Question

A fall in glomerular filtrate rate (GFR) activates
A. Juxtaglomerular cells to release renin
B. Adrenal cortex to release aldosterone
C. Adrenal medulla to release adrenaline
D. Posterior pituitary to release vasopressin

Answer 1

Hint: Nephron is the unit of the kidney which helps to clean and detoxify our body. Accumulation of toxic substances can even lead to death. This is the reason dialysis is performed when kidney failure occurs. A single healthy kidney can also help people to survive throughout their life. The amount of water-soluble substances and water is maintained by this cell.

Complete answer:
Nephron is the microscopic structural and functional unit of the kidney. It is composed of renal corpuscle and renal tubule. The renal corpuscle consists of capillaries called a glomerulus and Bowman's capsule. A healthy adult has 1 to 1.5 million nephrons per kidney. GFR estimates the amount of blood that passes through glomeruli in a minute.

Option A: Juxtaglomerular cells to release rennin: GFR decline will activate juxtaglomerular to release rennin which will ultimately activate RAAS (rennin angiotensin aldosterone system). It is a signalling pathway. It regulates the body blood pressure.

Option B: Adrenal cortex to release aldosterone: When there is a decrease in blood pressure, the renin-angiotensin 2 system regulates the adrenal glands to increase the blood pressure.

Option C: Adrenal medulla to release adrenaline: Corticotropin-releasing hormone by hypothalamus stimulates secretion of adrenaline by the medulla.

Option D: Posterior pituitary to release vasopressin: Changes in blood volume and osmolarity in the blood causes the release of vasopressin.
So the answer is option A. Juxtaglomerular cells to release renin

Note:
Blood is filtered when it passes through three layers- the endothelial cells of the capillary wall, its basement membrane, the podocytes of the lining of the capsule. There is maximum reabsorption of all the minerals and substances that are not to be flushed out. At the end of the tubule, urine is flushed out which is composed of water, metabolic waste, and toxins.