Renal 3 Flashcards
How can there be water intake in the body, from largest to smallest source?
from liquids
from food
from metabolic produced
How can there be water output in the body, from largest to smallest source?
urine
insensible loss
feces
sweat
How is there sodium intake and output?
Intake: food
Output: Urine, sweat and feces
Depending on the intake, water output can vary from _____ to ______ per day. Sodium chloride output can vary from ________ to _______ per day. (these numbers are extreme and should not be reached)
0.4L to 25L per day
0.05g to 25g per day
What are the basic renal processes of sodium and water? (filtration, secretion and reabsorption)
Both are freely filtered
Not secreted
Most (2/3) of reabsorption in the proximal tubule, hormonal control and fine-tuning in the DCT orCD
Sodium reabsorption is an ________ process occurring in __________
active process
all the tubular segments except the descending tubule
Water reabsorption is a _________ and is (dependent/independent) upon ___________
diffusion process
dependent
sodium reabsoprtion
Explain the process of active sodium reabsorption.
On the basolateral membrane, Na/K pump brings K in and Na out to make a gradient of sodium into the cell
On the apical membrane, sodium moves along its gradient into the cell, the specific method of transport depends on the segment of the tubule
How is the movement (reabsorption) of sodium into the cell at different segments of the tubules?
(proximal tubule and CCD)
Proximal tubule: Na/H antiporter, Na/glucose cotransporter
CCD: diffusion of Na via channels
How is sodium balance maintained?
If sodium intake increases, urinary sodium excretion increases
If sodium intake decreases, urinary sodium excretion decreases
How is total body sodium measured?
The body cannot sense the sodium concentration itself. Instead, the baroreceptors sense the changes in blood pressure
Is plasma concentration of sodium a marker for total body sodium?
No, the plasma concentration reflects the relative relationship of total body Na AND WATER
Sodium excretion can be regulated by… (2)
GFR (minor role)
Sodium reabsorption (most)
Explain how GFR can regulate sodium excretion in a case where there is an increased loss in sodium.
increase loss in sodium (with water proportionally)
decreased venous* and atrial pressure*
decreased stroke volume and cardiac output
decreased arterial blood pressure* –> less GFR
*Baroreceptor reflex increases sympathetic activity
Increase constriction of the Afferent Arteriole
Decreased GFR
decrease the excretion of water and Na
What is the key hormone in sodium reabsorption control?
Aldosterone
What is the function of aldosterone in sodium reabsorption? and where?
Aldosterone stimulates sodium reabsorption in the DCT and CCD
The presence of aldosterone influences the sodium excretion. What is the secretion of aldosterone for high/low sodium concentrations?
In high sodium, there is no aldosterone (2% of the filtered load is excreted) some reabsorption
In low sodium, there is aldosterone (0% of the filtered load is excreted), all reabsorption
Where does aldosterone act on the reabsorption process of sodium?
Increases the action of the Na/K pump
Increase Na movement into the cell
Increases K movement out of the cell
Upregulates the expression of Na and K channels
Explain how aldosterone is part of the renin-angiotensin system (describe all RAAS and then include aldosterone action)
The liver constantly makes angiotensinogen
When kidneys release renin it makes angiotensin 1
ACE makes it into angiotensin 2
The adrenal cortex releases aldosterone (bc of the angiotensin 2, increased plasma K (done by aldosterone itself) and ACTH)
Where and by what is renin secreted?
into the afferent arteriole of the glomerulus by juxtaglomerular cells (also stores)
We know how aldosterone is secreted because of renin and it’s effects. How is renin regulated?
Increased activity of the renal sympathetic nerves
Decreased arterial pressure
decrease GFR
Is water retention a direct action of aldosterone?
No, water follows the sodium reabsorption
How does blood pressure influence sodium excretion?
Increased blood pressure will increase sodium excretion
How can ANP (atrial natriuretic peptide) affect the sodium excretion?
Increased total blood volume (increased extracellular fluid) stimulates ANP, which inhibits sodium reabsorption
