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Chapter 17 (VPHY 3100)
Chapter 17 (VPHY 3100)
211
Physiology
Undergraduate 3
11/17/2020
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Term
some functions of the kidneys
 Definition
-regulate volume and components of ECF (plasma and interstitial fluid) through filtering of blood plasma into urine -Regulate BP through volume of blood plasma -Regulate [waste products] in blood -Regulate concentration of electrolytes (Na+, K+, H+, HCO3- & other ions) -Regulate pH of body fluids -Secrete erythropoietin +Hypoxia → ↑ erythropoietin → ↑RBC production
Term
the primary function of the kidneys
 Definition
regulate volume and components of ECF (plasma and interstitial fluid) through filtering of blood plasma into urine
Term
how kidneys are stimulated to secrete erythropoietin
 Definition
Hypoxia → ↑ erythropoietin → ↑RBC production
Term
depiction of the kidneys in the context of the urinary system
 Definition
[image]
Term
the structure of the kidney
 Definition
[image]
Term
some structural components of the kidney
 Definition
-outer cortex
-inner medulla
-Collecting ducts of nephrons (ahead)
Term
outer cortex of the kidney
 Definition
-outer component
-contains many capillaries
Term
inner medulla of the kidneys
 Definition
-inner component of the kidneys
-has 7-18 renal pyramids separated by renal columns
Term
Collecting ducts of nephron
 Definition
ahead of the kidneys, they empty into minor calyces which unite to form a major calyx
Term
path by which urine goes from kidneys to urination
 Definition
Path of urine = nephrons -> minor calyces -> major calyces -> renal pelvis -> ureters -> urinary bladder -> urethra -> exits
[image]
Term
nephron
 Definition
the functional unit of the kidney
[image]
Term
3 muscles to focus on concerning the bladder
 Definition
-Detrusor – smooth muscle – bladder wall
-Internal urethral sphincter – smooth muscle
-External urethral sphincter – skeletal muscle
[image]
Term
Micturition center
 Definition
part of the pons involved in urination
-not doing anything during the filling phase
Term
depiction of the sympathetic process of filling the bladder
 Definition
[image]
Term
some things that happen during the process of filling the bladder
 Definition
-Filling of bladder – sympathetic relaxation of detrusor and constriction of internal urethral sphincter.
-Somatic motor fibers stimulate external (lower) urethral sphincter (voluntary).
-Afferent fibers along pelvic nerve detect stretch -> stimulate sympathetic outflow from hypogastric nerve, and constant somatic firing from pudendal nerve.
[image]
Term
why the filling of the bladder is a sympathetic process
 Definition
because a nerve is actively mediating the the detrusor muscle of the bladder wall and the internal and external sphincters are being constricted
Term
the neurotransmitter(s) involved in the sympathetic process of filling the bladder
 Definition
norepinephrine for the involuntary and acetylcholine for the voluntary
Term
depiction of the parasympathetic process of emptying the bladder
 Definition
[image]
Term
some things that happen during the parasympathetic process of emptying the bladder
 Definition
-As bladder fills, afferent firing along pelvic nerve ↑↑ -> [periaqueductal grey integrates signals from spinal cord and central regions] -> triggers micturition center in pons ->…
--> Full bladder – pons signals inhibition of sympathetic and activation of parasympathetic neurons → contraction of detrusor & relaxation of internal (upper) urethral sphincter.
-Somatic motor fibers control external (lower) urethral sphincter (voluntary) – relax.
[image]
Term
the neurotransmitter(s) involved in the parasympathetic process of emptying the bladder
 Definition
acetylcholine
Term
depiction of the blood vessels in the kidneys
 Definition
[image]
Term
Renal plasma (blood) flow
 Definition
Renal plasma (blood) flow = volume of plasma (blood) delivered to kidneys over time (mL/min). *RPF is 22% of cardiac output.
Term
the path blood takes through the vessels in the kidneys
 Definition
Renal artery → interlobar artery → arcuate a. → interlobular a. → afferent arteriole → glomerulus (1st capillary) → efferent arteriole → peritubular capillaries (2nd capillary) with vasa recta surrounding loop of Henle → venous blood [image]
Term
function of the glomerulus
 Definition
filtration of blood
Term
how many nephrons are in a kidney?
 Definition
>106 units in a kidney
Term
the 2 main components of the nephron
 Definition
1. Vascular component
2. Tubular components
[image]
Term
vascular component of the nephron
 Definition
glomerulus – all of RPF passes through the glomeruli
[image]
Term
the tubular components of the nephron and the path taken
 Definition
Nephron tubule: glomerular (Bowman’s) capsule → proximal convoluted tubule (PCT) → loop of Henle (LOH) (descending limb -> thin ascending limb -> thick ascending limb) → distal convoluted tubule (DCT) → collecting duct (CD) cortical then medullary → empties into calyx
[image]
Term
types of nephrons
 Definition
1. Cortical nephron
2. Juxtamedullary nephron
[image]
Term
Cortical nephron
 Definition
originates in outer 2/3 of cortex -about 85% of nephrons are cortical nephrons *More involved in solute reabsorption and waste secretion. [image]
Term
Juxtamedullary nephron
 Definition
originates in inner 1/3 cortex *Important for producing concentrated urine. -Has longer LOH & well-developed vasa recta. [image]
Term
RPF
 Definition
Renal plasma (blood) flow
Term
GFR
 Definition
Glomerular filtration rate
Term
depiction of the structure of the glomerular structure
 Definition
[image]
[image]
Term
some components of the glomerular structure
 Definition
-Glomerulus
-Glomerular (Bowman’s) capsule
[image]
[image]
Term
Glomerulus
 Definition
tangle of capillaries within the glomerular structure
-Recall glomerulus is tuft of blood vessels
+Afferent arteriole in
+Efferent arteriole out
-Glomerular capsule + glomerulus = renal corpuscle
[image]
Term
renal corpuscle
 Definition
Glomerular capsule + glomerulus = renal corpuscle
[image]
Term
Ultrafiltrate (filtrate)
 Definition
fluid that enters glomerular space -> proximal convoluted tubule
Term
Glomerular (Bowman’s) capsule
 Definition
Surrounds glomerulus – 2 layers
-Inner layer (podocytes) lines blood vessels
-Outer layer – rounded and encompasses entire glomerulus
-Glomerular (Bowman’s) space in-between
[image]
Term
An ultrafiltrate in glomerulus must pass through, in order
 Definition
`(1) Fenestrated capillary – large pores in the endothelium.
(2) Basement membrane
(3) Slits in the processes of podocytes, which comprise the inner layer of the glomerular capsule.
-Slit diaphragms span the slits.
[image]
Term
the part of the glomerular structure the ultrafiltrate passes through
 Definition
[image]
Term
fenestrated
 Definition
having perforations, apertures, or transparent areas
Term
how fenestrated capillaries help form filtrate
 Definition
-100-400 times more permeable to plasma H2O, and solutes (electrolytes, glucose, etc.). -Small enough to prevent RBCs, platelets, WBCs, and large proteins from passing through pores.
Term
Plasma proteins are mostly excluded from the filtrate due to...
 Definition
large size and negative charge.
-The basement membranes and slit diaphragms of podocytes are lined with negative charges which repel negatively-charged proteins.
Term
why glomerular filtrate has low protein concentration
 Definition
*Filtered proteins reabsorbed by renal epithelial cells -> no proteins in urine.
[image]
Term
What are two general causes of proteinuria?
 Definition
1: proteins get through the glomerulus
2: proximal tubular cells not reabsorbing the protein
[image]
Term
glomerular filtration formed under...
 Definition
(1) hydrostatic P of blood (major, due to BP) [and colloid osmotic P of glomerular filtrate (very minor)]
[image]
Term
glomerular filtration countered by...
 Definition
(2) Hydrostatic P of glomerular filtrate
(3) Colloid osmotic P of plasma
[image]
Term
Net filtration pressure of glomerular filtration
 Definition
10 mm Hg
[image]
Term
Glomerular filtration rate (GFR)
 Definition
-Volume of filtrate produced by both kidneys each minute; this is the rate at which urine forms
-~115 mL/min in women, 125 mL/min in men -> 7.5 L/hour -> 180 L/day
-Correlates with renal function.
Term
the stages of chronic kidney disease and their associated glomerular filtration rates (GFRs)
 Definition
[image]
Term
*Volume of urine per day
 Definition
*Volume of urine is ~ 1-2 L/day (1%) --> 99% of filtrate is reabsorbed.
[image]
Term
why we pee out only 1-2 L of the 180 L produced by glomerular filtration rate (GFR)
 Definition
because volume of urine is ~ 1-2 L/day (1%) --> 99% of filtrate is reabsorbed
[image]
Term
Obligatory water loss
 Definition
minimal urine volume required to excrete metabolic waste (400 - 600 mL)
[image]
Term
Filtration (in the context of the nephron)
 Definition
from the glomerulus to form the filtrate.
[image]
Term
Reabsorption (in the context of the nephron)
 Definition
brings water and solutes out of the filtrate back into the plasma along the rest of the nephron.
[image]
Term
Secretion (in the context of the nephron)
 Definition
secreting solutes into the filtrate for excretion or elimination.
[image]
Term
Quantity of a solute excreted
 Definition
Quantity of a solute excreted = (quantity filtered + quantity secreted) - quantity reabsorbed
[image]
Term
Renal Excretion Rate
 Definition
Quantity of a solute excreted per min (mg/min)
Renal Excretion Rate = V (rate of urine formation, mL/min) x U (concentration of solute x in urine, mg/mL)
[image]
Term
Renal excretion or elimination rate
 Definition
Amount of substance removed per unit time = mg/min.
[image]
-Recall renal plasma flow (A) = mL/min.
-Recall GFR (B) = mL/min.
Term
Renal plasma clearance rate
 Definition
-Ability of kidneys to remove a specific solute (x) from plasma and excrete those molecules in the urine.
-*The volume of plasma from which a solute is completely removed by kidney per unit time = mL/min.
[image]
-Recall renal plasma flow (A) = mL/min.
-Recall GFR (B) = mL/min.
Term
how and why inulin is used to measure glomerular filtration rate (GFR)
 Definition
-If a substance is neither reabsorbed nor secreted, then the amount excreted = amount filtered
-Renal excretion of inulin – filtered but neither reabsorbed nor secreted.
-Have to administer inulin and then collect urine and blood samples.
-Its clearance rate is equal to GFR. Example, 120 mL/min.
[image]
Term
Creatinine
 Definition
a metabolite of muscle creatine formed at a constant rate
Term
how and why creatinine is used to measure glomerular filtration rate (GFR)
 Definition
-Creatinine – a metabolite of muscle creatine formed at a constant rate.
-The creatinine excretion is the function of muscle mass, less affected by diet, age, and sex.
-Measure of the plasma creatinine is a good indicator of GFR.
-Creatinine freely filters through the glomeruli and is only slightly secreted by PCT  clearance close to GFR, a little above that of inulin (~127 mL/min).
-Just measuring plasma creatinine gives a rough idea of renal function (GFR).
+(There are other non-renal reasons such as dehydration and urinary obstruction which will also affect plasma creatine.)
[image]
Term
How does determining creatinine clearance differ from determining inulin clearance?
 Definition
you make your own creatinine; you don't have to introduce creatinine
Term
What happens to plasma creatinine if glomerular filtration rate (GFR) decreases?
 Definition
increases
Term
What happens to urine creatinine if glomerular filtration rate (GFR) decreases?
 Definition
decreases
Term
depiction of the entire pathway of renal absorption
 Definition
[image]
Term
the 2 routes by which renal reabsorption can occur
 Definition
-transcellular
-paracellular
Term
transcellular route of renal reabsorption
 Definition
through tubular cells
Filtrate -> Apical membrane tubular cell -> Basal membrane tubular cell -> Interstitial fluid -> Capillary
[image]
Term
paracellular route of renal reabsorption
 Definition
between tubular cells
Filtrate -> interstitial fluid -> capillary
[image]
Term
Which fluid compartment does transcelluar route involve that paracellular does not?
 Definition
the intracellular route
[image]
Term
PCT
 Definition
proximal convoluted tubule
Term
LOH
 Definition
loop of Henle
Term
solute concentration in different parts of the PCT and LOH
 Definition
[image]
Term
some hormones that regulate salt and water transport in the distal nephron
 Definition
-Vasopressin (ADH)
-Aldosterone
Term
constituative reabsorption
 Definition
reabsorption that does not change and is not hormonally regulated
-Approximately 65% of the filtered salt & water is reabsorbed across PCT, 20% is reabsorbed across loop of Henle (LOH).
-Salt transport in the above regions (PCT & LOH) are NOT under hormonal regulation.
Term
the parts of the nephron where the kidneys can tweak the amount of salt and water that get reabsorbed
 Definition
the distal convoluted tubule (DCT) and the collecting duct (CD)
-Only 15% of the initial filtrate gets there. This 15% is reabsorbed variably, depending on level of hydration and the concentration of electrolytes in the body.
Term
the remaining 15% of initial filtrate that gets to the DCT and CD is reabsorbed variably, depending on...
 Definition
level of hydration and the concentration of electrolytes in the body.
Term
how Na+ is transported across the apical membrane in the PCT
 Definition
by facilitated diffusion (2° active transport) using Na+-glucose cotransporter, no energy spent [image]
Term
how Na+ is transported across the basolateral membrane in the PCT
 Definition
by (1°) active transport using Na+-K+ pump, energy required [image]
Term
how Na+ gets into systemic capillaries
 Definition
Diffuses across interstitial space into systemic capillaries.
[image]
Term
energy requirements of reabsorption in the PCT
 Definition
uses 6% of total energy expenditure of the body to reabsorb 65% of the filtrate
Term
what Cl- does in the reabsorption process in the PCT
 Definition
-follows Na+ (electrical attraction) –paracellular [image]
Term
what water does in the reabsorption process in the PCT
 Definition
*Water (~115 L/day) follows the osmotic pressure of salt out of PCT into interstitium then to blood (peritubular capillaries) -> no change in osmolarity. -PCT highly permeable to H2O -Aquaporin channels [image]
Term
water usually follows the Na+ ions, except in...
 Definition
the loop of Henle
Term
the mOsm right after the reabsorption in the PCT
 Definition
total [solute] remains at 300 mOsm (isotonic)
Term
Glucose and amino acids in blood are easily filtered by...
 Definition
glomeruli
Term
Normally all of the filtered glucose and amino acids are reabsorbed by...
 Definition
facilitated diffusion (2° secondary active transport) in the PCT.
-Carrier-mediated transport displays saturation.
Term
Renal transport threshold
 Definition
minimal plasma [substance] that results in excretion of that substance in the urine
Term
Renal plasma threshold for glucose
 Definition
180-200 mg/dL
Term
Glycosuria
 Definition
occurs when the transport carriers for glucose become saturated due to hyperglycemia
Term
Diabetes mellitus (DM) – When hyperglycemia results in glycosuria, a large volume of urine will be formed. Why?
 Definition
because glucose in the urine is osmotically active, holding lots of water in the filtrate that becomes urine
Term
an instrument that can be used to detect glycosuria
 Definition
urine dipstick
[image]
Term
Primarily ______ nephrons responsible for water and salt reabsorption in the loop of Henle.
 Definition
juxtamedullary
Term
depiction of the loop of Henle
 Definition
[image]
Term
Concentration gradient in renal medulla in and around the loop of Henle.
 Definition
-In order for H2O to be reabsorbed, medullary interstitial fluid must be hypertonic relative to tubular fluid. -Osmotic pressure of interstitial fluid can reach 1,200-1,400 mOsm. -Osmotic pressure of tubular fluid in descending LOH always lags a little behind until the bottom of the LOH deep in the medulla. +Starts at 300 mOsm entering LOH and reaches ~1200 mOsm at bottom. [image]
Term
the requirement for H2O to be reabsorbed in the context of the loop of Henle
 Definition
In order for H2O to be reabsorbed, medullary interstitial fluid must be hypertonic relative to tubular fluid. [image]
Term
some membranes at the thick ascending limb of the loop of Henle
 Definition
-apical membrane
-basolateral membrane
[image]
Term
what happens at the apical membrane of the loop of Henle?
 Definition
Na+ diffuses from the filtrate into the cells, accompanied by the facilitated transport of K+ and Cl- (ratio 1 Na+ : 1 K+ : 2 Cl-) [image]
Term
what happens at the basolateral membrane of the loop of Henle?
 Definition
Na+ actively transported to interstitium by Na+/K+ pump, Cl- follows Na+ passively [image]
Term
the part of the loop of Henle that's impermeable to water
 Definition
the ascending limb
[image]
Term
what happens as a result of the Na+ being removed from the ascending limb of the loop of Henle?
 Definition
As Na+ removed from ascending LOH, H2O remains -> tubular fluid (filtrate) becomes increasingly dilute (hypotonic) while the interstitial fluid in the medulla becomes relatively hypertonic. [image]
Term
Filtrate going out of ascending limb LOH to DCT is hypertonic or hypotonic?
 Definition
hypotonic
Went from 1200 at the bottom to 100 mOsm.
[image]
Term
the part of the loop of Henle that's permeable to water, but not to salts; doesn't even do active transport of salts
 Definition
the descending limb of the loop of Henle
[image]
Term
the direction the water moves in the context of the descending limb of the loop of Henle
 Definition
-surrounding hypertonic interstitial fluid draws H2O out of descending limb into capillaries. -As osmolarity of surrounding fluid ↑ -> more H2O exits -> fluid volume ↓ in tubule -> higher [Na+] and osmolarity of tubular fluid -> enters ascending limb. [image]
Term
depiction of the countercurrent multiplier system involving the loop of Henle
 Definition
[image]
Term
importance of countercurrent flow in the loop of Henle
 Definition
Countercurrent flow in opposite directions in ascending and descending limbs LOH and close proximity of loop’s limbs allow interactions.
[image]
Term
how the positive feedback (multiplier system) works in the loop of Henle
 Definition
The more salt the ascending limb extrudes -> the more concentrated the interstitial fluid -> the more water diffuses out of descending limb -> gradual increasing concentration of renal interstitial fluid, followed by LOH tubular fluid, from the cortex to inner medulla.
[image]
Term
osmolarity gradient in the interstitium around the loop of Henle
 Definition
Osmolarity ↑ as go from cortex to deep medulla
[image]
Term
the NaCl, H2O, and osmolarity in the thin descending limb
 Definition
-Amount of NaCl remains the same. -Amount of H2O ↓ -Osmolarity ↑ [image]
Term
the NaCl, H2O, and osmolarity in the thick ascending limb
 Definition
-Amount of H2O remains the same.
-Amount of NaCl ↓
-Osmolarity ↓
[image]
Term
the result of the medullary hypertonicity created by the countercurrent multiplier system
 Definition
H2O and NaCl conservation
Term
Vasa Recta
 Definition
Net of capillaries around LOH
[image]
Term
properties of the vasa recta that enable it to do countercurrent exchange
 Definition
-Walls are permeable to H2O, NaCl, & urea – passive transport. -Slow, low pressure blood flow in medulla = low hydrostatic P. -Colloid osmotic P inside vasa recta >>> surrounding interstitium. -As descend into hypertonic medulla +H2O exits the capillaries +NaCl enters the capillaries -As ascend to decreasing tonicity of cortex +H2O enters the capillaries +NaCl exits the capillaries [image]
Term
The countercurrent exchange of vasa recta
 Definition
-Hypertonic salts in interstitial fluid diffuse into blood of the descending capillary loop then passively diffuse out of the ascending capillary loop. +No net movement of salts. +*Hypertonicity of renal medullary interstitium maintained. -H2O moves out of descending limbs, but enters ascending limbs to a greater extent. +*Water returned to systemic circulation. [image]
Term
the ultimate result of the entire countercurrent mechanism
 Definition
-Ultimately, H2O and NaCl are reclaimed from filtrate. -Enough of each remains in plasma of vasa recta to maintain homeostatic levels. [image]
Term
the flow of water and NaCl in the vasa recta
 Definition
-H2O leaves descending vasa recta -H2O enters ascending vasa recta -NaCl enters descending vasa recta -NaCl leaves ascending vasa recta [image][image]
Term
the flow of water and NaCl in the loop of Henle
 Definition
-H2O leaves descending LOH -NaCl leaves ascending LOH [image][image]
Term
the role of the countercurrent multiplier in the entire countercurrent mechanism
 Definition
Countercurrent multiplier creates medullary hypertonicity.
[image]
Term
the role of the countercurrent exchange in the entire countercurrent mechanism
 Definition
Countercurrent exchange maintains medullary hypertonicity (salt remains in medulla) and conserves water in the body (water returns to circulation).
[image]
Term
where urea comes from
 Definition
Nitrogenous end product of protein metabolism -> renal elimination important
Term
structure of urea
 Definition
[image]
Term
Some urea is recycled. What is its function?
 Definition
contributes to total osmolarity of medullary interstitial fluid; helps maintain hypertonicity of interstitial fluid
Term
how urea is transported
 Definition
facilitated diffusion by urea transporters
Term
path of urea from medullary CD to ascending limb of loop of Henle
 Definition
Urea diffuses out of medullary CD -> interstitial fluid -> into ascending limb LOH
Term
DCT and cortical CD [permeable or impermeable] to urea.
 Definition
impermeable
Term
the amounts of Na+ and K+ that get reabsorbed before going into the distal convoluted tubule and make it to the distal convoluted tubule, respectively
 Definition
Approximately 85% of filtered Na+ & K+ is reabsorbed before the filtrate reaches the distal convoluted tubule (DCT), i.e. remaining 15% filtrate goes to DCT. [image]
Term
among the filtrate that makes it to the distal convoluted tubule, what happens to the Na+ in the absence of aldosterone?
 Definition
80% of the Na+ is reabsorbed in the distal convoluted tubule [image]
Term
how aldosterone regulates salt reabsorption
 Definition
it regulates remaining 20% (2-3% of the total filtrate, or ~30 g of Na+/day) of the 15% of filtrate that makes it to the distal convoluted tubule, thus affecting 2-3% of salt re-absorption.
-Aldosterone targets DCT (minor) and collecting ducts (major).
[image]
Term
Aldosterone targets...
 Definition
-DCT (minor)
-collecting ducts (major)
[image]
Term
depiction of how Na+ and K+ are handled in the renal tubules
 Definition
[image]
Term
the effect of aldosterone
 Definition
Aldosterone acts on late DCT (minor) and cortical CD (major) to reabsorb Na+ and secrete K+, thus promoting further Na+ retention and K+ loss from blood. [image]
Term
how Na+ and K+ move at the apical membrane of the DCT/CD
 Definition
they follow their diffusion gradients; this leads to saving sodium and peeing potassium
[image]
Term
how Na+ and K+ move at the basal membrane of the DCT/CD
 Definition
active transport (Na+ / K+ pump) [image]
Term
how aldosterone causes Na+ retention and K+ loss
 Definition
by going into the collecting tubule cells, binding to the intracellular receptor, and causing increased expression of the Na+ channels and the Na+ / K+ ATPases [image]
Term
the cause and effect of aldosterone secretion
 Definition
-*Stimulated directly by a rise in blood K+ and indirectly by a fall in blood Na+. -Aldosterone stimulates K+ (and H+) secretion in exchange for Na+ reabsorption. -*Aldosterone-induced Na+ reabsorption allows fine-tuning of plasma [Na+]. -*Aldosterone-induced K+ secretion is the main means by which K+ can be eliminated in the urine. +There is aldosterone-independent K+ secretion into the filtrate (minor). [image]
Term
some characteristics of the medullary CD
 Definition
-important in water reabsorption/conservation due to hypertonic interstitial fluid. -The medullary CD is permeable to water but impermeable to salts --> the high [NaCl] in the medullary interstitial fluid cannot enter the medullary CD. [image]
Term
how Antidiuretic hormone (ADH, vasopressin) stimulates H2O reabsorption
 Definition
Antidiuretic hormone (ADH, vasopressin) from the posterior pituitary stimulates incorporation of aquaporins into apical epithelial cell membranes of medullary CD --> ↑ H2O re-absorption from tubules along concentration gradient. [image]
Term
What effect does aldosterone have on blood volume?
 Definition
increases it
[image]
Term
What effect does ADH have on blood volume?
 Definition
increases it
[image]
Term
2 hormones that are involved in water conservation
 Definition
-aldosterone
-ADH
Term
What happens when excess water needs to be excreted? ADH secretion?
 Definition
we don't have release of that because we want the water to stay in the collecting ducts
[image]
Term
What happens when excess water needs to be excreted? Osmolarity of filtrate in collecting duct?
 Definition
gets fairly dilute
[image]
Term
What happens when excess water needs to be excreted? Blood volume?
 Definition
decreases
[image]
Term
What happens when water needs to be conserved? ADH secretion?
 Definition
it would occur
[image]
Term
What happens when water needs to be conserved? Osmolarity of filtrate in collecting duct?
 Definition
increases
[image]
Term
What happens when water needs to be conserved? Blood volume?
 Definition
decreases
[image]
Term
Diabetes insipidus (DI)
 Definition
a disease associated with inadequate secretion of ADH or defects in renal ADH receptors.
[image]
Term
result of Diabetes insipidus (DI)
 Definition
Medullary CD become less permeable to water --> ↓ water re-absorption into the plasma --> high volume and very dilute urine.
[image]
Term
general diagram of the pathophysiology of ADH
 Definition
[image]
Term
What are the derivations of the names of diabetes mellitus and diabetes insipidus?
 Definition
-diabetes basically means siphoning off water (it was understood that this condition caused excess urination)
-mellitus means sweet (physicians would taste the urine, sweet in this case)
-insipidus means not having a strong taste (physicians would taste the urine; nearly tasteless in this case)
Term
some ions the kidneys regulate
 Definition
-Na+ -K+ -H+ -Cl- -HCO3- -PO4-3 [image]
Term
effect of the kidneys regulating Na+
 Definition
Regulation of plasma [Na+] --> volume of blood plasma --> regulation of BP.
Term
effect of the kidneys regulating K+
 Definition
Control of plasma of [K+] for proper function of cardiac & skeletal muscles.
Term
the goal of the kidneys regulating ions
 Definition
to match ingestion with urinary excretion
Term
Role of juxtaglomerular (JG) apparatus
 Definition
Involved in renin -> -> aldosterone secretion
Term
Atrial natriuretic peptide (ANP)
 Definition
acts as an endogenous diuretic by stimulating excretion of Na+, Cl- and H2O; opposite to aldosterone. -Inhibits effects of aldosterone and ADH.
Term
What does natriuretic mean?
 Definition
sodium and urine
Term
Juxtaglomerular Apparatus
 Definition
Region in each nephron where the afferent arteriole contacts the thick ascending limb LOH (about to enter DCT) [image]
Term
types of cells in the juxtaglomerular apparatus
 Definition
-granular cells
-macula densa cells
-mesangial cells
[image]
Term
Macula densa cells
 Definition
detect [Na+] and flow -part of juxtaglomerular apparatus [image]
Term
Granular cells
 Definition
secrete renin
-part of juxtaglomerular apparatus
[image]
Term
mesangial cells
 Definition
type of smooth muscle cells in the juxtaglomerular apparatus
Term
overall function of juxtaglomerular apparatus
 Definition
Renal autoregulation
[image]
Term
Renal autoregulation
 Definition
(intrinsic mechanisms) maintains steady renal blood flow and GFR
[image]
Term
the overall local effects of macula densa cell signaling
 Definition
-When ↓ systemic arterial P --> chemicals released locally (NO, PGs) --> the afferent arterioles dilate --> maintains GFR in a constant range.
-Tubuloglomerular feedback – macula densa in ascending limb senses an increased flow of filtrate --> secretes ATP as a signal to afferent arterioles to constrict.
[image]
Term
why is renal autoregulation of renal blood flow and GFR important?
 Definition
if you had constantly widely fluctuating GFR and blood flow, that would really disrupt the cincentration gradient in the medulla and impair your ability to reabsorb sodium, reabsorb water, lose potassium, things like that
Term
Tubuloglomerular feedback
 Definition
macula densa in ascending limb senses an increased flow of filtrate --> secretes ATP as a signal to afferent arterioles to constrict. This lowers it back to the homeostatic level of filtrate being formed.
[image]
Term
Granular cells (juxtaglomerular cells)
 Definition
-Modified smooth muscle cells in the wall of afferent arterioles.
-Receive local (paracrine) signals from macula densa.
-Secrete renin causing systemic effects:
1) ↓ systemic arterial P --> --> ↑ renin secretion.
2) ↑ systemic arterial P --> --> ↓ renin secretion.
[image]
Term
how Granular cells (juxtaglomerular cells) regulate blood pressure
 Definition
The renin-angiotensin-aldosterone (RAA) system – (“negative” feedback response)
-↓ in BP → detected by granular cells → ↑ renin secretion → renin converts angiotensinogen (produced by the liver → angiotensin (AT) I
-Angiotensin-converting enzyme (ACE) converts AT I → AT II (bioactive)
-*AT II effects:
(1) → vasoconstriction → ↑ BP
(2) → ↑ aldosterone secretion (a steroid H from adrenal cortex) → ↑ in renal Na+ re-absorption → ↑ in water re-absorption → ↑ blood vol → ↑ BP
[image]
Term
the pathway showing how the renin secreted by granular cells regulates blood pressure
 Definition
[image]
Term
how sympathetic innervation helps to regulate GFR
 Definition
-Sympathetic innervation -> constriction of the afferent arterioles -> reduces GFR -> thus preserves blood volume to muscles and heart.
-Only with severe sympathetic input, e.g., shock, hemorrhage.
[image]
Term
GFR
 Definition
Glomerular filtration rate (mL/min)
Term
Summary of Local and Systemic Effects of Juxtaglomerular Apparatus and Renal Autoregulation
 Definition
[image]
Term
overview of how the renal-angiotensin-aldosterone system (RAAS) increases blood volume and pressure
 Definition
[image]
Term
depiction of how CO2, acids, buffers, and blood cells interact with each other
 Definition
[image]
Term
Blood pH is maintained within narrow pH range (7.40) by...
 Definition
lungs and kidneys
[image]
Term
normal pH of blood
 Definition
7.40
Term
Kidneys help regulate blood pH by...
 Definition
excreting H+ and/or reabsorbing HCO3- [image] -CA: catalyzed by carbonic anhydrase. -Henderson-Hasselbalch equation -pH = 6.1 + log ( [HCO3-] / [CO2] ) -[CO2] is adjusted by lungs, [HCO3-] by kidneys
Term
acidosis
 Definition
-When blood pH < 7.35 -↑ H+ ions
Term
alkalosis
 Definition
-When blood pH > 7.45 -↓ H+ ions
Term
the most important buffer in blood and what it does
 Definition
-HCO3- -Excess H+ is buffered by HCO3-
Term
the role of the proximal convoluted tubule in the handling of HCO3- and H+
 Definition
-Main site of HCO3-- reabsorption. -Na+/H+ antiporter – another source of Na+ reabsorption. -Role of carbonic anhydrase – HCO3- can not cross membranes. -H+ keeps cycling – small amounts of extra H+ secreted for excretion. [image]
Term
how bicarbonate (HCO3-) goes through the membrane of the proximal tubule
 Definition
by way of a Na+ / HCO3- cotransporter along Na+'s concentration gradient
Term
the role of the distal convoluted tubule / collecting ducts in the handling of HCO3- and H+
 Definition
-Active transport of H+ across apical membrane -> filtrate. +H+ ATPase uniporter +H+/K+ ATPase antiporter -Combines with phosphate and ammonia buffers in filtrate -> excreted. -Other mechanisms exist to ↑ HCO3- entering plasma and ↓ H+ entering filtrate. [image]
Term
depiction of the relationship between Na+, K+, and H+
 Definition
[image]
Term
Hyperkalemia
 Definition
too much K+
Term
how Na+ reabsorption in DCT and CD influences K+
 Definition
Na+ re-absorption in DCT and CD creates electrical gradient for K+ secretion (see aldosterone). [image]
Term
how plasma [K+] indirectly affects [H+]
 Definition
-↓ in ECF [K+] (hypokalemia) --> ↑ H+ secretion in distal tubule & cortical CD --> metabolic alkalosis. -Hyperkalemia --> metabolic acidosis. -Severe acidosis --> H+ is secreted at the expense of K+ --> ↑ ECF [K+] --> hyperkalemia. [image]
Term
the ions that get secreted into the filtrate and when
 Definition
Often H+ or K+ is being secreted into filtrate at the expense of the other in acute situations. [image]
Term
the ions that get moved into the plasma and cells and when
 Definition
Similar situation occurs in plasma with movement of excess H+ or K+ into cells while the other moves into plasma. [image]
Term
what hyperkalemia leads to
 Definition
acidosis
Term
why urine tends to be slightly acidic (pH 5-7)
 Definition
because kidneys reabsorb almost all HCO3- and excrete H+
Term
Nephron cannot produce urine with pH < 4.5 because...
 Definition
it has buffers
Term
H+ are prevented from contributing to the acidity of the urine by...
 Definition
being combined with HPO4-2 or NH3. -*Buffering reactions +HPO4 + H+ --> H2PO4- +NH3 + H+ --> NH4+ (ammonium ion)
Term
some buffering reactions that occur in the nephron to affect the pH of the urine
 Definition
HPO4 + H+ --> H2PO4- NH3 + H+ --> NH4+ (ammonium ion)
Term
how hypoventilation leads to respiratory acidosis
 Definition
Hypoventilation --> accumulation of CO2 in the tissues --> ↑ PCO2 --> [HCO3-] / [CO2] --> ↓ pH
Term
the compensatory response for respiratory acidosis caused by hypoventilation
 Definition
↑ renal secretion of H+ (as NH4+ and monophosphate) and ↑ re-absorption of HCO3- --> ↑ [HCO3-] / [CO2] --> ↑ pH --> blood pH close to normal
Term
how hyperventilation leads to respiratory alkalosis
 Definition
Hyperventilation --> too little CO2 --> [HCO3-] / [CO2] --> ↑ pH
Term
the compensatory response for respiratory alkalosis caused by hyperventilation
 Definition
↓ re-absorption of HCO3- --> ↓ [HCO3-] / [CO2] --> ↓ pH ↓ blood pH close to normal
Term
the equation that regulation of blood pH boils down to
 Definition
CO2 + H2O <--> H2CO3 <--> H+ + HCO3-
Term
Metabolic acidosis
 Definition
excess of nonvolatile acids
Term
some things that can cause metabolic acidosis
 Definition
-↑ acid intake or production -↓ renal excretion of H+ -Ketoacidosis in diabetes -lactic acidosis -loss of HCO3- (for buffering) in diarrhea -renal tubular disorders or renal failure -toxicants
Term
the pathway that leads to metabolic acidosis
 Definition
↑ acid intake, production, or ↓ renal excretion of H+ --> ↓ ratio of [HCO3-] / [CO2] --> ↓ pH --> metabolic acidosis
Term
Compensatory response for metabolic acidosis
 Definition
hyperventilation by lungs --> ↓ CO2 --> ↑ ratio of [HCO3-] / [CO2]
Term
Metabolic alkalosis
 Definition
too much HCO3- or too little nonvolatile acids (e.g. from vomiting stomach acid)
Term
the cause and effect leading to metabolic acidosis
 Definition
↑ HCO3- or acid loss --> ↑ ratio of [HCO3-] / [CO2] --> ↑ pH --> metabolic alkalosis
Term
compensatory response for metabolic alkalosis
 Definition
hypoventilation by lungs --> ↑ CO2 --> ↓ ratio of [HCO3-] / [CO2]
Term
depiction of the pulmonary and renal responses to acidosis
 Definition
[image]
Term
depiction of the pulmonary and renal responses to alkalosis
 Definition
[image]
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