mitochondria)–> … (separate pathways)… aldosterone, cortisol
synthesis of androgens and estrogens: pathway
cholesterol (mitochondria)–> pregnenolone (smooth ER)–> progesterone (smooth ER)–> testosterone–> estradiol, estrone, estriol
androgens precursors to all estrogens b/c of AROMATIZATION
aromatization
-conversion of androgens (testosterone) to estrogens via 3 step reaction: hydroxylation, oxidation, and demethylation
lipid based hormones
- prostaglandins: 20 carbon fatty acid skeletons
7 types of hormonal regulation
- physiological by-products generated in response to action
- stimulatory/inhibitory effects of hormones
- positive feedback
- negative feedback
- receptor regulation
a. up-regulation
b. down-regulation - hetero-specific priming
- pulsatile secretion
calcium and parathyroid hormone
ex: parathyroid hormone: when blood levels of calcium decrease, the parathyroid hormone is released leading to an increased concentration of blood calcium to an optimal level, leading to a negative feedback on the parathyroid to stop releasing parathyroid hormone
positive feedback
production of a product stimulations additional hormone production
-hormone–> target tissue–> product–> endo gland–> more hormone…
negative feedback
product feeds back on the source of the hormone to stop hormone production
up-regulation
hormone causes an increase in the production of receptors for that hormone
down-regulation
overproduction of a hormone–> occupation of all available receptor’s so that there is no biological effects
-ex: high insulin–> decrease in number of insulin receptors
heterospecific priming
hormones recegulating receptors of other hormones, so that one hormone induces the production of receptor’s for another hormone
pulsatile secretion
episodic secretion of hormones in bursts/spurts
- benefits? a hormone-free period recovery period allows for receptors to necessarily be replenished–> allow for a biological response
ex: pulsatile secretions of GnRH–> pulsatile secretions of LH–> testosterone–> negative feedback of testosterone on GnRH…
