PHGY 216 Final Exam – Complete Study Guide With Practice Questions & Detailed 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
,PHGY 216 Final Exam – Complete Study Guide With Practice Questions & Detailed Answers
- 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
,PHGY 216 Final Exam – Complete Study Guide With Practice Questions & Detailed Answers
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
- Therefore, by controlling salt levels, ECF volume is being controlled
- To maintain salt balance, salt input must equal salt output
Salt Input - (answer)- Regulation of salt input is poor as it is dependent upon dietary salt
- It is necessary on a daily basis to replace the salt lost in the feces and sweat, which is about 0.5g/day
for normal activity levels (higher activity levels will increase the amount lost in sweat)
- The average input for Canadians is around 3.5 g/day
Salt Output - (answer)- The excess salt must be eliminated, which occurs in the kidneys
, PHGY 216 Final Exam – Complete Study Guide With Practice Questions & Detailed Answers
- The three pathways to eliminate salt are in the feces, sweat, and the kidneys
- The kidneys have the greatest role in salt elimination
Control of ECF Osmolarity - (answer)- Water moves down its concentration gradient until the osmotic
pressure across a membrane is equalized
- Because of this, regulating osmolarity is very important in preventing changes in cell volume
- When there is a decrease in ECF water the osmolarity increases and the ECF is hypertonic
- Since there is normally a balance in the osmolarity of the ICF and ECF, hypertonicity of the ECF causes
water to move out of the cells into the ECF until the osmotic pressure is equalized
- This loss of water from cells can cause them to shrink
- When there is an increase in ECF water, the osmolarity would decrease and the ECF would become
hypotonic
- This would result in water moving into the cells until the osmotic pressures were equalized and this
movement would cause the cells to expand
- If the ECF was very hypotonic, the amount of water moving into the cells would cause them to burst
Osmolarity - (answer)- Defined as a measure of the concentration of a particular solute in solution
- A high osmolarity means that there is more solute, and therefore less water, in solution
Hypertonic - (answer)A hypertonic solution is one in which the concentration of solutes within that
solution is greater than that of another solution that is separated by a membrane
Hypotonic - (answer)A solution that has a lower osmotic pressure than the surrounding cells
Hypotonicity - (answer)- Hypotonicity of the ECF is usually associated with overhydration, or excess free
water, and has three major causes: renal failure, rapid water ingestion, and over secretion of
vasopressin
- The osmolarity of the ECF must be regulated to prevent these undesirable shifts of water into or out of
the cell
Renal Failure - Hypotonicity - (answer)These individuals are not able to produce a concentrated urine
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
,PHGY 216 Final Exam – Complete Study Guide With Practice Questions & Detailed Answers
- 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
,PHGY 216 Final Exam – Complete Study Guide With Practice Questions & Detailed Answers
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
- Therefore, by controlling salt levels, ECF volume is being controlled
- To maintain salt balance, salt input must equal salt output
Salt Input - (answer)- Regulation of salt input is poor as it is dependent upon dietary salt
- It is necessary on a daily basis to replace the salt lost in the feces and sweat, which is about 0.5g/day
for normal activity levels (higher activity levels will increase the amount lost in sweat)
- The average input for Canadians is around 3.5 g/day
Salt Output - (answer)- The excess salt must be eliminated, which occurs in the kidneys
, PHGY 216 Final Exam – Complete Study Guide With Practice Questions & Detailed Answers
- The three pathways to eliminate salt are in the feces, sweat, and the kidneys
- The kidneys have the greatest role in salt elimination
Control of ECF Osmolarity - (answer)- Water moves down its concentration gradient until the osmotic
pressure across a membrane is equalized
- Because of this, regulating osmolarity is very important in preventing changes in cell volume
- When there is a decrease in ECF water the osmolarity increases and the ECF is hypertonic
- Since there is normally a balance in the osmolarity of the ICF and ECF, hypertonicity of the ECF causes
water to move out of the cells into the ECF until the osmotic pressure is equalized
- This loss of water from cells can cause them to shrink
- When there is an increase in ECF water, the osmolarity would decrease and the ECF would become
hypotonic
- This would result in water moving into the cells until the osmotic pressures were equalized and this
movement would cause the cells to expand
- If the ECF was very hypotonic, the amount of water moving into the cells would cause them to burst
Osmolarity - (answer)- Defined as a measure of the concentration of a particular solute in solution
- A high osmolarity means that there is more solute, and therefore less water, in solution
Hypertonic - (answer)A hypertonic solution is one in which the concentration of solutes within that
solution is greater than that of another solution that is separated by a membrane
Hypotonic - (answer)A solution that has a lower osmotic pressure than the surrounding cells
Hypotonicity - (answer)- Hypotonicity of the ECF is usually associated with overhydration, or excess free
water, and has three major causes: renal failure, rapid water ingestion, and over secretion of
vasopressin
- The osmolarity of the ECF must be regulated to prevent these undesirable shifts of water into or out of
the cell
Renal Failure - Hypotonicity - (answer)These individuals are not able to produce a concentrated urine
