**Question:** Which of the following is NOT caused by sympathetic stimulation?

A. Increased heart rate
B. Increased blood pressure
C. Increased sweating
D. Decreased respiratory rate

**Core Concept:** Sympathetic stimulation refers to activation of the sympathetic branch of the autonomic nervous system, which is responsible for the body's "fight or flight" response. Sympathetic stimulation leads to various physiological changes, including increasing heart rate, blood pressure, and sweating, while decreasing respiratory rate.

**Why the Correct Answer is Right:** Decreased respiratory rate (Option D) is not typically associated with sympathetic stimulation. Instead, it is more often seen during parasympathetic activity, which occurs during rest and relaxation. In contrast, increased heart rate (A), blood pressure (B), and sweating (C) are typical responses to sympathetic stimulation.

**Why Each Wrong Option is Incorrect:**

A. Increased heart rate: Sympathetic stimulation directly increases the heart rate through activation of beta-adrenergic receptors on cardiomyocytes, leading to increased contractility and heart rate.
B. Increased blood pressure: Sympathetic stimulation causes vasoconstriction in the peripheral blood vessels, leading to increased total peripheral resistance and elevated blood pressure.
C. Increased sweating: Sympathetic stimulation activates the eccrine glands in the skin, leading to increased production of sweat and subsequent cooling of the body.

**Clinical Pearl:** Understanding the physiological responses to sympathetic stimulation is crucial for diagnosing and treating various medical conditions. For example, in cases of high blood pressure, a healthcare professional might consider evaluating the patient's autonomic nervous system function and ruling out conditions like pheochromocytoma (a tumor of the adrenal medulla) or other disorders affecting autonomic control.

**Correct Answer:** D. Decreased respiratory rate (Option D) is not typically caused by sympathetic stimulation and is more likely due to parasympathetic activation.