Which chemical mediator is primarily responsible for dolor during inflammation?

BTSC 3 August 2025

Pathology & Genetics

Easy

Appeared in: BTSC 3 August 2025

Explanation

Dolor, the Latin term for pain, is a cardinal sign of inflammation.
Bradykinin is a potent peptide mediator that directly stimulates sensory nerve endings (nociceptors), causing the sensation of pain.
It is formed from a plasma precursor, kininogen, by the enzyme kallikrein as part of the kinin system cascade.
Along with prostaglandins, bradykinin is considered a principal mediator of pain in acute inflammation.

Option A: Serotonin (5-HT) is a vasoactive amine that primarily increases vascular permeability and causes smooth muscle contraction. While it contributes to the inflammatory process, it is not the principal mediator of pain.
Option B: Haemoglobin is an oxygen-transport protein located within red blood cells. It has no established role as a chemical mediator in the inflammatory response.
Option D: Fibrinogen is a plasma protein that is converted to fibrin to form a blood clot, which walls off the area of injury. While fibrinopeptides released during this process have some minor inflammatory actions, fibrinogen itself is not a primary mediator of pain.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Chemical mediators of inflammation and pain (dolor) as background academic context rather than a clinical decision trigger.
Understanding that Bradykinin and Prostaglandins cause inflammatory pain helps nurses appreciate the mechanism of action of analgesics like NSAIDs, which work by inhibiting prostaglandin synthesis.
Nurses assess for pain (dolor) as a key indicator of inflammation and infection, which guides interventions and the evaluation of treatment effectiveness.
What if? If a patient has hereditary angioedema, they have a deficiency of C1 inhibitor, leading to uncontrolled activation of the kinin system. This results in excessive bradykinin production, causing episodes of severe, non-pitting edema and pain, but without itching (as it's not histamine-mediated).

How to Approach the Question

First, identify the key terms in the question: 'chemical mediator', 'dolor', and 'inflammation'.
Recall that 'dolor' is the medical term for pain, one of the five cardinal signs of inflammation.
Systematically evaluate each option's primary function in the body's physiological processes.
Eliminate options with clearly unrelated primary functions, such as Haemoglobin (oxygen transport) and Fibrinogen (clotting).
Differentiate between the remaining inflammatory mediators (Serotonin and Bradykinin) based on their principal roles. Recall or deduce that Bradykinin is a potent, direct pain-producing substance.

Concept Tested & Keywords

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