1. Explain the importance of the nephron loop acting as a countercurrent multipl
ID: 71375 • Letter: 1
Question
1. Explain the importance of the nephron loop acting as a countercurrent multiplier, and why it is essential to regular nephron function.
2. A marathon runner with healthy kidneys experiences hematuria after a race. Explain what hematuria is, and discuss whether or not it is an emergency in this case.
3. Caffeine, alcohol, and furosemide (Lasix) are all diuretics, but they increase urine volume in different ways. Explain how each diuretic acts to increase urine production.
Caffeine:
Alcohol:
Furosemide:
http://www.youtube.com/watch?v=vNvZaGcLzEo
Explanation / Answer
1. Nephron loop also called as loop of Henle. In a countercurrent multiplier system, the urine gets concentrated for excretion by utilizing electrolyte pumps that typically takes place in the loop of Henle (consist of 2 limbs). Of these, the ascending limb is impermeable to water due to the absence of aquaporin transporter protein (water pumping channels) but permeable to solutes like Na+, Cl, and K+ which are actively transported into the medullary space that make the filtrate hypotonic. Therefore interstitial fluid becomes hypertonic and attracts water (the single effect of the countercurrent multiplication process). The descending limb which is permeable to water (presence of aquaporin 1 in its tubular wall) but not solutes. Therefore water moves across the tubular wall into the medullary space, making the filtrate hypertonic. Active transport of ions from the thick ascending limb generates an osmotic pressure that withdrawn water from the descending limb into the hyperosmotic medullary space to produce hypertonic filtrate. By this countercurrent flow within these two limbs multiplies the osmotic gradient between tubular fluid and interstitial space.
2. The increased red blood cells excretion through urine is called hematuria. It is an abnormal feature commonly found in infections, kidney stones, blood cell disorders, cancers and also in streousness excersize. It can be occasionally seen in marthon runners might be due to blood leakage into the urinary tract (bladder trauma), it can also expected with dehydration and blood cell breakdown. I don't think it is emergency case, to control this hematuria, it is required to void 30 minutes before marthon run that keep some urine in the bladder to soften the slap.
3. Caffeine typically increases the golmerular blood pressure or blood pressure within capillaries in the kidney that results in increase of blood filtration and urine output. In addition, it prevents Na+ resorption and increase blood Na+ levels that increases urination and decreases water filtration. It also reversibly blocks the action of adenosine. Alcohol usually inhibits the production and release of vasopressin (ADH) is an anti-diuretic hormone that increases the water absorption in the kidney. But alcohol affects the ADH release leads to increased output of urine. Furosemide blocks the absorption of Na+, Cl- and water in nephron tubules of kidney tubules from filtered fluid results in increase of the urine output.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.