Parasympathetic Nervous System Exam

1. Ms Hanan has been treated for myasthenia gravis for several years. She reports to the emergency department complain- ing of recent onset of weakness of her hands, diplopia, and difficulty swallowing. She may be suffering from a change in response to her myasthenia therapy, that is, a cholinergic or a myasthenic crisis. Which of the following is the best drug for distinguishing between myasthenic crisis (insufficient therapy) and cholinergic crisis (excessive therapy)?

Atropine

Edrophonium

Physostigmine

Pralidoxime

Edrophonium is the best drug for distinguishing between myasthenic crisis and cholinergic crisis. Edrophonium is a short-acting cholinesterase inhibitor that temporarily improves muscle strength in myasthenia gravis patients. In a myasthenic crisis, where there is insufficient therapy, edrophonium will improve muscle strength. On the other hand, in a cholinergic crisis, where there is excessive therapy, edrophonium will worsen muscle weakness. Therefore, the response to edrophonium helps differentiate between the two crises. Atropine, Physostigmine, and Pralidoxime are not used for this purpose.

Explanation

Edrophonium is the best drug for distinguishing between myasthenic crisis and cholinergic crisis. Edrophonium is a short-acting cholinesterase inhibitor that temporarily improves muscle strength in myasthenia gravis patients. In a myasthenic crisis, where there is insufficient therapy, edrophonium will improve muscle strength. On the other hand, in a cholinergic crisis, where there is excessive therapy, edrophonium will worsen muscle weakness. Therefore, the response to edrophonium helps differentiate between the two crises. Atropine, Physostigmine, and Pralidoxime are not used for this purpose.

2. Probable signs of atropine overdose include which one of the following?

Gastrointestinal smooth muscle cramping

Increased heart rate

Increased gastric secretion

Pupillary constriction

Atropine is a medication that blocks the action of acetylcholine in the body, leading to various effects. An overdose of atropine can cause an excessive increase in heart rate due to the medication's ability to block the parasympathetic nervous system, which normally slows down the heart rate. This excessive increase in heart rate is a probable sign of atropine overdose.

Explanation

Atropine is a medication that blocks the action of acetylcholine in the body, leading to various effects. An overdose of atropine can cause an excessive increase in heart rate due to the medication's ability to block the parasympathetic nervous system, which normally slows down the heart rate. This excessive increase in heart rate is a probable sign of atropine overdose.

3. A Farmer has been accidentally exposed to a high concentration of a highly toxic agricultural organophosphate insecticide. If untreated, the cause of death from such exposure would probably be

Cardiac arrhythmia

Gastrointestinal bleeding

Heart failure

Respiratory failure

Exposure to a highly toxic agricultural organophosphate insecticide can lead to respiratory failure. Organophosphate compounds inhibit the activity of cholinesterase, an enzyme that breaks down acetylcholine in the body. This leads to an accumulation of acetylcholine, causing overstimulation of the respiratory muscles and ultimately paralysis. Without proper treatment, the individual's ability to breathe will be compromised, leading to respiratory failure and potentially death.

Explanation

Exposure to a highly toxic agricultural organophosphate insecticide can lead to respiratory failure. Organophosphate compounds inhibit the activity of cholinesterase, an enzyme that breaks down acetylcholine in the body. This leads to an accumulation of acetylcholine, causing overstimulation of the respiratory muscles and ultimately paralysis. Without proper treatment, the individual's ability to breathe will be compromised, leading to respiratory failure and potentially death.

4. Accepted therapeutic indications for the use of anti-muscarinic drugs include all of the following EXCEPT

Motion sickness

Parkinson’s disease

Atrial fibrillation

Bladder spasm

Anti-muscarinic drugs are commonly used to treat conditions characterized by overactivity of the parasympathetic nervous system, such as motion sickness, Parkinson's disease, and bladder spasms. However, they are not indicated for the treatment of atrial fibrillation, which is an abnormal heart rhythm. Atrial fibrillation requires specific antiarrhythmic medications or procedures to restore normal heart rhythm. Therefore, atrial fibrillation is the correct answer as it is not an accepted therapeutic indication for the use of anti-muscarinic drugs.

Explanation

Anti-muscarinic drugs are commonly used to treat conditions characterized by overactivity of the parasympathetic nervous system, such as motion sickness, Parkinson's disease, and bladder spasms. However, they are not indicated for the treatment of atrial fibrillation, which is an abnormal heart rhythm. Atrial fibrillation requires specific antiarrhythmic medications or procedures to restore normal heart rhythm. Therefore, atrial fibrillation is the correct answer as it is not an accepted therapeutic indication for the use of anti-muscarinic drugs.

5. Actions and clinical uses of muscarinic cholinoceptor agonists include which one of the following?

Bronchodilation (asthma)

Improved aqueous humor drainage (glaucoma)

Decreased gastrointestinal motility (diarrhea)

Increased sweating (fever)

Muscarinic cholinoceptor agonists are drugs that stimulate muscarinic receptors, which are found in various tissues in the body. One of the clinical uses of these agonists is to improve aqueous humor drainage in the eye, which is beneficial in the treatment of glaucoma. Glaucoma is a condition characterized by increased intraocular pressure, and by improving the drainage of aqueous humor, the pressure can be reduced, helping to prevent damage to the optic nerve and preserve vision. Therefore, the correct answer is "Improved aqueous humor drainage (glaucoma)."

Explanation

Muscarinic cholinoceptor agonists are drugs that stimulate muscarinic receptors, which are found in various tissues in the body. One of the clinical uses of these agonists is to improve aqueous humor drainage in the eye, which is beneficial in the treatment of glaucoma. Glaucoma is a condition characterized by increased intraocular pressure, and by improving the drainage of aqueous humor, the pressure can be reduced, helping to prevent damage to the optic nerve and preserve vision. Therefore, the correct answer is "Improved aqueous humor drainage (glaucoma)."

6. Which one of the following drugs has a very high affinity for the phosphorus atom in parathion (insecticide) and is often used to treat life-threatening insecticide toxicity?

Atropine

Benztropine

Bethanechol

Pralidoxime

Pralidoxime has a very high affinity for the phosphorus atom in parathion, making it an effective treatment for life-threatening insecticide toxicity. Atropine, benztropine, and bethanechol are not specifically used for this purpose.

Explanation

Pralidoxime has a very high affinity for the phosphorus atom in parathion, making it an effective treatment for life-threatening insecticide toxicity. Atropine, benztropine, and bethanechol are not specifically used for this purpose.