& x20; The most common ionized mediator of hormone action in our body is? & x20; - RUHS, Jaipur, M.Sc Nursing Entrance Exam-2016

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2016

Applied Physiology

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2016

Explanation

Calcium (Ca2+) is a universal intracellular second messenger, crucial for signal transduction.
Many hormones that cannot enter the cell bind to surface receptors, triggering a rapid release of Ca2+ from intracellular stores like the endoplasmic reticulum.
This surge in cytoplasmic Ca2+ acts as a signal, often by binding to the protein calmodulin.
The activated Ca2+-calmodulin complex then modulates the activity of various enzymes (like kinases and phosphatases) to execute the hormone's physiological effect.

Option B: Magnesium's primary role is as a cofactor for hundreds of enzymes, especially those involving ATP. It stabilizes membranes and nucleic acids but does not function as a primary, rapidly mobilized second messenger for hormone signals.
Option C: Iron is essential for oxygen transport as a component of hemoglobin and for cellular energy production within the electron transport chain. Its levels are tightly regulated, but it does not act as a signaling molecule or second messenger for hormone action.
Option D: Potassium is the primary intracellular cation responsible for establishing the resting membrane potential of cells and for the repolarization phase of an action potential. While its movement across the membrane is critical for excitability, it is not the mediator of the hormone's message itself.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Role of ions as second messengers in hormone action as background academic context rather than a clinical decision trigger.
Nurses must carefully monitor serum calcium levels, as both hypocalcemia and hypercalcemia can severely disrupt physiological processes, including hormone signaling, cardiac rhythm, muscle contraction (tetany), and nerve function.
Disorders of the parathyroid gland, which regulates calcium, directly impact these calcium-mediated processes. For example, hypoparathyroidism can lead to life-threatening hypocalcemia.
What if? If a patient develops acute hypercalcemia, the primary nursing action is to promote hydration with intravenous saline to increase renal excretion of calcium and to ensure patient safety due to risks of confusion, weakness, and cardiac arrhythmias.

How to Approach the Question

First, analyze the question's keywords: 'most common', 'ionized mediator', and 'hormone action'.
'Ionized mediator' points to a charged ion (like Ca2+, K+) that acts as a signaling molecule.
'Hormone action' often involves 'second messengers' that relay a signal from a hormone on the cell surface to the cell's interior.
Recall the major second messenger systems in the body. The two most prominent are the cyclic AMP (cAMP) system and the phosphatidylinositol system.
Recognize that the phosphatidylinositol system's primary function is to increase intracellular levels of ionized calcium (Ca2+).
Evaluate the roles of the other options: Magnesium is an enzyme cofactor, Iron is for oxygen transport, and Potassium is for membrane potential. None of these fit the description of a primary second messenger for hormones as well as calcium does.

Concept Tested & Keywords

QGfjaTXB1umSyZPjQkZnqO

E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) pp. 499-501, 498-500

E6 Medicine Harrison 22e Part 2 p. 1166-1168