Answer:
-b. Unlike the other countercurrent systems, a countercurrent multiplier system expends energy in active transport.
Explanation:
The countercurrent multiplier system entailing the loop of Henle consumes energy to actively transport NaCl from the filtrate in the higher part of the ascending limb of the loop. This consumed energy separates distinctively a countercurrent multiplier system from the different types of countercurrent systems.
Countercurrent multiplication transports sodium chloride from the tubular fluid into the interstitial space inside of the kidneys. It is a simultaneous process that involves the following steps:
●The single effect.
The single effect is controlled by active transport of sodium chloride away from the tubular fluid in the thick ascending limb into the interstitial fluid, that results hyperosmotic condition. This causes water to flow passively down its concentration gradient away from the tubular fluid in the descending limb into the interstitial region, to attain equilibrium.
●Fluid flow.
As urine is continually being produced, new tubular fluid enters the descending limb, which pushes the fluid at higher osmolarity down the tube and an osmotic gradient begins to develop.
As the fluid persist to flow via the loop of Henle, these two steps are continous resulting in an osmotic gradient to continiously multiply until it attains a steady state. The length of the loop of Henle is proportional to the size of the gradient - the longer the loop, the more the osmotic gradient.
The attached image gives an Illustration of the nephron with various pressures pinpointed at varying regions of it.
Absorbed water is recovered into the circulatory system through the vasa recta, which encompass the tips of the loops of Henle since the blood flow via capillaries is extremely slow, such that solutes reabsorbed back to the bloodstream diffuse and is recovered into the interstitial fluid, which sustains the solute concentration gradient in the medulla (countercurrent exchange).
The concentration of urine is regulated by antidiuretic hormone, which functions in water conservation, increasing water permeability in the late distal tubule and collecting ducts, raising the active transport of sodium chloride in the thick ascending limb of the loop of Henle, and promoting countercurrent multiplication and urea recycling.
