Lecture 16 -- review questions Flashcards
what is a fluid compartment?
areas separated by selectively permeable membranes that differ in chemical composition
what are the 2 fluid compartments of the body?
intracellular fluid compartment
extracellular fluid compartment
which fluid compartment contains the most volume of water?
ICF
where is the transcellular fluid found?
in epithelial-lined cavities
what is interstitial fluid?
fluid b/n cells and vessels
what do ECF and ICF stand for?
ECF == extracellular fluid
ICF == intracellular fluid
what are the most abundant extracellular and intracellular cations?
most abundant ECF cation –> Na+
most abundant ICF cation –> K+
what are the most abundant extracellular and intracellular anions?
most abundant ECF anion – Cl-
most abundant ICF anion – Pi
how is the osmolarity of the ECF compared with the ICF? (isotonic, hyper, or hypo?)
isotonic
both @ 300
which is the most significant solute in determining total body water and water distribution among fluid compartments? Why?
Na+
water moves by osmosis based on solute concentration –> most abundant solute is Na+
how does water move between the intracellular and extracellular fluid compartments?
moves by osmosis –> passive flow based on osmotic gradients
what is osmosis?
passive flow down osmotic gradients
water flows from areas of low solute concentration to high solute concentration
what do isotonic, hypertonic, and hypotonic mean?
isotonic – same [solute]
hypertonic – higher [solute]
hypotonic – lower [solute]
what happens to water movement from inside the cells when extracellular fluid osmolality increases (=ECF water loss)?
water flows from ICF to ECF
what are the most severe consequences of fluid excess in the body?
pulmonary and cerebral edema
death
increase of levels of which hormone can cause volume excess?
aldosterone
in case of volume excess, how is the ECF’s tonicity (iso-, hyper-, or hypo-) compared with the ICF? Why?
isotonic –> ECF has same concentration of Na+ and water, there is just more of ECF
what are the two other names for hypotonic hydration?
water intoxication
positive water balance
increase of levels of which hormone can cause hypotonic hydration?
hypotonic hydration == water intoxication == positive water balance
ADH –> more water gets reabsorbed into bloodstream but not Na+
in the case of water intoxication, how is the ECF’s tonicity (iso-, hyper-, or hypo-) compared with the ICF? Why?
hypotonic –> ECF has a lot of water but didn’t increase solute [ ] with it
which type of fluid excess can you develop if you drink plenty of plain water (or pure distilled water with no ions at all)?
hypotonic hydration = water intoxication = positive water balance
more water but not more Na+
what are the most severe consequences of fluid deficiency for your body?
circulatory (hypovolemic) shock
neurological dysfunction
what is hypovolemia?
volume depletion
proportionate amounts of water and Na+ are lost
in volume depletion (hypovolemia), which is affected by ECF: Na+ levels, water levels, or both?
both
–> proportionate amounts of water and Na+ are lost
–> total body water decreases
–> osmolarity remains normal
what is dehydration also called?
negative water balance
in dehydration, which is affected: ECF Na+ levels, water levels, or both?
water levels –> lose water but Na+ remains
Given the following conditions, classify them as possible causes of volume depletion (hypovolemia) or dehydration (negative water balance):
- hemorrhage
- diabetes mellitus
- severe burns
- chronic vomiting
- diabetes insipidus (lowered ADH)
- chronic diarrhea
- Addison disease (lower aldosterone)
- lack of drinking water
volume depletion (hypovolemia):
- hemorrhage
- severe burns
- chronic vomiting
- chronic diarrhea
- Addison disease
dehydration (negative water balance):
- diabetes insipidus (lowered ADH)
- diabetes mellitus
- lack of drinking water
where is the thirst center located?
hypothalamus
will an increase in blood levels of Na+ stimulate or inhibit the thirst center?
how about a decrease of this ion?
increase of Na+ will stimulate the thirst center
decrease of Na+ will inhibit the thirst center
a decrease in blood pressure will stimulate the thirst center thru which hormone?
low BP –> angiotensin II stimulates thirst center
which gland secretes ADH?
posterior pituitary gland
when is ADH released? (think about plasma volume, blood pressure, and ECF osmolarity)
low plasma volume
low blood pressure
high ECF osmolarity
what type of urine does ADH produce? (hyper-, hypo-, or isotonic)
hypertonic
ADH wants to take water out of urine –> creates hypertonic urine
does high or low blood osmolarity decrease ADH secretion?
low blood osmolarity –> no need for water in blood –> decrease ADH secretion
how is the permeability of the collecting duct to water without ADH?
barely permeable to water
barely any water is reabsorbed –> a lot of water lost to urine
what would produce hypotonic urine: high or low ADH secretion?
low ADH secretion –> no water gets reabsorbed –> more water stays in urine –> hypotonic urine
if the body’s fluids’ osmolarity decreases, would your urine become hypo or hypertonic? How about the opposite?
low blood osmolarity –> no ADH secreted –> urine is hypotonic
high blood osmolarity –> ADH secreted –> urine is hypertonic
which are the 5 main functions of the ANP in Na+ homeostasis and renal function?
LOWERS BLOOD PRESSURE
1) lowers aldosterone production in zona glomerulosa –> more urine –> lowers BP
2) dilates AA in glomerulus to increase GFR –> more urine –> lowers BP
3) lowers renin production –> stops angiotensin II from being produced –> (angiotensin II causes vasoconstriction to increase BP so no angiotensin II == no vasoconstriction) –> lowers blood pressure
4) suppresses Na+ reabsorption in kidneys –> more urine –> lowers blood pressure
5) lowers ADH secretion –> more urine –> lowers blood pressure
does ANP increase or decrease the secretion of aldosterone?
which would be the consequence of this? (more or less Na+ excretion thru urine?)
decreases secretion of aldosterone
more urine excretion in urine
which 2 sodium transporters in the renal tubule does ANP inhibit?
where are they?
NaK2Cl channel in ascending limb of loop of Henle –> lowers the amount of Na+ that gets reabsorbed –> lowers the amount of water that gets reabsorbed
ENaC channel in collecting duct –> lowers Na+ and water absorption
does ANP produce vasoconstriction or vasodilation of the afferent arteriole?
which consequence does it have for the GFR (increase or decrease)?
ANP vasodilates afferent arteriole –> more urine and less blood –> lower BP
increases GFR
Does ANP increase or decrease the secretion of renin? By which cells (ie which cells produce renin)?
decrease secretion of renin by juxtaglomerular (granular) cells
no renin == no angiotensin II == lowers BP
does ANP increase or decrease the secretion of ADH?
Which would be the consequence of this? (more or less urine volume?)
decrease ADH secretion
raises urine volume
lowers blood volume and blood pressure
what is the overall effect of ANP on blood pressure: increase or decrease it?
decrease BP
aldosterone regulates Na+ reabsorption by secreting another cation; which one?
K+
by which 3 mechanisms does aldosterone promote sodium reabsorption and potassium excretion acting in the principal cells?
acts on DCT and CD
(1) increase the Na+/K+ ATPase –> use ATP to pump Na+ out of renal tubule into blood and K+ from blood into renal tubule
(2) increase Na+ reabsorption at ENaC –> Na+ flows from urine into renal tubule
(3) increase K+ secretion –> K+ leaves renal tubule into urine
overall effect:
Na+ gets reabsorbed from urine –> renal tubule –> blood
K+ gets secreted from blood –> renal tubule –> excreted in urine
what is the overall effect of aldosterone on blood pressure: increase or decrease it?
raise BP
In which renal tubule segment (PCT, Nephron loop, DCT, CD) is most of the K+ reabsorbed?
PCT
(K+ is reabsorbed at PCT, then secreted/excreted at DCT/CD)
where does fine-tuning of potassium excretion occur in the renal tubule?
DCT and CD
regulated by aldosterone, Na+ delivery, flow rate
which are the main functions of principal and intercalated cells concerning K+ homeostasis (reabsorption or secretion)?
PSIR –> parents should include rhinos
principal –> secrete K+ by reabsorbing Na+ during hyperkalemia
intercalated –> reabsorb K+ during K+ deficit
will high levels of K+ in the blood (hyperkalemia) stimulate or inhibit aldosterone secretion? Why?
stimulate aldosterone secretion
aldosterone increases Na+ reabsorption and increases K+ excretion
when will the intercalated cells reabsorb K+: in hyperkalemia or hypokalemia (= low K+ in the blood)?
hypokalemia
