Toynbee test is used to the function of –
**Core Concept:** The Toynbee test is a clinical test used to assess the function of the sympathetic nervous system, specifically the sudomotor function of the autonomic nervous system. The sympathetic nervous system controls various physiological functions, including sweating, blood pressure, and pupil size.
**Why the Correct Answer is Right:** The Toynbee test is performed by pinching the skin of the patient's earlobe or other small area and observing the response to the pinch. When a healthy individual is pinched, they exhibit an immediate, transient increase in sweating (hyperhidrosis) followed by a reduction in sweating (hypo- or anhidrosis) after pinch release. This reflex is mediated by the sympathetic nervous system and its sudomotor function.
**Why Each Wrong Option is Incorrect:**
A. False: This option does not relate to the sympathetic nervous system or its function.
B. False: Although the sympathetic nervous system controls blood pressure, the Toynbee test specifically evaluates sweating.
C. False: The test evaluates sweating, not pupil size (which is regulated by the parasympathetic nervous system).
D. False: This option is unrelated to the sympathetic nervous system or its function.
**Why the Correct Answer is Right:** The correct answer, D, is right because the Toynbee test evaluates the sudomotor function of the sympathetic nervous system, which is responsible for controlling sweating. The test involves pinching the skin and observing the subsequent sweating response. This helps in assessing the integrity of the sympathetic nervous system and its sudomotor function.
**Clinical Pearl:** The Toynbee test is a simple, non-invasive method to evaluate the function of the sympathetic nervous system and its sudomotor function. A normal response with an immediate increase in sweating followed by reduction in sweating after pinch release indicates a healthy sympathetic nervous system. This test can be useful in assessing various conditions, such as sympathetic nervous system dysfunction, peripheral neuropathy, or autonomic disorders.