salt and water balance 1

Question 1

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

Answer 1

ensures the body holds onto fluid

Question 2

describe the control of ADH

Answer 2

• 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

Question 3

what causes the release of ADH

Answer 3

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

Question 4

describe non-physiological stimuli to the secretion of ADH

Answer 4

drugs, CNS disorders, pain, stress

Question 5

describe the action of ADH

Answer 5

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

Question 6

what is it called when your ADH levels are constantly low

Answer 6

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

Question 7

describe nephrogenic diabetes insipidus

Answer 7

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

Question 8

describe central diabetes insipidus

Answer 8

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

Question 9

how can you differentiate between diabetes insipidus central vs nephrogenic

Answer 9

• 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

Question 10

describe syndrome of inappropriate ADH secretion (SIADH)

Answer 10

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

Question 11

what factors promote renin release from granular cells

Answer 11

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

Question 12

describe the effects of angiotensin 2 binding to AT1 receptors

Answer 12

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

Question 13

ways of blocking angiotensin 2 effects

Answer 13

ACE inhibitors