Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
12 Cards in this Set
- Front
- Back
|
O2 diffuses across vasa recta also
|
- High PO2 diffuses across to lower PO2 of ascending vasa recta
- Ultimately, lowest vasa recta has very low PO2 - This is the cost of generating high concentration loop of Henle! |
|
|
Renal medullary size determines urine concentration
|
- Only mammals and birds generate hyperosmotic urine!
- Kangaroo rat in desert has giant medulla - Doesn't need to take in any water - makes super concentrated urine! |
|
|
Control of how concentrated/dilute our urine is
|
- Aquaporin activity of collecting duct via Arginine vasopressin (AVP) or anti-diuretic hormone (ADH)
- They are the same thing... - If AVP is low - Urine Osm is less than plasma Osm - High AVP - can max out 1200 osm/L |
|
|
Response time of aquaporins to vasopressin
|
- Very fast!
- When AVP exposed to CD's -> permeability shoots up within minutes - When taken away -> goes down again very quickly! - No protracted response! |
|
|
Aquaporin types in nephron
|
- AQP1 = proximal tubule
- facilitates lots of water reabsorption - AQP2 = apical side of collecting duct - Key in AVP regulation - Chronic dehydration = increased expression |
|
|
AQP2 control mechanism via AVP
|
- V2 = AVP receptor on basolateral side (interstitial)
- AVP bind to V2 - signals via cAMP -> PKA - AQP2 proteins contained in vesicles - Vesicles are phosphorylated, move to apical surface - Constant endocytosis of aquaporins - only stay on the surface for a short time - This explains the sensitivity of AVP |
|
|
Osmotic steady state
|
- Plasma usually maintained around 290-200 mOsm/L
- Kidney works with neural systems, etc. - to keep this constant - Intra and extra cellular concentrations of ions are different - However, total osmolarity of both are ~290 mOsm/L |
|
|
Plasma osmolarity calculation
|
- Posm = ([Na]*2) + ([glucose]/18) + ([BUN]/2.8) = mOsm/L
- Rough calculation = just multiply plasma [Na+] x 2 - The 2x accounts for Cl-, HCO3- that follow Na+ |
|
|
Osmolar gap reason
|
- Sometimes measured value is higher than calculated value
- Indicates presence of some other foreign substance in blood - Normal is less than 10 - Gap > 15 = can be ethanol, methanol, or something else at toxic levels - Can also indicate an alcoholic or diabetic ketoacidosis |
|
|
Tonicity vs. osmolarity
|
- Tonicity describes cell behavior
- Water is permeable, ions are not - State of net water movement - Osmolarity = how many particles in given volume |
|
|
Body water distribution
|
60% of our body weight
- 2/3 intracellular, 1/3 extracellular - Extracellular water = plasma, interstitial fluid - Kidney works on plasma! - Starling forces control Plasma <-> interstitial fluid - Tonicity controls intracellular intake/output |
|
|
Effects of adding fluids to body
|
- Pure water - will increase intra, extracellular volume, decrease both osmolarities
- Saline = isotonic with system = extravolume in extracellular, no movement into intracellular! - Na+ permeability of cell membranes basically negligible because cell doesn't let it come in too much - 5% NaCl = Extracellular fluid has higher osmolarity - Fluid comes out of intracellular -> extracellular to equalize - Total volume also increases |
