Autonomic Nervous System — MCQs
Which of the following conditions is primarily treated by sympathectomy?
All of the following are trigeminal autonomic cephalgias except
TRUE statement regarding nerve supply of adrenal gland:
Mechanism by which Ach decreases heart rate is by:
Effects of beta blockers on the heart are all of the following except:
Which of the following does not have sympathetic noradrenergic fibers?
Match the following: A) Glossopharyngeal nerve B) Spinal accessory nerve C) Facial nerve D) Mandibular nerve 1) Shrugging of shoulder 2) Touch sensation from the posterior one-third of the tongue 3) Chewing 4) Taste from the anterior two-thirds of the tongue
Which neurotransmitter is associated with parasympathetic stimulation?
All of the following are seen in the Horner's syndrome, Except
Match the following drugs in Column A with their contraindications in Column B. | Column A | Column B | | :-- | :-- | | 1. Morphine | 1. QT prolongation | | 2. Amiodarone | 2. Thromboembolism | | 3. Vigabatrin | 3. Pregnancy | | 4. Estrogen preparations | 4. Head injury |
Autonomic Nervous System Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following conditions is primarily treated by sympathectomy?
- A. Buerger's disease
- B. Acrocyanosis
- C. Hyperhidrosis (Correct Answer)
- D. Raynaud's disease
Explanation: ***Hyperhidrosis*** - **Sympathectomy** (especially thoracic sympathectomy) is a definitive treatment for severe, localized **hyperhidrosis** (excessive sweating) that has not responded to conservative therapies. - The procedure aims to interrupt the sympathetic nerves responsible for stimulating sweat glands, commonly in the palms, soles, or axillae. *Buerger's disease* - While **sympathectomy** was historically used, its efficacy in **Buerger's disease** (thromboangiitis obliterans) is questionable and largely replaced by smoking cessation and other treatments for limb salvage. - The primary issue is **inflammation** and **thrombosis** of small and medium-sized arteries and veins, not primarily sympathetic overactivity. *Acrocyanosis* - **Acrocyanosis** is a benign condition characterized by persistent, painless, blue discoloration of the extremities due to vasospasm of small skin arteries and arterioles. - Treatment is generally reassurance and avoidance of cold, and **sympathectomy** is rarely, if ever, indicated or effective due to the non-progressive and cosmetic nature of the condition. *Raynaud's disease* - **Raynaud's disease** is a vasospastic disorder, but **sympathectomy** is usually reserved for severe cases with impending tissue loss or critical ischemia that fail medical management. - Medical management with calcium channel blockers is the primary treatment, as the condition involves episodic vasospasm of digital arteries.
Question 2: All of the following are trigeminal autonomic cephalgias except
- A. Short lasting unilateral neuralgiform headache attacks
- B. Tension type headache (Correct Answer)
- C. Episodic cluster headache
- D. Paroxysmal hemicranias
Explanation: ***Tension type headache*** - **Tension-type headaches** are characterized by a bilateral, pressing, or tightening quality, *without* the prominent autonomic symptoms seen in trigeminal autonomic cephalgias [1]. - They are generally not associated with activation of the **trigeminal autonomic reflex**, which is central to TACs. *Short lasting unilateral neuralgiform headache attacks* - These are characterized by **short-lasting** attacks of severe, unilateral head pain accompanied by **prominent trigeminal autonomic features**. - This category includes SUNCT (Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing) and SUNA (Short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms) and are indeed trigeminal autonomic cephalgias. *Episodic cluster headache* - **Cluster headaches** are the most well-known of the trigeminal autonomic cephalgias, characterized by severe, unilateral pain in the orbital, supraorbital, or temporal regions [1]. - They are invariably accompanied by **ipsilateral autonomic symptoms** like lacrimation, conjunctival injection, nasal congestion, and ptosis [2]. *Paroxysmal hemicranias* - This condition involves frequent, short-lasting attacks of **severe, unilateral pain** typically in the orbital, supraorbital, or temporal regions. - It is consistently associated with prominent **ipsilateral autonomic features** and shows an absolute response to **indomethacin**, distinguishing it from other TACs.
Question 3: TRUE statement regarding nerve supply of adrenal gland:
- A. Adrenal cortex has no nerve supply
- B. Adrenal medulla has no nerve supply
- C. Release of catecholamines is not affected by nerve supply
- D. Preganglionic fibres from lower thoracic spinal segments bypass sympathetic chain (Correct Answer)
Explanation: ***Preganglionic fibres from lower thoracic & upper lumbar spinal segments bypass sympathetic chain*** - The adrenal medulla is innervated by **preganglionic sympathetic fibers** originating from the **T5-T11 spinal cord segments**, which travel through the splanchnic nerves and synapse directly on chromaffin cells, effectively bypassing the sympathetic chain ganglia [1], [2]. - This direct innervation allows for a **rapid, systemic catecholamine release** in response to stress. *Adrenal cortex has no nerve supply* - The **adrenal cortex** receives some **autonomic innervation**, primarily sympathetic, though it is less dense and its direct role in steroidogenesis is not fully understood. - While hormonal signals are primary for cortical regulation, nerve fibers are present and may modulate blood flow or cellular activity. *Adrenal medulla has no nerve supply* - The **adrenal medulla** is a modified sympathetic ganglion whose **chromaffin cells** are directly innervated by **preganglionic sympathetic fibers** [1], [2]. - This direct neural input is crucial for its rapid response in releasing **catecholamines** into the bloodstream. *Release of catecholamines is not affected by nerve supply* - The release of **catecholamines** (epinephrine and norepinephrine) from the **adrenal medulla** is directly and primarily controlled by **preganglionic sympathetic innervation** [1], [2]. - Without this nerve supply, the stress-induced release of these hormones would be severely impaired, highlighting the critical role of neural input.
Question 4: Mechanism by which Ach decreases heart rate is by:
- A. Prolongation of action potential duration
- B. Reduction in calcium influx
- C. Inhibition of sympathetic activity
- D. Delayed diastolic depolarization (Correct Answer)
Explanation: ***Delayed diastolic depolarization*** - Acetylcholine (ACh) binding to muscarinic receptors on nodal cells increases **potassium permeability**, leading to a more negative maximal diastolic potential. - This slows the rate of **spontaneous depolarization** (pacemaker potential), thereby delaying the point at which the threshold for an action potential is reached and reducing heart rate. *Prolongation of action potential duration* - ACh typically **shortens** the action potential duration in atrial and nodal cells by increasing potassium efflux, which hyperpolarizes the cell and hastens repolarization. - A prolonged action potential duration would generally lead to a **slower heart rate** by increasing the refractory period, but this is achieved through different ionic mechanisms and is not the primary mechanism of ACh. *Reduction in calcium influx* - While ACh does reduce the inward **calcium current (ICa)** in nodal cells, contributing to a slower heart rate and weaker contractility, this effect primarily influences the upstroke and peak of the action potential. - The more **fundamentally important mechanism** for heart rate reduction is the impact on the pacemaker potential's slope, which is governed by altered ion conductances, predominantly potassium. *Inhibition of sympathetic activity* - ACh acts directly on **muscarinic receptors** on cardiac cells to decrease heart rate, which is a parasympathetic effect. - It does not directly inhibit sympathetic nerve activity but rather **counteracts sympathetic effects** by directly modulating cardiac cell physiology.
Question 5: Effects of beta blockers on the heart are all of the following except:
- A. Decreases duration of systole (Correct Answer)
- B. Decrease in heart rate
- C. May decrease cardiac output initially.
- D. May precipitate heart failure in acute settings.
Explanation: ***Decreases duration of systole*** - Beta-blockers primarily prolong the **duration of systole** by extending the **ejection time** and slowing ventricular relaxation. - They also increase the **diastolic filling time** by reducing heart rate, impacting overall cardiac cycle duration. *Decrease in heart rate* - Beta-blockers block **beta-1 adrenergic receptors** in the heart, leading to a decrease in **sympathetic stimulation** and thus a reduced heart rate. - This effect is beneficial in conditions like **tachycardia** and **angina**, as it reduces myocardial oxygen demand. *May decrease cardiac output initially.* - By reducing heart rate and contractility, beta-blockers can initially decrease **cardiac output**, especially in patients with pre-existing **ventricular dysfunction**. - This effect is often transient, as chronic use can lead to beneficial remodeling and improved efficiency in some conditions. *May precipitate heart failure in acute settings.* - In patients with acutely decompensated heart failure or severe left ventricular dysfunction, beta-blockers can acutely worsen cardiac function due to their **negative inotropic effects**. - Therefore, beta-blockers are typically initiated cautiously at low doses in stable heart failure patients and are contraindicated in acute decompensation.
Question 6: Which of the following does not have sympathetic noradrenergic fibers?
- A. Heart
- B. Eye
- C. Sweat gland (Correct Answer)
- D. Blood vessels
Explanation: ***Sweat gland*** - While sweat glands are innervated by the **sympathetic nervous system**, their postganglionic fibers are **cholinergic**, releasing **acetylcholine** rather than noradrenaline. - This is an important exception where sympathetic stimulation leads to acetylcholine release, causing sweating. *Blood vessels* - Most blood vessels, particularly resistance vessels such as **arterioles**, receive substantial **sympathetic noradrenergic innervation** that causes vasoconstriction. - This sympathetic tone is crucial for regulating **blood pressure** and distributing blood flow. *Heart* - The heart is richly innervated by **sympathetic noradrenergic fibers** that increase **heart rate**, **contractility**, and **conduction velocity** via beta-1 adrenergic receptors. - This makes noradrenaline a key neurotransmitter in the sympathetic regulation of cardiac function. *Eye* - The eye receives sympathetic noradrenergic innervation primarily to the **dilator pupillae muscle**, causing **mydriasis** (pupil dilation) upon activation. - These fibers also contribute to the sympathetic control of the **tarsal muscle** (Müller's muscle) in the eyelid.
Question 7: Match the following: A) Glossopharyngeal nerve B) Spinal accessory nerve C) Facial nerve D) Mandibular nerve 1) Shrugging of shoulder 2) Touch sensation from the posterior one-third of the tongue 3) Chewing 4) Taste from the anterior two-thirds of the tongue
- A. A-3 , B-1 , C-4 , D-2
- B. A-2 , B-3 , C-4 , D-1
- C. A-4 , B-1 , C-2 , D-3
- D. A-2 , B-1 , C-4 , D-3 (Correct Answer)
Explanation: ***A-2 , B-1 , C-4 , D-3*** - **A) Glossopharyngeal nerve (CN IX)** is responsible for **general sensation and taste from the posterior one-third of the tongue** [1]. (2). - **B) Spinal Accessory nerve (CN XI)** innervates the **sternocleidomastoid** and **trapezius muscles**, which are involved in shrugging the shoulders (1). - **C) Facial nerve (CN VII)** carries **taste sensation from the anterior two-thirds of the tongue** [1] (4) via the chorda tympani. - **D) Mandibular nerve (V3)**, a branch of the trigeminal nerve, innervates the muscles of mastication, enabling **chewing** (3). *A-3 , B-1 , C-4 , D-2* - This option incorrectly associates the **glossopharyngeal nerve** with chewing, which is a function of the mandibular nerve (V3). - It also incorrectly associates the **mandibular nerve** with touch sensation from the posterior one-third of the tongue, which is a function of the glossopharyngeal nerve [1]. *A-2 , B-3 , C-4 , D-1* - This option incorrectly links the **spinal accessory nerve** with chewing; this nerve primarily controls shoulder and neck movements. - It also incorrectly assigns shrugging of the shoulder to the **mandibular nerve** instead of the spinal accessory nerve. *A-4 , B-1 , C-2 , D-3* - This choice incorrectly attributes **taste from the anterior two-thirds of the tongue** to the glossopharyngeal nerve, which supplies the posterior one-third [1]. - It also incorrectly links **touch sensation from the posterior one-third of the tongue** to the facial nerve, which is involved in taste from the anterior two-thirds [1].
Question 8: Which neurotransmitter is associated with parasympathetic stimulation?
- A. Serotonin
- B. Dopamine
- C. Glutamate
- D. Acetylcholine (Correct Answer)
Explanation: ***Acetylcholine*** - **Acetylcholine** is the primary neurotransmitter released by postganglionic neurons in the **parasympathetic nervous system**, mediating its effects on target organs - It acts on **muscarinic receptors** (at target organs) and **nicotinic receptors** (at ganglia) to produce characteristic "rest and digest" responses like decreased heart rate, increased digestive activity, pupillary constriction, and increased glandular secretions - Both preganglionic and postganglionic parasympathetic neurons release acetylcholine (cholinergic transmission) *Serotonin* - **Serotonin** (5-HT) is a monoamine neurotransmitter primarily involved in mood regulation, sleep, appetite, and gut motility - While it modulates some autonomic functions, it is not the primary effector neurotransmitter for the parasympathetic system *Dopamine* - **Dopamine** is a catecholamine neurotransmitter known for its role in reward, motivation, motor control, and executive functions - It plays a role in the sympathetic nervous system in some contexts (e.g., renal blood flow regulation at low doses) but is not associated with parasympathetic stimulation *Glutamate* - **Glutamate** is the main excitatory neurotransmitter in the central nervous system, crucial for learning and memory - It has no direct role in the peripheral parasympathetic nervous system
Question 9: All of the following are seen in the Horner's syndrome, Except
- A. Dilated pupil (Correct Answer)
- B. Drooping of upper eyelid
- C. Enophthalmos
- D. Loss of sweating on same side of face
Explanation: ***Dilated pupil*** - **Horner's syndrome** results from damage to the sympathetic pathway, leading to **miosis** (constricted pupil) due to unopposed parasympathetic activity [2]. - A **dilated pupil** would be indicative of a different pathology, such as oculomotor nerve palsy [3]. *Drooping of upper eyelid* - This symptom, known as **ptosis**, is a classic feature of Horner's syndrome due to the paralysis of the **superior tarsal muscle** (Müller's muscle), which is innervated by the sympathetic nervous system [1], [2]. - The degree of ptosis is typically mild to moderate. *Enophthalmos* - **Enophthalmos**, or the apparent sinking of the eyeball into the orbit, is often seen in Horner's syndrome. - This is partly an illusion caused by the ptosis and sometimes attributed to a loss of tone in the **orbitalis muscle** (if present and sympathetically innervated). *Loss of sweating on same side of face* - This is known as **anhydrosis** and occurs on the **ipsilateral side of the face and neck** due to the disruption of sympathetic innervation to the sweat glands. - The extent of anhydrosis depends on the level of the lesion along the sympathetic pathway [4].
Question 10: Match the following drugs in Column A with their contraindications in Column B. | Column A | Column B | | :-- | :-- | | 1. Morphine | 1. QT prolongation | | 2. Amiodarone | 2. Thromboembolism | | 3. Vigabatrin | 3. Pregnancy | | 4. Estrogen preparations | 4. Head injury |
- A. A-1, B-3, C-2, D-4
- B. A-4, B-1, C-3, D-2 (Correct Answer)
- C. A-3, B-2, C-4, D-1
- D. A-2, B-4, C-1, D-3
Explanation: ***A-4, B-1, C-3, D-2*** - **Morphine** is contraindicated in **head injury** as it can increase intracranial pressure and mask neurological symptoms. - **Amiodarone** is contraindicated in patients with **QT prolongation** due to its risk of inducing more severe arrhythmias like Torsades de Pointes. - **Vigabatrin** is contraindicated during **pregnancy** due to its potential for teratogenicity and adverse effects on fetal development. - **Estrogen preparations** are contraindicated in patients with a history of **thromboembolism** due to their increased risk of blood clot formation. *A-1, B-3, C-2, D-4* - This option incorrectly matches **Morphine** with QT prolongation and **Estrogen preparations** with head injury, which are not their primary contraindications. - It also incorrectly links **Vigabatrin** with thromboembolism and **Amiodarone** with pregnancy. *A-3, B-2, C-4, D-1* - This choice incorrectly associates **Morphine** with pregnancy and **Vigabatrin** with head injury, which are not the most critical or direct contraindications. - It also misaligns **Amiodarone** with thromboembolism and **Estrogen preparations** with QT prolongation. *A-2, B-4, C-1, D-3* - This option incorrectly matches **Morphine** with thromboembolism and **Amiodarone** with head injury, which are not their most significant contraindications. - It also incorrectly links **Vigabatrin** with QT prolongation and **Estrogen preparations** with pregnancy.
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