Which cation is found at the highest concentration in intracellular fluid?
Potassium
✓
Sodium
Calcium
Magnesium
Correct Answer
Potassium
Potassium is the dominant cation inside cells, kept high by the sodium-potassium pump, and it largely sets the resting membrane potential. Sodium is the main cation of extracellular fluid, not intracellular fluid. Calcium is kept at very low concentration in the cytosol. Magnesium is present in cells but at far lower concentration than potassium.
Category: Fluid Compartments
Question 2
Which plasma protein is chiefly responsible for the colloid osmotic pressure of blood?
Fibrinogen
Albumin
✓
Insulin
Hemoglobin
Correct Answer
Albumin
Albumin is the most abundant plasma protein and generates most of the colloid osmotic pressure that pulls fluid back into capillaries. Fibrinogen is a clotting protein present in much smaller amounts. Insulin is a hormone found at tiny concentrations. Hemoglobin is carried inside red blood cells rather than dissolved in plasma.
Category: Fluid Compartments
Question 3
What is the portion of extracellular fluid that bathes cells in the tissue spaces outside blood vessels called?
Plasma
Lymph
Interstitial fluid
✓
Cytosol
Correct Answer
Interstitial fluid
Interstitial fluid fills the spaces between cells and is the largest share of the extracellular fluid. Plasma is the extracellular fluid held inside blood vessels. Lymph is fluid that has entered lymphatic vessels. Cytosol is fluid inside cells, so it is intracellular.
Category: Fluid Compartments
Question 4
At the arterial end of a capillary, which force is greater, causing net filtration of fluid out of the vessel?
Blood colloid osmotic pressure
Intrapleural pressure
Atmospheric pressure
Capillary hydrostatic pressure
✓
Correct Answer
Capillary hydrostatic pressure
Capillary hydrostatic pressure is the push of blood against the vessel wall, and it is highest at the arterial end, so fluid filters out there. Blood colloid osmotic pressure opposes filtration and wins at the venous end, where reabsorption occurs. Intrapleural pressure acts in the chest cavity around the lungs. Atmospheric pressure is the pressure of outside air and does not drive capillary exchange.
Category: Capillary Fluid Exchange
Question 5
Osmoreceptors that detect rising blood osmolality and trigger the sensation of thirst are located in which part of the brain?
Hypothalamus
✓
Medulla oblongata
Cerebellum
Thalamus
Correct Answer
Hypothalamus
Osmoreceptors in the hypothalamus sense when blood becomes too concentrated, stimulating the thirst center and the release of antidiuretic hormone. The medulla oblongata controls breathing and heart rate. The cerebellum coordinates movement. The thalamus relays sensory signals to the cortex.
Category: Water Balance
Question 6
ADH increases water reabsorption by causing collecting duct cells to insert which structures into their apical membranes?
Gap junctions
Aquaporins
✓
Calcium channels
Glucose transporters
Correct Answer
Aquaporins
Aquaporins are water channel proteins, and ADH moves them into the apical membrane so water can leave the filtrate and return to the blood. Gap junctions connect neighboring cells and do not regulate water reabsorption. Calcium channels carry calcium ions, not water. Glucose transporters move glucose and are not controlled by ADH.
Category: Water Balance
Question 7
Alcohol increases urine output mainly by inhibiting the release of which hormone?
Aldosterone
Renin
Antidiuretic hormone
✓
Calcitonin
Correct Answer
Antidiuretic hormone
Antidiuretic hormone normally makes the collecting ducts more permeable to water, so blocking its release lets more water escape in the urine. Aldosterone conserves water indirectly through sodium reabsorption but is not the hormone alcohol suppresses. Renin is a kidney enzyme that starts the angiotensin cascade. Calcitonin regulates blood calcium.
Category: Water Balance
Question 8
Severe liver disease that lowers plasma protein levels tends to cause edema by reducing which force?
Capillary hydrostatic pressure
Venous hydrostatic pressure
Arterial blood pressure
Blood colloid osmotic pressure
✓
Correct Answer
Blood colloid osmotic pressure
The liver makes albumin, and when plasma proteins fall, blood colloid osmotic pressure drops, so less fluid is pulled back into capillaries and it collects in the tissues. Capillary hydrostatic pressure pushes fluid out, so lowering it would reduce edema. Venous hydrostatic pressure also favors filtration when high, so lowering it would not cause edema. Arterial blood pressure is generated by the heart, not by plasma proteins.
Category: Capillary Fluid Exchange
Question 9
Which ion is the most abundant anion in extracellular fluid?
Chloride
✓
Bicarbonate
Phosphate
Sulfate
Correct Answer
Chloride
Chloride is the predominant extracellular anion and helps maintain fluid balance and electrical neutrality alongside sodium. Bicarbonate is the second most abundant anion in blood. Phosphate is concentrated inside cells and in bone. Sulfate is present only in small amounts.
Category: Electrolyte Balance
Question 10
Which hormone is released when blood calcium falls and raises it by freeing calcium from bone?
Calcitonin
Parathyroid hormone
✓
Aldosterone
Glucagon
Correct Answer
Parathyroid hormone
Parathyroid hormone raises blood calcium by releasing it from bone, reducing its loss in urine, and promoting calcitriol formation for intestinal absorption. Calcitonin has the opposite effect and lowers blood calcium. Aldosterone regulates sodium and potassium. Glucagon raises blood glucose, not calcium.
Category: Electrolyte Balance
Question 11
An abnormally high blood calcium level, as seen in primary hyperparathyroidism, is called what?
Hypocalcemia
Hyperkalemia
Hypercalcemia
✓
Hypernatremia
Correct Answer
Hypercalcemia
Hypercalcemia is an elevated blood calcium level, and excess parathyroid hormone causes it by releasing calcium from bone. Hypocalcemia is a low blood calcium level, as seen in hypoparathyroidism. Hyperkalemia is a high blood potassium level. Hypernatremia is a high blood sodium level.
Category: Electrolyte Balance
Question 12
Which enzyme speeds the reaction of carbon dioxide with water to form carbonic acid?
Lactase
Pepsin
ATP synthase
Carbonic anhydrase
✓
Correct Answer
Carbonic anhydrase
Carbonic anhydrase, abundant in red blood cells and kidney tubule cells, catalyzes the interconversion of carbon dioxide and water with carbonic acid. Lactase digests the milk sugar lactose. Pepsin breaks down proteins in the stomach. ATP synthase makes ATP in mitochondria.
Category: Buffer Systems
Question 13
In the bicarbonate buffer system of blood, what is the normal ratio of bicarbonate to carbonic acid?
20:1
✓
1:20
10:1
1:1
Correct Answer
20:1
Blood normally holds about 20 parts bicarbonate to 1 part carbonic acid, which keeps pH near 7.4 and makes the system well suited to absorbing added acid. A ratio of 1:20 would mean far more acid than base and a very low pH. A ratio of 10:1 would correspond to a lower pH than normal. A ratio of 1:1 would place blood pH well into the acidic range.
Category: Buffer Systems
Question 14
Which organs adjust blood bicarbonate levels to correct pH, a response that takes hours to days?
Lungs
Kidneys
✓
Liver
Stomach
Correct Answer
Kidneys
The kidneys control blood bicarbonate by reabsorbing it and secreting hydrogen ions, which is powerful but slow. The lungs control carbonic acid by exhaling carbon dioxide and act within minutes. The liver does not directly regulate blood bicarbonate. The stomach secretes acid for digestion but does not regulate blood pH.
Category: Respiratory and Renal Control
Question 15
Breathing too fast and deeply during an episode of extreme anxiety is most likely to produce which acid-base disorder?
Respiratory acidosis
Metabolic acidosis
Respiratory alkalosis
✓
Metabolic alkalosis
Correct Answer
Respiratory alkalosis
Hyperventilation blows off too much carbon dioxide, lowering carbonic acid and raising blood pH, which is respiratory alkalosis. Respiratory acidosis results from retaining carbon dioxide. Metabolic acidosis is a primary loss of bicarbonate or gain of nonvolatile acid. Metabolic alkalosis is a primary excess of bicarbonate.
Category: Acid-Base Disorders
Question 16
Diabetic ketoacidosis, in which ketone bodies accumulate in the blood, is an example of which disorder?
Respiratory alkalosis
Respiratory acidosis
Metabolic alkalosis
Metabolic acidosis
✓
Correct Answer
Metabolic acidosis
Ketone bodies are nonvolatile acids that use up bicarbonate, so diabetic ketoacidosis is a metabolic acidosis. Respiratory alkalosis comes from losing too much carbon dioxide. Respiratory acidosis comes from retaining carbon dioxide. Metabolic alkalosis is an excess of bicarbonate, the opposite problem.
Category: Acid-Base Disorders
Question 17
Prolonged vomiting of stomach contents is most likely to cause which acid-base disorder?
Metabolic alkalosis
✓
Respiratory acidosis
Respiratory alkalosis
Metabolic acidosis
Correct Answer
Metabolic alkalosis
Vomiting removes hydrochloric acid from the stomach, leaving relatively more bicarbonate in the blood and producing metabolic alkalosis. Respiratory acidosis is caused by impaired breathing that retains carbon dioxide. Respiratory alkalosis is caused by hyperventilation. Metabolic acidosis is more typical of severe diarrhea, which loses bicarbonate.
Category: Acid-Base Disorders
Question 18
A patient with emphysema who cannot exhale carbon dioxide effectively is most likely to develop which disorder?
Metabolic alkalosis
Respiratory acidosis
✓
Respiratory alkalosis
Metabolic acidosis
Correct Answer
Respiratory acidosis
Retained carbon dioxide forms carbonic acid and lowers blood pH, which is respiratory acidosis. Metabolic alkalosis is a primary excess of bicarbonate. Respiratory alkalosis results from exhaling too much carbon dioxide. Metabolic acidosis is a primary loss of bicarbonate or gain of nonvolatile acid rather than a breathing problem.
Category: Acid-Base Disorders
Question 19
When blood pH falls because bicarbonate is low, which response provides the fastest compensation?
Decreased breathing rate
Reduced bicarbonate reabsorption
Increased breathing rate
✓
Decreased hydrogen ion secretion
Correct Answer
Increased breathing rate
Faster, deeper breathing removes carbon dioxide and therefore carbonic acid, raising pH within minutes. Decreased breathing rate would retain carbon dioxide and make the acidosis worse. Reduced bicarbonate reabsorption would lose more base and lower pH further. Decreased hydrogen ion secretion would keep more acid in the blood.
Category: Acid-Base Disorders
Question 20
Water generated in the final steps of aerobic cellular respiration is called what?
Insensible water
Free water
Bound water
Metabolic water
✓
Correct Answer
Metabolic water
Metabolic water is produced when oxygen accepts electrons and hydrogen at the end of aerobic respiration, adding a small daily amount to total water intake. Insensible water refers to water lost unnoticed through the skin and breath. Free water is water not accompanied by solute. Bound water is water held by molecules or tissues, not water made by metabolism.
Category: Water Balance