LECTURE - Neuroendocrinology Flashcards
the master gland
pituitary gland
how does the brain sense the homeostatic status of the body?
hypothalamus- pituitary axis
hormones used for signalling can be
small molecules or peptides
negative feedback loop
signalling turned off by lower levels of the system
hypothalamus-pituitary axis four levels of organizations
primary = endocrine gland secondary = pituitary tertiary = hypothalamus quaternary = target tissue
- produces both tropic and non-tropic hormones *
non-tropic vs tropic hormones
- non-tropic = pituitary/hypothalamus straight to target tissue
- tropic = from hypothalamus/pituitary to endocrine gland to tissue of interest = negative feedback exists
what links the hypothalamus and pituitary gland?
nerve endings and blood vessels
- hypothalamic-pituitary portal system
does the posterior pituitary release tropic or non-tropic hormones?
non-tropic
- do not signal via an endocrine gland
= have direct effect on target tissues
- hormones reach target organs via blood circulation
- ADH => kidney
- oxytocin => uterus and mammary glands
oxytocin
- 9 amino acid peptide; isoleucine (Ile)
- made in hypothalamus
- stored in posterior pituitary and released in blood when needed
- uterine contraction during labour and milk secretion during breastfeeding
- not tested for clinically
- male function unknown
synthetic analog to induce labour
pitocin = similar to oxytocin
antidiuretic hormone
- 9 amino acid peptide similar to oxy; but phenylalanine and arginine
- water reabsorption in kidney
- vasoconstriction
- major stimuli = increase in serum osmolality (high conctn in solutes)
- OR decrease in BP (hypotension)
challenges in the lab for measuring ADH
- rapidly cleared from the body
- poor in vitro stability
- low plasma conctn (pmol/L)
surrogate marker for ADH
copeptin
copeptin
- part of the protein complex comprising ADH
- produced in equimolar amounts as ADH
increase in osmotic pressure or decrease in water =
hypothalamus is stimulated and initiates posterior pit to release ADH => blood => kidneys = reabsorb water
- feedback mechanism; if enough = brain stops!
ADH causes the kidneys to:
- reabsorb water
- decrease serum sodium concentration
_____ blood pressure would signal to the hypothalamus/pituitary to release ADH
low
- low BP and low blood volume
- increases vasoconstriction
impaired ADH results in this disorder
diabetes insipidus
psychogenic polydipsia
- excessvive water intake
- psychological
- obsessive compulsion to drink too much H2O
- ADH = decrease
- urine volume = increase
- urine osm = decrease
- seum osm = decrease
central diabetes insipidus
- ADH not produced; a deficiency
- hypothalamus or pituitary is affected
> could be due to trauma, oraffected hypothalamus function - ADH = decrease
- urine volume = increase
- urine osm = decrease
- seum osm = increase (patient not drinking lots of water)
nephrogenic diabetes insipidus
- ADH not detected; present but no effects
- kidney is affected system; lithium toxicity?
- ADH = increased
- urine volume = increased
- urine osm = decreased
- seum osm = increased
DDAVP
synthetic ADH used in water deprivation test
what is dynamic testing?
testing the patient’s response to certain hormones (something is induced)
- ex: water deprivation test
we know what is the body’s natural response, if patient results are abnormal = defect is evident
increased ADH action
- too much ADH produced
- syndrome of inappropriate ADH (SIADH)
- ADH is higher than it should be
- urine volume = decreased
- urine osmolality = increased
- serum osmolality = decreased
dynamic tetsig to diagnose SIADH
- water loading test
- overnight fast => lots of water in short time period
=> measure urine output throughout
=> excreted H2O <70% of consumed water = SIADH
what might water loaing test lead to?
life-threatening hyponatremia
= rarely performed
water deprivation test
- fasting = no food or water for 8-10 hrs
- measure urine and serum osm throughout
- if Osm urine is greater than 1000 mOsm = NOT DI
- is >300 Osm serum = give DDAVP
- decrease in urine volume and increases in Osm urine = central DI
- no change = nephrogenic DI
this links the CNS and endocrine glands
neuroendocrine system
T or F. posterior hormones dont signal via endocrine glands but rather have a direct effect on target tissues
t!
T or F. blood pressur and serum osm are detected by hypothalamus
T!
ADH acts in the kidney at the _________ _____ and cause reabsorption of water
collecting ducts
