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Flashcards in salt and water balance 1 Deck (13):

what does ADH do, assuming all other factors are normal?

ensures the body holds onto fluid


describe the control of ADH

- osmoreceptors sense high osmolarity and result in the release of ADH from the posterior pituitary
- a decrease in volume is sensed by the medullary vasomotor center sending inputs to the hypothalamus to release ADH


what causes the release of ADH

- increased osmolality
- decreased volume of the ECF
(greater change in BV needed to release ADH in comparison to osmolality due to sensitivity of receptors)


describe non-physiological stimuli to the secretion of ADH

drugs, CNS disorders, pain, stress


describe the action of ADH

1. increased osmolality
2. osmoreceptors sense change
3. ADH is released
4. ADH binds to V2 receptor on interstitial side
5. aquaporins then inserted on the tubular-lumen side
6. reabsorption of water occurs


what is it called when your ADH levels are constantly low

diabetes insipidus, which is a defect in ADH action or secretion
- central or nephrogenic


describe nephrogenic diabetes insipidus

- collecting tubules unresponsive to ADH
- concentrated urine cannot be produced
- can be caused by common drugs
- less commonly hereditary
- not treatable


describe central diabetes insipidus

- inadequate ADH secreted
- problem with hypothalamus or posterior pituitary
- due to brain injury, tumour or infection
- rarely hereditary
- treated with ADH analogs


how can you differentiate between diabetes insipidus central vs nephrogenic

- measure levels of ADH (absent = central)

- water deprivation test = deprive them of water then give them ADH analog if urine osmolarity doesn't change = nephrogenic


describe syndrome of inappropriate ADH secretion (SIADH)

- plasma ADH levels higher than normal
- commonly due to brain injury
- plasma osmolarity lower than normal
- treatment = restrict patient from consuming water


what factors promote renin release from granular cells

- decreased afferent arteriole pressure
- increased SNS
- decreased macula densa NaCl delivery


describe the effects of angiotensin 2 binding to AT1 receptors

- increased aldosterone
- vasoconstriction
- increased proximal reabsorption of Na+
- increased thirst
- increased ADH release
- decreased renal BF, but maintains GFR


ways of blocking angiotensin 2 effects

ACE inhibitors