39 Questions
What is a cause of acute hyperkalemia?
Acute renal failure
Which of the following is a response to decreased plasma calcium levels?
Increased activation of vitamin D
What is a key factor in magnesium homeostasis?
Renal excretion
What is the normal range for ECF potassium (K+) concentration?
3.5-5.5 mEq/L
What percentage of K+ is intracellular?
98%
What is the typical fractional excretion of K+ (FEK) with normal dietary intake?
10-20%
Where does 70% of K+ get reabsorbed?
Proximal tubule (PT)
Which hormone primarily regulates K+ balance in the distal collecting duct?
Aldosterone
What effect does acidosis have on K+ secretion?
Decreases K+ secretion
What is the plasma K+ level for hypokalemia?
< 3.5 mEq/L
Which medical treatment for acute hyperkalemia stabilizes cardiac membrane potential?
Calcium gluconate infusion
What is the primary mechanism of action of β2 agonists in treating acute hyperkalemia?
Drive K+ into the ICF
Which of the following stimulates aldosterone secretion in response to increased serum K+?
Increased plasma K+
What is the primary effect of thiazide and loop diuretics on potassium balance?
Inhibit Na+ reabsorption upstream of cortical collecting duct
What is the effect of insulin on potassium movement?
Stimulates K+ uptake by liver and skeletal muscle
What is the main function of free ionized Ca++ in the body?
Acting as a vital second messenger for blood coagulation
Which form of calcium is not filtered into the interstitial fluid or glomerulus?
Protein-bound Ca++
What is the most common urinary calculi formed from calcium?
Calcium oxalate
What stimulates calcium reabsorption from the distal tubule in response to low plasma calcium?
Parathyroid hormone (PTH)
What is the primary role of parathyroid hormone (PTH) at the kidney in response to low plasma calcium?
Increasing calcium reabsorption from the distal tubule
What is the percentage of calcium reabsorption regulated in the thick ascending limb (TAL)?
65%
What effect do loop diuretics have on divalent cations such as calcium and magnesium?
Cause urinary loss of divalent cations
What is the primary mechanism of compensatory response to low effective circulating volume in the renal system?
Activation of the renin-angiotensin-aldosterone axis
What is the main function of free ionized magnesium in the body?
Acting as an essential cofactor in enzymatic reactions
Where is approximately 65% of magnesium reabsorption regulated?
Thick ascending limb (TAL)
In which form is approximately 50% of plasma magnesium present?
Free ionized magnesium
What is the effect of loop diuretics on magnesium excretion?
Cause urinary loss of magnesium
What is the primary effect of high tubular flow at the macula densa?
Stimulates nitric oxide synthase to produce Nitric Oxide (NO) for vessel relaxation/dilation
What stimulates renin release in the kidneys?
Low perfusion and low Na+
What is the primary response of the renin-angiotensin-aldosterone system and ADH to low effective circulating volume?
Activation
What effect does angiotensin II have on renal perfusion pressure and extracellular fluid (ECF) volume?
Increases renal perfusion pressure and ECF volume
What is the primary effect of aldosterone on water and potassium balance?
Causes H2O retention and K+ excretion
What stimulates renin secretion in the kidneys?
Low perfusion and low Na+
What is the primary mechanism by which the kidneys regulate blood pressure?
Affecting Na+ and H2O balance
What activates nitric oxide synthase to produce Nitric Oxide (NO) in the kidneys?
High tubular flow
What is the coupling factor for renin secretion in the kidneys?
Renal baroreceptor
What is the primary role of the renin-angiotensin-aldosterone system and ADH in response to low effective circulating volume?
Activation
What is the primary effect of angiotensin II on renal perfusion pressure and extracellular fluid (ECF) volume?
Increases renal perfusion pressure and ECF volume
What is the primary effect of aldosterone on water and potassium balance?
Causes H2O retention and K+ excretion
Study Notes
Renal Regulation of Blood Pressure
- Low effective circulating volume may not correspond to low total body volume
- Examples of edema of varying etiologies: congestive heart failure, nephrotic syndrome, cirrhosis
- With normal circulating volumes, activity of renin, angiotensin, aldosterone, and sympathetic nerves is generally low
- Kidneys regulate blood pressure by affecting Na+ and H2O balance
- Tubuloglomerular feedback stimulates renin release
- High tubular flow is sensed at the macula densa
- High tubular flow activates nitric oxide synthase to produce Nitric Oxide (NO) which leads to vessel relaxation/dilation
- Renin secretion is coupled to the renal baroreceptor
- Renin is released in response to low perfusion and low Na+
- Renin-angiotensin-aldosterone system + ADH responds to low effective circulating volume
- Angiotensin II increases renal perfusion pressure and ECF volume
- Aldosterone causes H2O retention and K+ excretion
Test your knowledge of the renal regulation of blood pressure with questions on the role of renin, angiotensin, aldosterone, and other mechanisms involved in maintaining blood pressure balance in the body.
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