Question:

Aldosterone is a steroid hormone and is important in the control of sodium and potassium ion concentration in mammals. It upgrades sodium ion concentration in the ECF by promoting reabsorption of sodium ions from renal tubules and excretion of potassium ions in urine.

Updated On: Jul 28, 2022
  • If both assertion and reason are true and reason is the correct explanation of assertion
  • If both assertion and reason are true but reason is not the correct explanation of assertion
  • If assertion is true but reason is false
  • If both assertion and reason are false
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The Correct Option is A

Solution and Explanation

Both assertion and reason are true and reason is the correct explanation of assertion. Aldosterone is a steroid hormone (mineralocorticoid) produced by the outer-section (zona glomerulosa) of the adrenal cortex in the adrenal gland to regulate sodium and potassium balance in the blood. At the late distal tubule & collecting duct, aldosterone has two main actions: Acting on mineralocorticoid receptors (MR) on principal celts in the distal tubule of the kidney nephron, it increases the permeability of their apical (luminal) membrane to potassium and sodium and activates their basolateral Na / K pumps, stimulating ATP hydrolysis leading to phosphorylation of the pump and a conformational change in the pump exposes the Naions to the outside. The phosphorylated form of the pump has a low affinity for Naions, hence reabsorbing sodium (Na ions and water into the blood, and secreting potassium (K) ions into the urine. (Chlorine anions are also reabsorbed in conjunction with sodium cations to maintain the system?? electrochemical balance.) Aldosterone stimulates H secretion by intercalated cells in the collecting duct, regulating plasma bicarbonate (HCO) levels and its acid/base balance. Aldosterone may act on the central nervous system via the posterior pituitary gland to release vasopressin (ADH) which serves to conserve water by direct actions on renal tubular resorption. Aldosterone is responsible for the reabsorption of about 2% of filtered sodium in the kidneys, which is nearly equal to the entire sodium content in human blood under normal GFR (glomerular filtration rate).
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Concepts Used:

Biomolecules - Hormones

Hormones are defined as important chemicals that act as messengers of the body. These are the chemicals that are secreted by special glands, known as endocrine glands and these distributed throughout the body. It helps in controlling of physiological functions. Moreover, they are important while maintaining homeostasis in the body. The entire endocrine system is a network of glands. Hormones are almost same as the nervous system. Functioning of various body functions it plays an important role. The only difference between the nervous system and hormones that nervous system uses nerve impulses and neurotransmitters for communication, while the endocrine system uses chemical messengers named hormones.

Types of Hormones:

  • Peptide Hormones: Peptide hormones include amino acids that are soluble in water. Insulin is a vital peptide hormone that is produced by the pancreas.
  • Steroid Hormones: Unlike peptide hormones, steroid hormones are fat-soluble and can easily pass through a cell membrane with ease. Sex hormones like testosterone, estrogen, etc. are some of the kinds of steroid hormones.