Which feature best distinguishes sympathetic nervous system activity from parasympathetic nervous system activity in a patient presenting with acute stress?

Explanation

## Distinguishing Sympathetic vs Parasympathetic Activity ### Sympathetic Nervous System Effects **Key Point:** The sympathetic nervous system mediates the "fight-or-flight" response and produces widespread, coordinated effects across multiple organ systems. In acute stress, sympathetic activation produces: 1. **Cardiovascular:** Increased heart rate (β₁ adrenergic), increased contractility, increased blood pressure 2. **Ocular:** Pupillary dilation (mydriasis) via radial muscle contraction 3. **GI tract:** Decreased motility and secretion (sphincter contraction) 4. **Respiratory:** Bronchial dilation 5. **Metabolic:** Increased glucose mobilization ### Parasympathetic Nervous System Effects **Key Point:** The parasympathetic nervous system mediates the "rest-and-digest" response with discrete, organ-specific effects. Parasympathetic activation produces: 1. **Cardiovascular:** Decreased heart rate (via vagal acetylcholine on M₂ receptors) 2. **Ocular:** Pupillary constriction (miosis) via sphincter muscle contraction 3. **GI tract:** Increased motility and secretion 4. **Respiratory:** Bronchial constriction 5. **Glands:** Increased salivation, lacrimation, and accommodation ### Comparison Table | Feature | Sympathetic | Parasympathetic | |---------|-------------|------------------| | Heart rate | ↑ (β₁) | ↓ (M₂) | | Pupil size | Dilated (mydriasis) | Constricted (miosis) | | GI motility | ↓ | ↑ | | Salivation | ↓ | ↑ | | Bronchi | Dilated | Constricted | | Blood pressure | ↑ | ↓ | | Sweating | ↑ | Minimal | **High-Yield:** The combination of **tachycardia + mydriasis + decreased GI motility** is the classic triad of sympathetic dominance and is the single best discriminator in acute stress scenarios. **Clinical Pearl:** In a patient with acute anxiety or panic attack, you will see the sympathetic pattern (option 1). In a patient with vasovagal syncope or cholinergic toxicity, you will see the parasympathetic pattern (options 3 and 4). **Mnemonic:** **SLUDGE** = Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis — all parasympathetic (cholinergic excess). The opposite of SLUDGE = sympathetic dominance.