Endocrinology and Metabolism Flashcards
what 4 things does the endocrine system control?
1) development and growth
2) energy regulation (storage and mobilization)
3) internal homeostasis (fluids, regulating body temp, ions)
4) reproduction (sex, pregnancy, lactation)
what does endocrine mean?
hormones travel through the blood stream
what does paracrine mean?
hormones travel to neighbouring cells in same organ
what does autocrine mean?
acts on secreting cell (ie: acts on itself)
what glands are endocrine only? (4pts)
pituitary
parathyroid
thyroid
adrenal
what glands/organs have a mixed function (as in, are more than just endocrine or paracrine)? (11pts)
hypothalamus thymus heart stomach pancreas duodenum kidney skin ovaries testes placenta
what are the 3 chemical classifications of hormones?
amino hormones
peptide and protein hormones
steroid hormones
what are amino hormones derived from?
tyrosine
what are some examples of amino hormones?
catecholamines
epinephrine/norepinephrine
thyroid hormones (thyroxine (T4), triolodothyronine (T3))
how are peptide/protein hormones made?
encoded in genes, which is a Ca2+ dependent event (exocytosis)
translated in rough ER, processed in Golgi, stored in secretory vehicles
what is an example of peptide/protein hormones?
insulin
what are steroid hormones derived from?
cholesterol
what are some examples of steroid hormones?
glucocorticoids mineralocorticoids androgens estrogens progestins
which hormone groups can easily cross the membrane and why? which can’t?
protein - hydrophilic (can’t cross)
steroid - lipophilic (can cross)
what is the function of steroid-binding globulins?
travel in the blood with steroid hormones
what are the 3 main hypothalamic-pituitary axes?
hypo-pit-gonadal axis (HPG)
hypo-pit-adrenal axis (HPA)
hypo-pit-thyroid axis (HPT)
how does the hypo-pit-gonadal axis work? (4pts)
1) hypo releases gonadotropin-releasing hormone (GnRH)
2) GnRH acts on pit, releasing follicle stimulating hormone (FSH) and luteinizing hormone (LH)
3) FSH and LH act on gonads, releasing either testosterone and inhibin (males) or estrogen, progesterone, and inhibin (females)
4) hormones released by gonads act either on pit (short) or hypo (long) to stop hormone production
which feedback is less common: negative or positive?
positive
when is positive feedback used?
when signal amplification is needed
give 2 examples of positive feedback control in the body
1) mid-cycle surge of LH and FSH stimulated by high levels of estrogen to achieve ovulation
2) oxytocin (made in hypo and released by post. pit) during partuition and suckling
Give 3 examples of metabolic control by hormones in the body
1) 5-alpha reductase: conversion of testosterone to bioactive dihydrotestosterone (DHT)
2) Aromatose: converts testosterone to estrogen
3) Thyroxine (T4) converted to triiodotyronine (T3)
what are endocrine rhythms?
rhythmic releases of hormones throughout the day
what is the function of endocrine rhythms?
maintains target organ sensitivity and prevents down regulation (loss of sensitivity) of receptors
how do hormone receptors work to transmit a signal?
act as allosteric effectors
hormone binding to a specific receptor results in conformational change of receptor that conveys a signal to target cell
how do second messengers work?
bind to cell surface receptors releases second messenger molecules inside cell
what are some examples of second messengers? (6pts)
cAMP cGMP phospholipids diacylglycerol inositol triphosphate Ca2+
how does cAMP work as a second messenger?
activated receptor (with alpha, beta, and gamma parts) stimulates adenylate cyclase adenylate cyclase converts ATP to cAMP which goes to activate other proteins that alter cellular function
how do phospholipids work as as second messenger?
stimulated receptor activates phospholipase C
phospholipase C converts PIP2 to DAG and IP3
DAG activates other enzymes and IP3 causes Ca release, ultimately altering cell function
what happens when insulin binds to receptors as kinases? how is it related to second messenger systems?
causes receptor to dimerise which then undergoes transautophosphorylation
linking protein binds to phosphate group and activates second messenger system
