Chapter 26 Fluid, Electrolyte, and Acid-Base Balance
Match the following:
1) Dissociate in water.
2) Do not dissociate.
3) The fluid compartments
outside the cell.
4) Fluid compartments located
within the cell.
5) Spaces between cells.
Match the following:
6) Magnesium excess.
7) Calcium depletion.
8) Sodium excess.
9) Potassium excess.
10) Sodium depletion.
Match the following:
11) An atypical accumulation of
fluid in the interstitial space.
12) A condition of unusually low
levels of plasma proteins
resulting in tissue edema.
13) A disorder entailing deficient
production by the adrenal
14) Regulates sodium ion
concentrations in the
15) Special neurons in the
hypothalamus that sense the
ECF solute concentration and
trigger or inhibit ADH release
from the posterior pituitary
B) Addisonʹs disease
Match the electrolyte composition for the following:
16) Sodium ions are highest in
17) Potassium ions are highest in
18) Phosphate ions are highest in
19) Bicarbonate ions are highest
20) Proteins are highest in
A) Intracellular fluid
B) Interstitial fluid
C) Blood plasma
1) Adipose tissue is one of the most hydrated of all tissues in the human body.
2) The most abundant cation in intracellular fluid is sodium.
3) Electrolytes determine most of the chemical and physical reactions of the body.
4) Solutes, regardless of size, are able to move freely between compartments because water
carries them along the osmotic gradients.
5) The thirst center in the brain is located in the hypothalamus.
6) Dehydration can be caused by endocrine disturbances such as diabetes mellitus or diabetes
7) It is impossible to overhydrate because people need as much water as they can drink to carry
out ordinary body functions.
8) Water imbalance, in which output exceeds intake, causing an imbalance in body fluids, is
9) Salts are lost from the body in perspiration, feces, and urine.
10) Hypoproteinemia reflects a condition of unusually high levels of plasma proteins and causes
11) While the sodium content of the body may be altered, its concentration in the ECF remains
stable because of immediate adjustments in water volume.
12) Sodium is pivotal to fluid and electrolyte balance and to the homeostasis of all body systems.
13) When aldosterone release is inhibited, sodium reabsorption cannot occur beyond the collecting
14) Aldosterone stimulates the reabsorption of sodium while enhancing potassium secretion.
15) Pressure diuresis decreases blood volume and blood pressure.
16) Aldosterone is secreted in response to low extracellular potassium.
17) To remain properly hydrated, water intake must equal water output.
18) The main way the kidney regulates potassium ions is to excrete them.
19) Atrial natriuretic peptide reduces blood pressure and blood volume by inhibiting nearly all
events that promote vasodilation and potassium and water retention.
20) Premenstrual edema may be due to enhanced reabsorption of sodium chloride.
21) Heavy consumption of salt substitutes high in potassium can present a serious clinical
problem when aldosterone release is not normal.
22) Hypercalcemia causes muscle tetany.
23) The two hormones responsible for the regulation of calcium are pituitary hormone and
24) Calcitonin targets the bones and causes the release of calcium from storage when serum levels
25) The normal pH of blood is 7.35 - 7.45.
26) Most acidic substances (hydrogen ions) originate as by-products of cellular metabolism.
27) Weak acids are able to act as chemical buffering systems for the body because they partially dissociate.
28) The phosphate buffer system is relatively unimportant for buffering blood plasma.
29) The single most important blood buffer system is the bicarbonate buffer system.
30) One of the most powerful and plentiful sources of buffers is the protein buffer system.
31) As ventilation increases and more carbon dioxide is removed from the blood, the hydrogen
ion concentration of the blood decreases.
32) Regulation of the acid-base system is accomplished mainly through respiratory control, and the kidneys also play a small role.
33) Severe damage to the respiratory system rarely will result in acid-base imbalances.
34) Respiratory acidosis results when lungs are obstructed and gas exchange is inefficient.
35) Prolonged hyperventilation can cause alkalosis.
Fill-in-the-Blank/Short Answer Questions
1) ________ occurs when carbon dioxide is eliminated faster than it is produced.
Answer: Respiratory alkalosis
2) The female hormone ________ seems to decrease sodium reabsorption, thus promoting sodium and water loss by the kidney.
3) The preferred intracellular negative ion is ________.
Answer: hydrogen phosphate
4) The most important ECF buffer of HCl is ________.
Answer: sodium bicarbonate
5) The most important hormone that regulates calcium ions in the body is ________.
Answer: PTH (parathyroid hormone)
6) Molecules that can act reversibly as acids or bases depending upon the pH of their environment are called ________.
7) The breakdown of phosphorus-containing proteins releases ________ acid.
8) Arterial blood pH below 7.35 is called ________.
Answer: acidemia or acidosis
9) ________ reduces blood pressure and volume by inhibiting nearly all events that promote
vasoconstriction and the retention of sodium ions and water.
Answer: Atrial natriuretic peptide
10) What provides the shortest-term mechanism for preventing acid-base imbalances in the body? The longest-term mechanism?
Answer: Chemical buffers act within a fraction of a second to resist a pH change. The longest-term mechanism is the kidney system, which ordinarily requires from several hours to a day or more to effect changes in blood pH.
11) What is the effect of acidosis on the body? Of alkalosis?
Answer: When the body is in acute acidosis, the nervous system becomes so severely depressed
that the person goes into a coma and death soon follows. Alkalosis causes overexcitement of the nervous system. Characteristic signs include muscle tetany, extreme nervousness, and convulsions. Death often results from respiratory arrest.
12) Describe the mechanisms by which the kidneys remove hydrogen ions from the body.
Answer: Virtually all of the H+ that leaves the body in urine is secreted into the filtrate. The
tubule cells, including collecting ducts, appear to respond directly to the pH of the ECF and to alter their rate of H+ secretion accordingly. The secreted H+ ions are obtained from the dissociation of carbonic acid within the tubule cells. For each H+ ion actively secreted into the tubule lumen, one sodium ion is reabsorbed into the tubule cell from the filtrate, thus maintaining the electrochemical balance.
13) Describe the influence of rising PTH levels on bone, the small intestine, and the kidneys.
Answer: Parathyroid hormone (PTH) activates osteoclasts that break down the bone matrix,
resulting in the release of Ca2+ and PO43- to the blood. PTH enhances intestinal absorption of Ca2+ indirectly by stimulating the kidneys to transform vitamin D to its active form, which is necessary for calcium absorption by the small intestine. PTH
increases the reabsorption of calcium by the renal tubules, which simultaneously decreases phosphate ion reabsorption.
14) When the blood becomes hypertonic (too many solutes), ADH is released. What is the effect of
ADH on the kidney tubules?
Answer: The release of ADH causes the kidney tubules to reabsorb excess water, resulting in the
excretion of concentrated urine.
15) Why would an infant with colic be suffering from respiratory alkalosis?
Answer: If the infant is uncomfortable and cries forcefully for long periods of time, this would be
similar to hyperventilation. Hyperventilation would cause respiratory alkalosis because
the infant is losing carbon dioxide rapidly.
16) How does the respiratory system influence the buffer systems of the body?
Answer: The respiratory system maintains a constant bicarbonate level in the bloodstream by
outgassing carbon dioxide. In the event of a respiratory problem the bicarbonate system
might not be a constant.
17) Identify and describe the operation of the three major chemical buffers of the body.
the hydrogen ions released by a strong acid, thus converting it to a weaker acid, which lowers the
pH only slightly. For a strong base, the carbonic acid will be forced to donate more H+ to tie up
the OH- released by the base, with the net result of replacement of a strong base by a weak one.
The pH rise is very small. The phosphate buffer system, composed of the sodium salts of
dihydrogen phosphate and monohydrogen phosphate, acts in a similar fashion to the bicarbonate
system. NaH2PO4 acts as a weak acid; Na2HPO4 acts as a weak base. Hydrogen ions released
by strong acids are tied up in weak acids; strong bases are converted to weak bases. Amino acids
of the protein buffer system release H+ when the pH begins to rise by dissociating carboxyl
groups, or bind hydrogen ions with amine groups to form NH3+ when the pH falls.
18) When does a person experience greater thirst, during periods when ADH release is elicited or
during periods when aldosterone release is elicited?
Answer: A person experiences greater thirst during periods when ADH release is elicited.
1) A patient is admitted to the hospital in complete collapse. His blood pH is 6.8, and his HCO3- is 20 mEq/L. What diagnosis would you give and what prognosis? A medical history reveals that
this patient is a chronic alcoholic.
Answer: The pH and bicarbonate levels and the history of alcoholism indicate metabolic
acidosis. With a pH below 7.0, the patient will go into a coma and death soon follows.
2) A pregnant woman complains to her doctor that her ankles and feet stay swollen all of the
time. She is very worried about this. As her doctor, what would you tell her?
Answer: She is showing edema, an atypical accumulation of fluid in the spaces between cells
(interstitial spaces). This is caused by her pregnancy due to a high blood volume that increases
capillary hydrostatic pressure and enhances capillary permeability. She should be monitored for
the edema during the pregnancy, but it should clear up at the end of the pregnancy.
3) Helen is a 62-year-old smoker. Her physician has diagnosed her as having emphysema that
has caused her to hypoventilate. She is tired and sedentary. Besides having difficulty breathing,
what other condition is contributing to her tiredness?
Answer: Helen is suffering from respiratory acidosis because she is retaining too much carbon
dioxide. Her shallow breathing, due to the damage to her lungs from the disease, is the cause. In
order to release the carbon dioxide, one must be able to breathe normally (deep breathing would
4) Recently Alex's family noticed that he is craving salt to the point where he uses it excessively on his food. He also has a need to consume strange substances such as clay and burnt match tips.
What might be the cause of this strange behavior?
4) Recently Alex's family noticed that he is craving salt to the point where he uses it excessively
on his food. He also has a need to consume strange substances such as clay and burnt match tips.
What might be the cause of this strange behavior?
5) After traveling from Los Angeles to Denver, Claire finds she is not feeling well and checks
into a clinic for help. The clinic's diagnosis is respiratory alkalosis. What has caused this
Answer: Respiratory alkalosis is always caused by hyperventilation. Claire is experiencing the
effect of the high altitude and was overcompensating or trying to do too much the first day in
6) A patient is 72 years old and was admitted to the hospital for severe shortness of breath and
edema to her lower extremities. She was diagnosed with heart failure. A symptom of heart
failure is generalized edema. Explain the finding of generalized edema in heart failure.
Answer: Edema is an atypical accumulation of fluid in the interstitial space, leading to tissue
swelling. Heart failure is one cause of edema.
7) A 13-year-old girl is admitted to the psychiatric unit for anorexia. Her body weight is 89 lbs. and height is 64 inches. She admits to frequent self-induced vomiting and abuse of laxatives. She was treated on the medical unit with intravenous fluids. Now that she is on the psychiatric unit she is experiencing fluid retention as evidenced by mild puffiness and bloating.
Explain these symptoms.
Answer: It is not uncommon for anorexics who are chronically fluid depleted to develop a
compensatory increased production of aldosterone, which causes the kidneys to conserve sodium
8) A patient's anxiety caused her to develop respiratory alkalosis. The nurse instructs the patient to take some slow deep breaths.
Explain why this would be effective.
Answer: Instructing the patient to breathe more slowly will increase the patient's blood level of
CO2. Having the patient breathe into a paper bag would also increase blood CO2 levels.
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