Body Fluid Homeostasis Flashcards
Name some hormones involved with body fluid homeostasis
vasopressin, aldosterone, renin angiotensin
What is vasopressin
anti-diuretic hormone
What releases vasopressin
posterior pituitary gland
What releases vasopressin into the capillaries
neuro-secretory neurons in the hypothalamus
What is the function of vasopressin
regulate body fluid osmolality, conserve water
Describe the relationship between body fluid osmolality and vasopressin
if body fluid osmolality increases - vasopressin release increases
Where are hypothalamic osmoreceptors located
supra-optic and paraventricular nuclei of hypothalamus
What stimulates hypothalamic osmoreceptors
increase in osmolality
What does activation of the hypothalamic osmoreceptors cause
generation of AP in neuro-secretory neurons - vasopressin release
What causes increased release of vasopressin
increased osmolality plasma, solute ingestion, water deficiency, MDMA
What causes decreased release of vasopressin
decreased osmolality plasma, excessive fluid ingestion, alcohol
What channels does vasopressin act on
AQP2
What is the effect of vasopressin
fall in body fluid osmolality, increased reabsorption of water
What is the main symptom of diabetes insipidus
large amounts of dilute urine produced
What is the cause of central diabetes insipidus
dont release vasopressin
Where is the defect in central diabetes insipidus
neuro-secretory neurons - dont function properly
How is central diabetes insipidus treated
nasal spray containing vasopressin
What is the cause of nephrogenic diabetes insipidus
no response to vasopressin
Where is the defect in nephrogenic diabetes insipidus
defect in V2 receptor or mutations in gene for AQP2
What releases aldosterone
outer layer zona glomerulosa of adrenal gland
What is aldosterone
mineralocorticoid
What is the function of aldosterone
regulates mineral content of the body
What is aldosterone released in response to
rise in plasma potassium, decrease in ECF volume
What does aldosterone act on
distal tubule, collecting duct - principal and alpha cells
What is the effect of aldosterone
increases reabsorption of sodium and water, increased secretion of potassium and hydrogen
TRUE or FALSE - Aldosterone is membrane permeable as its a steroid
TRUE
What does aldosterone bind to
cytosolic receptor
What does aldosterone stimulate
synthesis of ENaC
What is the difference in the way vasopressin and aldosterone work
vasopressin - non genomic, aldosterone - genomic
What does aldosterone increase
H+ and K+ secretion
Which hormone has the slower response - vasopressin or aldosterone
aldosterone
What is the NET effect of aldosterone
decrease plasma K+ and H+, increase ECF volume
Why do Liddle’s patients exhibit hypertension
high rate of Na+ reabsorption across principal cells
What is suppressed in Liddle’s syndrome
aldosterone release
What are the characteristics of pseudohypoaldosteronism
lost ability to respond to aldosterone
What does the renin-angiotensin system regulate
body fluid volume, plasma Na+, plasma K+
Where is renin released from
juxtaglomerular apparatus
What do macula densa cells monitor
changes in tubular fluid
What do macula densa cells send signalling molecules to
afferent arteriole
What stimulates the release of renin
sympathetic nervous system
What is the source of renin
kidney
What does angiotensin II cause
release of aldosterone, vasoconstriction, increased BP, increased plasma sodium
What do ACE inhibitors cause
vasodilation, reduction of aldosterone
What is the NET effect of vasopressin increase
increased water reabsorption and ECFV, decreased osmolality,
What is the NET effect of a decrease in aldosterone
increased water and sodium loss, decreased ECFV
