Autonomic Nervous System Pharmacology: Adrenergic and Cholinergic Agonists and Antagonists

Vocabulary flashcards covering autonomic nervous system divisions, adrenergic receptors, sympathomimetics, sympatholytics, cholinergic receptors, parasympathomimetics, and anticholinergics.

Autonomic Nervous System (ANS)

An involuntary nervous system, also called the visceral system, that acts on smooth muscles and glands to regulate the heart, respiratory system, GI tract, bladder, eyes, and glands.

Sympathetic Nervous System

A division of the autonomic nervous system, also known as the adrenergic system, that uses norepinephrine as its primary neurotransmitter to prepare the body for fight-or-flight responses.

Parasympathetic Nervous System

A division of the autonomic nervous system, also known as the cholinergic system, that uses acetylcholine as its primary neurotransmitter to mediate rest-and-digest responses.

Alpha1 Receptor

An adrenergic receptor located in blood vessels, eyes, bladder, and prostate that, upon stimulation, causes vasoconstriction, increased blood pressure, mydriasis, decreased salivary secretion, and urinary sphincter contraction.

Alpha2 Receptor

An adrenergic receptor located in postganglionic sympathetic nerve endings that, when stimulated, inhibits norepinephrine release, causes vasodilation, decreases blood pressure, and reduces GI motility and tone.

Beta1 Receptor

An adrenergic receptor located primarily in the heart and kidneys that increases heart rate, myocardial contractility, and renin secretion when stimulated.

Beta2 Receptor

An adrenergic receptor located in smooth muscles of the lungs, GI tract, liver, and uterus that causes bronchodilation, GI and uterine relaxation, and liver glycogenolysis.

Monoamine Oxidase (MAO)

An enzyme located inside the neuron that inactivates norepinephrine through enzymatic degradation.

Catechol-O-methyltransferase (COMT)

An enzyme located outside the neuron that degrades and inactivates norepinephrine.

Direct-Acting Sympathomimetics

Adrenergic agonists, such as epinephrine or norepinephrine, that directly stimulate adrenergic receptor sites.

Indirect-Acting Sympathomimetics

Sympathomimetic drugs, such as amphetamine, that stimulate the release of norepinephrine from terminal nerve endings.

Mixed-Acting Sympathomimetics

Sympathomimetic drugs, such as ephedrine and pseudoephedrine, that both directly stimulate adrenergic receptors and trigger the release of norepinephrine from terminal nerve endings.

Catecholamines

Chemical structures of endogenous (epinephrine, norepinephrine, dopamine) or synthetic (isoproterenol, dobutamine) substances that produce a sympathomimetic response.

Epinephrine

A nonselective adrenergic agonist acting on alpha1, beta1, and beta2 receptors to promote cardiac stimulation, bronchodilation, and reversal of anaphylactic reactions.

Albuterol

A selective beta2-adrenergic agonist that relaxes bronchial smooth muscle and causes bronchodilation to treat and prevent bronchospasm.

Clonidine

A selective central-acting alpha2-adrenergic agonist used to treat hypertension by decreasing sympathetic outflow from the CNS.

Methyldopa

A central-acting alpha-adrenergic agonist converted to alpha-methylnorepinephrine in the brain stem to decrease peripheral vascular resistance and lower blood pressure.

Phentolamine Mesylate

An alpha-adrenergic antagonist administered (5 to 10 mg diluted in 10 to 15 mL normal saline) into extravasation sites to prevent dermal necrosis from IV norepinephrine or dopamine.

Atenolol

A selective beta1-adrenergic blocker that decreases heart rate, myocardial contraction force, and cardiac output while suppressing the renin-angiotensin-aldosterone system.

Adrenergic Neuron Antagonists

Drugs, such as reserpine, that block the release of norepinephrine from sympathetic terminal neurons to decrease blood pressure.

Acetylcholine (ACh)

The neurotransmitter at autonomic ganglia and parasympathetic terminal nerve endings that innervates muscarinic and nicotinic receptors.

Acetylcholinesterase (AChE)

An enzyme, also called cholinesterase, that inactivates acetylcholine by breaking it down into choline and acetic acid.

Muscarinic Receptors

Cholinergic receptors located in smooth muscle, glands, and the heart that stimulate smooth muscle tone and slow heart rate when activated.

Nicotinic Receptors

Cholinergic receptors located at neuromuscular junctions that affect skeletal muscle contraction.

Direct-Acting Cholinergic Agonists

Parasympathomimetic drugs, such as bethanechol chloride, that act directly on cholinergic receptors to activate a tissue response.

Indirect-Acting Cholinergic Agonists

Cholinesterase inhibitors that inhibit acetylcholinesterase, permitting acetylcholine to accumulate and continuously stimulate muscarinic and nicotinic receptors.

Bethanechol Chloride

A direct-acting muscarinic cholinergic agonist used primarily to treat urinary retention and neurogenic bladder by increasing detrusor muscle contraction.

Pilocarpine

A direct-acting cholinergic agonist that constricts pupils (miosis) to open the Schlemm canal and promote drainage of aqueous humor in glaucoma.

Reversible Cholinesterase Inhibitors

Cholinesterase inhibitors, such as neostigmine, pyridostigmine, and edrophonium, that temporarily bind cholinesterase for minutes to hours to treat myasthenia gravis or glaucoma.

Atropine Sulfate

A classic anticholinergic (muscarinic antagonist) that blocks acetylcholine to increase heart rate, dilate pupils, and reduce salivary and bronchial secretions preoperatively.

Benztropine

An antiparkinson anticholinergic agent that blocks cholinergic receptors and dopamine reuptake to decrease involuntary movements, tremors, and rigidity.

Tolterodine Tartrate

An antimuscarinic agent that selectively blocks cholinergic receptors in the urinary bladder to control urinary frequency, urgency, and incontinence.

Pralidoxime Chloride

An antidote given to reverse toxicity caused by cholinesterase inhibitors and organophosphate pesticide exposure.