Question

What is renal threshold?
A) At which all the substances are reabsorbed actively.
B) The highest concentration of substances up to which it is totally reabsorbed from the glomerular filtrate.
C) At which no substance is filtered in the glomerulus.
D) At which the filtration of substance starts.

Answer 1

Renal is the term linked with kidney. The kidney filters harmful substances from the blood. If the harmful substances are not filtered beyond the threshold level, several abnormalities can arise. The threshold concentration is considered as normal.

Complete answer:
Renal threshold is the amount of substance dissolved in the blood which the kidney does not allow to pass into the urine. The substances include the bicarbonate ions, glucose, proteins creatinine etc. It is the highest concentration of the substance which is reabsorbed from the glomerular filtrate. Above this concentration, the substances are filtered out in urine.

The threshold level is different for different substances. It depends on the need of the substance. The urea is removed at lower concentrations whereas glucose is removed at higher concentration. The condition at which the renal threshold level of glucose increases is referred to as diabetes. In

The renal threshold level varies from species to species and also depends upon the physiological conditions. For example, the threshold level is altered during the disease or illness. Animals have different threshold levels during hibernation. The threshold level defines the normal physiology of an individual.

Thus, the correct answer is option ‘B’.

Note: The reabsorption of the substances takes place at the proximal convoluted tubules. The reabsorption of substances takes place from the tubules to the capillaries based on the concentration gradient.