Urinary System Final Exam

True or False: the osmolarity of the initial filtrate is essentially the same as that of plasma

True - most if not all of the plasma solutes with the exception of most proteins, are able to enter the filtrate freely; therefore the osmolarity of both are about the same

The internal urethral sphincter is composed of ______ muscle

smooth

Steps of Vasopressin action in the collecting duct

1. vasopressin binds to receptor on basolateral membrane

2. adenylate cyclase produces cAMP

3. protein kinase A is activated

4. protein phosphorylation increases fusion of aquaporin 2-containing vesicles with luminal membrane

5. aquaporin 2 channels permit entry of water into collecting duct cells

In the distal tubule and cortical collecting duct, aldosterone ______

stimulates the synthesis of ion channels and pumps mediating Na+ reabsorption

The movement of substances from peritubular capillaries into the tubular lumen is referred to as tubular _______

secretion

Angiotension I is converted to _______ by an enzyme found on the apical surface of capillary endothelial cells

angiotensin II

The active reabsorption of _____ from the renal filtrate is the primary driving force responsible for reabsorption of water, glucose, amino acids, and other organic substances

Na+

Assume we measure the clearance of a drug and find that it is smaller than the GFR as determined by creatinine clearance. This means that the drug is undergoing ______

tubular reabsorption

Urine begins with the filtration of plasma from glomerular capillaries into ______ space

Bowman’s

Vasopressin physiologically regulates the insertion of ______ of collecting duct cells

aquaporin 2 in the apical membrane

The formation of renal filtrate is opposed by the ______

hydrostatic pressure in Bowman’s Capsule and high colloid (osmotic) pressure of the plasma proteins

Why does glucose appear in the urine in a person with poorly-controlled diabetes mellitus?

the plasma glucose concentration exceeds the normal renal threshold

Substances can be excreted at a higher rate than they are filtered by the kidney if they are _____ by nephron tubules

secreted

True or False: the amount of water and ions reabsorbed by the nephron is typically more than 99% if the amount filtered

True

When blood pressure increases, this inhibits the secretion of the enzyme _____ from the juxtaglomerular apparatus

renin

The kidneys eliminate or replenish H+ from the body by altering plasma _____ concentration

HCO3- (bicarbonate)

Glucose, amino acids, and other organic substances are moved from the renal filtrate into the renal epithelial cells with Na+ by ______

secondary active transport

The concentration of NaCL and other small solutes in Bowman’s space is _____ their concentration in the glomerular capillaries

virtually the same as

After supplying the tubules with blood, the _______ capillaries then join to form the veins by which the blood leaves the kidney

peritubular

When plasma concentration of a substance slightly exceeds the renal threshold for that substance _______

filtration rate exceeds reabsorption rate and excretion occurs

The movement of substances from peritubular capillaries into the tubular lumen is referred to as tubular ______

secretion

Renin-angiotensin-aldosterone cascade elements in order from stimulus to end-product

1. Juxtaglomerular cells stimulate

2. renin released

3. angiotensin II produced

4. aldosterone release stimulated

5. increased sodium ion reabsorption

Substances that have been reabsorbed from the renal filtrate normally move from the renal interstitium into the peritubuluar capillaries by a combination of ______

diffusion and bulk flow

What does the renal filtration barrier normally exclude?

large, negatively charged proteins and erythrocytes and other formed elements

The hormone produced by cells in the upper chamber of the heart and secreted in response to stretching of the atrial walls due to increased blood volume is called ______

atrial natriuretic peptide (or ANP, ANH, or ANF)

What would result in increased glomerular filtration rate?

dilation of afferent arterioles and/or constriction of efferent arterioles

The reabsorption of water is physiologically controlled mainly in the _____

cortical collecting duct and medullary collecting duct

Peritubular capillaries…

are the second set of capillaries encountered by blood flowing through the kidney

surround the renal tubules in the renal cortex

receive substances reabsorbed from the renal tubules

In people with poorly controlled diabetes mellitus, glucose appears in the urine because the ______ of glucose exceeds the ______

filtered load; renal threshold

How can molecules that were not filtered at Bowman’s capsule be cleared from the plasma before blood leaves the kidney?

they can be secreted into the nephron tubules from the peritubular capillaries

What is NOT a mechanism by which water and solutes are moved from the nephron tubule into the renal interstitium?

bulk flow

The segments of the nephron where the epithelial cell permeability to water are under the greatest physiological control are the ______

cortical and medullary collecting ducts

What is an effect of vasopressin?

it increases urine osmolarity

What region of the nephron tubule does fluid flow through last?

medullary collecting duct

The glomerular filtrate normally ______

contains small solutes but no cells and few proteins

The reabsorption of some substances from the tubular lumen is by _____, often across the tight junctions connecting the tubular epithelial cells. The reabsorption of all other substances involves ______ transport, which requires the participation of transport proteins in the plasma membranes of tubular cells.

diffusion; mediated (facilitated)

Active transport of Na⁺ out of tubular epithelial cells via primary active transport ________

lowers the intracellular concentration of Na⁺

establishes a concentration gradient for movement of Na⁺ into the cells from the tubular fluid

What accurately describes part of the homeostatic response to a decrease in total body Na⁺?

a decrease in the amount of Na+ filtered

an increase in the amount of Na+ reabsorbed

The outer kidney is called the _____; the inner kidney is termed the ______

cortex; medulla

True or False: half of the plasma calcium bound to plasma proteins and virtually all of the plasma fatty acids that are bound to plasma protein are not filtered

True - low molecular weight substances that would other wise be filterable are bound to plasma proteins and therefore not filtered

True or False: not all of the plasma that is delivered to the glomeruli is filtered into the glomerular capsules

True - only about 20% of plasma is filtered as it passes through glomerular capillaries

A decrease Na+ delivery causes the _____ to release paracrine factors that diffuse to the nearby juxtaglomerular cells, thereby activating them and causing the release of renin

macula densa

The final volume and osmolarity of urine produced ______

is regulated by vasopressin

When plasma volume is high, the transmission of impulses from cardiovascular baroreceptors to the hypothalamus ______, which ______ vasopressin secretion.

increases; decreases

Three layers of the filtration barrier found in the renal corpuscle?

basement membrane, capillary endothelium, and single-celled epithelial lining of Bowman’s capsule

Which is NOT a factor contributing to the countercurrent multiplier system that creates the concentrated renal medullary interstitium?

A. Hairpin loops of vasa recta that minimizes solute washout from the medullary interstitium

B. Impermeability to water of the ascending limbs of the loops of Henle of juxtamedullary nephrons

C. Reabsorption of NaCl in the ascending limbs of the loops of Henle of juxtamedullary nephrons

D. The countercurrent anatomy of the loop of Henle of juxtamedullary nephrons

E. Trapping urea in the medulla

F. The isosmotic reabsorption of Na⁺ and water from the proximal convoluted tubules of juxtamedullary nephrons

The isosmotic reabsorption of Na⁺ and water from the proximal convoluted tubules of juxtamedullary nephrons

Conditions that result in increased renin secretion will also cause ______

increased retention of sodium, increased retention of water, and increased aldosterone production

The contraction of the _____ sphincter can prevent urination even when the detrusor muscle contracts strongly

external urethral

Formation of renal filtrate into Bowman’s space is favored by _____

increased hydrostatic pressure of the blood and larger glomerular capillary surface area

What generalizations about Na⁺ and water handling by the nephron are normally true?

Na⁺ reabsorption is an active process occurring in all tubular segments except the descending loop of Henle.

Water reabsorption is by osmosis (passive) and is dependent upon Na⁺ reabsorption.