Autonomic innervation of pelvic organs US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Autonomic innervation of pelvic organs. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Autonomic innervation of pelvic organs US Medical PG Question 1: A 68-year-old man presents to his primary care physician complaining of a bulge in his scrotum that has enlarged over the past several months. He is found to have a right-sided inguinal hernia and undergoes elective hernia repair. At his first follow-up visit, he complains of a tingling sensation on his scrotum. Which of the following nerve roots communicates with the injured tissues?
- A. S1-S3
- B. L1-L2 (Correct Answer)
- C. S2-S4
- D. L4-L5
- E. L2-L3
Autonomic innervation of pelvic organs Explanation: ***L1-L2***
- The **ilioinguinal nerve** and **genitofemoral nerve**, which are commonly injured during inguinal hernia repair, arise from the **L1 and L2 spinal nerves**.
- These nerves provide sensory innervation to the **scrotum**, **inguinal region**, and **medial thigh**, explaining the patient's tingling sensation.
*S1-S3*
- These nerve roots typically contribute to the **sciatic nerve** and innervate the posterior thigh, leg, and foot, and are not directly involved in scrotal sensation relevant to an inguinal hernia repair.
- They also contribute to the **pudendal nerve**, which primarily supplies the perineum and external genitalia, but injury to this nerve is less common in routine inguinal hernia repair.
*S2-S4*
- These nerve roots primarily form the **pudendal nerve**, which innervates the **perineum** and external genitalia (including some scrotal sensation), but injury to these specific nerves is not a typical complication of routine inguinal hernia repair.
- They also contribute to the **pelvic splanchnic nerves**, controlling bladder and bowel function, which are unrelated to the described sensory deficit.
*L4-L5*
- These nerve roots primarily contribute to nerves supplying the **lower limb**, such as the **femoral nerve** and **sciatic nerve**, and do not directly innervate the scrotum.
- Injury to these roots would typically result in motor or sensory deficits of the **thigh and leg**, not isolated scrotal tingling.
*L2-L3*
- While L2 contributes to nerves supplying the inguinal region and scrotum (genitofemoral nerve), the **ilioinguinal nerve** originates from L1.
- The **lateral femoral cutaneous nerve**, which originates from L2-L3, innervates the **lateral thigh**, and its injury would cause tingling there, not in the scrotum.
Autonomic innervation of pelvic organs US Medical PG Question 2: A 19-year-old man is brought to the emergency department following a high-speed motor vehicle collision in which he was a restrained passenger. He complains of pelvic pain and urinary retention with overflow incontinence, along with associated lower extremity weakness. Examination shows perineal bruising and there is pain with manual compression of the pelvis. Injury to which of the following structures is most likely responsible for this patient's urinary incontinence?
- A. Ilioinguinal nerve
- B. Obturator nerve
- C. Genitofemoral nerve
- D. Pelvic splanchnic nerves (Correct Answer)
- E. Superior gluteal nerve
Autonomic innervation of pelvic organs Explanation: ***Pelvic splanchnic nerves***
- Urinary retention with overflow incontinence and lower extremity weakness following a pelvic trauma suggests damage to the **sacral spinal segments** or the **pelvic splanchnic nerves**.
- These nerves carry **parasympathetic fibers** that stimulate bladder contraction (detrusor muscle) and relaxation of the internal urethral sphincter, which are crucial for normal micturition.
*Ilioinguinal nerve*
- This nerve supplies sensory innervation to the **genitalia** and part of the inner thigh, and motor innervation to the internal oblique and transversus abdominis muscles.
- Damage to this nerve would primarily cause sensory deficits or abdominal muscle weakness, not urinary retention or lower extremity weakness.
*Obturator nerve*
- The obturator nerve primarily innervates the **adductor muscles of the thigh** and provides sensory innervation to the medial thigh.
- Injury would result in difficulty with hip adduction and sensory loss in the medial thigh, not bladder dysfunction or diffuse lower extremity weakness.
*Genitofemoral nerve*
- This nerve provides sensory innervation to the **anterior compartment of the thigh** and the external genitalia, and motor innervation to the cremaster muscle.
- Damage would typically manifest as altered sensation in these areas or an absent cremasteric reflex, without directly affecting bladder function.
*Superior gluteal nerve*
- The superior gluteal nerve innervates the **gluteus medius, gluteus minimus, and tensor fasciae latae muscles**, which are crucial for hip abduction and stabilization during walking.
- Injury would lead to a characteristic **Trendelenburg gait**, but would not directly cause urinary incontinence or retention.
Autonomic innervation of pelvic organs US Medical PG Question 3: A 41-year-old woman presents with back pain for the past 2 days. She says that the pain radiates down along the posterior right thigh and leg. She says the pain started suddenly after lifting a heavy box 2 days ago. Past medical history is irrelevant. Physical examination reveals a straight leg raise (SLR) test restricted to 30°, inability to walk on her toes, decreased sensation along the lateral border of her right foot, and diminished ankle jerk on the same side. Which of the following nerve roots is most likely compressed?
- A. Fourth lumbar nerve root (L4)
- B. Second sacral nerve root (S2)
- C. Third sacral nerve root (S3)
- D. Fifth lumbar nerve root (L5)
- E. First sacral nerve root (S1) (Correct Answer)
Autonomic innervation of pelvic organs Explanation: ***First sacral nerve root (S1)***
- **Inability to walk on toes** (weakness of gastrocnemius and soleus), **decreased sensation along the lateral border of the foot**, and a **diminished ankle jerk** are classic signs of S1 radiculopathy.
- The radiating pain down the posterior leg, restricted straight leg raise due to a sudden onset after lifting, points towards a **disc herniation** compressing the S1 nerve root.
*Fourth lumbar nerve root (L4)*
- Compression of L4 typically causes **weakness in knee extension** (quadriceps), diminished patellar reflex, and sensory loss over the medial aspect of the shin.
- The patient's symptoms (inability to walk on toes, diminished ankle jerk) are not consistent with L4 nerve root involvement.
*Second sacral nerve root (S2)*
- S2 radiculopathy primarily affects sensation in the posterior thigh and calf and can cause **weakness in knee flexion** and **plantarflexion**, but the complete constellation of symptoms (especially ankle jerk reflex) is more indicative of S1.
- Isolated S2 compression without S1 involvement is less common with these specific signs.
*Third sacral nerve root (S3)*
- S3 nerve root compression typically presents with **perineal numbness** and issues with bowel or bladder function due to its involvement in these functions.
- The described motor and sensory deficits are not characteristic of S3 radiculopathy.
*Fifth lumbar nerve root (L5)*
- L5 radiculopathy is characterized by **weakness in foot dorsiflexion** (foot drop) and toe extension, leading to inability to walk on heels, and sensory loss on the dorsum of the foot.
- While L5 compression can cause radiating pain and a restricted straight leg raise, the specific deficit of **inability to walk on toes** and a **diminished ankle jerk** are not typical of L5 involvement.
Autonomic innervation of pelvic organs US Medical PG Question 4: A 25-year-old woman presents with shooting pain along the lateral aspect of her right thigh. The pain is exacerbated by standing or walking for long periods. Physical examination reveals tenderness at the anterior superior iliac spine. Which of the following nerves is most likely affected?
- A. Common peroneal nerve
- B. Obturator nerve
- C. Sciatic nerve
- D. Lateral femoral cutaneous nerve (Correct Answer)
Autonomic innervation of pelvic organs Explanation: ***Lateral femoral cutaneous nerve***
- This presentation is classic for **meralgia paresthetica**, caused by compression of the **lateral femoral cutaneous nerve** as it passes under the inguinal ligament, leading to pain and numbness on the **lateral thigh**.
- Tenderness at the **anterior superior iliac spine** points to the inguinal ligament region where this nerve is most vulnerable to compression.
*Common peroneal nerve*
- Injury to the common peroneal nerve typically causes **foot drop** and sensory deficits over the **dorsum of the foot** and **lateral leg**, not the lateral thigh.
- It is often compressed at the **fibular head**, which is anatomically distinct from the anterior superior iliac spine.
*Obturator nerve*
- The obturator nerve innervates the **medial thigh muscles** and provides sensation to the medial thigh; its compression would cause pain in this region, not the lateral thigh.
- Injury often leads to **adductor weakness** and is typically associated with pelvic trauma or surgery.
*Sciatic nerve*
- Sciatic nerve pain typically radiates down the **posterior aspect of the leg** into the foot (**sciatica**), often associated with lumbar disc herniation.
- Sensory deficits would follow the dermatomal distribution of its branches (**tibial** and **common peroneal nerves**).
Autonomic innervation of pelvic organs US Medical PG Question 5: A 56-year-old man comes to the clinic complaining of sexual dysfunction. He reports normal sexual function until 4 months ago when his relationship with his wife became stressful due to a death in the family. When asked about the details of his dysfunction, he claims that he is “able to get it up, but just can’t finish the job.” He denies any decrease in libido or erections, endorses morning erections, but an inability to ejaculate. He is an avid cyclist and exercises regularly. His past medical history includes depression and diabetes, for which he takes citalopram and metformin, respectively. A physical examination is unremarkable. What is the most likely explanation for this patient’s symptoms?
- A. Testosterone deficiency
- B. Autonomic neuropathy secondary to systemic disease
- C. Psychological stress
- D. Damage to the pudendal nerve
- E. Medication side effect (Correct Answer)
Autonomic innervation of pelvic organs Explanation: ***Medication side effect***
- The patient's inability to ejaculate while maintaining normal libido, erections, and morning erections is highly suggestive of **ejaculatory dysfunction** caused by the **citalopram**, a selective serotonin reuptake inhibitor (SSRI).
- SSRIs, like citalopram, are known to commonly cause sexual side effects, including **delayed ejaculation** and **anorgasmia**, by increasing serotonin levels, which can inhibit the ejaculatory reflex.
*Testosterone deficiency*
- Testosterone deficiency usually presents with **decreased libido**, **erectile dysfunction**, and a reduction in **morning erections**, which are not reported by this patient.
- While it can impact sexual function, the specific symptom of inability to ejaculate with preserved erections points away from low testosterone.
*Autonomic neuropathy secondary to systemic disease*
- **Autonomic neuropathy**, often seen in patients with **diabetes**, can lead to ejaculatory dysfunction, including **retrograde ejaculation**.
- However, the patient's normal erections and libido, along with the recent onset coinciding with a stressful event and medication use, make medication a more likely primary cause in this scenario.
*Psychological stress*
- **Psychological stress** can certainly contribute to sexual dysfunction, leading to decreased libido or erectile difficulties.
- However, the patient explicitly states his erections and libido are normal, and he only experiences an inability to ejaculate, which is less commonly the sole manifestation of stress.
*Damage to the pudendal nerve*
- **Pudendal nerve damage** typically results in issues with **erectile function**, sensation in the perineum, and potentially urinary or fecal incontinence.
- This patient's preserved erections and specific issue with ejaculation make pudendal nerve damage an unlikely primary cause.
Autonomic innervation of pelvic organs US Medical PG Question 6: Which neurotransmitter is primarily responsible for parasympathetic effects on heart rate?
- A. Norepinephrine
- B. Dopamine
- C. Acetylcholine (Correct Answer)
- D. Epinephrine
Autonomic innervation of pelvic organs Explanation: ***Acetylcholine***
- **Acetylcholine** is the primary neurotransmitter released by postganglionic parasympathetic neurons.
- It acts on **muscarinic receptors** (M2 receptors) in the heart to decrease heart rate.
*Norepinephrine*
- **Norepinephrine** is primarily associated with the **sympathetic nervous system**, increasing heart rate and contractility.
- It acts on **beta-1 adrenergic receptors** in the heart.
*Dopamine*
- **Dopamine** is a precursor to norepinephrine and epinephrine, and primarily functions as a neurotransmitter in the **central nervous system** and in regulating renal blood flow.
- While it can have cardiac effects, it is not the primary neurotransmitter for parasympathetic actions on heart rate.
*Epinephrine*
- **Epinephrine** (adrenaline) is a hormone released by the adrenal medulla and a neurotransmitter in the sympathetic nervous system, causing an **increase in heart rate** and contractility.
- It works through **beta-1 adrenergic receptors**, antagonistic to parasympathetic effects.
Autonomic innervation of pelvic organs US Medical PG Question 7: A 48-year-old man with retroperitoneal sarcoma requires extensive resection including portions of the sympathetic chain from T10-L2 and the celiac/superior mesenteric ganglia. Preoperative evaluation is needed to predict postoperative autonomic consequences. The multidisciplinary team must evaluate which combination of deficits is most likely based on the precise anatomical structures being resected and the potential for compensation.
- A. Pan-sympathetic failure including cardiovascular collapse due to loss of all preganglionic outflow
- B. Minimal deficits due to complete bilateral compensation from contralateral sympathetic chain
- C. Complete loss of lower extremity sweating and thermoregulation with normal GI and genitourinary function due to enteric nervous system compensation
- D. Severe orthostatic hypotension, GI dysmotility, and ejaculatory dysfunction with preserved upper body sympathetic function (Correct Answer)
- E. Isolated loss of visceral pain sensation with completely preserved motor and secretory autonomic functions
Autonomic innervation of pelvic organs Explanation: ***Severe orthostatic hypotension, GI dysmotility, and ejaculatory dysfunction with preserved upper body sympathetic function***
- Resection of the **celiac and superior mesenteric ganglia** and the **sympathetic chain (T10-L2)** drastically reduces total peripheral resistance and venous return regulation, leading to **severe orthostatic hypotension**.
- Disrupting the **lumbar sympathetic chain (L1-L2)** interrupts the pathways for **emission**, while ganglionic resection causes **GI dysmotility** via loss of inhibitory sympathetic input.
*Complete loss of lower extremity sweating and thermoregulation with normal GI and genitourinary function due to enteric nervous system compensation*
- While **anhidrosis** occurs, the **enteric nervous system** cannot fully compensate for the loss of extrinsic sympathetic modulation, leading to significant GI dysfunction.
- Genitourinary function is significantly impacted as the **sympathetic input** required for the contraction of the internal urethral sphincter and seminal vesicles is removed.
*Isolated loss of visceral pain sensation with completely preserved motor and secretory autonomic functions*
- Although **visceral afferents** are interrupted, the resection of **preganglionic and postganglionic motor fibers** guarantees motor and secretory deficits.
- Sympathetic fibers are essential for the **vasoconstriction** and inhibitory signaling to the gut, which cannot remain "completely preserved" after such extensive resection.
*Pan-sympathetic failure including cardiovascular collapse due to loss of all preganglionic outflow*
- **Pan-sympathetic failure** is avoided because segments above **T10** (supplying the head, neck, and upper extremities) and the **adrenal medulla** (if T10-L2 is the primary resection) provide partial function.
- Cardiovascular collapse is unlikely because the **cardiac sympathetic nerves (T1-T4)** remain intact, maintaining heart rate and contractility.
*Minimal deficits due to complete bilateral compensation from contralateral sympathetic chain*
- Sympathetic innervation of the viscera is **bilateral**, but the **celiac and superior mesenteric ganglia** are midline structures; their resection leaves no contralateral alternative.
- Extensive **bilateral resection** of the chain segments at this level ensures profound deficits that cannot be compensated for by remaining neural pathways.
Autonomic innervation of pelvic organs US Medical PG Question 8: A 62-year-old man with atrial fibrillation undergoes catheter ablation of the pulmonary vein ostia. Post-procedure, he develops gastroparesis, but his cardiologist notes preserved heart rate variability and normal baroreceptor responses. Surgical anatomy review suggests the ablation may have damaged autonomic structures. Evaluate the most likely anatomical explanation for isolated gastric dysmotility with preserved cardiovascular autonomic function.
- A. Injury to the celiac ganglion via retrograde thermal conduction
- B. Direct damage to the enteric nervous system myenteric plexus
- C. Thermal injury to epicardial vagal branches specifically innervating the stomach via the gastric plexus (Correct Answer)
- D. Damage to the stellate ganglion causing isolated sympathetic denervation of the stomach
- E. Disruption of the entire vagal trunk causing pan-autonomic dysfunction
Autonomic innervation of pelvic organs Explanation: ***Thermal injury to epicardial vagal branches specifically innervating the stomach via the gastric plexus***
- The **vagus nerves** descend behind the heart and form the **esophageal plexus** near the **posterior wall of the left atrium**, making them vulnerable to energy during **pulmonary vein ablation**.
- Damage at this level can disrupt parasympathetic supply to the stomach, causing **gastroparesis**, while sparing the cardiac branches that already branched off superiorly, thereby preserving **heart rate variability**.
*Damage to the stellate ganglion causing isolated sympathetic denervation of the stomach*
- The **stellate ganglion** is located at the **C7-T1** level and supplies sympathetic fibers to the head, neck, and upper limbs; it is anatomically distant from the left atrium ablation site.
- Injury to this ganglion would present with **Horner Syndrome**, not isolated gastric dysmotility.
*Disruption of the entire vagal trunk causing pan-autonomic dysfunction*
- Complete **vagal trunk** damage would result in systemic symptoms, including significant changes in **heart rate variability** and loss of **baroreceptor reflex** sensitivity.
- The preservation of cardiovascular autonomic function indicates that the injury was localized and **distal to the cardiac branches**.
*Injury to the celiac ganglion via retrograde thermal conduction*
- The **celiac ganglion** is located in the **upper abdomen** around the root of the celiac trunk, making it an unlikely target for direct or retrograde thermal injury from the heart.
- This ganglion primarily handles **sympathetic output**; its injury would not typically cause the delayed gastric emptying characteristic of **vagal (parasympathetic) denervation**.
*Direct damage to the enteric nervous system myenteric plexus*
- The **myenteric (Auerbach’s) plexus** is located within the muscular layers of the **stomach wall**.
- Catheter ablation occurs in the **thoracic cavity** at the pulmonary veins; it cannot directly reach or damage the intrinsic nerves located within the abdominal viscus.
Autonomic innervation of pelvic organs US Medical PG Question 9: A 35-year-old woman with familial dysautonomia (Riley-Day syndrome) presents with absent corneal reflexes, impaired lacrimation, and absent fungiform papillae on the tongue, but preserved parotid gland function. Genetic testing confirms IKBKAP gene mutation affecting neural crest cell migration. Evaluate which embryological principle explains this specific pattern of autonomic and sensory deficits while certain parasympathetic functions remain intact.
- A. Preferential loss of sympathetic neurons with compensatory parasympathetic hyperfunction
- B. Uniform degeneration of both sympathetic and parasympathetic systems proportionally
- C. Selective degeneration of all parasympathetic ganglia with preserved sympathetic function
- D. Failed migration of neural crest cells destined for cranial sensory and parasympathetic ganglia, with preserved placode-derived neurons (Correct Answer)
- E. Isolated defect in myelination of all autonomic preganglionic fibers
Autonomic innervation of pelvic organs Explanation: ***Failed migration of neural crest cells destined for cranial sensory and parasympathetic ganglia, with preserved placode-derived neurons***
- **Riley-Day syndrome** (IKBKAP mutation) results in the failed development of **neural crest-derived** structures, specifically sensory and autonomic neurons, which explains the **absent corneal reflex** and **fungiform papillae**.
- Certain craniofacial neurons and glandular functions may be spared if they arise from **ectodermal placodes** rather than the neural crest, explaining the complex pattern of deficits.
*Selective degeneration of all parasympathetic ganglia with preserved sympathetic function*
- This syndrome actually involves significant **sympathetic denervation**, leading to signs like postural hypotension and **instability of blood pressure**.
- The deficits are not limited to the parasympathetic system; they involve a widespread loss of **small-fiber sensory** and sympathetic neurons.
*Isolated defect in myelination of all autonomic preganglionic fibers*
- The primary pathology in familial dysautonomia is **neuronal cell death** and failed migration, not primarily a **demyelinating** process.
- Prefibrillar or preganglionic fiber loss occurs, but the most characteristic finding is the **reduced number** of neurons in the **dorsal root** and autonomic ganglia.
*Preferential loss of sympathetic neurons with compensatory parasympathetic hyperfunction*
- While sympathetic loss is prominent, there is no **parasympathetic hyperfunction**; instead, there is impaired **lacrimation** and other parasympathetic deficits.
- Defective **sweating** and gastrointestinal dysmotility reflect a combined failure of both autonomic limbs rather than a compensatory mechanism.
*Uniform degeneration of both sympathetic and parasympathetic systems proportionally*
- The degeneration is not uniform; different populations of **neural crest-derived cells** show varying levels of sensitivity to the **IKBKAP protein** deficiency.
- Features like the **preservation of parotid gland function** (CN IX innervation) highlight that specific autonomic pathways are more resilient than others like the lacrimal pathway.
Autonomic innervation of pelvic organs US Medical PG Question 10: A 50-year-old man undergoes bilateral truncal vagotomy for refractory peptic ulcer disease. Postoperatively, he develops gastroparesis, but surprisingly maintains normal pancreatic enzyme secretion and normal bile flow during meals. Analysis of his preserved functions suggests alternate autonomic pathways are compensating. Which anatomical principle best explains the preservation of these exocrine functions despite vagotomy?
- A. The pancreas and biliary system receive redundant parasympathetic innervation from pelvic splanchnic nerves
- B. Sympathetic innervation alone is sufficient to maintain basal pancreatic and biliary secretion
- C. Enteric nervous system provides autonomous control independent of vagal input
- D. Parasympathetic innervation to pancreas and gallbladder travels via splanchnic nerves below the vagotomy level
- E. Hormonal regulation via secretin and CCK can maintain function independent of neural control (Correct Answer)
Autonomic innervation of pelvic organs Explanation: ***Hormonal regulation via secretin and CCK can maintain function independent of neural control***
- The intestinal phase of digestion is primarily mediated by **Secretin** and **Cholecystokinin (CCK)**, which stimulate pancreatic secretion and gallbladder contraction regardless of vagal status.
- These hormonal pathways act as a safeguard, ensuring that **pancreatic enzymes** and **bile flow** continue to meet digestive demands even after a **truncal vagotomy**.
*The pancreas and biliary system receive redundant parasympathetic innervation from pelvic splanchnic nerves*
- **Pelvic splanchnic nerves** (S2-S4) provide parasympathetic innervation only to the **hindgut** (distal third of the transverse colon to the rectum).
- They do not extend superiorly enough to provide autonomic control to the **pancreas** or **biliary system**, which are derivatives of the foregut.
*Sympathetic innervation alone is sufficient to maintain basal pancreatic and biliary secretion*
- **Sympathetic fibers** originating from the **celiac ganglion** generally inhibit gastrointestinal secretions and promote vasoconstriction.
- They cannot substitute for the excitatory **pro-secretory** effects of the parasympathetic system (vagus nerve).
*Enteric nervous system provides autonomous control independent of vagal input*
- While the **enteric nervous system (ENS)** can coordinate local peristalsis and mucosal secretion, it lacks the broad integrative capacity to fully stimulate large-scale **exocrine glands** like the pancreas without extrinsic input.
- The ENS works in tandem with the vagus, but it cannot completely replicate the **vago-vagal reflex** necessary for the cephalic and gastric phases of secretion.
*Parasympathetic innervation to pancreas and gallbladder travels via splanchnic nerves below the vagotomy level*
- **Splanchnic nerves** typically refer to the **greater, lesser, and least splanchnic nerves**, which carry **sympathetic** preganglionic fibers, not parasympathetic ones.
- There are no known significant anatomical pathways where **parasympathetic fibers** bypass the truncal vagus to reach the hepatobiliary tree via inferior spinal levels.
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