Introduction to Endocrinology Flashcards
endocrine glands secrete via WHAT
exocrine glands secrete via WHAT
what are the three main types of hormones? (3)
endocrine glands secrete via bloodstream
exocrine glands secrete via duct
types of hormones:
- peptides (insulin)
- biological amines (thyroid hormones, dopamine)
- steroids (cortisol, vitamin D). produced from cholesterol
how do peptides, biological amines and steroids become activated?
undergo peptide hormone processing: preproX -> preX -> active X (e.g. insulin / PTH)
biological amines: also undergo metabolism to be activated
steroids: metabolised from cholesterol. get interchanged under effect of different streroidgenic ezymes
where do u find hormone receptors (3)
what are
- nucleus (typically steroid hormones)
- cytoplasm
- plasma membrane
what are the effect of nucleus hormone receptors?
explain how thryoid hormone receptor
- nucleus hormone receptors usually cause up / down regulation of gene transcription
thryoid hormone receptor
- thyroid binds to homodimer receptor
- causes conformational change in homodimer receptor: falls apart and recruits retinoic acid r (creating heterodimer) & coA
- transcription activated
how many transmembrane domains to GPCRs have?
general overview of how GPRCs work?
what is effect of hormone binding to GCPR in endocrine cells ?(3)
- GPCRs have 7 transmembrane domains
- cause conformational change on ligand binding -> interacts with second messengers (cAMP, PIP3, DAG)
effect of hormone binding to GCPR in endocrine cells
- increase all of processes that lead to hormone production
- causes release of hormone
- endocrine cells will multiply
what type of receptor is used for insulin?
how work ? v general
- *tyrosine kinase receptor:**
- leads to autophosphorylation of Tyr residues
- downstream signallong pathways lead to altered gene experssion or enzyme upregulation
how how hormones complex?
- single hormones have multiple effects
- multiple hormones with shared effects
- different hormones are able to recognise the same receptor
adaptations of endocrine organs? (3)
- high vasculature (bc secrete into blood)
- cells in the gland are very close to capillaries
- interact with own organ first e.g. in adrenal gland: hormones from cortex can see tissues in the medulla first -> to influence own response of organ
how is the pituitary gland split up? (2)
what are both parts controlled by?
anterior pituitary (aka adenohypophysis): ectodermal origin
posterior pituitary (neuohypophysis): neural origin
both controlled by hypothalamus
what does anterior pituitary gland control / cause release of? (5)
posterior pit ? (2)
- *anterior pituitary gland:**
- ACTH (causes cortisol production from adrenal gland)
- growth hormone (muscle)
- TSH - thyroid stimulating hormone (causes thyroid hormones to be released from thyroid)
- LH & LSH (men & women)
- prolactin (milk production)
- *posterior pit. gland:**
- Oxytocin (milk release when suckling)
- ADH
how does hypothalamus communicate with the anterior pit. gland? and posterior pit gland?
- hypothalamic hormone binds to anterior pituitary cell target (all are stimulatory except Dopamine which is inhibitory) via portal system
- causes release of anterior pituitary hormone - releaed into blood
- hypothalamus have long axons that cause release of posterior pituitary hormones (ADH and oxytocin)
which are the only two hormones that are released frm posterior pituitary gland?
ADH
Oxytocin
what is the hypothalamic-pituitary-adrenal axis (HPA axis)
how is it controlled? (3)
- CRH (corticotropin releasing hormone) from hypo causes release of ACTH from anterior pituitary gland; causes release of cortisol from adrenal gland
controlled by:
- *- long loop: cortisol controls this system via negative feedback on CRH (**more cortisol released, causes inhibition of more cortisol)
- short loop: ACTH causes negative feedback on CRH
- ultrashort loop: ACTH feedbacks back itself & inhibits.
Adrenal gland has different cells: ZG, ZF and ZR that all secrete different hormones
how do u produce many different hormones from same organ?
- different enzymes expressed in the different zones (e.g. ZG/ ZF/ ZR will express different horomones) - causes cholerestrol to be turned into different things
what type of hormones are thyroid hormones?
produced from what?
what is active / inactive names?
how does it circulate around body?
biological amines - produced from tyrosine
T4 (inactive) is produced by thyroid gland -> converted to T3 to be active (via deiodinise enzyme)
circulates as T3, but attached to thryoid binding globulin
main role of thryoid hormones? (1)
how controlled?
- negative feedback - how? (1)
- how else (4)
- increases metabolic rate
- negative feedback control: T3 inhibits pituitary release of TSH
- local control mechanism:
i) deiodinase expression
ii) thyroid hormone uptake transporter expression
iii) thyroid hormone receptor expression
iv) release from thyroid binding globulin
how does pit. gland control FSH & LH hormone release?
why is it more complex in women then men?
hypothalamic hormones: GnRH + kisspeptin
regulate release of: FSH and LH from pituitary.
FSH & LH cause sex steroid release (testosterone / oestrogen) , ovulation, spermatogenesis.
in women: estradiol +ve and -ve feedback depends on stage of menstruation
growth hormone (GH) mechanism?
caused from a release of WHAT in hypothalamus?
direct and indirect effects of GH?
inhibited by?
- hypothalamus: releases growth hormone releasing hormone (GHRH)
- causes release of GH from _anterior pit.
direct effects:_
- growth of muscle and bone tissue
i_ndirect effects:_ causes release of IFG-1 (insulin-like growth factor - similar to GH) from liver
- acts on same times as above
negative feedback occurs
somatostatin (SS) has inhibitory effect.
which hormone is released when have hypocalcemia?
what is it effects? (3)
what is 1. inhibited by?
fall in calcium: PTH (parathryoid hormone) rises - restores calcium back to normal by:
- Increased renal Ca++ reabsorption.
- Increased bone Ca++ release.
- Increased gut absorption via release of vitamin D (1,25vitD).
The release if PTH is inhibited by raised Ca++ levels.
where is endocrine fucntion of pancreas located?
islets of langerhans
what does aldosterone do? (3)
aldosterone has two different roles:
- restores BP, reabsorbed salt & water lvls (not excrete as much)
- restores K loss !
(two totally differnet systems! )
what does renin cause to occur?
renin initiates RAAs system - release of aldosterone
in response to hypotension: renin released:
- renin converts angiotensin -> ANG1
- ANG1 converted to ANGII by ACE (from lungs)
- ANG II -> direct vasoconstriction + binding to ANG II receptors in ZG -> to produce aldosterone:
i) Aldosterone -> vasoconstriction + remodelling - (inflammation in heart + vasculature).
ii) aldosterone -> ‘sodium savour’ - Na reabsorption + water reabsorption -> Have to exchange K+ at the ENAC channels on the distal tubule. Aldosterone release triggered by RAAS and high serum K+ levels.
what are the two differing roles of ADH :)
ADH:
- regulates osmolality of blood serum (increases reabsorbtion & causes dilution of blood serum)
- vasoconstriction of arterial BP
