BIOS 256 EXAM 3 PRACTICE SCRIPT
UPDATED 2026 TESTED SOLUTIONS
⫸ What percentage of body water is found in adult men? Answer:
About 60%
⫸ What percentage of body water is found in adult women? Answer:
About 50%
⫸ What happens to body water content with age? Answer: It declines to
about 45% in old age
⫸ What are the two main fluid compartments of the body? Answer:
Intracellular fluid (ICF) and extracellular fluid (ECF)
⫸ What are the subcompartments of extracellular fluid? Answer: Blood
plasma and interstitial fluid
⫸ What are nonelectrolytes? Answer: Organic molecules that do not
dissociate in water and carry no charge
⫸ What are electrolytes? Answer: Substances that dissociate into ions in
water and conduct electricity
,⫸ What are the major ECF ions? Answer: Major cation: Na⁺; major
anion: Cl⁻
⫸ What are the major ICF ions? Answer: Major cation: K⁺; major
anion: HPO₄²⁻
⫸ Which solutes make up most dissolved materials in body fluids?
Answer: Proteins and some nonelectrolytes (60-97%)
⫸ How does water move between compartments? Answer: By osmosis,
following solute concentration changes
⫸ What regulates body water balance? Answer: Water intake equals
water output
⫸ What triggers the thirst mechanism? Answer: Decrease in plasma
osmolality and dry mouth, stimulating the hypothalamic thirst center
⫸ What quenches thirst? Answer: Moistening of mucosa and distention
of stomach/intestines
⫸ What is obligatory water loss? Answer: Minimum water lost to
excrete wastes (≈500 mL/day) plus insensible losses
, ⫸ What hormone controls water reabsorption? Answer: Antidiuretic
hormone (ADH)
⫸ What happens when ADH levels are low? Answer: Dilute urine; less
water reabsorbed
⫸ What happens when ADH levels are high? Answer: Concentrated
urine; more water reabsorbed
⫸ What promotes ADH secretion? Answer: High ECF osmolality or
low blood volume/pressure
⫸ What is dehydration? Answer: Water output exceeds intake, causing
weight loss, fever, confusion, shock
⫸ What is hypotonic hydration? Answer: Excessive water intake or
renal insufficiency causing low Na⁺ and cell swelling
⫸ What is edema? Answer: Abnormal accumulation of fluid in
interstitial space
⫸ Why is sodium important? Answer: It regulates ECF volume, blood
pressure, and overall fluid balance
⫸ What triggers aldosterone release? Answer: Renin-angiotensin-
aldosterone mechanism due to low blood pressure or Na⁺
UPDATED 2026 TESTED SOLUTIONS
⫸ What percentage of body water is found in adult men? Answer:
About 60%
⫸ What percentage of body water is found in adult women? Answer:
About 50%
⫸ What happens to body water content with age? Answer: It declines to
about 45% in old age
⫸ What are the two main fluid compartments of the body? Answer:
Intracellular fluid (ICF) and extracellular fluid (ECF)
⫸ What are the subcompartments of extracellular fluid? Answer: Blood
plasma and interstitial fluid
⫸ What are nonelectrolytes? Answer: Organic molecules that do not
dissociate in water and carry no charge
⫸ What are electrolytes? Answer: Substances that dissociate into ions in
water and conduct electricity
,⫸ What are the major ECF ions? Answer: Major cation: Na⁺; major
anion: Cl⁻
⫸ What are the major ICF ions? Answer: Major cation: K⁺; major
anion: HPO₄²⁻
⫸ Which solutes make up most dissolved materials in body fluids?
Answer: Proteins and some nonelectrolytes (60-97%)
⫸ How does water move between compartments? Answer: By osmosis,
following solute concentration changes
⫸ What regulates body water balance? Answer: Water intake equals
water output
⫸ What triggers the thirst mechanism? Answer: Decrease in plasma
osmolality and dry mouth, stimulating the hypothalamic thirst center
⫸ What quenches thirst? Answer: Moistening of mucosa and distention
of stomach/intestines
⫸ What is obligatory water loss? Answer: Minimum water lost to
excrete wastes (≈500 mL/day) plus insensible losses
, ⫸ What hormone controls water reabsorption? Answer: Antidiuretic
hormone (ADH)
⫸ What happens when ADH levels are low? Answer: Dilute urine; less
water reabsorbed
⫸ What happens when ADH levels are high? Answer: Concentrated
urine; more water reabsorbed
⫸ What promotes ADH secretion? Answer: High ECF osmolality or
low blood volume/pressure
⫸ What is dehydration? Answer: Water output exceeds intake, causing
weight loss, fever, confusion, shock
⫸ What is hypotonic hydration? Answer: Excessive water intake or
renal insufficiency causing low Na⁺ and cell swelling
⫸ What is edema? Answer: Abnormal accumulation of fluid in
interstitial space
⫸ Why is sodium important? Answer: It regulates ECF volume, blood
pressure, and overall fluid balance
⫸ What triggers aldosterone release? Answer: Renin-angiotensin-
aldosterone mechanism due to low blood pressure or Na⁺
