Human Physio. – CH19

Plasma can gain solutes and/or water from which of the following?

both the gastrointestinal tract and bone

Fluid and electrolyte balance occur when

solutes and water enter and exit the plasma at the same rate.

A substance is in negative balance when

it exits plasma at a greater rate than it enters plasma.

A substance is in positive balance when

it enters plasma at a greater rate than it exits plasma.

The regulation of water and ion excretion occurs primarily within the

both collecting ducts and late distal tubules.

The regulation of sodium and water balance in the kidneys occurs primarily through the unique action of
which cells in the distal tubules and collecting ducts?

principal cells

The regulation of acid-base balance in the kidneys occurs primarily through the unique action of which cells
in the distal tubules and collecting ducts?

intercalated cells

Which of the following is a source of water input?

both digestive tract and metabolism

What regulates the rate of water loss?

kidney

What is the force that moves water out of the distal tubules and collecting ducts?

an osmotic gradient

A greater plasma volume than normal is called

hypervolemia.

If a person is normovolemic and consumes a large quantity of a hyperosmotic solution, it will

cause cells to shrink due to an increase in the osmolarity of extracellular fluid.

Under which of the following conditions do cell volumes not change and the osmolarity in both extracellular
and intracellular fluids remain the same?

osmotic equilibrium

A student in your physiology lab is thirsty and decides to sneak a drink of deionized or distilled water. The
student drinks a fairly large quantity of this water in a short period of time. What will happen to the
student’s cells?

It will cause the student’s cells to swell.

Seawater has an osmolarity of around 1000 mOsm, mostly from dissolved sodium. Given what you know
about the osmolarity in most of the cells in the body, why is it dangerous to drink seawater?

In the digestive system, the seawater would draw more water out of the bloodstream than would be absorbed, leading to severe dehydration.

Which of the following is NOT a mechanism of dissipating heat during exercise?

secretion of ADH

Which of the following conditions is NOT indicative of a decrease in plasma osmolarity?

neural hyperexcitability

Kidneys compensate for changes in plasma volume and osmolarity by adjusting the rate of water

reabsorption only.

What solute is primarily responsible for producing the osmotic gradient that drives water reabsorption?

sodium

Which of the following accurately describes the thick ascending limb of the loop of Henle?

impermeable to water and contains Na+/K+/Cl- cotransporters

The osmotic gradient in the medullary region of the kidneys is established and maintained by which of the
following?

Na+/K+/Cl- cotransporters in the ascending limb of the loop of Henle

If nothing else is removed from the filtrate once it reaches the late distal tubules, the urine excreted would
have which of the following properties?

low osmolarity and large volume

What solute maintains the medullary interstitial fluid osmotic gradient?

urea

Which of the following correctly describes water movement across the epithelial cells lining the collecting
duct?

Water can permeate the apical membrane through aquaporin-2 and the basolateral membrane through aquaporin-3, but aquaporin-2 is only present in the presence of ADH.

A person must void what volume of urine per day?

440 mL

In the early portion of the collecting duct (in cortical interstitial fluid), an increase in water permeability will
result in a(n)

decrease in filtrate volume.

From where is ADH released?

posterior pituitary

Antidiuretic hormone binds to receptors on ________ cells in the collecting ducts and distal tubules where it
________.

principal : causes insertion of aquaporin-2 into the apical membrane

At high concentrations of antidiuretic hormone, the extent of water reabsorption in the collecting ducts is
________, causing urine output to ________.

high : decrease

What is the strongest stimulus for the release of antidiuretic hormone from the posterior pituitary?

increase in plasma osmolarity

In diabetes insipidus, blood levels of ________ are decreased causing an increase in ________.

ADH : urine volume

Which of the following diseases is associated with decreased responsiveness of the renal tubules to ADH?

nephrogenic diabetes insipidus

In diabetes insipidus, why does polyuria occur?

A lack of ADH decreases water reabsorption.

Which of the following conditions would be associated with hypernatremia?

increased plasma sodium

Which of the following statements on sodium movement in the renal tubules is TRUE?

Sodium is actively transported across the basolateral membrane of both the proximal and distal tubule.

In the renal tubules, where is the Na+/K+ pump located?

in the basolateral membrane of the proximal tubules

Which of the following best describes sodium movement in the proximal tubule?

Sodium is transported across the basolateral membrane by the Na+/K+ pump and across the apical membrane by secondary active transport.

Which of the following best describes sodium movement in the distal tubule?

Sodium is transported across the basolateral membrane by the Na+/K+ pump and across the apical membrane by diffusion through sodium channels.

Aldosterone is released from the ________ in response to ________.

adrenal cortex : increases in plasma potassium

Which of the following is an effect of aldosterone on principal cells?

increased number of open Na+/K+ channels in the apical membrane

Which of the following is associated with actions of aldosterone on principal cells?

increased potassium secretion

Renin is released by ________ cells of the ________.

granular : afferent arteriole

What enzyme converts angiotensinogen into angiotensin I?

renin

What enzyme converts angiotensin I into angiotensin II?

angiotensin converting enzyme (ACE)

ACE inhibitors prevent angiotensin converting enzyme (ACE) from performing its role in the body. Which
statement best describes why doctors prescribe ACE inhibitors?

ACE inhibitors reduce blood pressure by blocking the conversion of angiotensin I to angiotensin II.

Angiotensin II acts directly in the hypothalamus to stimulate what?

an increase in thirst

Which of the following conditions triggers the release of renin?

low blood pressure

Angiotensinogen is synthesized by what organ?

liver

What stimulates atrial natriuretic peptide release?

distension of the atrial wall due to an increase in plasma volume

The primary function of atrial natriuretic peptide (ANP) is to

increase sodium secretion thereby decreasing sodium reabsorption.

Atrial natriuretic peptide causes which of the following effects in principal cells?

decreased number of open sodium channels in the apical membrane

The extent of potassium excretion is regulated primarily by the

amount secreted into the distal tubule.

Hyperkalemia refers to an excess of what?

potassium

Potassium secretion is regulated by

aldosterone.

Which of the following structures is NOT involved in the regulation of plasma calcium?

skeletal muscle

The bone can supply calcium to the plasma by what process?

resorption

A decrease in plasma calcium will initiate an increase in the release of which of the following?

both parathyroid hormone and 1,25-dihydroxy vitamin D3

Exposure of the skin to sunlight converts ________ to vitamin D3.

7-dehydrocholesterol

What form of osteoporosis would be localized to a specific bone?

disuse osteoporosis

Which type of cell carries out bone formation?

osteoblasts

Which type of cell carries out bone resorption?

osteoclasts

Which statement best describes why estrogen may contribute to osteoporosis?

A decrease in estrogen stimulates the production of interleukin-6 that then stimulates osteoclast activity.

The last step to synthesis of 1,25-dihydroxy vitamin D3 occurs in what organ?

kidney

What hormone decreases plasma calcium levels?

calcitonin only

The effects of antidiuretic hormone (ADH) are not restricted to regulating water movement; it also affects
sodium reabsorption by

increasing the synthesis of sodium channels in principal cells.

Angiotensin II and atrial natriuretic peptide are able to alter the reabsorption of water through a similar
pathway that involves altered

release of antidiuretic hormone (ADH).

Which of the following is NOT a response to hemorrhage?

decreased renin secretion

The hemorrhage-induced decrease in blood flow to the kidneys will

increase the production of erythrocytes.

The hydrogen ion concentration or pH of arterial blood is regulated by the combined actions of the ________
and ________.

lungs : kidneys

The activity of the respiratory system can increase pH by

a hyperventilation-induced decrease in PCO2.

Which statement BEST distinguishes metabolic acidosis from respiratory acidosis?

Metabolic acidosis is a disturbance in blood pH caused by something other than an abnormal PCO2.

A person walks into the emergency room with rapid and shallow breathing and a feeling of
light-headedness. A blood test shows high levels of bicarbonate ions and a pH of 7.34. What could explain
these symptoms?

respiratory acidosis with renal compensation

During hyperventilation, why do some people detect a tingling sensation in their hands and feet?

hyperexcitability of afferent neurons

Which of the following is NOT a metabolic disturbance that can result in a metabolic acidosis?

excessive vomiting

What is the most rapid defense against changes in blood pH?

buffering of hydrogen ions

How does severe diarrhea cause a metabolic acidosis?

loss of bicarbonate

How does severe vomiting cause a metabolic alkalosis?

loss of hydrogen ions

How might a high-protein diet cause metabolic acidosis?

production of phosphoric acid and sulfuric acid

How might heavy exercise cause metabolic acidosis?

production of lactic acid

How might a high-fat diet cause metabolic acidosis?

breakdown of fat into fatty acids

Which of the following ions acts as a buffer to minimize changes in intracellular pH?

phosphate

The role of a buffer is to

limit the change in pH with changing hydrogen ion concentrations.

What is the secondary defense against changes in pH that requires minutes to be activated?

respiratory compensation

Respiratory compensation for changes in pH is originated by

peripheral chemoreceptors.

When an increase in hydrogen ions remains after one hour, this will lead to a(n)

increase in hydrogen ion secretion from the kidneys.

The most important buffer system in the extracellular fluid is

bicarbonate.

If hydrogen ions are added to a solution, the pH will

decrease.

If hydrogen ions are taken out of a solution, the pH will

increase.

Which of the following is an effect of the transporters in the proximal tubules?

reabsorption of bicarbonate

In the basolateral membrane of proximal tubular cells, bicarbonate is moved out of the cells by

both HCO3-/Cl- countertransporters and Na+/HCO3 – cotransporters.

In the proximal tubule, hydrogen ions are transported into the filtrate by

both Na+/H+ countertransporters and H+ primary active transporters.

Bicarbonate crosses the apical membrane of the proximal tubule by

conversion to carbon dioxide.

Under severe acidic conditions, the proximal tubules can convert ________ into bicarbonate.

glutamine

In order to compensate for a hyperventilation, the

kidneys decrease the reabsorption of bicarbonate.

A patient is exhibiting several signs of acid-base imbalance. Blood tests reveal that blood pH is 7.3, and
bicarbonate and carbon dioxide levels in blood are both low. What is the state of this patient?

metabolic acidosis with respiratory compensation

A patient is exhibiting several signs of acid-base imbalance. Blood tests reveal that blood pH is 7.5, and
bicarbonate and carbon dioxide levels in blood are both low. What is the state of this patient?

respiratory alkalosis with renal compensation

What hormone activates the cAMP second messenger system in principal cells of the distal tubules and
collecting ducts?

ADH

What hormone increases water reabsorption by inserting aquaporin-2 proteins into the apical membrane of
principal cells?

ADH

What hormone stimulates the release of aldosterone?

angiotensin II

Release of what hormone is stimulated by high levels of potassium?

aldosterone

What hormone decreases calcium levels in blood?

calcitonin

What hormone increases calcium resorption from bone?

parathyroid hormone

What hormone increases excretion of sodium?

atrial natriuretic peptide

Most sodium reabsorption is driven by the Na+/K+ pump located in what region?

proximal tubule basolateral membrane

Aquaporin-3 is located on what membrane in the absence of ADH?

principal cells basolateral membrane

Receptors for ADH are located where?

principal cells basolateral membrane

Potassium channels located where are necessary for its reabsorption?

proximal tubule basolateral membrane

Potassium channels located where are necessary for its secretion?

principal cells apical membrane

Carbonic anhydrase is located where?

proximal tubule apical membrane

Sodium-glucose cotransporters are located where?

proximal tubule apical membrane

ADH increases the insertion of aquaporin-2 where?

principal cells apical membrane

Aldosterone increases the number of potassium channels where?

principal cells apical membrane

What would the following blood values indicate? Blood pH = 7.3, [HCO3
-] is low, PCO2 is low.

metabolic acidosis with respiratory compensation

What would the following blood values indicate? Blood pH = 7.3, [HCO3
-] is high, PCO2 is high.

respiratory acidosis with renal compensation

What would the following blood values indicate? Blood pH = 7.5, [HCO3
-] is high, PCO2 is high.

metabolic alkalosis with respiratory compensation

The transport of material across the gastrointestinal tract normally leads to a net gain of solutes and water by
the body.

True

In a state of negative balance, the quantity of a substance in the plasma tends to increase.

False

Defense mechanisms against acid-base disturbances include buffers, respiratory, and renal compensation.

True

The balance of a solute depends solely on its intake to and output from the body.

False

A metabolic alkalosis will cause a decrease in ventilation and an increased excretion of bicarbonate.

True

Consumption of salty foods without drinking water will increase plasma osmolarity and cause cells to
shrink.

True

Plasma volume is directly related to blood pressure.

True

Under normal conditions, the total solute concentration of the plasma and the interstitial fluid is
approximately 300 mOsm.

True

In both the proximal and distal tubules, the reabsorption of sodium involves the active transport of sodium
across the basolateral membrane.

True

As the body becomes dehydrated, the osmolarity of the body fluids decreases.

False

A primary source of acid from internal respiration is CO2.

True

In comparison with the renal cortex, fluid in the proximal tubule is hyperosmotic.

False

Renal and respiratory compensation refers to the kidneys’ and lungs’ (respectively) ability to restore pH
without affecting the cause of the acid-base disturbance.

True

Urea diffuses from the collecting duct into the medullary interstitial fluid maintaining to the medullary
interstitial fluid osmotic gradient.

True

The thick ascending limb of the loop of Henle is impermeable to water.

True

Osmolarity of the fluid in the descending limb of the loop of Henle is greater than the osmolarity of the fluid
in the ascending limb of the loop of Henle at any given level in the renal medulla.

True

The maximum osmolarity of urine is 1200 mOsm to 1400 mOsm.

True

The minimum osmolarity of urine is 300 mOsm.

False

The obligatory water loss refers to the lowest volume of urine that must be produced to eliminate solutes.

True

Acidosis results in potassium retention, whereas alkalosis results in potassium depletion.

True

Antidiuretic hormone increases water reabsorption by increasing the permeability of the distal tubule and
collecting duct to water.

True

If plasma volume is below normal, the changes originated by the kidneys will be able to return the plasma
osmolarity back to normal.

False

Alterations in acid-base balance that originate from the respiratory system involve alterations in CO2 content
within the blood.

True

Calcium homeostasis is regulated through the digestive tract.

False

If glomerular filtration decreases, water excretion tends to decrease as well.

True

In the proximal tubule, sodium moves from the lumen into the tubule epithelial cell by diffusion through
sodium channels.

False

Aldosterone stimulates an increase in sodium reabsorption at the same time it stimulates an increase in
potassium secretion.

True

Hyperkalemia refers to high levels of potassium in the plasma.

True

Calcium is permanently embedded in the rigid structure of bone.

False

1,25-dihydroxy vitamin D3 acts to increase the absorption of calcium in the digestive tract and increase
reabsorption of calcium in the distal tubules of the kidney.

True