Physiology 5 - Endocrine Control of Fluid Volume Flashcards
Hormonal control of salt and water balance only affects which parts of the nephron?
Distal convoluted tubule and collecting ducts
What is the role of ADH?
Increase water reabsorption
What is the role of aldosterone?
Increase sodium reabsorption and potassium secretion
Aldosterone results in increased secretion and hence excretion of which two ions?
Potassium and hydrogen
What is the role of ANP?
Decrease sodium reabsorption
Parathyroid hormone is responsible for increasing the reabsorption of which ion?
Calcium
Parathyroid hormone is responsible for decreasing the reabsorption of which ion?
Phosphate
In the late portion of the distal tubule, which ions are reabsorbed in the basal state?
Calcium, sodium, potassium
In the late portion of the distal tubule, which ion is secreted in the basal state?
Hydrogen
In the late portion of the distal tubule, what change occurs in reabsorption/secretion in response to aldosterone?
Potassium is secreted, not reabsorbed
Where is ADH formed?
Hypothalamus
Where is ADH secreted from?
Posterior pituitary gland
What is the half life of ADH?
10-15 minutes
What is the most important stimulus for ADH release?
Hypothalamic osmoreceptors in response to increased plasma osmolarity
Is ADH secreted in response to dehydration or over-hydration?
Dehydration
Is ADH secreted in response to a high or low plasma osmolarity?
High
Which receptor does ADH bind to on the basolateral membrane of the distal tubule and late collecting duct?
Vasopressin 2 receptor
Binding of ADH to its receptor on the cells of the distal tubule/collecting duct has what effect on the cells?
Increased permeability to water
How does binding of ADH cause the cells of the distal tubules/collecting ducts to become more permeable to water?
Insertion of aquaporins
Does a high ADH concentration cause urine to be hypertonic or hypotonic?
Hypertonic
What happens to the amount of solute excreted in urine in response to ADH?
It is the same as always
What condition occurs in individuals who cannot produce or respond to ADH?
Diabetes insipidus
Nephrogenic diabetes insipidus is very common in individuals who are prescribed which drug long term?
Lithium
What effect does alcohol have on ADH release?
Inhibits
Where is aldosterone secreted from?
Adrenal cortex
What two things activate secretion of aldosterone?
Raised plasma potassium concentration and activation of RAAS
What happens to the plasma volume and blood pressure in response to aldosterone?
Increased
Under normal circumstances, is potassium excreted in the urine?
No
A decrease in plasma sodium promotes the indirect secretion of aldosterone how?
Secretion of renin
When secreted, renin combines with what to form angiotensin I?
Angiotensinogen
Which part of RAAS is responsible for stimulating the adrenal cortex to secrete aldosterone?
Angiotensin II
What are the three factors which cause increased renin release from granular cells?
Low pressure in the afferent arteriole, low sodium concentrations in the tubular fluid, increased sympathetic activity
How does aldosterone allow more sodium to be reabsorbed from the tubular fluid?
Increased number of Na+/K+ ATPase pumps
Where is ANP released from?
Atrial muscle cells
ANP is released in response to what?
Stretch of atrial muscle cells
What effect does ANP have on plasma volume?
Decreased
