Traffic - week 14 Flashcards
The Kidney is the…
major functional organ, other organs carry urine out of the body
basic functions of the kidneys (kid - front door)
- water balance and osmolarity
- electrolyte (ion) balance
- maintain plasma volume, long term regulation of blood pressure
- acid/base balance
- excrete wastes (urea, uric acid, creatinine) and other materials
- secrete erythropoietin
- secrete renin (Na+ balance)`
- converts vitamin D to its active form
nephron is the…(mattias)
functional unit of the kidney
1. arrangement forms cortex and medulla
glomerulus (cloud - perturbed - tuft -afferent and efferent- plant)
a. tuft of capillaries that filters blood
b. renal artery branches to form afferent and efferent arteriole for each nephron
(1) efferent arteriole divides to form
peritubular capillaries (supply renal tissue with blood)
tubule parts (cloud - cartoon - umbrella - collection plate - couch)
a. glomerular capsule surrounds glomerulus and collects filtrate
b. PCT
c. loop
d. DCT
e. collecting duct/tubule-drains fluid from several nephrons to renal pelvis
juxtaglomerular apparatus (jax - dracula - granola - cat tree)
a. regulates kidney function
b. macula densa
c. granular cells
2 types of nephrons (jax - dip - piano)
a. cortical - lie mainly in cortex (80%)
b. juxtamedullary - loops dip to end of medulla (important in urine concentration/conserving water)
3 renal processes - GTT
GTT
- glomerular filtration
- tubular reabsorption
- tubular secretion
glomerular filtration (glom plaza)
about 20% of plasma entering glomerulus is filtered. entire plasma volume filtered 65 times/day.
tubular reabsorption (tubing goldmine)
selective recovery of filtered substances
tubular secretion (tub)
selective transfer of materials from plasma in peritubular capillaries to filtrate
Glomerular Filtration (high cloud - perm)
filtered substances pass through highly permeable filtration membrane.
glomerular capillary blood pressure forces…(filter - afferent vs. efferent)
fluid through filtration membrane
1. higher than in other capillaries
a. diameter of afferent arteriole larger than
efferent arteriole, blood dams up and filtration occurs throughout glomerulus
autoregulation (auto soldier)
allows GFR to remain constant despite changes in BP (vasoconstriction/dilation of afferent arteriole)
sufficient in MAP 80-180 mmHg range
autoregulation - myogenic mechanism (art - constricts)
arteriolar smooth muscle constricts when stretched, relaxes with decreased pressure
autoregulation - tubuloglomerular feedback mechanism (tube feedback in car)
macula densa detects changes in rate of filtrate flow or osmotic changes and signals granular cells to release vasoactive substances
extrinsic sympathetic control (extrinsic soldier)
(1) GFR changed based on need (override autoregulation to reg BP)
(2) baroreceptor reflex
(3) can alter Kf by closing off part of capillaries and filtration slits
Tubular Reabsorption (% - nym)
- typically nephrons reabsorb 99% of the water, 100% of the sugar, 99.5% of the salt that is filtered
Na+ reabsorption (mountain pump - bedroom closet door)
- occurs via Na+-K+ ATPase in the basolateral membrane
a. creates gradients for diffusion
b. tied to reabsorption of other substances (glucose, amino acids, water, Cl-, urea)
renin-angiotensin-aldosterone system is in response to…(angie - low Na+ - bathroom)
decreased NaCl/dec. ECF volume/dec. BP, macula densa signals granular cells to release renin (an enzyme)
angiotensinogen➝ (I)
angiotensin I
angiotensin I ➝ angiotensin II in lungs (angie vaso and art - front door)
(1) vasoconstriction of arterioles
(2) stimulates thirst
(3) stimulates vasopressin release (H2O
reabsorption)
atrial natriuretic peptide (ANP) inhibits… (amp - atrium)
Na+ reabsorption. released from atria in response to increased stretch from inc ECF/inc BP
Glucose and amino acids (soccer - corner)
cotransport systems driven by Na+-K+ pumps in PCT
water reabsorption is…reaborbed…(nym)
passively reabsorbed throughout most of nephron (not ascending limb of loops)
urea reabsorption (corner)
only waste product reabsorbed
Tubular Secretion (dave secretes)
enhances removal of some substances
- transepithelial transport (opposite of reabsorption)
- H+ secretion
H+ secretion (tubular secretion) (drop)
important in acid/base balance
K+ reabsorption in….(pick fries - tv)
PCT is automatic (active)
organic anion and cation secretion (pick carrier - fridge)
- special carriers for each in PCT
- prostaglandins and other chemical messengers
- other substances like drugs or pollutants
a. liver must convert substance to anionic form
Variations in urine solute concentration (controlling amount of H2O excreted) (culture)
- countercurrent mechanism (medullary countercurrent system)
establishing the gradient (countercurrent multiplication) - by loop (arm and leg loop)
- descending limb permeable to H2O but not Na+
- ascending limb pumps out Na+ but is impermeable to H2O
- as Na+ is pumped out of ascending limb,water leaves descending limb by diffusion
a. leads to gradient of 300-1200 mosm/L in medulla
b. urea also contributes to gradient
variable H2O reabsorption (umbrella - bar)
- filtrate in DCT very dilute
- without vasopressin DCT and collecting duct impermeable to H2O
a. H2O not reabsorbed, urine dilute
when vasopressin present (umbrella perm camp - kitchen table)
DCT and collecting ducts become permeable to H2O
a. cAMP second messenger system-results in insertion of H2O channels in tubule
b. water reabsorbed as it flows through medullary gradient
countercurrent exchange in vasa recta (purple heart - kitchen door)
medullary gradient does not dissipate because of the construction of the blood supply
Micturition (urination) (internal/external)
- urethra has two sphincter muscles that prevent leaking of urine
1. internal urethral sphincter made of smooth muscle (involuntary)
2. external urethral sphincter made of skeletal muscle (voluntary)
micturition reflex occurs…(stretch - epi and ml)
when stretch receptors in bladder are activated and parasympathetic fibers stimulated. occurs at 250-400 ml urine
parasympathetic stimulation causes…(epi - road trip)
bladder to contract, opening internal sphincter and inhibiting motor neurons to external sphincter
a. we become conscious of having to urinate, but we can temporarily override reflex until it’s convenient
glomerular capillaries are…(perfect-collagen)
100x more permeable than other capillaries basement membrane (collagen for strength and glycoproteins with a negative charge that repels plasma proteins)
inner layer of glomerular capsule (cloud - pod - couch)
podocytes wrap around capillaries and form
filtration slits
increased flow ➝(in tl)
vasoconstriction ➝ decreased GFR
decreased flow ➝ (need to open)
vasodilation ➝ increased GFR
baroreceptor - extrinsic sympathetic control - decreased plasma volume ➝(keep it)
generalized vasoconstriction, including afferent arteriole ➝ decreased GFR ➝ conservation of fluids
glomerular filtration rate (GFR) (kf - net - door)
GFR = Kf x net filtration pressure (Kf= filtration coefficient, collective properties of filtration membrane)
tubular reabsorption can be…(___or___)
active or passive
1. if any step is active, reabsorption of that substance
is considered active
Na+ reabsorption occurs in the…(pick - bed - and percentage)
PCT and loop-automatically reabsorb most Na+ (92%).
DCT and collecting tubule-hormonal control, reabsorption according to need
80% water reabsorption…(follow)
osmotically follows solute reabsorption (water flows through channels into cells or through leaky tight junctions)
20% water reabsorption…(umbrella - need)
according to need in DCT and collecting tubule (hormonal control - vasopressin)
H+ secretion is actively…(balloon - fridge)
secreted in PCT, DCT and collecting tubules according to need (inc H+ ➝ increased secretion of H+)
H+ secretion can be coupled to…(H loves salt)
Na+ reabsorption instead of K+ (basolateral pump in distal nephron)
K+ secretion is controlled…(umbrella - potatoes - tv)
secretion of K+ in DCT and collecting tubule
Na+-K+pump creates gradient
important in maintaining membrane potential
inc plasma K+➝ (cal)
in caldosterone➝in cK+secretion
dec plasma K+ ➝ (alden)
dec aldosterone ➝ dec K+ secretion
controlling amount of H20 secreted - long loops of…(jax - slide - kitchen)
juxtamedullary nephrons establish a vertical osmotic gradient in interstitial fluid of medulla
vasa recta prevent loss of gradient
controlling amount of H20 secreted - water can be reabsorbed from…(collection plate)
collecting tubules as it flows through gradient (under control of vasopressin)
vasa recta are…(blood - runner)
blood vessels that run near long loop
baroreceptor - extrinsic sympathetic control - increased BP ➝ (think sympathetic)
vasodilation ➝ increased GFR ➝ eliminate more fluids
controlled secretion of K+ in…(umbrella - potatoes - corner)
DCT and collecting tubule
a. Na+-K+pump creates gradient
c. important in maintaining membrane potential
glomerular filtration is a…process (everything but…)
non selective process-everything but cells and plasma proteins are filtered
macula densa - (umbrella sailing by cloud)
specialized cells of DCT as it passes by glomerulus
granular cells - juxtaglomerular (smooth - art)
(juxtaglomerular cells or JG cells) are specialized smooth muscle cells of arterioles
- different portions of tubule specialize in…(specialize)
particular substances
- most substances pass through tubule cells (transepithelial transport)
(angiotensin I ➝ angiotensin II in lungs) - adrenal cortex releases….(alden - umbrella - desk)
aldosterone - promotes insertion of more Na+ channels and Na+-K+ pumps into cells of DCT and collecting tubule (Cl- and H2O follow Na+)
countercurrent exchange in vasa recta - follows loop and…(countercurrent market)
exchanges of NaCl and H2O occur so that the blood equilibrates with the surrounding interstitial fluid
decrease Na+ reabsorption ➝ (less salt, lower..)
decrease ECF and BP
as H2O reabsorbed in PCT….(opposite of bar)
urea becomes more concentrated and then moves down its concentration gradient (50% reabsorbed)
