11 - Regulation of Plasma Osmolarity PPT Flashcards
How do we determine osmolarity?
Solute concentration and ECF volume
How is the body’s water controlled?
Through fluid intake and renal excretion
How does the body use ADH to help regulate water?
When there’s high body fluid osmolarity (high solute):
1. The post. pituitary secretes ADH
2. ADH increases the permeability of the DCT and collecting ducts to water
3. Large amounts of water are reabsorbed, urine volume is decreased
When there’s excess water in the body (low solute):
1. Osmolarity decreases, ADH secretion decreases
Rate of ADH secretion determines whether the kidney secretes a __________ or ___________ urine.
- diluted
- concentrated
(TRUE/FALSE): After ingesting excess water, the kidneys rid the body of excess water and excess solutes.
(FALSE): The body absorbs/retains solutes to a greater extent than water.
What’re the obligatory solute and urine volumes (aka, how much solute and urine we must pass per day)?
- 600 milliosmoles of solute per day
- 0.5L of urine per day
What must we have to form concentrated urine?
- high ADH
- high osmolarity of renal medullary interstitial fluid (so the water can be reabsorbed out of the urine)
What substance contributes to 40-50% of the renal medullary interstitium’s osmolarity?
U R E A
Diabetes Insipidus patients cannot produce ADH, and therefore form…
… a large volume of diluted urine.
If Diabetes Insipidus patients constantly produce diluted urine, how does that affect their hydration?
Diluted urine means it has a high water content- they’re excreting all the water they’ve got! Severe dehydration occurs without synthetic ADH medication.
What is the disease called when someone does not respond appropriately to ADH, and what is the treatment?
Nephrogenic Diabetes Insipidus, treatment is to correct the underlying renal disorder.
When else is ADH released?
During increased arterial pressure and decreased blood volume (RAAAAAAS)
What do we release to retain water during dehydration?
This is the million-gazillion dollar question.
ADH
What substances/sensation will increase ADH secretion?
Nausea, nicotine, and morphine
Idea: “Stimulants stimulate ADH”
What substance will decrease ADH secretion?
Alcohol
Idea: “Depressants decrease ADH”
Name the factors that stimulate or increase thirst!
- ADH stimulants
- Angiotensin-II
- Dryness of mouth and esophagus
Name the factors that relieve thirst!
- DRINKING WATER
- GI distention
