**Question:** According to Bezold-Brucke effect:

A. Increase in heart rate
B. Decrease in heart rate
C. No effect on heart rate
D. Increase in blood pressure

**Core Concept:** Bezold-Brucke effect is a physiological phenomenon where a decrease in body temperature leads to an increase in heart rate. This effect is named after German anatomist Justus Friedrich Wilhelm Bezold and Austrian physiologist Joseph Emil Braun.

**Why the Correct Answer is Right:** The Bezold-Brucke effect is primarily mediated by the sympathetic nervous system, specifically the activation of the medulla oblongata and the sympathetic preganglionic neurons. When body temperature decreases, these neurons send a signal to the cardiac ganglion, located in the paravertebral ganglia, which then transmits the signal to the sinoatrial node (SA node) in the heart. This stimulation of the SA node leads to an increase in heart rate. This is why option A is correct - an increase in heart rate occurs during a decrease in body temperature as per the Bezold-Brucke effect.

**Why Each Wrong Option is Incorrect:**

Option B is incorrect because the Bezold-Brucke effect actually results in an increase in heart rate, not a decrease.

Option C is incorrect as the Bezold-Brucke effect does have an effect on heart rate, so choosing "no effect" is not accurate.

Option D is incorrect because the Bezold-Brucke effect primarily influences heart rate, not blood pressure. Although a secondary effect of increased heart rate is a potential increase in blood pressure, this question specifically focuses on the heart rate aspect.

**Clinical Pearl:** The Bezold-Brucke effect plays a role in thermoregulation, helping the body maintain a stable body temperature by adjusting heart rate in response to changes in core body temperature. Understanding this effect is crucial for medical professionals to properly diagnose and treat patients exhibiting symptoms related to altered body temperature, such as hypothermia or hyperthermia.