Chapter Questions - Fluid, Electrolyte, and Acid-Base Balance
Which do you have more of, extracellular or intracellular fluid? Plasma or interstitial fluid?
You have more intracellular fluid then extracellular fluid and you have more extracellular fluid than plasma in your body.
What is the major cation in the ECF? In ICF? What are the intracellular anion counterparts of ECF’s chloride ions?
Na+ is the major cation in the ECF and K+ is the major cation in the ICF. The counterparts of ECF’s cloride ions are HPO2- and protein ions.
If you eat salty pretzels without drinking, what happens to the volume of your extracellular fluid?
If you eat salty pretzels without drinking your extracellular fluid will expand because the water will flow by osmosis from the intercellular space to the extracellular space.
What change in plasma is most important for triggering thirst? Where is that change sensed?
An increase in the osmolality of the plasma is the most important trigger of thrist. The change is sensed by osmoreceptors in the hypothalimus.
ADH, by itself, cannot reduce an increase in osmolality in body fluids. Why not? What other mechanism is required?
ADH can only conserve the water that is already in the body. It can not add water. In order to increase the osmolality the thirst mechanisim is required.
For each of the following, state whether it might result in dehydration, hypotonic hydration, or edema: (a) loss of plasma proteins due to liver failure; (b) copious sweating; (c) using ecstasy (MDMA), which promotes ADH secretion.
A loss of plama proteins causes edema, copious sweating causes dehydration, using X (MDMA) causes hypertonic hydration.
Jacob has Addison’s disease (insufficient aldosterone release). How does this affect his plasma Na+ and K+ levels? How does this affect his blood pressure? Explain?
Insufficient aldosterone release would cause Jacobs plama K+ to be elevated. The decrease in plama Na+ would cause a decrease in blood pressure because plasma Na+ is directly related to blood volume, which is a major determinant of blood pressure.
Renal handling of Nacan be summed up as “The kidneys reabsorb almost all of the Naas filtrate passes through its tubules.” Make a similar summary for K.
The kidney’s handling of K+ can be summed up as “The kidneys reabsorb most of the filtered K+ in the proximal parts of the kidney tubules then secrete just the right ammount in the distal parts.”
What hormone is the major regulator of Ca2in the blood? What are the effects of hypercalcemia? Hypocalcemia?
The major regulator of calcium in the blood parathyroid hormone. Hypercalcemia decreases excitability of neurons and muscle cells and may cause life theatening cardiac arrhythmias. Hypocalcemia increases excitability & causes muscle tetany.
Define acidemia and alkalemia.
Acidemia is an arterial pH below 7.35 and alkalemia is pH above 7.45
To minimize a shift in pH brought about by adding a strong acid to a solution, would it be better if the solution contained a weak base or a strong base?
a weak base would be at minimizing the shift in pH caused by adding a strong acid solution because its ability to loosly tie up H+ allows it to act as a buffer
What are the body’s three major chemical buffer systems? What is the most important buffer inside cells?
The three major buffer systems of the body are the bicarbonate buffer system, the phosphate buffer system and the protien buffer system. The most important buffer system inside the cell is the protein buffer system.
Joanne, a diabetic patient, is at the emergency department with acidosis due to the production of ketone bodies. Would you expect her ventilation to be increased or decreased? Why?
The ventilation would be increased. Th acidosis caused by the accumilation of ketone bodies will stimulate the peripheral chemoreceptors, and this will cause more CO2 to be blown off in an attempt to restore pH to normal.
Reabsorption of HCO3- is always tied to the secretion of which ion?
The reabsorbtion of HCO3- is always linked with secretion of H+
What is the most important urinary buffer of H+?
The most important urinary buffer of H+ is the phosphate buffer system.
List the two mechanisms by which tubule and collecting duct cells generate new HCO3-.
The tubule and collecting duct cells generate new HCO3- either by excreting ammonium ion (NH4+) or by excreting buffered H+ ions
What two abnormalities in plasma are key features of an uncompensated metabolic alkalosis? An uncompensated respiratory acidosis?
Key features of an uncompensated metabolic alkalosis are an increase in blood pH and an increase in blood HCI3-. Key features of an uncompensated respiratory acidosis are a decrease in blood pH and an increase in blood PCO3-
How do the kidneys compensate for respiratory acidosis?
The kidneys compensate for respiratory acidosis by excreting more H+ and generating new HCO3- to buffer the acidosis
Infants have a higher urine output than adults relative to their body weight. In addition to their relatively higher fluid intake, what are the reasons for this?
Infants immature kidneys are not as proficient at concentrating urine. In addition, they have a high metabolic rate, so they produce more metabolic water and also have larger amounts of metabolic wastes and acids that need to be excreted with water.