PHGY 216 FINAL EXAM QUESTIONS AND
CORRECT ANSWERS
Water Balance - ANSWER - Every cell in the body requires a well-regulated environment
in order to survive and function
- Body water plays a large role in creating this environment, which is comprised of
intracellular and extracellular fluid
- When we talk about the major body compartments for water (fluid) there are three key
pools: ICF, plasma, and interstitial fluid, which remain distinct due to the presence of
"barriers" between them
Intracellular Fluid (ICF) - ANSWER This is the fluid within the cells and comprises about
two thirds of total body fluid
Extracellular Fluid (ECF) - ANSWER - This is the fluid surrounding the cells which includes
the plasma, the interstitial fluid, lymph, and transcellular fluid (such as cerebrospinal
fluid) and comprises about one third of total body fluid
- The plasma is about one fifth of the ECF, the interstitial fluid is about four fifths of the
ECF, and the lymph and the transcellular fluid are considered negligible
Transcellular Fluid - ANSWER The portion of total body water contained within epithelial
lined spaces
Barriers Between Body-Fluid Compartments - ANSWER - Several barriers separate the
,body-fluid compartments
- This limits the movement of water and solutes between the various compartments to
differing degrees
Barriers Between the Plasma and Interstitial Fluid - ANSWER - The plasma and the
interstitial fluid are separated by the blood vessel walls
- At the level of the capillaries, water and everything else in the plasma (except proteins)
can freely exchange with the interstitial fluid
- Because of this, the composition of the plasma and the interstitial fluid are essentially
identical, except for the plasma protein
- Consequently, any change in one of these compartments is quickly reflected in the
other compartments
Barriers Between the Intracellular Fluid and the ECF - ANSWER - This barrier is the
plasma membrane that surrounds each cell in the body
- The ICF contains proteins that do not exchange with the ECF
- There is an unequal distribution of ions across this barrier because the barrier does not
allow the passive movement of either ICF or ECF constituents across the plasma
membrane, preventing them from equilibrating through diffusion
ECF Volume and Osmolarity - ANSWER - All exchanges of water and other constituents
between the ICF and the external world are dependent upon the ECF
- Even though cells tightly regulate their own ICF, it can be said that overall control of
fluid balance is dependent upon regulating the ECF
- In order to maintain fluid balance in the body the ECF volume and osmolarity are
,regulated
ECF Volume - ANSWER - This is closely regulated to maintain blood pressure
- The maintenance of salt balance is important in the long-term regulation of ECF
volume
ECF Osmolarity - ANSWER - This is closely regulated to prevent the swelling or shrinkage
of cells
Control of ECF Volume - ANSWER - ECF volume directly influences blood pressure by
changing plasma volume
- Increasing ECF volume will increase plasma volume ,and thus increase arterial blood
pressure
- Consequently there are mechanisms in place to adjust blood pressure until the ECF
volume is returned to normal values
- There are short term control factor including the baroreceptor reflex and fluid shifts
- There are long term control factors including fluid input and output
The Baroreceptor Reflex - ANSWER - Baroreceptors are mechanoreceptor that are
located in the carotid artery and the aortic arch (areas within major arteries of the body),
and they detect changes in arterial blood pressure
- Through the effects of the autonomic nervous system on the heart and blood vessels,
teh baroreceptor reflex regulates blood pressure
- When pressure falls too low, cardiac output and total peripheral resistance will increase
, to raise blood pressure
- When blood pressure rises above normal, both decrease to reduce blood pressure
Total Peripheral Resistance - ANSWER - The resistance to blood flow due to the
constriction of blood vessels
- Higher total peripheral resistance leads to increased blood pressure
Cardiac Output - ANSWER The amount of blood pumped by the heart per minute
Fluid Shifts - ANSWER - A decrease in plasma volume can temporarily be compensated
for by a shift of the fluids out of the interstitial compartments to the plasma
- The opposite is also true, an increase in plasma volume can cause fluid to shift to the
interstitial compartment
Fluid Input/Output - ANSWER - The short term control mechanisms are only temporary
and can only compensate for fairly minor changes in ECF fluid volumes
- Long-term regulation of blood pressure is a primary function of the kidneys and the
thirst mechanism, controlling fluid output and input, respectively
- Control of urine output by the kidneys is critical for long-term regulation of blood
pressure
Control of Salt - ANSWER - Sodium, and the anions that are associated with it (mainly
chloride), account for more than 90% of the ECF's solutes
- Whenever salt is transported across a membrane, water follows due to osmosis
CORRECT ANSWERS
Water Balance - ANSWER - Every cell in the body requires a well-regulated environment
in order to survive and function
- Body water plays a large role in creating this environment, which is comprised of
intracellular and extracellular fluid
- When we talk about the major body compartments for water (fluid) there are three key
pools: ICF, plasma, and interstitial fluid, which remain distinct due to the presence of
"barriers" between them
Intracellular Fluid (ICF) - ANSWER This is the fluid within the cells and comprises about
two thirds of total body fluid
Extracellular Fluid (ECF) - ANSWER - This is the fluid surrounding the cells which includes
the plasma, the interstitial fluid, lymph, and transcellular fluid (such as cerebrospinal
fluid) and comprises about one third of total body fluid
- The plasma is about one fifth of the ECF, the interstitial fluid is about four fifths of the
ECF, and the lymph and the transcellular fluid are considered negligible
Transcellular Fluid - ANSWER The portion of total body water contained within epithelial
lined spaces
Barriers Between Body-Fluid Compartments - ANSWER - Several barriers separate the
,body-fluid compartments
- This limits the movement of water and solutes between the various compartments to
differing degrees
Barriers Between the Plasma and Interstitial Fluid - ANSWER - The plasma and the
interstitial fluid are separated by the blood vessel walls
- At the level of the capillaries, water and everything else in the plasma (except proteins)
can freely exchange with the interstitial fluid
- Because of this, the composition of the plasma and the interstitial fluid are essentially
identical, except for the plasma protein
- Consequently, any change in one of these compartments is quickly reflected in the
other compartments
Barriers Between the Intracellular Fluid and the ECF - ANSWER - This barrier is the
plasma membrane that surrounds each cell in the body
- The ICF contains proteins that do not exchange with the ECF
- There is an unequal distribution of ions across this barrier because the barrier does not
allow the passive movement of either ICF or ECF constituents across the plasma
membrane, preventing them from equilibrating through diffusion
ECF Volume and Osmolarity - ANSWER - All exchanges of water and other constituents
between the ICF and the external world are dependent upon the ECF
- Even though cells tightly regulate their own ICF, it can be said that overall control of
fluid balance is dependent upon regulating the ECF
- In order to maintain fluid balance in the body the ECF volume and osmolarity are
,regulated
ECF Volume - ANSWER - This is closely regulated to maintain blood pressure
- The maintenance of salt balance is important in the long-term regulation of ECF
volume
ECF Osmolarity - ANSWER - This is closely regulated to prevent the swelling or shrinkage
of cells
Control of ECF Volume - ANSWER - ECF volume directly influences blood pressure by
changing plasma volume
- Increasing ECF volume will increase plasma volume ,and thus increase arterial blood
pressure
- Consequently there are mechanisms in place to adjust blood pressure until the ECF
volume is returned to normal values
- There are short term control factor including the baroreceptor reflex and fluid shifts
- There are long term control factors including fluid input and output
The Baroreceptor Reflex - ANSWER - Baroreceptors are mechanoreceptor that are
located in the carotid artery and the aortic arch (areas within major arteries of the body),
and they detect changes in arterial blood pressure
- Through the effects of the autonomic nervous system on the heart and blood vessels,
teh baroreceptor reflex regulates blood pressure
- When pressure falls too low, cardiac output and total peripheral resistance will increase
, to raise blood pressure
- When blood pressure rises above normal, both decrease to reduce blood pressure
Total Peripheral Resistance - ANSWER - The resistance to blood flow due to the
constriction of blood vessels
- Higher total peripheral resistance leads to increased blood pressure
Cardiac Output - ANSWER The amount of blood pumped by the heart per minute
Fluid Shifts - ANSWER - A decrease in plasma volume can temporarily be compensated
for by a shift of the fluids out of the interstitial compartments to the plasma
- The opposite is also true, an increase in plasma volume can cause fluid to shift to the
interstitial compartment
Fluid Input/Output - ANSWER - The short term control mechanisms are only temporary
and can only compensate for fairly minor changes in ECF fluid volumes
- Long-term regulation of blood pressure is a primary function of the kidneys and the
thirst mechanism, controlling fluid output and input, respectively
- Control of urine output by the kidneys is critical for long-term regulation of blood
pressure
Control of Salt - ANSWER - Sodium, and the anions that are associated with it (mainly
chloride), account for more than 90% of the ECF's solutes
- Whenever salt is transported across a membrane, water follows due to osmosis
