18 Flashcards
Why would you create dilute urine
if there is too much water or too few ions in the body
- restablishes balance
if too muc dilute blood –> water intoxication –> deat
urine must be more dilute than blood
>300 mOsm/L
What nephron size is creates dilute urine
short
glomerulus in susperficial regions and nephron loop does not extend far into the renal medulla
What nephron size creates concentrated urine
long
Which section of the tubule is impermeable to water
thick ascending limb (loop)
Which section is permeable to water in teh presence of ADH
collecting ducts
Describe the path of the short loop nephron
- solutes reabsorbed and water follows them out of the tubule in the PCT
- filtrate enters the nephron loop and equilibrates (permeable to water at descending limb)
- loss of water (but not ions) makes the filtrate more concentrated and the osmolarity goes up - solutes transported out by symporters but water cannot follow
- filtrate loses solute and the osmolarity goes down - filtrate flows to the distal convoluted tubule and loses more solute (but not water)
- osmolarity falls even further - filtrate enters the collecting ducts –> no ADH –> impermebale to water
- more solute is pumped out until the most dilute urine is formed
What sets up the osmotic gradient (salt gradient) in the interstitial space
thick ascending limb of the nephron loop
- pumps out ions but not water
Why create concentrated urine
if too little water or too many ions in the body
urine must be more concentrated in ions than the blood
<300 mOsm/L
Describe the path of the long loop nephron
- solutes reabsorbed and water follows them out of the tubule
- filtrate enters nephron loop and equlibrates
- loss of water but not ions makes the filtrate more concentrated and the osmolarity goes up - solutes transported out by the symporters but water cannot follow
- filtrate loses solute and the osmolarity goes down - filtrate flows to the distal convoluted tubule and loses more solute (but not water) so osmolarity falls further
- filtrate enters collecting duct –> presence of ADH –> permeable to water
- water flows out to match the extremly high osmolarity of the surrounding interstitial fluid
What do diuretics do
inhibit the Na+-K+-2Cl- symporter in the ascending loop of the nephron
- alters the salt gradient of the interstitial space so there is more reduced water reuptake and more urine
What stimulates release of ADH from post pit
high osmolarity in the plasma –> interstitial fluid detected by osmoreceptors in the hypothalamus
How does ADH regulate hormones
promotes the synthesis of water pores (aquaporin 2) in CD
increases the actvity of the Na+-K+-2Cl- symporter
How does the RAA-pathway regulate hormones
decreased bp –> juxtaglomerular apparatus –> renin (from angiotensin) –> angiotensin 1 –> angiotensin 2 (ACE) –> aldosterone release or constriction of afferent arteriole –> increased blood volume
What is a urinalysis
analyzes the volume, physical, chemical and microscopic properties of urine
What is a blood analysis
looking at hte levels of waste products, electrolyte levels, blood osmolarity
