PHGY 216 Final Exam GUARANTEED PASS !!
Distinguish between cortical and juxtamedullary nephrons - (ANSWER)Cortical nephrons and juxtamedullary
nephrons are two types of nephrons, which are the functional units of the kidney. The main differences between
them are:
Location: Cortical nephrons are located mostly in the cortex of the kidney, while juxtamedullary nephrons have
their renal corpuscles near the border between the cortex and the medulla and their loops of Henle extend deep
into the medulla.
Length of the loop of Henle: Cortical nephrons have a shorter loop of Henle that only extends into the outer
medulla, while juxtamedullary nephrons have a longer loop of Henle that extends deep into the medulla.
Function: Cortical nephrons are involved mainly in filtration and reabsorption of small molecules, while
juxtamedullary nephrons are involved in the production of concentrated urine by establishing a concentration
gradient in the renal medulla.
Why is it advantageous that renal blood flow decreases during exercise? - (ANSWER)-During exercise, blood
flow to working muscles increases
-To maintain blood pressure and supply blood to working muscles, blood flow needs to be redistributed from
non-essential organs such as the kidneys
-Decreasing renal blood flow during exercise conserves fluids and electrolytes needed to maintain the body's
balance during exercise
-Decreased renal blood flow also reduces the rate of urine formation
-This redistribution of blood flow is temporary and the kidneys will resume their normal function once exercise
has ended
-Prolonged or excessive reduction in renal blood flow can lead to kidney damage or dysfunction
Discuss how extrinsic control of the GFR is accomplished and the importance of this mechanism -
(ANSWER)Extrinsic control of the glomerular filtration rate (GFR) is accomplished by regulating the diameter
of the afferent and efferent arterioles that supply blood to the glomeruli. This control is achieved through the
activity of the sympathetic nervous system and the renin-angiotensin-aldosterone system.
The sympathetic nervous system constricts the afferent arterioles, reducing blood flow to the glomeruli and
thereby decreasing the GFR. This mechanism is important in situations such as exercise, when the body needs
to redirect blood flow to the working muscles.
The renin-angiotensin-aldosterone system is activated when there is a decrease in blood pressure or blood
volume. It leads to the release of renin, which converts angiotensinogen to angiotensin I, which is then
converted to angiotensin II. Angiotensin II constricts the afferent arterioles, decreasing blood flow to the
Page 1 of 40
,glomeruli and thereby reducing the GFR. It also stimulates the release of aldosterone, which promotes sodium
reabsorption in the distal tubules and collecting ducts, increasing water reabsorption and restoring blood
volume.
Extrinsic control of the GFR is important because it helps to maintain a stable filtration rate, even under
conditions of varying blood pressure or volume. Without this control, the GFR could become too high or too
low, leading to electrolyte imbalances, dehydration, or other complications.
Show the steps of transepithelial transport - (ANSWER)1. Absorption or secretion: The first step in
transepithelial transport is the movement of molecules or ions from one side of the epithelial cell to the other.
This can either be absorption, where molecules move from the lumen (apical side) to the interstitial fluid
(basolateral side), or secretion, where molecules move from the interstitial fluid to the lumen.
2. Entry into the cell: To move across the epithelial cell, molecules must first enter the cell. This can occur
through several mechanisms, including passive diffusion, facilitated diffusion, or active transport.
3. Movement across the cell: Once inside the cell, molecules must cross the cell to reach the other side. This can
occur by simple diffusion, facilitated diffusion, or active transport.
4. Exit from the cell: Finally, the molecules must exit the epithelial cell to reach their final destination. This can
occur by passive diffusion, facilitated diffusion, or active transport.
5. Movement through the interstitial fluid: After exiting the epithelial cell, molecules must move through the
interstitial fluid to reach their final destination. This can occur by diffusion or bulk flow.
6. Entry into the capillary: The final step in transepithelial transport is the entry of molecules into the capillary.
This can occur by diffusion or bulk flow.
Describe the sequence of events that take place in the reninangiotensis aldosterone system in response to a fall
in NaCl, ECF volume, and arterial blood pressure - (ANSWER)The sequence of events in the renin-
angiotensin-aldosterone system (RAAS) in response to a fall in NaCl, ECF volume, and arterial blood pressure
can be summarized as follows:
1. A decrease in NaCl, ECF volume, or arterial blood pressure stimulates juxtaglomerular cells in the kidneys to
release the enzyme renin.
2. Renin cleaves angiotensinogen, a protein produced in the liver, into angiotensin I.
3. Angiotensin I is then converted to angiotensin II by the enzyme angiotensin-converting enzyme (ACE),
which is primarily located in the lungs.
4. Angiotensin II acts on the adrenal cortex to stimulate the release of aldosterone, a hormone that increases
Na+ reabsorption and K+ secretion in the distal tubule and collecting duct of the kidneys.
5. The increased reabsorption of Na+ and secretion of K+ leads to an increase in ECF volume and arterial blood
pressure.
6. Angiotensin II also causes vasoconstriction, which further increases arterial blood pressure.
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,7. Angiotensin II also stimulates thirst and the release of antidiuretic hormone (ADH), which promotes water
reabsorption in the kidneys.
Overall, the RAAS is an important mechanism for regulating Na+ and water balance, ECF volume, and arterial
blood pressure.
Explain how the kidneys regulate the plasma concentration of phosphate, but not of glucose, when the kidney
tubules display a transport maximum for both these substances. - (ANSWER)The kidneys are capable of
regulating the plasma concentration of phosphate by adjusting the expression of sodium-phosphate
cotransporters in the renal tubules. When plasma phosphate levels are high, the expression of these
cotransporters will be downregulated, leading to increased excretion of phosphate in the urine. Conversely,
when plasma phosphate levels are low, the expression of these cotransporters will be upregulated, leading to
increased reabsorption of phosphate.
However, glucose is not regulated in the same way because the expression of glucose transporters in the renal
tubules is fixed and not subject to the same level of regulation as the sodium-phosphate cotransporters.
Therefore, once the transport maximum for glucose is reached, any excess glucose will spill over into the urine.
List the three secretory processes accomplished by the kidney tubules - (ANSWER)1. Filtration: The first step
in urine formation, in which fluid and solutes are filtered from the blood into the glomerular capsule and then
into the renal tubules.
2. Secretion: The process by which substances are actively transported from the peritubular capillaries into the
renal tubules. This process allows the kidneys to eliminate substances such as excess potassium ions, hydrogen
ions, and certain drugs that were not filtered at the glomerulus.
3. Reabsorption: The process by which substances are actively or passively transported from the renal tubules
back into the peritubular capillaries. This allows the kidneys to retain important substances such as water,
glucose, and electrolytes that were filtered at the glomerulus.
Explain how most foreign organic compounds are eliminated from the body - (ANSWER)Most foreign organic
compounds are eliminated from the body by first undergoing biotransformation, or metabolism, in the liver or
other tissues. Biotransformation converts lipid-soluble compounds into water-soluble metabolites that can be
excreted by the kidneys or eliminated in bile. These water-soluble metabolites are then excreted from the body
by filtration and secretion in the kidney tubules. The process of elimination involves three steps: filtration,
secretion, and excretion.
During filtration, the blood is filtered through the glomerular capillaries, where small molecules like water,
electrolytes, and small organic molecules are selectively filtered into the Bowman's capsule. The filtrate then
passes through the renal tubules where it is subject to secretion, which is the process by which additional
substances, such as drugs or toxins, are transported into the tubular fluid. Finally, the filtered and secreted
substances are excreted in the urine. The efficiency of this process depends on the physicochemical properties
of the compound, including its size, shape, charge, and hydrophobicity.
Page 3 of 40
, State how the plasma clearance rate for each of the following substances compares to the GFR: a) a substance
that is filtered but not reabsorbed or secreted b) a substance that is filtered and reabsorbed but not secreted. C) a
substance that is filtered and secreted but not reabsorbed - (ANSWER)a) For a substance that is filtered but not
reabsorbed or secreted, the plasma clearance rate is equal to the GFR. This is because the substance is freely
filtered at the glomerulus, but it is not reabsorbed or secreted by the renal tubules.
b) For a substance that is filtered and reabsorbed but not secreted, the plasma clearance rate is less than the
GFR. This is because some of the substance is reabsorbed from the renal tubules back into the blood, reducing
the amount that is excreted in the urine. The plasma clearance rate for such a substance is equal to the GFR
minus the amount of the substance that is reabsorbed.
c) For a substance that is filtered and secreted but not reabsorbed, the plasma clearance rate is greater than the
GFR. This is because the substance is actively secreted from the blood into the renal tubules, increasing the
amount that is excreted in the urine. The plasma clearance rate for such a substance is equal to the GFR plus the
amount of the substance that is secreted.
Identify and explain which nephron component establishes, which component preserves and which component
uses the vertical osmotic gradient in the renal medulla - (ANSWER)The Loop of Henle establishes the vertical
osmotic gradient in the renal medulla. The thin descending limb of the loop is permeable to water but not to
solutes, which leads to the concentration of solutes in the interstitium of the medulla. The thick ascending limb
of the loop is impermeable to water but actively transports solutes out of the tubule, further contributing to the
concentration of solutes in the interstitium. The vasa recta is the component that preserves the vertical osmotic
gradient by its countercurrent exchange mechanism. As blood flows down into the medulla, it picks up solutes
from the interstitium, and as it flows up towards the cortex, it releases these solutes back into the interstitium,
maintaining the concentration gradient. Finally, the collecting duct uses the vertical osmotic gradient to
concentrate urine by allowing water to leave the tubule through aquaporin channels in response to the high
osmolarity of the interstitium.
Explain how vasopressin increases the permeability of the distal and collecting tubules to H2O - (ANSWER)-
Vasopressin (antidiuretic hormone) binds to receptors on the basolateral membrane of principal cells in the
collecting ducts and distal tubules.
- This binding activates adenylate cyclase, which catalyzes the production of cyclic AMP (cAMP) from ATP.
-cAMP activates protein kinase A, which then phosphorylates and activates aquaporin-2 (AQP2) channels on
the apical membrane of the principal cells.
- Once activated, AQP2 channels move to the apical membrane, where they facilitate the movement of water
molecules from the tubular lumen into the cytoplasm of the principal cells.
- From here, water diffuses through the interstitial space and into the capillaries, effectively decreasing urine
volume and increasing urine concentration.
Part of kidneys' energy supply is used to accomplish glomerular filtration? - (ANSWER)True
Page 4 of 40
Distinguish between cortical and juxtamedullary nephrons - (ANSWER)Cortical nephrons and juxtamedullary
nephrons are two types of nephrons, which are the functional units of the kidney. The main differences between
them are:
Location: Cortical nephrons are located mostly in the cortex of the kidney, while juxtamedullary nephrons have
their renal corpuscles near the border between the cortex and the medulla and their loops of Henle extend deep
into the medulla.
Length of the loop of Henle: Cortical nephrons have a shorter loop of Henle that only extends into the outer
medulla, while juxtamedullary nephrons have a longer loop of Henle that extends deep into the medulla.
Function: Cortical nephrons are involved mainly in filtration and reabsorption of small molecules, while
juxtamedullary nephrons are involved in the production of concentrated urine by establishing a concentration
gradient in the renal medulla.
Why is it advantageous that renal blood flow decreases during exercise? - (ANSWER)-During exercise, blood
flow to working muscles increases
-To maintain blood pressure and supply blood to working muscles, blood flow needs to be redistributed from
non-essential organs such as the kidneys
-Decreasing renal blood flow during exercise conserves fluids and electrolytes needed to maintain the body's
balance during exercise
-Decreased renal blood flow also reduces the rate of urine formation
-This redistribution of blood flow is temporary and the kidneys will resume their normal function once exercise
has ended
-Prolonged or excessive reduction in renal blood flow can lead to kidney damage or dysfunction
Discuss how extrinsic control of the GFR is accomplished and the importance of this mechanism -
(ANSWER)Extrinsic control of the glomerular filtration rate (GFR) is accomplished by regulating the diameter
of the afferent and efferent arterioles that supply blood to the glomeruli. This control is achieved through the
activity of the sympathetic nervous system and the renin-angiotensin-aldosterone system.
The sympathetic nervous system constricts the afferent arterioles, reducing blood flow to the glomeruli and
thereby decreasing the GFR. This mechanism is important in situations such as exercise, when the body needs
to redirect blood flow to the working muscles.
The renin-angiotensin-aldosterone system is activated when there is a decrease in blood pressure or blood
volume. It leads to the release of renin, which converts angiotensinogen to angiotensin I, which is then
converted to angiotensin II. Angiotensin II constricts the afferent arterioles, decreasing blood flow to the
Page 1 of 40
,glomeruli and thereby reducing the GFR. It also stimulates the release of aldosterone, which promotes sodium
reabsorption in the distal tubules and collecting ducts, increasing water reabsorption and restoring blood
volume.
Extrinsic control of the GFR is important because it helps to maintain a stable filtration rate, even under
conditions of varying blood pressure or volume. Without this control, the GFR could become too high or too
low, leading to electrolyte imbalances, dehydration, or other complications.
Show the steps of transepithelial transport - (ANSWER)1. Absorption or secretion: The first step in
transepithelial transport is the movement of molecules or ions from one side of the epithelial cell to the other.
This can either be absorption, where molecules move from the lumen (apical side) to the interstitial fluid
(basolateral side), or secretion, where molecules move from the interstitial fluid to the lumen.
2. Entry into the cell: To move across the epithelial cell, molecules must first enter the cell. This can occur
through several mechanisms, including passive diffusion, facilitated diffusion, or active transport.
3. Movement across the cell: Once inside the cell, molecules must cross the cell to reach the other side. This can
occur by simple diffusion, facilitated diffusion, or active transport.
4. Exit from the cell: Finally, the molecules must exit the epithelial cell to reach their final destination. This can
occur by passive diffusion, facilitated diffusion, or active transport.
5. Movement through the interstitial fluid: After exiting the epithelial cell, molecules must move through the
interstitial fluid to reach their final destination. This can occur by diffusion or bulk flow.
6. Entry into the capillary: The final step in transepithelial transport is the entry of molecules into the capillary.
This can occur by diffusion or bulk flow.
Describe the sequence of events that take place in the reninangiotensis aldosterone system in response to a fall
in NaCl, ECF volume, and arterial blood pressure - (ANSWER)The sequence of events in the renin-
angiotensin-aldosterone system (RAAS) in response to a fall in NaCl, ECF volume, and arterial blood pressure
can be summarized as follows:
1. A decrease in NaCl, ECF volume, or arterial blood pressure stimulates juxtaglomerular cells in the kidneys to
release the enzyme renin.
2. Renin cleaves angiotensinogen, a protein produced in the liver, into angiotensin I.
3. Angiotensin I is then converted to angiotensin II by the enzyme angiotensin-converting enzyme (ACE),
which is primarily located in the lungs.
4. Angiotensin II acts on the adrenal cortex to stimulate the release of aldosterone, a hormone that increases
Na+ reabsorption and K+ secretion in the distal tubule and collecting duct of the kidneys.
5. The increased reabsorption of Na+ and secretion of K+ leads to an increase in ECF volume and arterial blood
pressure.
6. Angiotensin II also causes vasoconstriction, which further increases arterial blood pressure.
Page 2 of 40
,7. Angiotensin II also stimulates thirst and the release of antidiuretic hormone (ADH), which promotes water
reabsorption in the kidneys.
Overall, the RAAS is an important mechanism for regulating Na+ and water balance, ECF volume, and arterial
blood pressure.
Explain how the kidneys regulate the plasma concentration of phosphate, but not of glucose, when the kidney
tubules display a transport maximum for both these substances. - (ANSWER)The kidneys are capable of
regulating the plasma concentration of phosphate by adjusting the expression of sodium-phosphate
cotransporters in the renal tubules. When plasma phosphate levels are high, the expression of these
cotransporters will be downregulated, leading to increased excretion of phosphate in the urine. Conversely,
when plasma phosphate levels are low, the expression of these cotransporters will be upregulated, leading to
increased reabsorption of phosphate.
However, glucose is not regulated in the same way because the expression of glucose transporters in the renal
tubules is fixed and not subject to the same level of regulation as the sodium-phosphate cotransporters.
Therefore, once the transport maximum for glucose is reached, any excess glucose will spill over into the urine.
List the three secretory processes accomplished by the kidney tubules - (ANSWER)1. Filtration: The first step
in urine formation, in which fluid and solutes are filtered from the blood into the glomerular capsule and then
into the renal tubules.
2. Secretion: The process by which substances are actively transported from the peritubular capillaries into the
renal tubules. This process allows the kidneys to eliminate substances such as excess potassium ions, hydrogen
ions, and certain drugs that were not filtered at the glomerulus.
3. Reabsorption: The process by which substances are actively or passively transported from the renal tubules
back into the peritubular capillaries. This allows the kidneys to retain important substances such as water,
glucose, and electrolytes that were filtered at the glomerulus.
Explain how most foreign organic compounds are eliminated from the body - (ANSWER)Most foreign organic
compounds are eliminated from the body by first undergoing biotransformation, or metabolism, in the liver or
other tissues. Biotransformation converts lipid-soluble compounds into water-soluble metabolites that can be
excreted by the kidneys or eliminated in bile. These water-soluble metabolites are then excreted from the body
by filtration and secretion in the kidney tubules. The process of elimination involves three steps: filtration,
secretion, and excretion.
During filtration, the blood is filtered through the glomerular capillaries, where small molecules like water,
electrolytes, and small organic molecules are selectively filtered into the Bowman's capsule. The filtrate then
passes through the renal tubules where it is subject to secretion, which is the process by which additional
substances, such as drugs or toxins, are transported into the tubular fluid. Finally, the filtered and secreted
substances are excreted in the urine. The efficiency of this process depends on the physicochemical properties
of the compound, including its size, shape, charge, and hydrophobicity.
Page 3 of 40
, State how the plasma clearance rate for each of the following substances compares to the GFR: a) a substance
that is filtered but not reabsorbed or secreted b) a substance that is filtered and reabsorbed but not secreted. C) a
substance that is filtered and secreted but not reabsorbed - (ANSWER)a) For a substance that is filtered but not
reabsorbed or secreted, the plasma clearance rate is equal to the GFR. This is because the substance is freely
filtered at the glomerulus, but it is not reabsorbed or secreted by the renal tubules.
b) For a substance that is filtered and reabsorbed but not secreted, the plasma clearance rate is less than the
GFR. This is because some of the substance is reabsorbed from the renal tubules back into the blood, reducing
the amount that is excreted in the urine. The plasma clearance rate for such a substance is equal to the GFR
minus the amount of the substance that is reabsorbed.
c) For a substance that is filtered and secreted but not reabsorbed, the plasma clearance rate is greater than the
GFR. This is because the substance is actively secreted from the blood into the renal tubules, increasing the
amount that is excreted in the urine. The plasma clearance rate for such a substance is equal to the GFR plus the
amount of the substance that is secreted.
Identify and explain which nephron component establishes, which component preserves and which component
uses the vertical osmotic gradient in the renal medulla - (ANSWER)The Loop of Henle establishes the vertical
osmotic gradient in the renal medulla. The thin descending limb of the loop is permeable to water but not to
solutes, which leads to the concentration of solutes in the interstitium of the medulla. The thick ascending limb
of the loop is impermeable to water but actively transports solutes out of the tubule, further contributing to the
concentration of solutes in the interstitium. The vasa recta is the component that preserves the vertical osmotic
gradient by its countercurrent exchange mechanism. As blood flows down into the medulla, it picks up solutes
from the interstitium, and as it flows up towards the cortex, it releases these solutes back into the interstitium,
maintaining the concentration gradient. Finally, the collecting duct uses the vertical osmotic gradient to
concentrate urine by allowing water to leave the tubule through aquaporin channels in response to the high
osmolarity of the interstitium.
Explain how vasopressin increases the permeability of the distal and collecting tubules to H2O - (ANSWER)-
Vasopressin (antidiuretic hormone) binds to receptors on the basolateral membrane of principal cells in the
collecting ducts and distal tubules.
- This binding activates adenylate cyclase, which catalyzes the production of cyclic AMP (cAMP) from ATP.
-cAMP activates protein kinase A, which then phosphorylates and activates aquaporin-2 (AQP2) channels on
the apical membrane of the principal cells.
- Once activated, AQP2 channels move to the apical membrane, where they facilitate the movement of water
molecules from the tubular lumen into the cytoplasm of the principal cells.
- From here, water diffuses through the interstitial space and into the capillaries, effectively decreasing urine
volume and increasing urine concentration.
Part of kidneys' energy supply is used to accomplish glomerular filtration? - (ANSWER)True
Page 4 of 40
