A 16-year-old boy presents to the emergency department with abdominal pain and tenderness. The pain began approximately 2 days ago in the area just above his umbilicus and was crampy in nature. Earlier this morning, the pain moved laterally to his right lower abdomen. At that time, the pain in the right lower quadrant became severe and constant and woke him up from sleep. He decided to come to the hospital. The patient is nauseous and had a low-grade fever of 37.8°C (100.1°F). Other vitals are normal. Upon physical examination, the patient has rebound tenderness but a negative psoas sign while the remaining areas of his abdomen are non-tender. His rectal exam is normal. Laboratory tests show a white cell count of 15,000/mm3. Urinalysis and other laboratory findings were negative. What conclusion can be drawn about the nerves involved in the transmission of this patient’s pain during the physical exam?

His pain is transmitted by right somatic nerve fibers.

His pain is transmitted bilaterally by somatic afferent nerve fibers of the abdomen.

His pain is transmitted by somatic afferent nerve fibers located in the right flank.

His pain is transmitted by the pelvic nerves.

His pain is mainly transmitted by the right splanchnic nerve.

A 14-year-old boy is brought to the emergency department because of acute left-sided chest pain and dyspnea following a motor vehicle accident. His pulse is 122/min and blood pressure is 85/45 mm Hg. Physical examination shows distended neck veins and tracheal displacement to the right side. The left chest is hyperresonant to percussion and there are decreased breath sounds. This patient would most benefit from needle insertion at which of the following anatomical sites?

2nd left intercostal space along the midclavicular line

5th left intercostal space along the midclavicular line

8th left intercostal space along the posterior axillary line

Subxiphoid space in the left sternocostal margin

5th left intercostal space along the midaxillary line

A 65-year-old man presents to the emergency department with vague, constant abdominal pain, and worsening shortness of breath for the past several hours. He has baseline shortness of breath and requires 2–3 pillows to sleep at night. He often wakes up because of shortness of breath. Past medical history includes congestive heart failure, diabetes, hypertension, and hyperlipidemia. He regularly takes lisinopril, metoprolol, atorvastatin, and metformin. His temperature is 37.0°C (98.6°F), respiratory rate 25/min, pulse 67/min, and blood pressure 98/82 mm Hg. On physical examination, he has bilateral crackles over both lung bases and a diffusely tender abdomen. His subjective complaint of abdominal pain is more severe than the observed tenderness on examination. Which of the following vessels is involved in the disease affecting this patient?

Celiac artery and superior mesenteric artery

An otherwise healthy 58-year-old man comes to the physician because of a 1-year history of episodic coughing whenever he cleans his left ear. There is no history of hearing loss, tinnitus, or vertigo. Stimulating his left ear canal with a cotton swab triggers a bout of coughing. The physician informs him that these symptoms are caused by hypersensitivity of a cranial nerve. A peripheral lesion of this nerve is most likely to manifest with which of the following findings on physical examination?

Ipsilateral sensorineural hearing loss

Ipsilateral deviation of the tongue

Inability to raise ipsilateral eyebrow

Decreased secretion from ipsilateral sublingual gland

Autonomic plexuses for USMLE Step 2 CK: High-Yield Anatomy Lessons

Autonomic Plexuses - The Body's Wiring Hubs

Autonomic Plexuses and Nerves of the Thorax and Abdomen

Complex networks of intersecting sympathetic & parasympathetic nerve fibers that innervate viscera.
Fibers travel with blood vessels to reach target organs.
Key Plexuses & Locations:
- Cardiac: Base of the heart.
- Pulmonary: Roots of the lungs.
- Celiac (Solar): Upper abdomen; largest plexus.
- Superior/Inferior Mesenteric: Around corresponding arteries.
- Superior/Inferior Hypogastric: Pelvic region.

⭐ The celiac plexus is a target for nerve blocks to manage intractable pain from abdominal cancers (e.g., pancreatic).

Thoracic Plexuses - Heart & Lung Control

Superficial and Deep Cardiac Plexuses

Cardiac Plexus: A nerve network at the heart's base controlling cardiac function.
- Location: Superficial (below aortic arch) and deep (anterior to tracheal bifurcation) parts.
- Sympathetic Input: Postganglionic fibers from T1-T4 ganglia; ↑ heart rate & contractility.
- Parasympathetic Input: Vagus nerve (CN X); ↓ heart rate.
Pulmonary Plexus: A mesh of nerves at each lung root.
- Location: Anterior and posterior to the primary bronchi.
- Sympathetic Input: From T2-T5 ganglia; causes bronchodilation.
- Parasympathetic Input: Vagus nerve (CN X); causes bronchoconstriction and ↑ mucus secretion.

⭐ High-Yield: Visceral afferents for cardiac pain travel with sympathetics to T1-T4 spinal cord levels, causing referred pain to the chest and medial arm.

Abdominopelvic Plexuses - Gut Feeling Generators

Abdominopelvic Autonomic Plexuses and Ganglia

These are mixed autonomic nerve networks on the abdominal aorta and its branches, integrating sympathetic and parasympathetic signals to viscera.

Celiac Plexus ("Solar Plexus"): Largest plexus.
- Sympathetic: Greater splanchnic nerves (T5-T9).
- Parasympathetic: Vagus nerve (CN X).
- Supplies: Foregut structures (stomach, liver, spleen, pancreas, proximal duodenum).
Superior Mesenteric Plexus:
- Sympathetic: Lesser splanchnic nerves (T10-T11).
- Parasympathetic: Vagus nerve (CN X).
- Supplies: Midgut structures (distal duodenum to splenic flexure).
Inferior Mesenteric Plexus:
- Sympathetic: Lumbar splanchnic nerves (L1-L2).
- Parasympathetic: Pelvic splanchnic nerves (S2-S4).
- Supplies: Hindgut structures (splenic flexure to upper rectum).

⭐ Exam Favorite: Visceral pain from these plexuses refers to dermatomes corresponding to the sympathetic spinal levels. Foregut pain is epigastric (T5-T9), midgut pain is umbilical (T10-T11), and hindgut pain is suprapubic (L1-L2).

High‑Yield Points - ⚡ Biggest Takeaways

Autonomic plexuses are networks of sympathetic and parasympathetic fibers innervating visceral organs.

The cardiac plexus controls heart rate and contractility; damage can cause arrhythmias.

The celiac (solar) plexus, the largest, supplies abdominal organs; foregut pain refers here.

The superior hypogastric plexus is key for ejaculation and can be damaged in retroperitoneal surgery.

The inferior hypogastric plexus supplies pelvic organs; injury causes urinary, fecal, and sexual dysfunction.

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