Renal Regulation of Ion Concentrations Flashcards
You encounter a patient who is experiencing symptoms of cardiac arrest. Would you expect their extracellular potassium levels to be high or low?
High
How much of the total body potassium is located in the extracellular fluid?
2%
What is the normal intracellular concentration of potassium ions?
140 mEq/L
An increase in extracellular potassium stimulates an increase in the secretion of what molecule?
aldosterone
Where does reabsorption occur in the nephron?
proximal tubule and the ascending limb of Henle
Where does secretion occur in the nephron?
late tubule and collecting duct.
How are principle cells stimulated to secrete potassium and aldosterone?
They are dependent upon potassium concentration and aldosterone.
Is there an inverse or direct relationship between aldosterone secretion and extracellular potassium secretion?
direct
Potassium concentration is indirectly affected by what molecule?
aldosterone
If the aldosterone system is blocked, how will potassium regulated be affected?
Potassium will not be as regulated; the aldosterone system imparis regulation of potassium concentration.
A high potassium diet is usually correlated with what?
A high secretion of potassium.
How does a in increased sodium diet affect potassium excretion?
It does not affect potassium excretion.
An increased intake of sodium decreases aldosterone (decreases K+ secretion) and increases distal tubular flow rate (increases K+ secretion). These counteract each other and there is not net change in potassium excretion.
Approximately what percentage of total plasma calcium is in the ionized form?
50%.
You encounter a patient who is experiencing acidosis. Do you expect high or low levels of calcium to be bound to the plasma proteins?
low
You encounter a patient with alkalosis. Do you expect high or low levels of calcium to be bound to the plasma proteins?
high
Almost all of the calcium in the body is stored where?
In the bones
What hormone is one of the most important regulators of bone uptake and release of calcium?
Parathyroid hormone
Vitamin D is activated by what hormone?
Parathyroid hormone
How much of the filtered calcium is reabsorbed, and what region of the nephron absorbs most of it?
99%; the proximal tubules absorb the most through paracellular (65%) and transcellular (20%) routes.
How is calcium reabsorbed in the proximal tubules?
Through paracellular (65%) and transcellular (25%) routes.
What region of the loop of henle absorbs calcium?
thick ascending limb.
How is calcium reabsorbed in the distal tubule?
via active transport.
What factors regulate tubular calcium reabsorption?
increased PTH
Plasma concentration of calcium
metabolic acidosis
Reabsorption in the distal tubule is stimulated by what hormone?
PTH
Calcium excretion is decreased by what factors?
Decreased PTH
Plasma concentration of phosophate
Metabolic acidosis
When parathryoid hormome is increased, what three regions of the body will subsequently increase calcium reabsorption?
intestines, kidneys and bones.
What is the phosphate transport maximum for reabsorption?
0.1 mM/min.
If it is above this value, excess is secreted.
If it is below this value, all filtered phosphate is reabsorbed in the proximal tubule.
What is the relationship between PTH and phosphate?
An increase in PTH causes an increase of extracellular phosphate, which is eventually lost in the urine.
During a fed state, insulin is released. What is the relationship of insulin and potassium?
Insulin stimulates potassium uptake by cells.
You encounter a patient who is experiencing Conn’s Syndrome (hyporkalemia). You order a blood test. Do you expect aldosterone levels to be high or low?
high
You encounter a patient who has Addison’s disease (hyperkalemia). You order a blood test. Do you expect aldosterone levels to be high or low?
low
What is the function of aldosterone?
It increases potassium uptake by cells.
It also stimulates active reabsorption o Na+ by principal cells via Na/K ATPase pump.
As extracellular potassium increases, what substance is secreted?
aldosterone
What is the function of catecholamies?
They stimulate potassium uptake by cells.
You encounter a patient who has metabolic acidosis. You order a blood test. Do you expect plasma (extracellular) concentrations of potassium to be high or low?
high
You encounter a patient who has metabolic alkalosis. You order a blood test. Do you expect their plasma (extracellular) levels to be high or low?
low
You perform a study on rats that have undergone strenous excercise and are experiencing hyperkalemia. What physiological symptoms do you expect the rats to have?
cell lysis and increased extracellular fluid osmolarity.
What are the major cells found in the late distal tubule and collecting tubules?
principal cells.
What type of pump is important in controlling K+ secretion?
Activity of the Na/K ATPase pump.
What three factors control K+ secretion?
Activity of the Na/K ATPase pump
Electrochemical gradients
Permeability of luminal membrane.
What three factors stimulate K+ secretion?
Increased extracellular K+ concentration
Increased aldosterone
Increased tubular flow rate
What is the function of intercalated cells?
To reabsorb potassium during potassium depletion.
They reabsorb through a H/K ATPase pump.
H+ is secreted into the lumen.
In order to excrete high levels of sodium, what must happen to blood pressure?
It has to increase.
At reduced angiotensin II levels, ____ levels of sodium can be maintained at reduced arterial pressures.
normal
At what concentration is extracellular potassium maintained?
4.2 mEq/L (+/- 0.3 mEq/L)
