Endocrinology and Metabolism

Question 1

what 4 things does the endocrine system control?

Answer 1

1) development and growth
2) energy regulation (storage and mobilization)
3) internal homeostasis (fluids, regulating body temp, ions)
4) reproduction (sex, pregnancy, lactation)

Question 2

what does endocrine mean?

Answer 2

hormones travel through the blood stream

Question 3

what does paracrine mean?

Answer 3

hormones travel to neighbouring cells in same organ

Question 4

what does autocrine mean?

Answer 4

acts on secreting cell (ie: acts on itself)

Question 5

what glands are endocrine only? (4pts)

Answer 5

pituitary
parathyroid
thyroid
adrenal

Question 6

what glands/organs have a mixed function (as in, are more than just endocrine or paracrine)? (11pts)

Answer 6

hypothalamus
thymus
heart
stomach
pancreas
duodenum
kidney
skin
ovaries
testes
placenta

Question 7

what are the 3 chemical classifications of hormones?

Answer 7

amino hormones
peptide and protein hormones
steroid hormones

Question 8

what are amino hormones derived from?

Answer 8

tyrosine

Question 9

what are some examples of amino hormones?

Answer 9

catecholamines
epinephrine/norepinephrine
thyroid hormones (thyroxine (T4), triolodothyronine (T3))

Question 10

how are peptide/protein hormones made?

Answer 10

encoded in genes, which is a Ca2+ dependent event (exocytosis)
translated in rough ER, processed in Golgi, stored in secretory vehicles

Question 11

what is an example of peptide/protein hormones?

Answer 11

insulin

Question 12

what are steroid hormones derived from?

Answer 12

cholesterol

Question 13

what are some examples of steroid hormones?

Answer 13

glucocorticoids
mineralocorticoids
androgens
estrogens
progestins

Question 14

which hormone groups can easily cross the membrane and why? which can’t?

Answer 14

protein - hydrophilic (can’t cross)

steroid - lipophilic (can cross)

Question 15

what is the function of steroid-binding globulins?

Answer 15

travel in the blood with steroid hormones

Question 16

what are the 3 main hypothalamic-pituitary axes?

Answer 16

hypo-pit-gonadal axis (HPG)
hypo-pit-adrenal axis (HPA)
hypo-pit-thyroid axis (HPT)

Question 17

how does the hypo-pit-gonadal axis work? (4pts)

Answer 17

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

Question 18

which feedback is less common: negative or positive?

Answer 18

positive

Question 19

when is positive feedback used?

Answer 19

when signal amplification is needed

Question 20

give 2 examples of positive feedback control in the body

Answer 20

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

Question 21

Give 3 examples of metabolic control by hormones in the body

Answer 21

1) 5-alpha reductase: conversion of testosterone to bioactive dihydrotestosterone (DHT)
2) Aromatose: converts testosterone to estrogen
3) Thyroxine (T4) converted to triiodotyronine (T3)

Question 22

what are endocrine rhythms?

Answer 22

rhythmic releases of hormones throughout the day

Question 23

what is the function of endocrine rhythms?

Answer 23

maintains target organ sensitivity and prevents down regulation (loss of sensitivity) of receptors

Question 24

how do hormone receptors work to transmit a signal?

Answer 24

act as allosteric effectors

hormone binding to a specific receptor results in conformational change of receptor that conveys a signal to target cell

Question 25

how do second messengers work?

Answer 25

bind to cell surface receptors releases second messenger molecules inside cell

Question 26

what are some examples of second messengers? (6pts)

Answer 26

cAMP
cGMP
phospholipids
diacylglycerol
inositol triphosphate
Ca2+

Question 27

how does cAMP work as a second messenger?

Answer 27

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

Question 28

how do phospholipids work as as second messenger?

Answer 28

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

Question 29

what happens when insulin binds to receptors as kinases? how is it related to second messenger systems?

Answer 29

causes receptor to dimerise which then undergoes transautophosphorylation
linking protein binds to phosphate group and activates second messenger system