Autonomic Nervous System Drugs Practice Questions

Q: All are true about atropine poisoning, except

Decreased temperature. ***Decreased temperature*** - Atropine is an **anticholinergic** agent that blocks muscarinic receptors, leading to decreased sweating and **hyperthermia** (increased temperature) in poisoning. - The phrase **"hot as a hare"** is a classic mnemonic for atropine poisoning, referring to this elevated body temperature. *Dysarthria* - **Dysarthria** (slurred or difficult speech) can be a symptom of atropine poisoning due to the **CNS effects** of anticholinergic toxicity. - Atropine crosses the blood-brain barrier and can cause a range of neurological symptoms including agitation, delirium, and impaired speech. *Dysphagia* - **Dysphagia** (difficulty swallowing) is a common symptom in atropine poisoning, related to the **drying of oral and pharyngeal secretions** due to anticholinergic effects. - The mouth becomes very dry, making it difficult to form a food bolus and swallow effectively. *Dilated pupils* - **Dilated pupils (mydriasis)** unresponsive to light are a hallmark sign of atropine poisoning, as atropine blocks parasympathetic innervation to the iris sphincter muscle. - This symptom is often described in the mnemonic as **"blind as a bat"** due to the associated blurred vision and photophobia.

Q: Mechanism of action of atropine in treatment of organophosphate poisoning is?

It has antimuscarinic activity. ***It has antimuscarinic activity*** - **Organophosphate poisoning** leads to **excessive acetylcholine** at muscarinic receptors, causing symptoms like miosis, bradycardia, and increased secretions. - **Atropine** is a **competitive antagonist** at these muscarinic receptors, thereby blocking the effects of excess acetylcholine. *It inhibits secretion of acetylcholine* - Atropine does not directly inhibit the secretion of **acetylcholine** from nerve terminals. - Its action is postsynaptic, specifically at the **receptor level**. *It is reactivator of acetylcholine esterase enzyme* - **Pralidoxime (2-PAM)** and other **oximes** are the drugs that reactivate **acetylcholinesterase**. - Atropine does not reactivate the enzyme; it only blocks the effects of acetylcholine. *It is agonist of acetylcholine receptors* - An **agonist** would mimic the effects of acetylcholine, which would worsen the symptoms of organophosphate poisoning. - Atropine is an **antagonist**, meaning it blocks the receptors.

Q: All of the following drugs are used for the treatment of urinary incontinence except:

Ipratropium. ***Ipratropium*** - **Ipratropium** is a short-acting muscarinic antagonist primarily used as a **bronchodilator** in obstructive lung diseases. - While it has anticholinergic properties, it is not typically used for **urinary incontinence** due to its limited systemic absorption and short duration of action, making it less effective for bladder control compared to other agents. *Oxybutynin* - **Oxybutynin** is a commonly prescribed **muscarinic antagonist** that acts by relaxing the bladder detrusor muscle, increasing bladder capacity and reducing involuntary contractions. - It is effective in treating **overactive bladder** and urge incontinence. *Tolterodine* - **Tolterodine** is a **muscarinic receptor antagonist** that specifically targets M2 and M3 receptors in the bladder, reducing bladder hyperreactivity. - It is used for the symptomatic treatment of **urge incontinence** and overactive bladder. *Darifenacin* - **Darifenacin** is a highly M3-selective muscarinic receptor antagonist, which means it primarily blocks the M3 receptors responsible for **detrusor muscle contraction**. - Its selectivity helps minimize side effects common to less selective anticholinergics and is used for the treatment of **overactive bladder** with symptoms of urgency, frequency, and urge incontinence.

Q: All of the following functions of vasopressin are mediated by V1 receptors, except

Water reabsorption. ***Water reabsorption*** - Vasopressin's effect on **water reabsorption** in the kidney collecting ducts is primarily mediated by **V2 receptors**. - **V2 receptors** activate a G protein-coupled signaling pathway leading to the insertion of **aquaporin-2 channels** into the apical membrane, increasing water permeability. *Vasoconstriction* - **Vasoconstriction** is a well-known function of vasopressin, mediated by its binding to **V1a receptors** (a subtype of V1 receptors) on vascular smooth muscle cells. - This activation leads to an increase in **intracellular calcium**, causing the muscle cells to contract and the blood vessels to narrow. *Smooth muscle contraction* - Vasopressin can induce **smooth muscle contraction** in various tissues, including the gastrointestinal tract and uterus, primarily through **V1 receptors**. - This effect is similar to its vasoconstrictor action, involving **calcium mobilization** and muscle fiber shortening. *None of the options* - This option is incorrect because **water reabsorption** is indeed mediated by V2 receptors, not V1 receptors. - The other functions listed (vasoconstriction and smooth muscle contraction) are correctly attributed to **V1 receptors**.

Q: All of the following are cycloplegics except :

Phenylephrine. ***Phenylephrine*** - **Phenylephrine** is a **sympathomimetic** agent that primarily acts as a **mydriatic** (dilates the pupil) by stimulating the **alpha-1 adrenergic receptors** in the iris dilator muscle [1], [2]. - It has **absolutely no cycloplegic effect**, meaning it does not paralyze the ciliary muscle or affect accommodation at all [1]. - This makes it the **only pure mydriatic** among the options, with zero cycloplegic action [3]. *Atropine* - **Atropine** is a potent **anticholinergic** agent that blocks **muscarinic receptors** in the ciliary body, causing **strong cycloplegia** (paralysis of accommodation) [1], [4]. - Duration of cycloplegia: **7-14 days**, making it the longest-acting cycloplegic. - Also causes mydriasis by paralyzing the iris sphincter muscle. *Cocaine* - **Cocaine** is a **local anesthetic** and **sympathomimetic** that inhibits norepinephrine reuptake, causing **mydriasis** [2]. - Unlike phenylephrine, cocaine can produce **weak cycloplegic effects** through its local anesthetic action and sympathetic stimulation, though much less than anticholinergics. - Primarily used diagnostically in ophthalmology (e.g., Horner's syndrome testing) [2]. - Since it does have some cycloplegic effect (albeit minimal), it is technically a cycloplegic, making **phenylephrine the correct answer** as the only drug with no cycloplegia at all. *Homatropine* - **Homatropine** is an **anticholinergic** agent with **moderate cycloplegic** potency. - Duration: **1-3 days** (shorter than atropine, longer than tropicamide). - Blocks **muscarinic receptors** in the ciliary body, causing cycloplegia and mydriasis.

Q: Which of the following would increase the levels of acetylcholine in the synaptic cleft?

Inhibition of acetylcholinesterase. ***Inhibition of acetylcholinesterase*** - **Acetylcholinesterase** is the enzyme responsible for breaking down acetylcholine in the synaptic cleft. - By **inhibiting** this enzyme, acetylcholine persists longer in the cleft, leading to increased levels and prolonged effects. *Administration of glucose* - **Glucose** is the primary energy source for cellular function, including neurotransmitter synthesis and release. - While essential for overall neuronal health, directly administering glucose does not specifically increase acetylcholine levels in the synaptic cleft. *Activation of nicotinic receptors* - **Nicotinic receptors** are postsynaptic receptors that bind acetylcholine, causing neuronal depolarization and muscle contraction. - Their activation mediates the effects of acetylcholine but does not influence the amount of acetylcholine present in the synaptic cleft. *Activation of muscarinic receptors* - **Muscarinic receptors** are another class of acetylcholine receptors, often found on target organs of the parasympathetic nervous system. - Like nicotinic receptors, their activation responds to acetylcholine but does not directly increase its concentration in the synaptic cleft.

Q: M2 cholinergic receptor is located at

Heart. ***Heart*** - The **M2 muscarinic acetylcholine receptor** is predominantly located in the **heart**, where its activation mediates parasympathetic effects. - Activation of M2 receptors in the heart leads to a **decrease in heart rate** and force of contraction. *Glands* - **Glandular secretions**, such as saliva, tears, and sweat, are primarily mediated by **M3 muscarinic receptors**. - While M2 receptors may have some minor presence, M3 is the dominant subtype for secretory functions. *Lungs* - **Bronchoconstriction** and increased **mucus secretion** in the lungs are primarily mediated by **M3 muscarinic receptors**. - M2 receptors are present, but their role is often considered to be inhibitory to other M3 effects or to modulate neurotransmitter release. *Skeletal muscle* - **Skeletal muscle contraction** is mediated by **nicotinic acetylcholine receptors (Nm)** at the neuromuscular junction. - Muscarinic receptors, including M2, are not directly involved in skeletal muscle contraction.

Q: Non-depolarizing neuromuscular blocker is characterized by

Reversed by neostigmine. ***Reversed by neostigmine*** - **Non-depolarizing neuromuscular blockers** are **competitive antagonists** at the **nicotinic acetylcholine receptors** at the neuromuscular junction. - **Neostigmine** is an **acetylcholinesterase inhibitor** that increases the concentration of acetylcholine in the synaptic cleft, thereby overcoming the competitive blockade. *Non competitive neuromuscular blocker* - Non-depolarizing neuromuscular blockers are, by definition, **competitive antagonists** at the **nicotinic acetylcholine receptors**. - A non-competitive blocker would bind to a different site on the receptor or an allosteric site to produce its effect. *Induces fasciculations* - **Fasciculations** (visible muscle twitching) are characteristic of **depolarizing neuromuscular blockers** like **succinylcholine**, as they initially activate the receptors before causing prolonged depolarization and paralysis. - Non-depolarizing blockers do not typically cause fasciculations because they prevent acetylcholine from binding and activating the receptors. *Persistent stimulator of nicotinic cholinergic receptors* - This describes the mechanism of action of **depolarizing neuromuscular blockers** like **succinylcholine**, which persistently activate the receptor, leading to initial fasciculations followed by sustained depolarization and paralysis. - **Non-depolarizing blockers** act as **antagonists**, preventing activation of the receptors.

Q: Drug used for d-TC reversal is

Neostigmine. ***Neostigmine*** - **Neostigmine** is an **acetylcholinesterase inhibitor** that increases the concentration of **acetylcholine** at the neuromuscular junction, effectively reversing the effects of competitive (d-TC) neuromuscular blockers. - It is commonly administered with an **anticholinergic agent** like atropine or glycopyrrolate to prevent undesired muscarinic side effects. *Diazepam* - **Diazepam** is a **benzodiazepine** primarily used as an **anxiolytic**, sedative, anticonvulsant, and muscle relaxant (central action), not for reversing neuromuscular blockade. - It potentiates the effect of **GABA**, leading to central nervous system depression. *Atropine* - **Atropine** is an **anticholinergic agent** that blocks muscarinic acetylcholine receptors. - While it is often co-administered with neostigmine to counteract its muscarinic side effects (e.g., bradycardia, salivation), it does not directly reverse the neuromuscular blockade caused by d-TC. *Atracurium* - **Atracurium** is an **intermediate-duration, non-depolarizing neuromuscular blocking agent** itself, similar in action to d-tubocurarine (d-TC). - Therefore, it would worsen, rather than reverse, the neuromuscular blockade.

Question 1

All are true about atropine poisoning, except

Accepted Answer

Decreased temperature

Answer

Dysarthria

Answer

Dysphagia

Answer

Dilated pupils

Question 2

Mechanism of action of atropine in treatment of organophosphate poisoning is?

Accepted Answer

It has antimuscarinic activity

Answer

It inhibits secretion of acetylcholine

Answer

It is reactivator of acetylcholine esterase enzyme

Answer

It is agonist of acetylcholine receptors

Question 3

All of the following drugs are used for the treatment of urinary incontinence except:

Accepted Answer

Ipratropium

Answer

Oxybutynin

Answer

Tolterodine

Answer

Darifenacin

Question 4

All of the following functions of vasopressin are mediated by V1 receptors, except

Accepted Answer

Water reabsorption

Answer

Vasoconstriction

Answer

Smooth muscle contraction

Answer

None of the options

Question 5

All of the following are cycloplegics except :

Accepted Answer

Phenylephrine

Answer

Atropine

Answer

Cocaine

Answer

Homatropine

Question 6

Which of the following would increase the levels of acetylcholine in the synaptic cleft?

Accepted Answer

Inhibition of acetylcholinesterase

Answer

Administration of glucose

Answer

Activation of nicotinic receptors

Answer

Activation of muscarinic receptors

Question 7

M2 cholinergic receptor is located at

Accepted Answer

Heart

Answer

Glands

Answer

Lungs

Answer

Skeletal muscle

Question 8

Non-depolarizing neuromuscular blocker is characterized by

Accepted Answer

Reversed by neostigmine

Answer

Non competitive neuromuscular blocker

Answer

Induces fasciculations

Answer

Persistent stimulator of nicotinic cholinergic receptors

Question 9

Drug used for d-TC reversal is

Accepted Answer

Neostigmine

Answer

Diazepam

Answer

Atropine

Answer

Atracurium

Question 10

To which muscle relaxant are patients with myasthenia gravis (MG) most sensitive?

Accepted Answer

Gallamine

Answer

Atracurium

Answer

Scoline

Answer

Decamethonium

Autonomic Nervous System Drugs — MCQs

Autonomic Nervous System Drugs — MCQs

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