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Renal System Flashcards

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1
Q

2 functions of kidney

A
  1. blood volume/osmolarity regulation

2. filtration

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2
Q

Micurition Reflex

A
  • stretch of urinary bladder is detected by stretch receptors
  • visceral afferent nerves go to sacral spinal cord
  • efferent signal, via parasympathetic nerves, cuases contraction of bladder and relaxation of internal urethral sphincter
  • conscious control of external urethral sphincter
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3
Q

capillaries and arterioles associated with nephron

A

2 of each

-countercurrent exchange

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4
Q

kidneys adjust blood composition using 3 fundamental processes

A
  1. filtration
    - bulk flow of water and solutes from blood into kidney tubules due to hydrostatic
  2. absorption
    - transport of substances out fo the tubules and back into the blood
  3. secretion
    - transport of substances from the blood into the tubules
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5
Q

blood flow to kidneys

A
  • renal artery has low resistance (short and large diameter)
  • branches of renal artery go directly to renal cortex
  • afferent arterioles in cortex carry blood to glomerulus
  • -the glomeruli are capillaries where filtration of the blood occurs
  • efferent arterioles carry blood from glomeruli to peritubular capillaries
  • -peritubular capillaries surround the renal tubules and participate in secretion and absorption of substances to and from the tubule
  • -loops of the peritubular capillaries descend into the medulla following the tubular loops of Henle. known as vasa recta
  • peritubular capillaries carry blood to branches of the renal vein
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6
Q

vasa recta

A

loops of the peritubular capillaries that descend into the medulla following the tubular loops of Henle

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7
Q

anatomy of a nephron

A
  • bowmans capsule
  • proximal tubule
  • loop of henle
  • distal tubule
  • collecting duct
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8
Q

bowmans capsule

A
  • receives filtrate from the glomeruli

- is involved in absorption of nutrients, water, and electrolytes

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9
Q

loop of henle

A

-involved in creating an osmotic gradient in the medulla that allows absorption of water from the distal tubule and collecting duct

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10
Q

distal tubule

A
  • involved in the fine tuning of Na+ and K+ absorption and secretion
  • also involved in absorption of water
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11
Q

collecting duct

A
  • involved in water absorption

- fluid that makes it through the collecting duct into the renal pelvis is urine

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12
Q

Filtration

A

s

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13
Q

why is blood pressure in the golmerular capillaries high

A

-efferent arteriole creates significant resistance downstream of the glomerular capillaries

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14
Q

adjustment of blood pressure in the glomerulus

A

adjusted by constriction and dilation of either the afferent or efferent arterioles

  • pressure in the glomerulus can be adjusted by contriction and dilation of either the afferent or efferent arterioles
  • pressure in the glomerular capillaires is normally near 50mmHg
  • pressur ein the bowmans capsule is normally near 10mmHg
  • oncotic pressure in the capillaries is near 25mmHg
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15
Q

filtration pressure

A

difference between capillary pressure and capsule pressure+oncotic pressure

  • ex: FP=50-(10+25)=15mmHg
  • small changes in capillary pressure make relatively large changes in filtation pressure
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16
Q

golmerular filtraiton rate

A

GFR

  • determined by filtration pressure
  • measured in ml/min
  • greater gfr, greater urine volume, increase urine volume, less blood volume
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17
Q

filtration layers

A

capillary endothelium-fenestrated (holes)

  • basement membrane
  • podocytes (form the visceral layer of bowmans capsule)
  • -filtration slits are between the pedicels of the podocytes
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18
Q

ultrafiltrate

A
  • fluid entering bowmans capsule
  • everything in plasma but proteins
  • water+all small solutes (Na, K, Cl, Ca, glucose, amino acids, urea, etc)
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19
Q

renal clearnace

A

clearance of a substance is the volume (ml) of plasma that is cleared of that substance per minute
-measurement of GFR

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20
Q

clearance equation

A

(V(ml/min)*U(mg/ml))/P(mg/ml)
V=volume of urine produced per minute
U= concentration of substance in the urine
P=concentration of the substance in the plasma

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21
Q

inulin clearance

A

a measure of the GFR

  • insulin is filtered, but not secreted or absorbed, so clearance of inulin=GFR
  • absorbed into arteriole
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22
Q

PAH clearance

A
  • measure of total renal plasma flow (RPF)
  • PAH is para-aminohippuric acid
  • PAH is 100% cleared from renal plasma (no PAH in renal vein)
  • total renal blood flow can be determined if CPAH and hematocrit are known
  • average hematocrit is 0.45 for males and 0.42 for females
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23
Q

RBF (renal blood flow) equation

A

CPAH/(1-hematocrit)

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24
Q

clearance of any other substance can be compared to what

A

GFR and RPF

  • if clearance is less than GFR it is being absorbed. If it is completely absorbed the the clearance is zero (glucose)
  • if clearance is greater than GFR it is being secreted. if it is completely secreted the clearance=RPF
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25
hematocrit and plasma makeup of blood
hematocrit=45% | plasma=55%
26
where do all the nutrients get absorbed
the proximal tubule - glucose, amino acids, lactate, etc - also about 80% of the Na+ Cl- and H2O
27
the proximal tubule absorption
- not highly regulated - fine tuning of absorption occurs further down the tubule - epithelium is similar to the small intestine epithelium - leaky epithelium: water goes through tight junctions so isotonic fluid is absorbed - Na+/K+-ATPase in basolateral membrane provides the primary driving force for the absorption - Na+/glucose-,Na+/amino acid-cotransporters in luminal membrane - facilitated diffusion of glucose, amino acids, Cl-
28
regulated absorption of H2O occurs where
-loop of henle, distal tubule, collecting duct
29
absorption of H2O process
- loop of Henle creates a hyperosmotic condition in the medulla, which consists of increasing osmotic strength as distance from the cortex increases - the descending limb is permeable to H2O, so H2O is absorbed (leaves the tubule) as the fluid flows deeper into the medulla. This H2O is carried away by the capillaries of the vasa recta - the ascending limb is impermeable to H2O and it actively absorbs NaCl, so the solutes tend to stay in the medulla, while the fluid arriving in the distal tubule is hypoosmotic. This process occurring in the loop of Henle is known as countercurrent multiplication
30
resulting conditions of countercurrent multiplicaiton
- about 12-15 liters/day of 100mOsm tubular fluid reaches the distal tubule - tissue fluid osmolarity is about 300 mOsm in the cortex - tissue fluid osmolarity increases from 300 to about 1400 mOsm in the deep parts of the medulla
31
the collecting duct and distal tubule use the osmotic gradient created by the loop of Henle to regulate the absorption of H2O
- The H2O concentration gradient favors absorption all the way along the distal tubule and collecting duct - the amount of H2O that is absorbed depends on the permeability of the tubules for H2O - if H2O permeability is low, little absorption takes place and large volume of dilute urine is produced - if H2O permeability is high, a lot of absorption takes place and a small volume of concentrated urine is produced
32
how to control H2O permeability
controlled by antidiuretic hormone (ADH) -ADH receptors on the distal tubule and collecting duct are linked to the Gs protein and lead to an increase in [cAMP] causes installation of water channels in luminal membranes by exocytosis
33
negative feedback loop that regulates tissue osmotic strength
- ADH secretion by the neurohypophysis is a part of the negative feedback loop - hypothalamus has osmotic strength receptors - increased osmotic strength of the CSF causes increased ADH secretion - ADH causes decreased urine volume and induces thirst
34
biggest determinant of water concentration/blood volume
Na+ - controls osmotic strength - more Na+, ADH conserves H2O, increased [H2O] - increased BV will increase VR and therefore increase CO and arterial Pressure
35
kidney anatomy responsible for absorption of Na+?
distal tubule - absorbs sodium and secretes potassium - aldosterone increases Na+ absorption and secretion of K+ and H+ - aldosterone is secreted by the adrenal cortex in response to angiotensin 2 - aldosterone causes increased transcription of genes for Na+, K+, and H+ transport proteins - -Na+/K+-ATPase, Na+/H+-countertransporter
36
Homeostasis of Body fluids
Renin-Angiotensin-aldosterone system
37
juxtaglomerular apparatus (JGA)
- JGA secretes renin if any of the following conditions are detected: - low pressure in afferent arteriole - large amounts of Na+ in the distal tubule - low MAP detected by the arterial baroreceptors (vis the sympathetic NS)
38
renin pathway
an enzyme that cleaves angiotensinogen to angiotensin 1 - angiotensin converting enzyme (ACE) completes activation by conversion to angiotensin 2 - angiotensin 2 increases blood volume and blood pressure several way
39
ways that angiotensin 2 increases blood volume and pressure
- causes aldosterone secretion from adrenal cortex - causes vasoconstriction of afferent arteriole, decreasing GFR - causes increased ADH secretion from neurohypophysis - causes general arteriole vasocontriction, increasing TPR causes increased thirst
40
angiotensin 2 receptors are linked to what protein
Gp-protein
41
atrial natriuretic hormone (ANH)
-stretch of the right atrium, exercise or caloric restriction causes increased release of ANH -the ANH receptor is a guanylate cyclase receptor enzyme -[cGMP] rises in the target cell and activates cGMP-dependent protein kinases the results are: -vasodilation: causes increased GFR and decreased TPR -decreased absorption of Na+ by distal tubule (a Na+ channel is phosphorylated by the cGMP-dependent kinase) -activation of enzymes for lipolysis (fat mobilization)
42
-most important effect of ANH
-lowering the blood pressure by reducing blood volume
43
pH
s
44
three systems interacting to control pH
1. buffer system: the major extracellular buffer is bicarbonate 2. respiratory system: can influence the bicarbonate buffer system 3. renal system: can absorb or secrete H+ or HCO3
45
what disregulates pH
- metabolic or respiratory influences | - can be differentially diagnosed by observation of the bicarbonate concentration
46
metabolic acidosis
low pH and low [HCO3]
47
respiratory acidosis
low pH and high [HCO3]
48
metabolic alkalosis
high pH and high [HCO3]
49
respiratory alkalosis
high pH and low [HCO3]
50
renal handling of H+ and HCO3
absorption of filtered HCO3 is normally the first step (humans tend to be acidotic, and therefore are generally secreting H+ into the urine)
51
steps of renal handling of H+ and HCO3
1. in the proximal tubule cell, CO2 is converted to H+ and HCO3 by carbonic anhydrase 2. the H+ is actively secreted into the tubule (H-ATPase or Na/H-exchange) 3. the H+ is actively secreted into the tubule (H-ATPase or Na/H-exchange) 4. the HCO3 produced inside the cell is transported to the blood in exchange for Cl- - the net effect of this is that HCO3 disappears from the tubule and appears in the blood, while H+ is removed from the body in the urine
52
additional secretion of H+ after filtered bicarbonate is recovered
- secreted H+ combines with one of the urinary buffers (amonia or phosphate) - phosphate is normally found in the tubule fluid. it is co-regulated with calcium. NH3 is made in the proximal tubule cell using glutamine from the liver - NH4 is one form of nitrogenous waste - Urea is the other. it is made by the liver: 2NH3+CO2->urea
53
acidosis
too low pH, increased H+, denatures proteins
54
alkalosis
pH too high, not enough H+
55
metabolic acidosis
- something we ate causes increased H+ - reaction goes opposite way, HCO3- decreases, increased CO2 - breathing faster decreases CO2, helps buffer system move faster - HCO3- is the limiting factor
56
acidosis reaction
H2O+CO2H+ + HCO3-
57
only way to eliminate excess H+
kidney excretes | -bicarbonate just binds it
58
respiratory acidosis
- result of hypoventilation - increase [CO2], increase H+ - hyperventilation causes alkalosis
59
Homeostasis of calcium-3 hormones
1. parathyroid hormone 2. dihydroxycholicalciferol (vitamin D) 3. calcitonin
60
vitamin D (dihydroxycholicalciferol)
- converted to cholecalciferol by the liver, kidney and skin | - it enhances Ca uptake by the small intestine
61
calcitonin
- causes increased activity of osteoblasts - it causes increased bone formation and decreased plasma [Ca] - takes calcium phosphate from bone, phosphate removed from calcium
62
parathyroid hormone
- most powerful of the three - causes activation of vitamin D to cholecalciferol - stimulates osteoclasts, causing mobilization of Ca and PO4 from bone - it enhances renal absorption of Ca and secretion of PO4

Physiology (11 decks)

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