Quiz 7: Drugs Affecting the Parasympathetic Nervous System

Nursing

The central nervous system (CNS) is the organ system controlling and coordinating all the systems in the body. It is a vast and complicated, but a well-arranged for the integration of the whole living body. CNS has divisions to control the voluntary and involuntary actions separately. Peripheral nervous system (PNS) aids CNS in its function. CNS constitutes 2 structures - brain and spinal cord. It sends and receives information through the structures called nerves. PNS constituting cranial and spinal nerves are divided into somatic and visceral nerves. Visceral nervous system is also called autonomic nervous system (ANS). ANS is again divided into sympathetic and parasympathetic nervous systems. The sympathetic system is activated during fight or flight reaction whereas the parasympathetic system is activated during the resting period. The parasympathetic nervous system stimulates only certain parts of the body, as in the case for urination and defecation. This system is stimulated and regulates the body functions mostly at the time of rest and restoration of energy. It helps in digestion and excretion. It increases the gastrointestinal activity and the activity of genitourinary systems. But it decreases the activity of the cardiovascular system.

The pharmacist should be thorough with the use of drugs and the interaction of each drug with other drugs. He/she has to go through the detailed information in PDR website and other related important resources. As the responsibility of a pharmacist, he/she has to provide appropriate information to the doctor regarding the drug-drug interactions. Dicyclomine is an anticholinergic drug which can block the action of acetylcholine. Its action is on the muscles of the stomach and intestines, called smooth muscles. Timolol is a non-selective beta blocker similar to propanolol and nadolol. It is used for the treatment of different disorders such as hypertension (to reduce blood pressure), myocardial infarction (to reduce cardiovascular mortality), migraine (for prophylaxis), glaucoma, chronic stable angina and essential tremor. It has oral and ophthalmic uses A pharmacist has to inform the doctor that the use of dicyclomine along with glaucoma drugs such as timolol can reduce or block the effect of glaucoma drugs. Their simultaneous use can increase the risk of side effects like increased drowsiness, dry mouth and blurred vision. Also according to PDR, an abrupt discontinuation of any beta-adrenergic blocking agent like timolol can result in the development of cardiovascular disorders like myocardial ischemia, myocardial infarction, ventricular arrhythmias or severe hypertension. This most adversely affect those who are already suffering from cardiovascular problems.

Cholinergic receptors also known as parasympathetic receptors are the receptors which are present in the peripheral nervous system. There are three types of cholinergic receptors and these include muscarinic receptors, nicotinic-neural receptors and nicotinic -muscle receptors. Alpha-1 receptors are adrenergic receptors also known as sympathetic receptors present on the smooth muscle cells of the blood vessels. Hence, the option (A) is incorrect. Nicotinic-neural (Nn) receptors are the cholinergic receptors of the sympathetic and parasympathetic nerves present at the sites of ganglion. These are located on the autonomic ganglia. Hence, the option (B) (D) are incorrect. Nicotinic-muscle (Nm) receptors are the cholinergic receptors present at the skeletal muscle neuromuscular junction. These are located on the skeletal muscle. Hence, the option (C) is incorrect. Muscarinic receptors are the cholinergic receptors present at the post ganglionic nerve endings of the parasympathetic nervous system. These are located on the internal organs and glands. Hence, the option img is correct.

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