RENAL PHYSIO

Which of the following causes hyper-kalemia? (A)Exercise (B)Alkalosis (C)Insulin injection (D)Decreased serum osmolarity (E)Treatment with β-agonists

(A)Exercise (Exercise causes a shift of K+from cells into blood. The result is hyper-kalemia. Hyposmolarity, insulin, β-agonists, and alkalosis cause a shift of K+from blood into cells. The result is hypokalemia)

Which of the following is an action of parathyroid hormone (PTH) on the renal tubule? (A)Stimulation of adenylate cyclase (B)Inhibition of distal tubule K+secretion (C)Inhibition of distal tubule Ca2+reab-sorption (D)Stimulation of proximal tubular phos-phate reabsorption (E)Inhibition of production of 1,25-dihy-droxycholecalciferol

(A)Stimulation of adenylate cyclase (PTH acts on the renal tubule by stimulating adenyl cyclase & generating cyclic adenosine monophosphate(cAMP). The major actions of the hormone are inhibition of phosphate reabsorption in the proximal tubule, stimulation of Ca2+reabsorption in the distal tubule, and stimulation of 1,25-dihydroxycholecalciferol production. PTH does not alter the renal handling of K+.)

Secretion of K+by the distal tubule will be decreased by (A)metabolic alkalosis (B)a high-K+diet (C)hyperaldosteronism (D)spironolactone administration (E)thiazide diuretic administration

(D)spironolactone administration (Because spironolactone is an aldosterone antagonist, it reduces K+secretion. )

Which of the following is a cause of metabolic alkalosis? (A)Diarrhea (B)Chronic renal failure (C)Ethylene glycol ingestion (D)Treatment with acetazolamide (E)Hyperaldosteronism (F)Salicylate poisoning

(E)Hyperaldosteronism (increased aldosterone levels cause increased H+secretion by the distal tubule and increased reabsorption of "new" HCO3-. )

In a patient with obstructed ureters, which one of the following 3 factors does the disease process increase in order to reduce the net glomerular filtration pressure? A) Bowman's space hydrostatic P B) Capillary oncotic pressure C) Glomerular capillary hydrostatic pressure

A) Bowman's space hydrostatic P (fluid back up, changes the hydrostatic P)

The rate of water reabsorption from the proximal tubule is determined primarily by the A. rate of dissolved particle (solute) reabsorption from the proximal tubule B. concentration of ADH (antidiuretic hormone) in the blood C. osmotic pressure developed by plasma proteins in the proximal tubule D. active transport of water molecules by the proximal tubule cells E. passive filtration due to the high hydrostatic pressure in the proximal tubule

A. The proximal tubule is very permeable to water, so water reabsorption follows solute (dissolved particle) reabsorption.

decreases Na+ & HCO3- reabsorption found in PT inc tubular flow exiting PT

Acetazolamide (CA inhibitior) (diuretic)

In what portion of, or at what point on the glucose titration curve, is the renal vein glucose concentration equal to the renal artery glucose concentration?

At all plasma glucose concentrations below threshold

Drinking which of the following would lead to the highest rate of ADH secretion and release? A. two liters of distilled water B. two liters of sea water (mainly hyperosmotic saline) C. two liters of iso-osmotic (isotonic) saline D. two liters of human blood plasma E. none of the above, since drinking two liters of any liquid leads to inhibition of ADH release

B Drinking two liters of sea water would increase extracellular osmolality, thus stimulating hypothalamic osmoreceptors and leading to a greater increase of ADH release than drinking two liters of the other solutions indicated.

The renal system does not play a direct role in regulating which of the following? A) Blood pressure B) Blood temperature C) Blood solute concentrations D) Blood pH

B) Blood temperature

As blood passes along the glomerular capillaries from the afferent to efferent arteriole, the net filtration pressure A. increases B. decreases C. first decreases, reaches a minimum about half way along the capillary, then increases D. first increases, reaches a maximum about half way along the capillary, then decreases E. remains constant

B. Hydrostatic pressure decreases because of capillary resistance. Osmotic pressure increases because plasma protein concentration increases as fluid is lost by filtration. So net filtration pressure decreases as blood passes along the glomerular capillary, and may even reach zero (no net filtration force) by the end of the capillary.

Where in the nephron is fractional excretion of Na highest?

Bowman's space or early proximal convoluted tubule

During water diuresis, where in the nephron is [TF/P]inulin lowest?

Bowman's space or early proximal convoluted tubule (this is lowest before any water reabsorption has occurred)

Drinking vodka (a beverage with a high ethanol content, for those of you unfamiliar with this substance) would be expected to cause excretion of a A. large volume of concentrated urine B. small volume of concentrated urine C. large volume of dilute urine D. small volume of dilute urine E. normal volume of urine of normal osmolality

C Ethanol inhibits release of ADH from the posterior pituitary, so a large volume of dilute urine would be excreted.

In a patient with severe renal artery stenosis (narrowing), all of the following would be expected to be increased above normal except A. plasma renin concentration B. plasma angiotensin II concentration C. blood pressure (hydrostatic pressure) in the glomerular capillaries D. resistance to blood flow in the efferent arteriole E. systemic arterial blood pressure

C. Blood flowing through the stenosis will encounter a high resistance, which will cause the pressure to drop on the downstream side of the stenotic area. This will lead to secretion of renin, which causes blood angiotensin II to increase, which will raise systemic arterial blood pressure and constrict the renal efferent arteriole. However, blood pressure in the glomerular capillaries will fall because of the drop in pressure as blood enters the glomerular vessels.

Stimulation of the osmoreceptors in the hypothalamus would be expected to cause all of the following to increase except A. ADH release from the pituitary B. water reabsorption from the renal collecting duct C. rate of urine formation D. osmolality of urine E. none of the above; that is, none are exceptions since all would be expected to increase

C. The increased ADH release would lead to increased water reabsorption from the later distal tubule and collecting ducts, so urine formation rate would decrease.

Which ADH disorder us represented by the following changes: increased, plasma osmolarity, dilute urine, decreased ADH?

Central diabetes insipidus

Urine is formed in a three-step process: which of the following gives the correct order in which these steps take place in the nephron? A) Tubular reabsorption, tubular secretion, glomerular filtration B) Tubular secretion, tubular reabsorption, glomerular filtration C) Glomerular filtration, tubular secretion, tubular reabsorption D) Glomerular filtration, tubular reabsorption, tubular secretion

D) Glomerular filtration, tubular reabsorption, tubular secretion

A 75 yr old man with CHF is being treated with a medication that blocks Na reabsorption in the late distal tubule & collecting ducts. Which of the following profiles is most likely to be found if the urine sample from this patient is analyzed? A) K+ dec, Na+ inc, water dec B) K+ inc, Na+ dec, water dec C) K+ inc, Na+ inc, water inc D) K+ no change, Na+ inc, water inc E) K+ inc, Na+ dec, water no change

D) K+ no change, Na+ inc, water inc (purpose of water pill to get rid of water, so inc water output; Na+ reabsorption is blocked, so inc in Na+ output; conserves K+ b/c of where thiazide blocks vs. "K+ wasting diuretics")

In a person who ingests a bag of potato chips (i.e. NaCl), what happens to intracellular volume: increased, decreased, or unchanged?

Decreased

What is the effect of dilation of the efferent arteriole on filtration fraction: increased, decreased, or unchanged?

Decreased

What is the effect of a loop diuretic (inhibitor of Na-K-2Cl cotransporter) on maximum urine osmolarity during production of hyperosmotic urine: increased, decreased, unchanged?

Decreased (this cotransporter is required for countercurrent multiplication, which establishes corticopapillary gradient)

Administration of an Angiotensin Converting Enzyme inhibitor (ACE inhibitor) to the above patient (pt w/ severe renal artery stenosis) might lead to acute renal failure by A. inhibiting renal tubule potassium reabsorption B. increasing renal resistance to blood flow C. causing plasma proteins to be excreted in the urine D. causing systemic arterial hypertension E. reducing glomerular filtration rate

E. The ACE inhibitor will reduce angiotensin II concentration, so arterial blood pressure will drop, which reduce glomerular capillary hydrostatic pressure and filtration.

Constriction of which arteriole leads to decreased renal plasma flow (RPF) & increased glomerular filtration rate (GFR)?

Efferent arteriole

Inhibition of tri-transporter found in taHI inc tubular flow exiting taHI inc Na+ excretion

Furosemide (diuretic)

Higher pressure (~50mmHg), fluid filtration, associated w/ Bowman's capsule

Glomerular capillaries

An increase in urine pH causes what change in the excretion of a weak acid: increased, decreased, or unchanged?

Increased

Regarding actions of the parathyroid hormone (PTH) on the kidney, which of the following is/are seen: inhibition of Na-phosphate excretion, decreased urinary Ca2+ excretion, decreased urinary cyclic AMP?

Inhibition of Na-phosphate cotransport, decreased urinary Ca2+ excretion

Rank the following substances in order of fractional excretion from highest to lowest: inulin, Na+, glucose (below threshold), K+ on a high potassium diet, and HCO3-

K+ on a very high-potassium diet, inulin, Na+, HCO3-, glucose (below threshold)

inhibition ENaC found in late DT, CT, CD inc tubular flow to CD dec Na+ reabsorption

K+ sparing diuretic Spironolactone

Which of the following cause(s) hyperkalemia: lack of insulin, hyperaldosteronism, loop diuretics, spironolactone, hyperosmolarity, metabolic alkalosis?

Lack of insulin, spironolactone, hyperosmolarity

During production of hyperosmotic urine, where in the nephron is [TF/P]osmolarity lowest?

Midpoint of distal convoluted tubule or early distal tubule

GFR is 120 mL/min, the plasma concentration of X is 10 mg/mL, the urine concentration of X is 100 mg/mL, and urine flow rate is 1.0 mL/min. Assuming that X is freely filtered, is there net reabsorption or net secretion of X, and what is the rate?

Net reabsorption, 1100 mg/min

What happens to the oncotic pressure of peritubular capillary blood following an increase in filtration fraction?

Oncotic pressure is increased (more fluid filtered out of glomerular caps leads to increased plasma protein concentration)

Lower pressure (15-20 mmHg), fluid reabsorption

Peritubular capillaries

Inhibition of Na+, Cl- cotransporter found in early DT inc tubular flow exiting early DT inc Na+ excretion

Thiazide (diuretic)

If GFR is constant and there is an increase in urine flow rate, how does the plasma inulin concentration change: increased, decreased, or unchanged?

Unchanged (GFR is constant & urine flow rate increases, urine inulin concentration decreases)

What are the units of glucose Tm?

mg/min (or amount/time)

What are the functions of the glomerular caps in determining size of particles moving?

size of fenestration holes, gaps between adjacent foot processes & the properties of the GBM

Which of the following is least likely to be present in the glomerular filtrate (the filtrate produced by the nephron before it enters the loop of Henle) of a healthy adult nephron? A) Amino acids B) Large molecular weight protein C) Electrolyte D) Glucose

B) Large molecular weight protein

Under which of the following conditions is the luminal membrane Na+ channel the main pathway for Na+ reabsorption? A) High ADH secretion B) low ADH secretion C) With aldosterone secretion D) No aldosterone secretion E) With aldosterone and ADH secretion

C) With aldosterone secretion (the luminal membrane Na+ channel & the hormone responsible in these channels = aldosterone, only in principal cells in late distal tubule and CD, & effect by insertion of aquaporins)

At which sites would the concentration of creatinine be expected to be highest? (Note: assume the person is normally hydrated.) A. glomerular filtrate B. end of the proximal tubule C. end of the loop of Henle D. urine E. the concentration would be the same in all of the above, since creatinine is neither secreted or reabsorbed

D. Remember that creatinine is filtered but neither reabsorbed nor secreted (approximately), so creatinine concentration depends on the amount of water remaining. The volume of urine is less that the volume of fluid at any of the other sites listed.

As fluid passes along a juxtamedullary nephron, where is its osmolality (total concentration of dissolved particles) lowest? (Note: assume a normal concentration of circulating ADH.) A. Bowman's capsule (glomerular filtrate) B. fluid leaving the proximal tubule and entering the loop of Henle C. fluid leaving the descending thin limb and entering the ascending thin limb of the loop of Henle D. fluid leaving the thick ascending segment of the loop of Henle and entering the distal tubule E. fluid leaving the collecting ducts (urine)

D. fluid leaving the thick ascending segment of the loop of Henle and entering the distal tubule

Which of the following would producean increase in the reabsorption of isosmoticfluid in the proximal tubule? (A)Increased filtration fraction (B)Extracellular fluid (ECF) volume expansion (C)Decreased peritubular capillary proteinconcentration (D)Increased peritubular capillary hydro-static pressure (E)Oxygen deprivation

(A)Increased filtration fraction

Which of the following substances has the highest renal clearance? (A)Para-aminohippuric acid (PAH) (B)Inulin (C)Glucose (D)Na+ (E)Cl-

(A)Para-aminohippuric acid (PAH) (PAH has the greatest clearance b/c it is both filtered & secreted. Inulin is only filtered. The other substances are filtered & subsequently reabsorbed; therefore, they will have clearances that are lower than the inulin clearance)

A person who takes an aspirin (salicylicacid) overdose is treated in the emergencyroom. The treatment produces a change inurine pH that increases the excretion of sali-cylic acid. What was the change in urine pH,and what is the mechanism of increased salicylic acid excretion? (A)Acidification, which converts salicylicacid to its HA form (B)Alkalinization, which converts salicylicacid to its A-form (C)Acidification, which converts salicylicacid to its A-form (D)Alkalinization, which converts salicylicacid to its HA form

(B)Alkalinization, which converts salicylicacid to its A-form (Alkalinization of the urine converts more salicylic acid to its A-form. The A-form is charged and cannot back-diffuse from urine to blood. Therefore, it is trapped in the urine and excrete)

Which of the following causes a decreasein renal Ca2+ clearance? (A)Hypoparathyroidism (B)Treatment with chlorothiazide (C)Treatment with furosemide (D)Extracellular fluid (ECF) volume expansion (E)Hypermagnesemia

(B)Treatment with chlorothiazide (Thiazide diuretics have a unique effect on the distal tubule; they increase Ca2+ reabsorption, thereby decreasing Ca2+ excretion and clearance)

Kidney inflammation may result in the appearance of albumin (a plasma protein) in the urine because A. more albumin enters the proximal tubule in the glomerular filtrate B. reabsorption of albumin from the proximal tubule is inhibited C. secretion of albumin into the distal tubule and collecting ducts is increased D. increased peritubular blood flow makes more albumin available for diffusion into the tubule E. reduced active transport of sodium ion reduces cotransport of other substances, including albumin

A. Loss of the glomerular filtration barrier negative charge, characteristic of nephritis, leads to increased filtration of negatively-charged plasma proteins. If the protein filtered load exceeds the limited capacity of the renal tubules to reabsorb protein (Tm-Protein), the urine will contain plasma proteins.

When the clearance of PAH is used to measure effective RPF, is the measurement done at the plasma concentrations of PAH that are about or below the Tm for secretion?

Below Tm (assumption that below the renal vein PAH =~ 0 is correct)

An increase secretion of renin would be expected to have what effect on sodium excretion and potassium excretion in urine? A. increase in Na+ excretion and increase K+ excretion B. increase in Na+ excretion and decrease K+ excretion C. decrease in Na+ excretion and increase K+ excretion D. decrease in Na+ excretion and decrease K+ excretion E. decrease in Na+ excretion but no effect on K+ excretion

C. Increase renin will eventually result in a rise in aldosterone, which increases Na-K pumping (antiport) in the renal distal tubule and collecting duct. Thus, Na reabsorption will increase (reduce excretion) and K secretion will increase (increase excretion).

Suppose a person loses the function of half his nephrons because of renal degenerative disease. Assuming the person survives and reaches a new steady state and that body urea production remains normal, which of the following would be expected to decrease below normal? A. plasma urea concentration B. renal urea excretion C. renal urea clearance D. urine urea concentration E. all of the above

C. Less urea would be cleared because less urea is be filtered. The reduced filtration would cause blood urea concentration to rise until the amount of urea excreted was equal to the amount of urea produced by protein metabolism even with the reduced plasma clearance.

The following values are measured for potassium ion in a human subject. Plasma K+ = 5 meq/liter Urine K+ = 50 meq/liter Renal creatinine clearance = 80 ml/min Urine formation rate = 1.5 ml/minute This patient's potassium clearance is closest to which of the following? A. 5 ml/minute B. 7.5 ml/minute C. 15 ml/minute D. 50 ml/minute E. 75 ml/minute

C. Remembering that CK = UK x V / PK, so CK = 50 x 1.5 / 5 = 15 ml/min.

Which is highest: clearance of PAH below Tm, clearance of glucose below threshold, or clearance or inulin?

Clearance of PAH below Tm (clearance of glucose below threshold is zero; clearance of inulin if GFR; clearance of PAH below Tm is RPF)

Presence of which of the following in the urine, even in small amounts, is indicative of a possible problem in the renal system of a patient? A) Sodium B) Urea C) Creatinine D) Glucose

D) Glucose

If 60% of a person's nephrons were destroyed, which of the following compounds would be likely to show increased blood concentration? A) Urea B) Creatinine C) Uric Acid D) All of the above

D) all of the above

Sodium is actively reabsorbed from the renal tubule in which of the following nephron segments? A. proximal tubule B. distal tubule C. thick ascending limb of the loop of Henle D. all of the above E. none of the above

D. Sodium is reabsorbed by active transport in all of the segments named, although it is not actively transported in either the descending or ascending thin limbs of the loop of Henle.

Which of the following is the stimulus for increased secretion of atrial natriuretic peptide (ANP)? A. increase blood plasma osmolality above normal B. decrease blood plasma osmolality below normal C. increase systemic arterial pressure D. increase venous blood volume and atrial pressure E. increase cardiac contractility (force of contraction)

D. increase venous blood volume and atrial pressure

Which of the following would be expected to cause renal inulin (or creatinine) clearance to increase? A. dilation of the afferent arteriole B. dilation of the efferent arteriole C. constriction of the afferent arteriole D. constriction of the efferent arteriole E. both A and D above

E. Both dilation of the afferent arteriole and constriction of the efferent arteriole would increase glomerular capillary hydrostatic pressure and thus increase GFR. Note that inulin (or creatinine) clearance is a measure of GFR.

Assuming the subject in the preceding question (pt w/ potassium clearance of 15 ml/min) is a normal adult, we can conclude that most likely potassium is A. filtered but not secreted or reabsorbed B. secreted but not filtered or reabsorbed C. reabsorbed but not secreted or filtered D. filtered and secreted E. filtered and reabsorbed

E. Since CK is less than GFR (80 ml/min, as measured by creatinine clearance in question 12), potassium must be filtered and reabsorbed.

Blood flow to regions of the kidney under normal conditions?

~90% to cortical glomeruli (shorter nephron, doesn't dive as deep into the kidney) <10% to juxtamedullary glomeruli (very long nephron)