EXAM 4 Module 7 Flashcards
overall goal of the kidneys is to…
maintain homeostasis
functions of the kidneys:
regulation of…
water concentration
inorganic ion composition (Na+, K+, Ca2+, H+)
acid-base balance
volume of internal environment (blood volume)
functions of the kidneys:
removal…
of metabolic waste products from blood and excretion into urine,
and excretion of foreign chemicals
functions of the kidneys:
synthesis of…
glucose (gluconeogenesis)
functions of the kidneys:
production of…
hormones/enzymes (erythropoietin, renin, 1,25-dihydroxyvitamin D)
erythropoietin (EPO) controls…
RBC production
renin influences…
blood pressure and Na+ balance
1,25 dihydroxyvitamin D influences…
Ca2+ balance
structure of the kidneys and urinary system top to bottom
- two kidneys
- ureters
- bladder
- urethra
two important parts of kidney
renal cortex (fingerlike stuff)
renal medulla (space in between)
two parts of nephron
renal corpuscle
tubule
function of renal corpuscle
filter
function of tubule
adds and removes substances
single layer of epithelial cells
two parts of renal corpuscle
glomerulus
Bowman’s capsule
plasma is filtered from _______ into _______
glomerular capillaries; Bowman’s capsule
when ~20% of plasma is filtered but not erythrocytes or most plasma proteins
ultrafiltrate of blood
three layers the filtrate has to cross
- capillary endothelial cells
- basement membrane
- podocyte filtration slit
renal corpuscle blood flow steps
- blood flows into afferent arteriole
- blood is filtered at glomerulus, rest of blood leaves via efferent arteriole (then nephron ultrafiltrate)
nephron ultrafiltrate flow steps
- filtrate enters Bowman’s space and then the proximal convoluted tubule
- filtrate passes into medulla through the loop of Henle (descending and ascending)
- filtrate passes back into cortex through the distal convoluted tubule
- filtrate passes back into the medulla through the collecting duct
- filtrate is excreted to renal pelvis
two types of nephrons
juxtamedullary nephron (long loop of Henle)
cortical nephron
two sets of capillaries
glomerular capillaries
peritubular capillaries
vasa recta surrounds…
loop of Henle
three basic renal processes
glomerular filtration
tubular secretion
tubular reabsorption
flow of glomerular filtration
blood -> tubule
flow of tubular secretion
blood -> tubule
flow of tubular reabsorption
tubule -> blood
amount excreted (urine) = …
amount filtered + amount secreted - amount reabsorbed
filtration of plasma from glomerular capillaries into Bowman’s space
bulk-flow process (substances are virtually at the same concentration as plasma)
glomerular filtration
glomerular filtration is regulated by…
pressure
filtration is determined by…
opposing Starling forces
pressure favoring filtration (pushing things in)
glomerular capillary hydrostatic pressure
pressures opposing filtration (against things moving in)
hydrostatic pressure in Bowman’s space
osmotic pressure of blood (due to higher protein in blood than in Bowman’s capsule)
net filtration pressure = …
glomerular capillary hydrostatic pressure - hydrostatic pressure in Bowman’s space - osmotic pressure of blood
in net filtration, positive flow is towards _______ and negative flow is towards _________
Bowman’s capsule; glomerular capillary
glomerular filtration is subject to…
physiological regulation 1 degree regulated by glomerular capillary blood pressure
*arteriole vasoconstriction:
if AFFERENT arteriole is constricted…
decreased capillary hydrostatic pressure
decreased filtration
*arteriole vasoconstriction:
if EFFERENT arteriole is constricted…
increased capillary hydrostatic pressure
increased filtration
arteriole vasodilation:
if AFFERENT arteriole is dilated…
increased capillary hydrostatic pressure
increased filtration
arteriole vasodilation:
if EFFERENT arteriole is dilated…
decreased capillary hydrostatic pressure
decreased filtration
movement from tubule to peritubular capillaries
functions to recover important substances
1 degree regulated by channels
tubular reabsorption
tubular reabsorption pathway
- substances pass from tubular lumen through OR between epithelial cells into interstitial fluid
- movement from interstitial fluid into peritubular capillary by diffusion
tubule-to-interstitial fluid movement can occur by…
diffusion OR
mediated transport
movement down a concentration gradient into interstitial fluid
does not require energy
diffusion
movement against a gradient from interstitial fluid, across luminal and basolateral cell membranes, into blood
requires active transport and energy
mediated transport
two types of mediated transport
primary active transport
secondary active transport
example of mediated transport:
Na+ via Na+/K+ -ATPase
Na+ moves downhill across luminal membrane by facilitated diffusion
Na+/K+ -ATPase actively transports Na+ uphill across basolateral membrane
primary active transport
example of mediated transport:
glucose via glucose/Na+ cotransport
glucose is cotransported across luminal membrane uphill coupled to Na+ transport downhill
glucose diffuses across basolateral membrane by facilitated diffusion
secondary active transport
required by mediated transport
maximum amount of material that can be transported per unit time
occurs when binding sites on transport protein are saturated
transport maximum (Tmax)
movement of substances from peritubular capillaries into tubular lumen
transcellular pathway
functions to excrete substances at a rate greater than filtered at the glomerular capillaries
tubular secretion
example of tubular secretion:
K+
K+ enters interstitial fluid by diffusion
K+ transported uphill into cell across basolateral membrane by primary active transport
K+ moves downhill into tubule by facilitated diffusion
result…
more K+ excreted than filtered
reabsorbs most of filtered water and non waste solutes
major site of solute reabsorption
proximal tubule
establishes the medullary osmotic gradient
loop of Henle
fine tuning for most substances
where most homeostatic controls operate
distal tubule + collecting ducts
distal segments
physiological fine tuning is determined by…
membrane protein (channel) concentration
concentration of membrane proteins is regulated by…
hormones
paracrine/autocrine factors
amount of fluid filtered
glomerular filtration rate (GFR)
amount of substance filtered
filtered load
measurement of GFR
volume of fluid filtered from glomeruli into Bowman’s space per unit time
measuring GFR:
if substance is
filtered
not reabsorbed
not secreted
then…
the amount of substance filtered MUST equal amount of substance excreted
substances measured in GFR
inulin
creatinine
substance that is
readily filtered
not reabsorbed or secreted
not naturally occurring in body (infusion)
inulin
substance that is
naturally occurring in body
muscle breakdown product
only approximate measure of GFR (some secretion)
creatinine
GFR in normal functioning kidneys
125 ml/min or 180 L/day
total plasma volume in normal functioning kidneys
3 L
entire plasma volume filtered 60 times per day
amount of substance filtered from the glomeruli into Bowman’s space per unit time
filtered load
measuring filtered load:
if we collect blood and urine sample and substance is not reabsorbed or secreted, then we can calculate…
GFR
if we know GFR, then…
filtered load of any substance = GFR multiplied by concentration of substance in plasma
volume of plasma from which a substance is completely removed per unit time
way to quantify total renal function
clearance
measuring clearance:
clearance of substance = …
mass of substance excreted per time / plasma concentration of substance
if clearance of substance < GFR,
clearance < 125ml/min
then…
net reabsorption
filtered load > amount in urine
LESS of substance in urine than filtered
if clearance of substance > GFR,
clearance > 125 ml/min
then…
net secretion
filtered load < amount in urine
MORE of substance in urine than filtered
if clearance of substance is freely filtered and completely secreted, this substance would measure…
total renal plasma flow
substance that is filtered and completely secreted
para-aminohippurate (PAH)
total renal plasma flow is determined by measuring the clearance of…
para-aminohippurate (PAH)
typical value of renal plasma flow
625 ml/min of plasma enters kidneys
(20% = 125ml/min)
two basic renal processes for Na+ and water
Na+ and water freely filtered
both extensively reabsorbed and NOT secreted
2/3 of Na+ and water reabsorption occurs in…
proximal tubule (mass reabsorption)
hormonal control occurs…
distal tubule and collecting ducts
Na+ reabsorption is an _______ process driven by Na+/K+ -ATPase transport of Na+ out of cell
water reabsorption occurs by ______ dependent upon Na+ reabsorption
(water follows salt)
active; diffusion
Na+ reabsorption occurs in all segments except…
descending loop of Henle
Na+ moves downhill into cell by varied mechanisms dependent upon these tubule segments…
proximal tubule
ascending loop of Henle
cortical collecting duct
Na+ reabsorption in proximal tubule:
basolateral membrane - active transport
Na+/K+ -ATPase lowers intracellular concentration
luminal membrane - downhill movement and…
cotransport OR counter-transport
Na+ reabsorption in ascending loop of Henle:
basolateral membrane - active transport
Na+/K+ -ATPase lowers intracellular concentration
luminal membrane - downhill movement and…
cotransport
Na+ reabsorption in cortical collecting duct:
basolateral membrane - active transport
Na+/K+ -ATPase lowers intracellular concentration
luminal membrane - downhill movement and…
facilitated diffusion
Na+ reabsorption is an _____ process, requires ______, and always driven by _______
active; energy; Na+/K+ -ATPase
measure of water, total solute concentration in a solution
osmolarity
typical value of plasma osmolarity
300 mOsmol/L
typical range of urine osmolarity
50 mOsmol/L (hypoosmotic) to 1400 mOsmol/L (hyperosmotic)
Na+ reabsorption leads to:
______ in tubular osmolarity
______ in interstitial osmolarity
diffusion of water into interstitial fluid via _______
decrease; increase; osmosis
water and solutes move by ______ into peritubular capillaries
bulk flow
flow of osmosis
diffusion of water across a selective barrier from hypoosmotic to hyperosmotic
water movement can only occur if the ________ is permeable
epithelium
water moves through channels called…
aquaporins
aquaporin numbers in collecting ducts are regulated by…
vasopressin (anti-diuretic hormone (ADH))
urinary concentration takes place in the…
medullary collecting duct
how urine becomes concentrated:
medullary interstitial fluid surrounding collecting ducts is very ________
in the presence of ________, water diffuses into interstitial fluid and enters blood
urine becomes concentrated
hyperosmotic; vasopressin (ADH)
interstitial fluid becomes hyperosmotic from…
the loop of Henle
countercurrent multiplication system that generates the hyperosmotic medullary fluid
loop of Henle
five factors of countercurrent multiplication
hairpin loop for countercurrent flow
selective active transport of Na+
selective permeability to water
trapping of urea
hairpin loop of vasa recta
in the hairpin loop (between proximal and distal tubule), __________ occurs forming countercurrent multiplier system
countercurrent flow
selective transport of Na+:
in the ascending limb,
active _______ of Na+
________ to water
reabsorption; impermeable
selective permeability to water:
in the descending limb,
no ________ of Na+
highly _______ to water
reabsorption; permeable
longer the loop, the greater the gradient
repetition of process leads to a gradient of osmolarity along the loop of Henle
multiplication
trapping of urea:
urea is trapped in interstitum to increase _______
urea is:
osmotically active
freely filtered
reabsorbed from collecting duct
secreted into loop of Henle
minimally removed by vasa recta
osmolarity
vasa recta is permeable to…
both water and Na+
hairpin loops run parallel to renal tubules to minimize loss of ______ from interstitum
Na+
if no hairpin turn, blood would leave very _______ and wash away medullary osmotic gradient
hyperosmotic
collecting duct permeability to water can be high or low, depends on the hormone…
vasopressin
only acts in cortical and medullary collecting ducts
increases aquaporin channels
increases water reabsorption
vasopressin
if high vasopressin, then __________ urine
concentrated (hyperosmotic)
if low vasopressin, then
collecting ducts are impermeable to water
collecting duct fluid remains _________
dilute urine
hypoosmotic
factors affecting countercurrent gradient and production of hyperosmotic urine
length of loop of Henle
flow rate through loop of Henle
rate of active transport of NaCl
if you increase flow rate and/or decrease active transport of Na+, then decreases the collecting duct/interstitial gradient and urine is…
more dilute (hypoosmotic)
clear pee
hypoosmotic
dark pee
hyperosmotic
increased Na+ increases extracellular volume by osmosis
if extracellular volume changes, so does plasma volume
plasma volume size helps determine…
blood pressure
basic renal processes of Na+
freely filtered
reabsorbed
not secreted
Na+ excretion = …
Na+ filtered - Na+ reabsorbed
Na+ excretion is initiated by…
cardiovascular baroreceptors
if lower total body Na+, then
decreased plasma volume
decreased blood pressure
_______ of renal afferent arterioles
decreased _____
decreased _____ filtered
constriction; GFR; Na+
if increased sympathetic nerve activity, then
constriction of afferent arterioles
decreased GFR
decreased _____________
glomerular capillary hydrostatic pressure
produced in adrenal cortex
stimulates Na+ reabsorption in the distal tubule and collecting ducts
fine tuned by aldosterone
long term regulation
controls aldosterone secretion
renin-angiotensin system (angiotensin II)
renin-angiotensin system:
kidneys -> renin -> blood -> angiotensinogen
liver -> angiotensinogen -> angiotensin I -> angiotensin II -> adrenal cortex
adrenal cortex -> aldosterone -> NaCl and H2O retention -> increase blood pressure
just know dat mothafucka
converts angiotensin I to angiotensin II
angiotensin converting enzyme (ACE)
renin is stored in ___________ of afferent arteriole
juxtaglomerular cells
stimulating renin secretion
increased renal sympathetic nerve activation
decreased stretch of intrarenal baroreceptors
decreased Na+ sensed by macula densa cells
all of these effects occur with decreased plasma volume leading to decreased blood pressure
net results of stimulating renin secretion
increased Na+ reabsorption
increased plasma volume
increased blood pressure back toward normal
if low Na+, then…
high renin
if high Na+, then…
low renin
high blood pressure
hypertension
treatment of hypertension
ACE blockers
angiotensin II receptor blockers (ARBs)
aldosterone receptor blockers
ACE blockers, angiotensin II receptor blockers (ARBs), and aldosterone receptor blockers decrease _____ reabsorption and lower ________
Na+, blood pressure
if plasma volume is too high,
atria stretches and releases atrial natriuretic peptide (ANP),
decreases plasma aldosterone,
afferent dilation and efferent constriction of arterioles,
increased GFR,
decreased Na+ reabsorption in tubules,
result in…
increased Na+ excretion
to reduce blood volume and pressure
______ determines extracellular volume and contributes to blood pressure
Na+
regulation of Na+ reabsorption occurs in _____ and ______ of kidneys
distal tubules; collecting ducts
both amount of Na+ filtered and Na+ reabsorbed are under _______ control
physiological
Na+ filtration (filtered load) is controlled by…
constriction/dilation of afferent/efferent arterioles
amount of blood flow to kidneys
Na+ reabsorption is controlled by…
aldosterone which is in turn controlled by renin-angiotensin system
ANP (at the tubules)
basic renal processes of water
freely filtered
reabsorbed
not secreted
water regulation is controlled by _________ in the collecting ducts to increase aquaporin channel numbers
hormone vasopressin
regulation of vasopressin secretion steps
- baroreceptor pathway (severe response)
- osmoreceptor pathway (minute to minute)
- central nervous system
baroreceptor pathway of vasopressin secretion:
requires _______ change in pressure
decreased cardiovascular baroreceptor firing
increase Na+ reabsorption
large
osmoreceptor pathway of vasopressin secretion:
changes in water alone (osmolarity)
does not have a large effect on ___________
altered osmolarity triggers osmoreceptors in the hypothalamus
extracellular volume
regulation of osmolarity:
water reabsorption alone through ________
Na+ and water reabsorption through ________
osmoreceptors
baroreceptors
osmoreceptor pathway of vasopressin secretion:
hypothalamic osmoreceptors are _________ to small changes in H2O
increases water excretion without changing _______ excretion
very sensitive; Na+
central nervous system control of vasopressin secretion:
release influenced by…
pain
fear
drugs
_____ inhibits vasopressin secretion
ethanol
water regulation occurs in kidney _______ controlled by ______
collecting ducts; vasopressin
vasopressin:
increases __________ in collecting ducts
increases __________ of collecting ducts
increases __________ by osmosis
increases __________ of urine (concentrated)
aquaporin channels
water permeability
water reabsorption
osmolarity
increased urine flow per unit time
diuresis
decreased water reabsorption
results from low vasopressin
no change in solute excretion
produces dilute hypoosmotic urine
water diuresis
decreased solute reabsorption
decreased water reabsorption
increased solute excretion
osmotic diuresis
pharmacological agents that increase urine volume by increasing excretion of Na+ and/or water
decrease volume of extra cellular fluid
used in treatment of hypertension, heart failure, edema
diuretics
diuretics: mechanisms of action
blockers of renin-angiotensin-aldosterone system decrease ____ and _____ reabsorption,
loop of Henle diuretics inhibit _____ reabsorption in ascending limb and decrease Na+ and water reabsorption,
osmotic diuretics filter but not reabsorb mannitol and draws ______ osmotically into tubule and urine
Na+ and water;
Na+;
water
K+ increased in blood
hyperkalemia
K+ decreased in blood
hypokalemia
basic renal processes of K+
freely filtered
reabsorbed
secreted
K+ secretion in cortical collecting duct:
K+ secreted because of _________
K+ secretion linked to Na+ reabsorption
large number of K+ channels
K+ secretion in proximal tubule:
no secretion because of ________
short circuit
factors influencing K+ excretion
- high K+ in plasma activation of Na+/K+ pump (makes it pump more K+ faster)
- high K+ in plasma stimulates aldosterone secretion (increases K+ excretion)
aldosterone release from adrenal cortex is stimulated by…
angiotensin II
increased plasma K+
aldosterone release from adrenal cortex is inhibited by…
ANP
low Ca2+ increases ______ of nerve and muscle
high Ca2+ causes _______
excitability; cardiac arrhythmias
Ca2+ regulation depends on…
bone distribution in body
kidney excretion
gastrointestinal tract absorption
calcium distribution:
_____% of body Ca2+ stored in bones
not freely filtered in kidneys
most of filtered Ca2+ is reabsorbed in proximal tubule
regulation by reabsorption in the __________
gastrointestinal tract absorption under _______
99%; distal convoluted tubule; hormonal control
Ca2+ balance regulation by…
parathyroid hormone (PTH)
PTH is produced by _____ and excretion is stimulated by _______ extracellular Ca2+
parathyroid glands; decreased
parathyroid hormone:
increases reabsorption in ______,
increases renal tubular Ca2+ reabsorption and stimulates formation of 1,25-dihydroxyvitamin D in _____,
increases intestinal Ca2+ reabsorption by 1,25-dihydroxyvitamin D in _______
bones;
kidneys;
GI tract
net result of PTH…
increased plasma Ca2+
two forms of acid
nonvolatile acid in form of fixed acids
volatile acid in form of CO2
H+ from metabolic products
phosphoric acid
sulfuric acid
lactic acid
loss of HCO3- in diarrhea and urine
nonvolatile acids
when HCO3- is lost from body, it’s the same as _________ and vice versa
gain of H+
generation of H+ from CO2
volatile acids
in buffering:
free _____ determines pH
H+ are in balance with buffers
H+ bound to a buffer does NOT affect ____
H+; pH
buffering systems (locks H+ up until balance is restored)
chemical buffering
respiratory control of CO2
renal control of HCO3-
immediate buffering, first line of defense
chemical buffering
buffering occurs within minutes
respiratory control of CO2
buffering over a period of hours and days
renal control of HCO3-
major intracellular buffers
phosphates
proteins
major extracellular buffer
HCO3-/CO2 buffer system
respiratory control of CO2:
regulates changes in H+ due to non-respiratory causes by altering…
PCO2
respiratory control of CO2:
increased H+ stimulates ventilation
causes ______ arterial PCO2 and ____ H+
returns ____ to normal
decreased; decreased; pH
renal control of HCO3-:
three main functions of kidneys in H+ regulation
reabsorb filtered HCO3-
secrete H+ at a rate equal to the fixed acid production
replenish HCO3- that was lost in buffering fixed acid
*kidneys are ultimate regulator of H+ balance
renal control of HCO3-:
net results…
normally all filtered bicarbonate is reabsorbed
H+ is not excreted
H+ excreted into urine as H2PO4- after ALL filtered bicarbonate is reabsorbed
net gain of HCO3- in plasma
H+ excreted into urine as NH4+
increased plasma H+
pH < 7.4
acidosis
decreased plasma H+
pH > 7.4
alkalosis
blood pH is largely determined by…
the ratio of HCO3- to PCO2
two categories of disturbances
respiratory
metabolic
kidneys compensate for primary respiratory disturbance by adjusting…
HCO3-
respiratory system compensates for primary metabolic disturbance by adjusting…
PCO2
know acid base disturbances cause and effect chart graph
practice right now
function of proximal tubule parts:
proximal tubule is major site of _________
loop of Henle establishes the ________
solute reabsorption; medullary hyperosmotic gradient
function of distal tubule parts:
distal tubule and collecting ducts do the _____ for most substances, where most ______ controls operate
physiological fine tuning determined by ________
concentration of membrane proteins regulated by ______ and ______
fine tuning; homeostatic;
membrane protein channel concentration; hormones and paracrine/autocrine factors
three muscles control micturition
(happens when bladder is stretched)
detrusor muscle
internal urethral sphincter
external urethral sphincter
smooth muscle that surrounds bladder
parasympathetic (contracts)
urination from STIMULATION
detrusor muscle
smooth muscle at base of bladder
sympathetic (relaxes)
urination from INHIBITION
internal urethral sphincter
skeletal muscle
somatic (relaxes)
urination from INHIBITION
external urethral sphincter
