Autonomic Nervous System: Cholinergics

Autonomic Nervous System: Cholinergics

• The autonomic nervous system regulates involuntary functions, and the parasympathetic division has a calming effect.

• Cholinergic agonists, also called parasympathomimetics, mimic the effects of the parasympathetic nervous system.

• Cholinergic receptors are of two types: nicotinic and muscarinic.

• Nicotinic receptors are located in ganglia, while muscarinic receptors affect smooth muscle, cardiac muscle, and glands.

• Cholinergic drugs can be direct-acting, binding to receptors, or indirect-acting, inhibiting the enzyme acetylcholinesterase.

• Cholinergics have various effects, including stimulating the intestine and bladder, pupils, cardiovascular system, and respiratory system.

• Adverse effects of cholinergics are due to overstimulation of the parasympathetic system and can include cardiovascular effects, central nervous system effects, gastrointestinal effects, or respiratory effects.

• Cholinergic crisis can arise from severe overstimulation of the parasympathetic system, causing circulatory collapse, hypotension, and cardiac arrest.

• Cholinergic-blocking drugs (anticholinergics, parasympatholytics, and antimuscarinics) block the actions of acetylcholine in the parasympathetic nervous system.

• Examples of natural plant alkaloids include atropine sulfate and scopolamine.

Cholinergic Blocking Drugs: Examples

• Synthetic and semisynthetic drugs include dicyclomine, glycopyrrolate, oxybutynin, and tolterodine.
• These cholinergic-blocking drugs affect the heart's conduction system (cardiovascular), central nervous system, eye system, gastrointestinal tract, genitourinary tract, and respiratory system.
• The cardiovascular effects often affect decreased heart rate with small doses and increased heart rate with large doses.
• The central nervous system effects commonly include decreased muscle rigidity and tremors with smaller doses, and drowsiness, disorientation, and hallucinations with large doses.
• The eye effects often include dilated pupils and decreased accommodation.
• Gastrointestinal effects often include relaxation of smooth muscles and decreased motility.
• Genitourinary effects often include urinary retention.
• Respiratory effects include decreased breathing secretions.
• Indications of cholinergic blocking drugs include those associated with the cardiovascular system, central nervous system, eye system, respiratory system, gastrointestinal system, or urological system.
• Contraindications of these drugs involve those associated with known drug allergies, angle-closure glaucoma, acute asthma, myasthenia gravis, acute cardiovascular instability, GI or GU tract obstructions, and illnesses.

Cholinergic-Blocking Drugs: Mechanism of Action

• The mechanism of action involves blockade of receptor sites in the autonomic nervous system controlling secretions.

Nursing Implications

• Assessing for allergies, presence of BPH, urinary retention, glaucoma, tachycardia, myocardial infarction, heart failure, hiatal hernia, or GI/GU obstruction is crucial.
• Baseline assessments of vital signs and systems overview are essential.
• Medications should be administered as prescribed.
• Doses should be spread evenly apart.
• Overdosing can lead to severe problems.
• Blurred vision can cause difficulty while driving or operating machinery.
• Sensitivity to light might need dark glasses or sunglasses.
• Pressure to the inner canthus prevents systemic absorption when administering ophthalmic solutions.
• Patients should check with physicians before taking other medications.
• An antidote to atropine overdose is physostigmine.
• Encourage patients to avoid strenuous exercise and maintain adequate fluid intake.
• Monitor patients for therapeutic and adverse effects and appropriate symptoms.

Explore the fascinating world of the autonomic nervous system, focusing on cholinergic mechanisms. This quiz covers the functions, types of cholinergic receptors, and the effects and adverse reactions of cholinergic drugs. Test your knowledge on this vital aspect of human physiology.