Lecture 17 Flashcards
What is the normal pH range of tissue fluid?
7.35-7.45
A ___ buffer is a system (for example the respiratory or urinary system) that stabilizes pH by controlling the body’s output of acids, bases, or CO2.
physiological
Any substance that binds H+ and removes it from solution as its concentration begins to rise, or releases H+ into solution as its concentration falls is classified as a ______ buffer. Examples include proteins, bicarbonate, and phosphate.
chemical
What are the three major chemical buffer systems of the body?
The phosphate buffer system
The protein buffer system
The bicarbonate buffer system
The most important buffer system in the blood is the bicarbonate buffer, which is a solution of ______ acid and bicarbonate ions.
weak
carbonic acid is a weak acid
Which would be considered a normal pH value for arterial blood?
7.4
The bicarbonate buffer system would not work very well in the human body if not for the action of the lungs and the kidneys doing which of the following?
Removing CO2 produced by the buffer system
Which two organ systems form physiological buffers that help stabilize pH by controlling the body’s output of acids, bases, or CO2? Select two options from the list below.
Urinary system
Respiratory system
The ______ buffer system is a solution of H(PO4)2 and H2(PO4).
phosphate
Which type of buffer is defined as a substance that binds H+ and removes it from solution as its concentration begins to rise, or releases H+ into solution as its concentration falls?
chemical
How can the respiratory system compensate for a drop in blood H+ concentrations?
Reduced pulmonary ventilation allows CO2 to accumulate, lowering the pH back to normal.
Name the three important chemical buffer systems in the body.
bicarbonate
phosphate
protein
Order the events during neutralization of hydrogen ions in the kidney from the moment H2CO3 forms until HCO3- returns to blood. Begin with the formation of H2CO3 in the blood at the top.
1) H+ in blood reacts w/ HCO3- to form H2CO3
2) H2CO3 decomposes into H2O and CO2, which enter the tubule cell
3) Tubule cells obtain CO2 from blood, and tubular fluid
4) CAH combines H2O and CO2 to re-form H2CO3
5) H2CO3 ionizes to form HCO3- (which returns to the blood) and H+
What is the complete chemical equation for the bicarbonate buffer system?
CO2 + H2O <-> H2CO3 <-> HCO3- + H+
If the pH of the tubular fluid drops too low, H+ concentration in the fluid is so high that tubular secretion ceases. What is the limiting pH for tubular secretion?
4.5
The bicarbonate system works quite well because the lungs and kidneys constantly remove which of the following? This prevents equilibrium from being reached.
CO2
The renal tubules are incapable of reabsorbing HCO3- directly. Instead, an enzyme breaks down the H2CO3 in the tubular fluid to form CO2, which can be reabsorbed. What is the name of the enzyme?
Carbonic anhydrase
Choose all the statements that are true regarding the phosphate buffer system.
- it plays an important role in the renal tubules
- it has a weaker buffering effect than an equal amount of bicarbonate buffer
- it plays an important role in the ICF where there is constant production of metabolic acids
- its optimal pH is 6.8
It plays an important role in the renal tubules.
It plays an important role in the ICF where there is constant production of metabolic acids.
Its optimal pH is 6.8.
Since there is so much chloride in the tubular fluid, why is H+ excreted as ammonium chloride (NH4Cl) and not simply excreted as hydrochloric acid (HCl)?
Because HCl is too strong of an acid and would drop the pH of the tubular fluid below the limiting pH
The addition of CO2 to the body fluids raises H+ concentration and lowers pH, while the removal of CO2 has the opposite effect. This is the basis for the strong buffering capacity of which system?
Respiratory
Which term refers to a tissue fluid pH above 7.45?
Alkalosis
Choose all the processes that occur in the kidney during the neutralization of acid.
- Tubular cells form ammonia, which acts as a base and reacts with H+ and Cl– to form ammonium chloride (NH4Cl)
- Tubular cells simply excrete most H+ ions as hydrochloric acid (HCl)
- For every HCO3- that enters the peritubular capillaries, a sodium ion does too
- The glomerular filtrate contains Na2HPO4 (dibasic sodium phosphate), which reacts with some of the H+
Tubular cells form ammonia, which acts as a base and reacts with H+ and Cl– to form ammonium chloride (NH4Cl)
For every HCO3- that enters the peritubular capillaries, a sodium ion does too
The glomerular filtrate contains Na2HPO4 (dibasic sodium phosphate), which reacts with some of the H+
What must be true in order for tubular secretion of hydrogen ions to take place?
There is a concentration gradient between the renal tubule cell and the tubular fluid.
Why are there are no bicarbonate ions in urine of a person with normal acid-base balance?
They are consumed by neutralizing H+.
Respiratory ______ occurs when the rate of alveolar ventilation fails to keep pace with the body’s rate of CO2 production. Carbon dioxide accumulates in the ECF and lowers its pH.
acidosis
Since HCl is a strong acid and would lower the pH of the tubular fluid below the limiting pH, H+ is instead excreted as which of the following?
Ammonium chloride
Which results when CO2 is eliminated faster than it is produced (for example, during hyperventilation)?
Respiratory alkalosis
A tissue fluid pH below 7.35 is defined as a state of Blank______.
acidosis
Increased production of organic acids, such as lactic acid in anaerobic fermentation and ketone bodies in alcoholism and diabetes mellitus can cause which of the following?
Metabolic acidosis
Order the events during neutralization of hydrogen ions in the kidney from the moment H2CO3 forms until HCO3- returns to blood. Begin with the formation of H2CO3 in the blood at the top.
(1) H+ in blood reacts w/ HCO3- to form H2CO3
(2) H2CO3 decomposes into H2O and CO2, which enter the tubule cell
(3) tubule cells obtain CO2 from blood, and tubular fluid
(4) CAH combines H2O and CO2 to re-form H2CO3
(5) H2CO3 ionizes to form HCO3- (which returns to the blood) and H+
If the pH of the tubular fluid drops too low, H+ concentration in the fluid is so high that tubular secretion ceases. What is the limiting pH for tubular secretion?
4.5
Metabolic ______ is rare, but can result from overuse of bicarbonates (such antacids and intravenous bicarbonate solutions) or from the loss of stomach acid by chronic vomiting.
alkalosis
______ acidosis occurs in hypoventilation, when carbon dioxide accumulates in the ECF and lowers its pH.
Respiratory
Choose all that are true regarding respiratory compensation.
- it is equally effective in correcting all causes of acidosis and alkalosis
- it corrects the pH of body fluids by expelling or retaining CO2
- it is effective in correcting for PCO2 imbalances
- it is slower than renal compensation, but better at restoring a fully normal pH
It corrects the pH of body fluids by expelling or retaining CO2.
It is effective in correcting for PCO2 imbalances.
Respiratory ______ results from hyperventilation, in which CO2 is eliminated faster than it is produced.
alkalosis
Describe renal compensation in response to acidosis.
The renal tubules increase the rate of H+ secretion.
- renal tubules secrete H+ into the urine
______ acidosis can result from increased production of organic acids, such as lactic acid in anaerobic fermentation and ketone bodies in alcoholism and diabetes mellitus.
Metabolic
Which is likely to be increased in the urine of a person with diabetic acidosis?
Ammonium chloride
Choose all the processes that occur in the kidney during the neutralization of acid.
- tubular cells form ammonia, which acts as a base and reacts w/ H+ and Cl- to form ammonium chloride (NH4Cl)
- the glomerular filtrate contains Na2HPO4 (dibasic sodium phosphate), which reacts w/ some of the H+
- for every HCO3- that enters the peritubular capillaries, a sodium ion does too
- tubular cells simply excrete most H+ ions as hydrochloric acid (HCl)
Tubular cells form ammonia, which acts as a base and reacts with H+ and Cl– to form ammonium chloride (NH4Cl)
The glomerular filtrate contains Na2HPO4 (dibasic sodium phosphate), which reacts with some of the H+
For every HCO3- that enters the peritubular capillaries, a sodium ion does too
Which of the following may cause metabolic alkalosis?
Overuse of intravenous bicarbonate solutions or aldosterone hypersecretion
how does aldosterone hypersecretion lead to metabolic alkalosis?
aldosterone causes more Na+ to be in the blood
More Na+ entering bloodstream = more HCO3- entering bloodstream = metabolic alkalosis
Describe respiratory compensation in response to alkalosis.
Pulmonary ventilation rate decreases.
Describe renal compensation in response to alkalosis.
The renal tubules decrease the rate of H+ secretion.
less H+ being secreted into urine = more H+ kept in bloodstream = help make basic blood more acidic
An increase in the amount of ammonium chloride in the urine most likely indicates which of the following?
Acidosis
Order the events during neutralization of hydrogen ions in the kidney from the moment H2CO3 forms until HCO3- returns to blood. Begin with the formation of H2CO3 in the blood at the top.
(1) H+ in blood reacts w/ HCO3- to form H2CO3
(2) H2CO3 decomposes into H2O and CO2, which enter the tubule cell
(3) tubule cells obtain CO2 from blood, and tubular fluid
(4) CAH combines H2O and CO2 to re-form H2CO3
(5) H2CO3 ionizes to form HCO3- (which returns to the blood) and H+
Choose all that are true regarding renal compensation.
- it adjusts for pH imbalances by changing the rate of H+ secretion by the kidneys
- it is slower than respiratory compensation, but better at restoring a fully normal pH
- it corrects the pH of body fluids by expelling or retaining CO2
- it is most effective at compensating for short term pH imbalances, such as acidosis resulting from an asthma attack
It adjusts for pH imbalances by changing the rate of H+ secretion by the kidneys.
It is slower than respiratory compensation, but better at restoring a fully normal pH.
Choose all the processes that occur in the kidney during the neutralization of acid.
- tubular cells form ammonia, which acts as a base and reacts w/ H+ and Cl- to form ammonium chloride (NH4Cl)
- The glomerular filtrate contains Na2HPO4 (dibasic sodium phosphate), which reacts with some of the H+
- For every HCO3- that enters the peritubular capillaries, a sodium ion does too
- Tubular cells simply excrete most H+ ions as hydrochloric acid (HCl)
Tubular cells form ammonia, which acts as a base and reacts with H+ and Cl– to form ammonium chloride (NH4Cl)
The glomerular filtrate contains Na2HPO4 (dibasic sodium phosphate), which reacts with some of the H+
For every HCO3- that enters the peritubular capillaries, a sodium ion does too
Describe renal compensation in response to acidosis.
The renal tubules increase the rate of H+ secretion.
