Biology · Excretory Products and Their Elimination · NEET
GFR is the amount of FILTRATE formed per minute, not the amount of blood. NCERT says about 1200 ml of blood passes through the glomeruli each minute, but only 125 ml of that becomes filtrate (GFR). So do not confuse the two numbers: blood flow to the glomerulus is about 1200 ml/min, while GFR is 125 ml/min. This exact wording trap appears in NEET.
Glomerular filtration is the PROCESS (blood is pushed through the three filtration layers to form filtrate, also called ultrafiltration). GFR is the RATE, a number, telling how much filtrate is made per minute (125 ml/min). One is the step; the other is the measured speed of that step.
They are the same thing over different time windows. 125 ml is per minute. Multiply by the minutes in a day (125 ml x 60 x 24 = 180,000 ml = 180 litres per day). So 125 ml/minute and 180 litres/day are one value in two units. NEET may give either, so keep both ready.
The kidney has a built-in control called autoregulation, carried out mainly by the Juxta Glomerular Apparatus (JGA). When GFR falls, the JG cells release the enzyme renin, which starts the Renin-Angiotensin mechanism (RAAS). This raises glomerular blood flow and brings GFR back to normal, so the kidney does not need the brain to control this.
ADH INCREASES GFR (indirectly). ADH causes constriction of blood vessels, which raises blood pressure; higher blood pressure raises glomerular blood flow and therefore raises GFR. The 2023 NEET statement 'ADH is responsible for decrease in GFR' is FALSE. Do not memorise ADH as a GFR-lowering hormone.
Which of the following statements are correct? A. An excessive loss of body fluid from the body switches off osmoreceptors. B. ADH facilitates water reabsorption to prevent diuresis. C. ANF causes vasodilation. D. ADH causes increase in blood pressure. E. ADH is responsible for decrease in GFR.
Arrange the following events occurring in Renin-Angiotensin mechanism in the correct order: A. Increase in blood pressure and Glomerular filtration rate B. Reabsorption of Na+ and water from distal parts of tubule due to Aldosterone C. Fall in Glomerular filtration rate D. Vasoconstriction by Angiotensin II and release of Aldosterone. E. Renin converts Angiotensinogen into Angiotensin I, followed by Angiotensin II.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
GFR is the amount of filtrate formed by the kidneys per minute; about 125 ml/min or 180 litres per day in a healthy adult.
The Juxta Glomerular Apparatus (JGA), formed where the DCT touches the afferent arteriole. When GFR falls, its JG cells release renin to bring GFR back to normal.
125 ml per minute, equal to 180 litres per day. Both units are examinable, so remember the pair.
No. Ultrafiltration (glomerular filtration) is the process of forming filtrate; GFR is the measured rate of that process (ml/min).
Yes. Higher blood pressure raises glomerular blood flow and therefore raises GFR; a fall in blood pressure lowers GFR and triggers the JGA/RAAS response.
