NR 570 FINAL EXAM 360 QUESTIONS & CORRECT
ANSWERS LATEST 2025
TWB
Total body water
Total Body Water (TBW)
Total amount of water present within the body, which includes body, fluids,
tissues, and organs
As a person ages, and the percent of body fat increases...
... The amount of total body water decreases slightly
Percent of TBW in men
Constitutes 60% of body weight in men
Percent of TBW in women
Constitutes 50% of body weight in women
Formula for TBW - men
TBW=0.6 x total body weight in kg
Formula for TBW - women
TBW = 0.5 x total body weight in kg
Two major components of TBW
Intracellular
Extracellular
How much of a persons TBW is intracellular compartment
2/3
,How much of a person's TBW is extracellular compartment
1/3
Intracellular fluid volume (ICFV)
Volume of fluid within the intracellular compartment
Extracellular fluid volume (ECFV)
Volume of fluid in the extracellular compartment
Extracellular fluid contents
Intravascular {1/3} (plasma volume or content within the blood vessels)
Interstitial fluid {2/3} (fluid between the cells and the blood vessels)
body water composition
Why does water pass freely between the intravascular and interstitial
compartments?
In response to changes in solute concentrations in order to maintain osmotic
equilibrium in extracellular fluid volume
Two major players in regulating extra cellular fluid volume
Na+
H2O
What tags along where ever sodium goes?
Water
Sodium largely confined to
Extracellular fluid compartment
,What system regulates the amount of total body sodium/size of extracellular fluid
volume
Renin-angiotensin-aldosterone system
Bouncing the amount of sodium and water serves two purposes:
1) maintains the concentration of extracellular sodium with a narrow range of
135-145 mEq/L
2) maintains the ECV within reasonable limits (euvolemia)
Volume status directly relates to the
Extracellular space
Causes of intracellular electrolyte and volume loss are directly related to
extracellular causes, which include
Obligatory water loss (normal homeostasis)
Insensible sources (exhalation and sweat)
Feces
Urine
External sources of volume can be delivered via
Oral fluids
Food
IV infusion
Internal water production from the oxidation of food
If excess water is ingested beyond what is required for homeostasis
It is excreted
What is excreted via urine?
Metabolic byproducts and ingested excess solutes
When urine volume is less than the solute excretory load
, Renal failure develops
Normal serum osmolality
(~280 mOsm/L)
* The normal is 2X the average serum sodium, or 2×140
How is osmolality measured?
The amount of total solute concentration in the extracellular fluid compartment
Tonicity
A measure of the effective osmotic pressure gradient
Hyperosmolar state
Sodium concentration is high in the ECFV
Dehydration
Na+
Water loss (disproportionate to that of sodium)
The body’s mechanisms are activated to:
-conserve water + increase the secretion of sodium = lower urine volume with
higher urine concentration
-size of ECFV should increase to return the serum osmolality to normal
Hypoosmolar state
Sodium concentration is low in the ECFV
Fluid overload
Na+
ANSWERS LATEST 2025
TWB
Total body water
Total Body Water (TBW)
Total amount of water present within the body, which includes body, fluids,
tissues, and organs
As a person ages, and the percent of body fat increases...
... The amount of total body water decreases slightly
Percent of TBW in men
Constitutes 60% of body weight in men
Percent of TBW in women
Constitutes 50% of body weight in women
Formula for TBW - men
TBW=0.6 x total body weight in kg
Formula for TBW - women
TBW = 0.5 x total body weight in kg
Two major components of TBW
Intracellular
Extracellular
How much of a persons TBW is intracellular compartment
2/3
,How much of a person's TBW is extracellular compartment
1/3
Intracellular fluid volume (ICFV)
Volume of fluid within the intracellular compartment
Extracellular fluid volume (ECFV)
Volume of fluid in the extracellular compartment
Extracellular fluid contents
Intravascular {1/3} (plasma volume or content within the blood vessels)
Interstitial fluid {2/3} (fluid between the cells and the blood vessels)
body water composition
Why does water pass freely between the intravascular and interstitial
compartments?
In response to changes in solute concentrations in order to maintain osmotic
equilibrium in extracellular fluid volume
Two major players in regulating extra cellular fluid volume
Na+
H2O
What tags along where ever sodium goes?
Water
Sodium largely confined to
Extracellular fluid compartment
,What system regulates the amount of total body sodium/size of extracellular fluid
volume
Renin-angiotensin-aldosterone system
Bouncing the amount of sodium and water serves two purposes:
1) maintains the concentration of extracellular sodium with a narrow range of
135-145 mEq/L
2) maintains the ECV within reasonable limits (euvolemia)
Volume status directly relates to the
Extracellular space
Causes of intracellular electrolyte and volume loss are directly related to
extracellular causes, which include
Obligatory water loss (normal homeostasis)
Insensible sources (exhalation and sweat)
Feces
Urine
External sources of volume can be delivered via
Oral fluids
Food
IV infusion
Internal water production from the oxidation of food
If excess water is ingested beyond what is required for homeostasis
It is excreted
What is excreted via urine?
Metabolic byproducts and ingested excess solutes
When urine volume is less than the solute excretory load
, Renal failure develops
Normal serum osmolality
(~280 mOsm/L)
* The normal is 2X the average serum sodium, or 2×140
How is osmolality measured?
The amount of total solute concentration in the extracellular fluid compartment
Tonicity
A measure of the effective osmotic pressure gradient
Hyperosmolar state
Sodium concentration is high in the ECFV
Dehydration
Na+
Water loss (disproportionate to that of sodium)
The body’s mechanisms are activated to:
-conserve water + increase the secretion of sodium = lower urine volume with
higher urine concentration
-size of ECFV should increase to return the serum osmolality to normal
Hypoosmolar state
Sodium concentration is low in the ECFV
Fluid overload
Na+
