Physiology Renal True/False Question Set
True/False: As plasma glucose concentration rises above normal, glucose reabsorption increases and then levels off.
A: True - It levels off after Tm glucose is reached.
True/False: In fluid in the distal part of the proximal convoluted tubule bicarbonate concentration is lower than in plasma.
A: True - Like glucose, HCO3- is usually completely reabsorbed in the proximal tubule.
True/False: When a patient's mean arterial blood pressure falls by 50 per cent renal vasoconstriction occurs.
A: True - Reflex sympathetic vasoconstriction due to greatly decreased baroreceptor stim- ulation.
True/False: Renal tubules normally reabsorb more k+ than cl-.
A: False - About 20 times as much chloride as potassium is filtered (this is the ratio of their plasma concentrations).
True/False: The cells of the distal convoluted tubule reabsorb about 50 per cent of the water filtered by the glomeruli.
A: False - About 80 per cent of the filtered water is reabsorbed before it reaches the distal tubules.
True/False: In fluid in the distal part of the proximal convoluted tubule ph is less than 6 when the kidneys are excreting an acid urine.
A: False - Acidification occurs mainly in the distal convoluted tubule.
True/False: A substance is being secreted by the renal tubules if its concentration in urine is greater than in plasma.
A: False - Again, this can be explained by a relatively greater reabsorption of water.
True/False: When a patient's mean arterial blood pressure falls by 50 per cent renal blood flow falls by less than 10 per cent.
A: False - Autoregulation cannot compensate for such large falls.
True/False: Transport maximum (Tm) - limited reabsorption of a substance implies that its renal clearance falls with its plasma concentration.
A: False - Clearance is zero at all levels below the threshold.
True/False: In the nephron, the osmolality of fluid in the bowman's capsules is less than that in the distal tubules.
A: False - Distal tubular fluid is hypotonic.
True/False: The cells of the distal convoluted tubule determine the final composition of urine.
A: False - Further modification takes place in the collecting ducts.
True/False: When a patient's mean arterial blood pressure falls by 50 per cent glomerular filtration falls by about 50 per cent.
A: False - It falls to about zero when glomerular capillary pressure falls below the sum of intracapsular pressure plus plasma oncotic pressure - around 30-40 mmHg.
True/False: The renal clearance of a substance is inversely related to its urinary concentration, u.
A: False - It is directly related to urinary concentration.
True/False: As plasma glucose concentration rises above normal, glucose excretion increases and then decreases.
A: False - It is initially zero and then rises linearly.
True/False: The renal clearance of a substance is directly related to its plasma concentration, p.
A: False - It is inversely related to plasma concentration.
True/False: Hydrostatic pressure in renal glomerular capillaries is lower than pressure in efferent arterioles.
A: False - It must be higher to maintain blood flow.
True/False: As plasma glucose concentration rises above normal, glucose clearance increases linearly.
A: False - It remains at zero until the Tm is reached and then it rises linearly.
True/False: The renal clearance of a substance must fall in the presence of metabolic poisons.
A: False - It rises if the substance is normally reabsorbed by an active process.
True/False: In fluid in the distal part of the proximal convoluted tubule glucose concentration is similar to that in plasma.
A: False - Most or all of the glucose is reabsorbed before the end of the proximal tubule.
True/False: In fluid in the distal part of the proximal convoluted tubule osmolality is about 25 per cent that of glomerular filtrate.
A: False - Osmolality changes little in the proximal convoluted tubule.
True/False: Hydrostatic pressure in renal glomerular capillaries falls by 10 per cent when arterial pressure falls by 10 per cent.
A: False - Redistribution of renal vascular resistance due to autoregulation tends to main- tain glomerular hydrostatic pressure and hence filtration.
True/False: In the nephron, the osmolality of fluid in the proximal convoluted tubule rises along its length.
A: False - The fluid remains isotonic with plasma.
True/False: Hydrostatic pressure in renal glomerular capillaries rises when afferent arterioles constrict.
A: False - The pressure drop across the afferent arterioles increases as they constrict.
True/False: If, during an infusion of para-aminohippuric acid, peripheral venous plasma PAH level is 0.02 mg/ml (not above renal threshold), urinary PAH level is 16 mg/ml and urinary flow rate 1 ml/min, then the pah level in renal venous blood must exceed 0.02 mg/ml.
A: False - The renal venous blood level would be negligible.
True/False: Transport maximum (Tm) - limited reabsorption of a substance implies that its reabsorption is critically related to tubular transit time.
A: False - This applies to the other type of active tubular reabsorption, gradient-time lim- ited reabsorption.
True/False: A substance is being secreted by the renal tubules if its concentration rises along the proximal convoluted tubule.
A: False - This can be explained by water reabsorption.
True/False: In the nephron, the osmolality of fluid in the tip of the loop of henle is less than that of plasma.
A: False - This fluid is hypertonic because of countercurrent concentration.
True/False: Tubular reabsorption of a filtered substance is likely to be active rather than passive if its renal clearance is lower than that of inulin.
A: False - This indicates reabsorption but not whether it is active (e.g. glucose) or passive (e.g. urea).
True/False: A substance is being secreted by the renal tubules if its excretion rate is increased by tubular enzyme poisons.
A: False - This suggests that the substance is normally reabsorbed by an active process.
True/False: As plasma glucose concentration rises above normal, glucose transport maximum tm increases linearly.
A: False - Transport maxima are constants.
True/False: A substance is being secreted by the renal tubules if its clearance rate is greater than 250 ml/minute.
A: True - A clearance value above the glomerular filtration rate (about 140 ml/minute) indicates secretion.
True/False: Renal tubules normally reabsorb more water every hour than the entire plasma volume.
A: True - About 99 per cent of the glomerular filtrate (about 8 litres/hour).
True/False: Renal tubules normally reabsorb all filtered plasma proteins.
A: True - Again some are filtered but do not appear in urine.
True/False: Tubular reabsorption of a filtered substance is likely to be active rather than passive if its urinary excretion rate:plasma concentration ratio is the same as for glucose.
A: True - Anything filtered in glomeruli and having zero clearance must be actively reabsorbed.
True/False: Transport maximum (Tm) - limited reabsorption of a substance implies that its reabsorption is complete below a certain threshold load.
A: True - As with glucose.
True/False: If, during an infusion of para-aminohippuric acid, peripheral venous plasma PAH level is 0.02 mg/ml (not above renal threshold), urinary PAH level is 16 mg/ml and urinary flow rate 1 ml/min, then the renal blood flow is nearer 1300 than 1500 ml/minute if the haematocrit is 0.40.
A: True - Blood flow=plasma flow/0.6=1333 ml/minute.
True/False: The cells of the distal convoluted tubule form nh4 ions.
A: True - By conversion of glutamine to glutamate; NH3 is a buffer for the H being excreted.
True/False: The renal clearance of a substance is expressed in units of volume per unit time.
A: True - Clearance = UV/P in units of volume/unit time.
True/False: The renal clearance of a substance is directly related to the rate of urine formation, v.
A: True - Clearance tends to fall at low urinary flow rates.
True/False: Tubular reabsorption of a filtered substance is likely to be active rather than passive if its excretion is increased by cooling the kidney.
A: True - Cooling impairs active metabolic processes.
True/False: In fluid in the distal part of the proximal convoluted tubule urea concentration is higher than in bowman's capsule.
A: True - Due to reabsorption of water.
True/False: When a patient's mean arterial blood pressure falls by 50 per cent there is an increase in the circulating aldosterone level.
A: True - Due to release of renin and angiotensin formation, aldosterone is secreted.
True/False: As plasma glucose concentration rises above normal, glucose filtration increases linearly.
A: True - Filtration rate is directly proportional to concentration.
True/False: If, during an infusion of para-aminohippuric acid, peripheral venous plasma PAH level is 0.02 mg/ml (not above renal threshold), urinary PAH level is 16 mg/ml and urinary flow rate 1 ml/min, then the renal plasma flow is nearer 800 than 1000 ml/minute.
A: True - Flow=PAH clearance=UV/P=16 X 1/0.02=800 ml/minute.
True/False: The cells of the distal convoluted tubule reabsorb sodium in exchange for hydrogen or potassium ions.
A: True - H+ secretion is related to the body's acid-base balance.
True/False: Hydrostatic pressure in renal glomerular capillaries falls along the length of the capillary.
A: True - Hydrostatic pressure falls due to vascular resistance; oncotic pressure rises due to loss of protein-poor filtrate; both these factors reduce filtration pressure along the length of the glomerular capillary.
True/False: In the nephron, the osmolality of fluid in the medullary interstitium can exceed one osmole per litre.
A: True - It can be about four times that of plasma.
True/False: If, during an infusion of para-aminohippuric acid, peripheral venous plasma PAH level is 0.02 mg/ml (not above renal threshold), urinary PAH level is 16 mg/ml and urinary flow rate 1 ml/min, then the pah level in renal arterial blood must be about 0.02 mg/ml.
A: True - Since PAH is excreted only by the kidneys, the PAH level in peripheral venous blood determines the level entering the arterial system, and hence the renal arter- ies.
True/False: If, during an infusion of para-aminohippuric acid, peripheral venous plasma PAH level is 0.02 mg/ml (not above renal threshold), urinary PAH level is 16 mg/ml and urinary flow rate 1 ml/min, then the pah level in glomerular filtrate must be about 0.02 mg/ml.
A: True - Since PAH is freely filtered.
True/False: A substance is being secreted by the renal tubules if its concentration is higher in arterial than in renal venous blood.
A: True - Some of the unfiltered fraction must have been secreted.
True/False: Hydrostatic pressure in renal glomerular capillaries is higher than in most capillaries at heart level.
A: True - The afferent arterioles offer relatively little resistance.
True/False: Transport maximum (Tm) - limited reabsorption of a substance implies that its excretion rate is zero until its tm value is reached.
A: True - The concept applies also to amino acids and proteins.
True/False: The cells of the distal convoluted tubule secrete hydrogen ions into the tubular lumen.
A: True - The rate is related to acid-base requirements.
True/False: Renal tubules normally reabsorb all filtered amino acids.
A: True - These are filtered but do not appear in normal urine.
True/False: Renal tubules normally reabsorb all filtered hco3 in respiratory acidosis.
A: True - This plus HCO3- manufactured in the kidney compensates the respiratory acido- sis.
True/False: Tubular reabsorption of a filtered substance is likely to be active rather than passive if its renal clearance rises at high plasma levels.
A: True - This suggests saturation of a carrier system.
True/False: Tubular reabsorption of a filtered substance is likely to be active rather than passive if its concentration in the tubular fluid is lower than in peritubular capillary blood.
A: True - This suggests transportation into the blood against a concentration gradient.
True/False: Transport maximum (Tm) - limited reabsorption of a substance implies that its reabsorption is active.
A: True - Tm limited reabsorption is one type of active tubular reabsorption.
True/False: In the nephron, the osmolality of fluid in the collecting duct rises when vasopressin is being secreted.
A: True - Vasopressin (ADH) promotes water, but not salt, reabsorption in collecting ducts.
True/False: When a patient's mean arterial blood pressure falls by 50 per cent urinary output ceases.
A: True - When glomerular filtration stops, urinary output stops.
