Renal and Acid-Base Physiology Flashcards Preview

A - Board Reveiew Misc > Renal and Acid-Base Physiology > Flashcards

Flashcards in Renal and Acid-Base Physiology Deck (34)

What percentage of body weight is water?

60% of body weight is water, it is the highest in newborns and adult males, lowest in adult females and adults with a high ammount of adipose tissue.


What fraction of total body weight is made up by extracellular fluid and intracellular fluid?

Intracellular fluid makes up 2/3 mostly of potassium and magnesium.

Extracellular fluid makes up 1/3 of the weight with mostly sodium in the plasma and chloride and bicarb.
Plasma makes up 1/4 of the ECF


What is the 60-40-20 rule?

60% bw is water
40 percent is intracellular
20 percent is extracellular fluid.


How would the infusion of isotonic NaCl effect the fluid compartments?

It would expand the ECF and would not effect the ICF. It would not change the osmolarity as it is isotonic however it would increase blood pressure as the ECF is increasing.


How would diahrrea effect the water compartments of the body?

Would lower ECF but would not cause an ion shift as no change occurs in the osmolarity.

Plasma concentration and hematocrit would increase because the loss of ECF would concentrate blood proteins and arterial blood pressure would decrease.


How would excessive salt intake effect the water compartments of the body?

The ECF osmolarity would increase. The ICF would shift water into the ECF until the osmolarity of both compartments were equal. As a result, ECF volume increases and ICF volume decreases.

This is known as volume expansion!


What is syndrome of innapropriate antidiuretic syndrome?

causes hypoosmotic gain in volume expansion.

Excess water is retained filling the ECF and causing its osmolarity todrop. Thus water from the ECF shifts into the ICF decreasing its osmolarity as well.


What occurs in adrenocortical insufficiency?

Excessive loss of salt leading to hyposomotic volume contraction.

Hematcrit increases here as ECF fluid moves from the ECF into the ICF.

Arterial blood pressure also decreases.


What is the equation for clerance?

Urine concentration * Urine volume / Plasma concentration


Which two systems will cause arteriole constriction of the efferent renal arteries?

Sympathetic nervous system and Angiotensin II


What effect do ACE inhibitors have at the renal arterioles?

Dialates renal efferent arteries resulting in a decrease in GFR.


What effects do prostaglandins have at the renal arterioles?

Prostaglandins dialate the renal arterioles, specifically via E2 and I2.


What effects does dopamine have on the renal arterioles?

Dialates the renal arterioles.


What effect does atrial natriueretic peptide *(ANP) have on the kidneys?

Dialates the afferent arteriole and constricts the efferent arteriole.
Overall it increases renal blood flow.


What is the tubuloglomerular feedback at the kidney?

The macula densa cells feel an increase in blood volume and constrict the afferent arteriole to maintain consistant GFR.


When would you use para-aminohippuric acid PAH?

PAH is completely filtered and secreted by the renal tubules thus it measures renal plasma flow.


When would you use inulin?

Inulin can be used to detect the GFR of the kidney as it is filtered but not reabsorbed or secreted.

So again it would be concentration of inulin in urine multiplied by the volume of urine and divided by the total plasma concentration of inulin to determine GFR.


How do BUN and serum creatinine relate to GFR?

When GFR decreases both BUN and Serum Creatinine increase.


When would BUN levels increase faster than creatinine levels?

BUN levels would increase faster than creatinine in prerena azotemia (hypovolemia)


Why does serum creatinine remain constant in the body even though GFR decreases with age?

Because the body loses muscle mass appropriately with age as well.


What keeps the anions out of the urine normally?

Negatively charged podocytes. In kidney damage, these charges are interupted and albumin and other negatively charged molecules can pass through to the urine.


What increases GFR in the arterioles?

Dialation of the afferent arteriole or constriction of the efferent arteriole.


What would cause an increase in the hydrostatic pressure of bowmans capsule?

Anything blocking or constricting the ureters would cause back flow and increase in glomerular hydrostatic filtration pressures.


What plasma glucose levels will result in excretion of glucose through the kidneys?

Any blood glucose levels higher than 250 assuming the kidneys are functioning correctly. at levels of 350 all of the glucose/sodium channels are saturated.

Normally glucose is uptake at the proximal convuluted tubule via a glucose/sodium channel. However, there are only so many of these channels. Hyperglycemia causes excess loss in urine glucose.


What is uniqueabout measuring GFR with PAH?

PAH isnt just filtered, it is also secreted and this has to be taken into account.
This is why it is important to saturate the patient with a known ammount of PAH to ensure that all of the secretion has remained constant while measuring GFR.

Inulin however is only excreted and filtered thus it perfectly matches GFR.


How can one increase the excretion of a weak acid from the kidneys?

By eliciting basic materials, the weak acid can be stuck in its A- charged form and will not be able to back flow.

The acidic form HA can back flow and is uncharged.


How is HCO3- reabsorbed in the proximal convuluted tubule?

Na+/H+ channels directly interact to reabsorb bicarbonate at the PCT.


How does the drug Acetazolamide work?

This is a carbonic anhydrase inhibitor present at the proximal convuluted tubule.
It prevents HCO3- from being reabsorbed.


Which portion of the tubule is impeneratable to water and thus reabsorbes sodium without water?

The thick ascending limb of henle where the Na/K/Cl pump works its magic.

The distal convulted tubule is impermeable to water as well and uses the Na/Cl pumps.


Which segment of the kidney is coined the diluting segment?

The thick ascending loop of henle.


Where in the tubule is sodium absorbed via the Na/Cl channel?

The distal convuluted tubule.
Thiazides work here.


How do principle cells work?

At the distal convuluted tubule these reabsorb sodium and water while secreting potassium.

Aldosterone increases Na+ reabsorption and K+ excretion through these cells. "ENaC cells"


How does ADH work?

This hormone works by inserting aquaporins into the collecting duct.


How do alpha interculated cells of the tubule work?

These secrete H+ via ATP and are effected by aldosterone.
In exchange they reabsorb K+ by a H/K ATPase.

Work to secrete under acidic conditions.

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