Acid/Base & Renal System Flashcards
give the normal pH, acidosis pH, and alkalosis pH
normal 7.4
acidosis < 7.4
alkalosis > 7.4
what are the three types of buffers
- bicarbonate
- phosphate
- ammonia
what are the 3 ways to regulate acid/base? which one is the fastest? slowest?
- buffers (fastest)
- respiratory
- kidney (slowest)
what is the reaction for bicarbonate? what enzyme does it use? what does it act as? what does it buffer?
CO2 + H2O <–> H2CO3 <–> H + HCO3
carbonic anhydrase
act as weak acid or weak base
buffers both acid/bases and the blood
what are H ions in the RBC buffered by
intracellular proteins and phosphate
how is bicarbonate transported outside of a RBC
it is exchanged with extracellular Cl by Band 3 membrane transporter
where in the kidney does the majority of bicarbonate reabsorption occur
80% in proximal tubule
15% thick ascending limb
5% collecting duct
what does phosphate do as a buffer
buffers acid and bases
bone mineralization
usually an intracellular fluid buffer
where is ammonia made? excreted? what does it do?
when does ammonia excretion increase?
made in proximal tubule
excreted in distal tubule
allows kidney to expel acid during acidosis
when pH falls (more acidic)
how is ammonia produced?
- glutamine metabolized to ammonium by phosphate dependent glutaminase (PDG)
- ammonium decomposes into NH3 and H so NH3 can diffuse into proximal tubule or NH4+ can be exchanged with Na
how does bicarbonate get reabsorbed in the proximal tubule
- lumen (filtrate) –> cell via diffusion of CO2
- cell –> blood via cotransport with Na
how does bicarbonate get reabsorbed in the collecting duct
type A cells use AE1 to exchange HCO3 for Cl
type B cells use AE4 to exchange HCO3 for Na
what is the importance for the anion gap?
what does it consist of?
what is it useful for diagnosing?
- unmeasured anions to make cations = anions
- contains albumin, phosphate, sulfate, and other anions
- metabolic acidosis (either titrational or loss of HCO3)
describe the respiratory and metabolic origin for acidosis
respiratory: increase CO2
metabolic: decrease HCO3
describe the respiratory and metabolic origin for alkalosis
respiratory: decreased CO2
metabolic: increase HCO3
what is the concentration of Na and K extracellularly vs intracellularly
intracellular Na: 15mM
extracellular Na: 140 mM
intracellular K: 140 mM
extracellular K: 4mM
what is edema? how does it develop?
edema: excess fluid in extracellular compartment of interstitial space/body tissues
1. increased capillary hydrostatic pressure
2. decreased plasma oncotic pressure/plasma protein
3. decreased lymphatic return
4. inflammation/increased capillary permeability
what are the different body fluid compartments and their osmolarity and primary electrolyte
all 290mOsm
extracellular fluid 40% Na, Cl
1. plasma 7%
2. transcellular 2-3%
3. interstitial fluid 12%
intracellular 60% K, PO4, proteins
describe relative changes in size of intracellular and extracellular fluid compartments after IV infusion of isotonic, hypertonic, hypotonic saline
isotonic (300mOsm)
IC volume: none
EC volume: increased
hypertonic (500mOsm)
IC volume: decrease
EC volume: increase
hypotonic (100 mOsm)
IC volume: increase
EC volume: increase
why would an animal with hypoproteinemia have a reduction in plasma volume in spite of normal or increased ECF volume?
hypoproteinemia: loss of plasma proteins (decreased plasma ontic pressure)
- plasma volume would decrease because fluid would be leaking into interstitial space which could lead to edema
what are the functions of the kidney
- filter toxic substances
- regulate water, electrolytes, and acid-base
- endocrine organ (erythropoiesis, calcium homeostasis, and blood pressure)
how does renal control acid-base
- retains/eliminates HCO3
- secretes H+
- secretes NH3 with H+ as NH4+
how much cardiac output do the kidneys receive
20% CO
contrast the two types of nephrons
which one is the majority
what does it depend on
- cortical nephrons ( loop of henle in cortex)
- juxtamedullary (loop of henle in medulla); capillar termed vasa recta
majority cortical
species dependent
what are the fundamental processes of the kidney
- filtration
- reabsorption
- secretion
what is the glomerulus? what types of cells does it have and their function?
capillary between two arterioles with high pressure
1. capillary endothelium fenestrations - filtration
2. podocytes - foot processes for filtration
3. (-) charged basement membrane - repels (-) charged proteins
what are the 4 factors that determine net filtration
- hydrostatic capillary pressure Pc
- oncotic capillary pressure Ppi
- hydrostatic bowman space pressure Pbs
- oncotic bowman space pressure Ppibs
what is the equation for net filtration
net filtration = Pc - Ppi - Pbs
what are the determinants of GFR
- filtration membrane permeability
- surface area availability
- net filtration pressure
what controls GFR
- renal blood flow (e.g. increase blood pressure increase GFR)
- arteriole resistance
a. constriction of afferent arteriole decreases GFR
b. constriction of efferent arteriole increases GFR but eventually decreases
what are the 4 types of regulation of GFR
- autoregulation
- renin-angiotensin-aldosterone system
- sympathetic NS
- atrial natriuretic peptides
what is the myogenic effect
afferent arteriole responding to stretch by constricting to decrease GFR
what is tubuloglomerular feedback
- macula densa sense increase osmolarity in tubules and release vasoconstrictors on afferent arteriole to decrease GFR
describe the renin-angiotensin aldosterone system
in response to low BP/BV
1. angiotensinogen (liver) –> angiotensin 1 via renin
2. ANG1 –> ANG2 via ACE
3. ANG2
a. system vasoconstriction to increase BP
b. constrict afferent/efferent arteriole to decrease GFR
c. increase aldosterone to increase Na/water reabsorption to increase BV
how does the sympathetic NS regulate GFR
release of NE to constrict afferent/efferent arterioles to decrease GFR
how do ANP regulate GFR
atrial myocytes respond to stretch (increase BV/BP) by releasing ANP
ANP will dilate afferent arteriole/ constrict efferent arteriole to increase GFR
what is renal clearance and its formula
renal clearance: rate of disappearance from plasma and appearance in urine
clearance = excretion rate (mg/min) / plasma conc. (mg/ml)
what things are freely filtered
inulin, creatinine, amino acids, glucose, and water
why do serum creatinine and BUN increase with significant reduction in glomerular filtration rate?
amount excreted doesn’t change so if there is an decrease in GFR the body needs to increase the amount in the blood to get the same amount secreted
give an example of paracellular transport and transcellular transport
paracellular: between cells, like Na/K/Ca/Mg in thick ascending limb
transcellular: passes through both membranes of cell, like bicarbonate transport
why is glucosuria seen in animals with uncontrolled diabetes mellitus? how does this contribute to polyuria?
glucosuria: glucose in the urine; seen in animals with uncontrolled diabetes because body is having to excrete excess glucose that is not reabsorbed
polyuria: frequent urination because excess glucose increase filtrate osmolarity –> more water in filtrate –> increased urination
what is reabsorbed in the proximal tubules
Na, Cl, HCO3, K, glucose, amino acids, water
how is Na reabsorbed in the proximal tubule
how is Cl reabsorbed in proximal tubule
how is HCO3 reabsorbed in proximal tubule
Na/K ATPase Pump
Cl paracellular transport
Na co-transport
what is secreted in the proximal tubules
H+, toxins/drugs (penicillin, morphine), organic acids and bases, creatine/bile acids
what is the major force for reabsorption of Na, Cl, and water in the proximal tubule
Na/K ATPase Pump
what is the loop of henle
countercurrent multiplier that establishes a hyperosmotic gradient for water reabsorption
what is primarily occuring in the descending limb?
what type of transport?
reabsorption of water impermeable to ions)
passive
what is the effect on volume and osmolarity in the proximal tubule
volume 70% decreased
osmolarity same 300mOsm (isotonic)
what is primarily occurring in the thick ascending limb?
what type of transport?
reabsorption of Na,K, Cl
active - Na/K/2Cl transporter
where and what is the target for loop diuretics?
what do they do?
Na/K/2Cl transporter in the thick ascending limb of LOH
loop diuretics: inhibit the transporter to prevent solute reabsorption to allow increase excretion of water
what is primarily occurring in the distal tubule?
what type of transport?
reabsorption of Na via Na/Cl transporter
impermeable to water
what is primarily occurring in the collecting duct?
what cells are located in this region?
water reabsorption (ADH/VP)
Na+ reabsorption (aldosterone)
K secretion (aldosterone)
principle cells & intercalated cells
what is the function of principle cells
reabsorb Na and secrete K, controlled by aldosterone
what is the function of intercalated cells (A and B)
type A during acidosis secrete H+
type B during alkalosis secrete HCO3
where is urea reabsorbed?
secreted?
why is it a major contributor to the medullary gradient?
where does it come from?
reabsorbed in proximal tubule and collecting duct
secreted in thin ascending limb of loop of henle
drives water reabsorption
liver
describe species differences regarding the loop of henle
long loop of henle in species that need a lot of water reabsorption (kangaroo rats) and short in animals with access to water (beavers)
why were there a number of flies attracted to the urine of dogs that had their pancreas removed?
pancreas produces insulin, without insulin glucose levels cannot be lowered causing excess to be excreted in the urine making it “sweet”
how does acetazolamide work?
how is it a diuretic?
does it lead to acidosis or alkalosis?
inhibits carbonic anhydrase = no bicarbonate reabsorption
leads to acidosis
diuretic because it leads to excess water excretion
