Nephro Physiology Flashcards
Hypernatremia: 2 causes
Hyponatermia: 2 causes
what is normal plasma Na+?
Hyper: increased Na+ or decreased Water
Hypo: decreased Na+ or increased water
Normal: 140-145mmol/L
What are the effects of neurologic function when cells shrink or swell?
- rapid shrinking can tear vessels and cause hemorrhage
- rapid swelling can cause herniation(protrusion).
What are the effects of an isotonic solution on cell volume? Hypotonic? Hypertonic?
Isotonic: nothing
Hypotonic: cell swells
Hypertonic: cell shrink
Blood flow through the kidneys: arteries to veins.
Aorta, renal artery, segmental artery, interlobar artery, arcuate artery, cortical radiate artery, afferent arteriole, GLOMERULUS, efferent arteriole, peritubular capillaries and vasa recta, cortical radiate veins, arcuate vein, interlobar vein, renal vein, inferior vena cava.
Where are principal cells located and what is their function?
-principle cells are located in the collecting ducts, they are important for reabsorbing water and are reactive to ADH.
WHat is the basic flow of fluid through the nephron?
afferent arteriole…glomerulus…proximal convoluted tubule…descending thin limb loop of henle, ascending thick limb loop of henle, distal convoluted tubule, collecting duct..
What cannot pass through the fenstrated endothelium of the glomerulus?
RBC and proteins
What makes up the glomerular capsule?
capillary wall,, fenestrated endothelium, basement membrane, and podocyte
Do cortical and juxtamedullary nephrons have a Vasa Recta?
no, only juxtamedullary nephrons do.
What are the Basic mechanisms of Urine Formation
- filtration
- reabsorption:removes useful solutes from filtrate and returns them to blood
- secretion: removes additional wastes from blood adds them to filtrate.
- excretion: removes water from urine, concentrates wastes
excretion = _____ - _____ + _____.
excretion = filtration - reabsorption + secretion
What is occurring at each segment of the nephron?
- Renal corpuscle: filtrate is produced.
- Proximal convoluted tubule: reabsorption of water ions, and organic nutrients. 65% of water is reabsorbed here
- Descending Loop: reabsorption of water, permeable to water.
- ascending limb: Na and Cl- ions are reabsorbed, not permeable to water.
- Distal convoluted tubule: secretion of ions, variable reabsorption of water, Na, and Ca ions (under hormonal control)
- Collecting duct: variable reabsoprtion of water and reabsoprtion or secretion of Na, K, H+, and bicarb.
- Papillary duct: deliver urine to minor calyx.
HOw many liters of water are filtered each day? Reabsorbed? Excreted?
Filtration: 180L/day
Reabsorbed: 179L/Day
Excretion: 1 L/Day
WHat is clearance? renal clearance?
Clearance: rate at which substances are removed from the plasma
Renal clearance: the volume of plasma completely cleared of a substance per min by the kidneys
How do you calculate clearance?
Clearance = (urine conc. of substance x urine flow rate) / plasma conc. of substance.
When does renal clearance equal GFR?
when a substance is freely filtered, but not reabsorbed or secreted.
What is used to estimate GFR?
Creatinine clearance
Relationship between GFR and serum creatinine conc?
ex. ?
- what is normal GFR? Creatinine Clearance?
Relationship: steady state, not linear. Creatinine clearance remains relatively stable until GFR has dropped to half of normal, at this point you start to see a change in the creatinine conc.
ex. GFR 60 = [Creat] 2.4 which is less than 50% kidney function.
Normal GFR: 125ml/min (180L/day)
Normal Creat: 1.8mg/100ml
What can be suggested if the BUN is higher than the BUN:Creat ratio? Creatinine higher than BUN:creat ratio?
BUN: suggest a problem with volume, the kidneys are not being adequately perfused.
Creat: suggest there is a kidney problem (parenchymal dz)
Net filtration pressure = _____ - _____ - ______.
net filtration = glomerular hydrostatic pressure - bowmans capsule pressure - glomerular oncotic pressure
What is GFR?
the amount of filtrate formed per minute by the two kidneys combined.
*99% of filtrate is reabsorbed so that only 1-2L of urine/day is excreted.
How does the kidney maintain the flow or alter the flow of blood through the glomerulus? How do they resist rises in blood pressure? Low BP?
Renal Autoregulation: the kidneys maintain a relatively stable GFR in spite of the changes in arterial blood pressure.
Increased BP:
1.constriction of the afferent arteriole to reduce blood flow into
the glomerulus
- Dilation of efferent arteriole to allow the blood to flow out more easily.
* change in opposite direction if blood pressure falls.
Increased afferent arteriole pressure leads to ____ Pressure in the Glomerulus and therefore _____GFR and ____ Renal blood flow.
increased afferent arteriole pressure leads to DECREASED Glomerular pressure and DECREASED GFR and therefore decreased Renal blood flow.
*GFR is directly related to the pressure in the glomerulus
Increased efferent arteriole pressure leads to ___ Pressure int he glomerulus and therefore ____ GFR and ____ renal blood flow.
Increased efferent arteriole pressure leads to INCREASED presssure in glomerulus and therefore INCREASED GFR and DECREASED blood flow entering the glomerulus.
What two mechanisms that influence GFR? Other mechanisms?
- Myogenic response
- Tubuloglomerular feedback (macula densa and renin)
Other factors:
-prostaglandins, fever, steroids, hyperglycemia all increase GFR
-Aging decreases GFR
Tubular reabsorption in Proximal Convoluted Tubules:
-reabsorbs how much filtrate and returns it to
the blood?
- what are the 6 mechanisms of reabsorption?
- what are the 3 pathways re-absorption takes place?
–65%
- Solvent Drag
- active transport of Na (Na/K pump against gradient)
- Secondary active transport of glucose amino acids and other nutrients (cotransport ex. Na dependent glucose transporter)
4.secondary water reabsorption via osmosis
(water follow Na)
5.secondary ion reabsorption via electrostatic attraction
(Negative Ions follow positive Na ions by electrostatic attraction)
6.endocytosis of large solutes.
- paracellular path (moves between cells)
- transcellular path (moves through cells)
- osmosis
What is Transport maximum? What happens when this has been met? Example?
there is a limit to the amount of solute that a renal tubule can reabsorb because there are limited numbers of transport proteins. if all transporters are occupied some solute will remain in the tubular fluid and appear
ex: glucose
Reabsorption in the Nephron Loop:
- descending thin limb permeable to what?
- ascending thick limb permeable to what?
- Descending thin limb is permeable to water.
- ascending thick limb is permeable to Na & other solutes, NOT water. Thus the tubular fluid becomes very diluted while extracellular fluid because very concentrated with solutes.
Reabsorption in Distal Convoluted Tubules
-early/late tubule permeability?
- early: NOT permeable to H20, not very permeable to urea
- late: permeable to water, depends upon ADH(principal cells), NOT very permeable to urea.
Angiotensin II increases Na+ and Water reabsorption, how?
- stimulates aldosterone release
- Directly increases Na+ absorption
- Constrics efferent arterioles
- decreases peritubular capillary hydrostatic pressure
- increases filtration fraction thereby increasing Na and H20 reabsorption
ACEi and Ang II antagonists decrease Na+ and blood pressure, how?
- decrease aldosterone
- directly inhibit Na reabsorption
- decrease efferent arteriolar resistance
….leading to natriuresis and diuresiss + Decreased blood pressure.
Atrial Natriuretic Factor
- secreted from where?
- how does this work?
- effects on Na and water reabsorption
-secreted by atrial myocardium in response to high blood pressure
Work:
-increases GFR, decreases aldosterone, decrease Renin release(AngII)
-inhibits sodium and water reabsorption, increases the output of both in the urine and thus reduces blood pressure and volume.
Tubular Secretion
-purpose
-purpose; waster removal and acid base balance
Collecting Ducts
- what does this do?
- what is the driving force of this tubular sections function?
- what regulates the function of this tubular region?
- concentrate urine & CD reabsorbs water back into blood
- High osmolarity of ECF generated by NaCl and urea provides the driving force for water reabsorption into the blood.
-ADH regulates this medullary portion, it is not permeable to NaCl but permeable to water depending on if ADH is present.
….if ADH is present(state of dehydration) water will be reabsorbed into the blood thus concentrating the urine.
Where does ADH synthesis occur?
What releases ADH ?
ADH synthesis occurs in the magnocellular neurons of the hypothalamus and is released by the posterior pituitary and exert their actions on the kidneys
