sodium kidney balance Flashcards
What is the importance of maintaining salt balance?
The kidneys maintain salt balance in order to maintain extracellular fluid volume constant-
Failure to maintain salt balance results in changes in blood volume
Are there receptors for monitoring plasma sodium concentration?
No. There are receptros for monitoring blood volume - which is determined by plasma sodium - these are called volume receptors
Where are high pressure volume receptors located? what is their response?
they are located in the aortic arch, carotid sinus and afferent arterioles of kidney
-their response alters sympathetic outflow and ADH secretion
what do the intrarenal high pressure receptors control?
They control the release of renin from smooth muscle cells
so when the blood pressure decreases, renin is released, and leads to reabsorptino of water
describe the renal effects following renin release
1) renin converts circulating angiotensin into angiotensin1
2) angiotensin 1 is converted to angiotensin 2 by ACE
3) angiotensin 2 stimulates the aldosterone release from adrenal cortex
4) aldosterone stimulates the sodium reabsorption (along with chrloride) in the collecting duct
What are the function of angiotensin2 ?
- stimulates aldosterone production by the adrenal cortex
- arteriolar vasoconstriction (increases blood pressure)
- stimulates ADH production and thirst
- enhances NaCl reabsorption by the proximal tubule, TAL, DT and CD
What is the function of aldosterone?
- stimulates reabsorption of NaCl by TAL, DT, and CD
- overall it increases the channels on the apical side and will increase the turnover rate of the NaK atpase channels
What is the response intrarenally to a decrease in blood volume?
- decreased blood volume = decreased pressure
- renin/angiotensin/aldosterone increased
- NaCl reabsorption in collecting ducts
- plasma osmolarity increased
- ADH secretion increased
- H2O reabsorption increased
- urinary retention of salt and water increased
- blood volume returns to normal
Where are the low pressure volume receptors located?
present in the wlals of the pulmonary vessels, atria and right ventricle of the heart
What are low pressure volume receptors sensitive to?
they are sensitive to distension
Describe the series of events that occur when there is high pressure detected by the low pressure volume receptors?
1) afferents travel to brainstem
2) modulates sympathetic nerve activity
3) modulates ADH release
4) release of atrial natriuretic peptide (ANP) and BNP
5) ANP and BNP vasodilate afferent and vasoconstrict efferent arterioles glomerulus - increasing the filtered load of Na+
6) they inhibit renin secretion, inhibit aldosterone production by adrenal cortex, inhibit NaCl reabsorption by the CD, inhibit ADH secretion by the posterior pituitary and ADH action on the CD
What is the response of decreased blood volume on the low pressure volume receptors?
1) increases sympathetic nerve activity
2) stimulates secretion of ADH
3) inhibition of ANP release (atria)
4) inhibition of BNP release (ventricles)
What is Euvolaemia?
the presence of the correct amount of blood in the body
What is Addisons disease?
a rare, chronic endocrine disorder in which the adrenal glands do not produce sufficient steroid hormones. Chracterized by a number of relatively nonspecific symptoms such as abdominal pain and weakness, but under certain circumstances, these may progress to Addisonian crisis - a severe illness which may include very low blood pressure and coma
treatment = cortisol
What causes sodium chloride retention and consequently increased blood volume?
1) chronic renal failure - no filtration - no control over excretion - most commonly cuased by diabetes
2) heart failure
3) excess adrenocortical hormones - hyperaldosteronism
