Chapter 6: Adrenergic (Sympathetic) Nervous System — VOCABULARY Flashcards

Vocabulary-style flashcards covering adrenergic nerve endings, receptors, drug classes, and common agents with their primary actions, indications, and adverse effects.

Norepinephrine (NE) storage and fate

NE is stored in adrenergic nerve endings; released when stimulated; NE can be reused or destroyed by monoamine oxidase (MAO).

Epinephrine (EPI) vs norepinephrine (NE) actions

Both stimulate internal organs to increase sympathetic activity; EPI relaxes smooth muscle and bronchodilates; NE does not bronchodilate. EPI promotes bronchodilation. (EPI also has alpha and beta effects.)

Alpha-1 adrenergic receptor

Located on smooth muscle membranes of arteries/veins and sphincters; mediates contraction of smooth muscle and vasoconstriction; contributes to pupil dilation (iris).

Alpha-2 adrenergic receptor

Located on adrenergic nerve endings; provides negative feedback by decreasing release of NE. “Decrease release of NE.”

Beta-1 adrenergic receptor

Primarily in the heart; increases heart rate, force of contraction, and AV conduction. (Cardiac stimulation.)

Beta-2 adrenergic receptor

Located in lungs, coronary vessels, skeletal muscle vessels; mediates bronchodilation, relaxation of smooth muscle, and vasodilation. (Bronchodilation and uterine relaxation related effects.)

Norepinephrine and beta-2 receptors

Norepinephrine does not stimulate beta-2 receptors (no beta-2 agonist activity).

Sympathomimetics

Drugs that stimulate the sympathetic nervous system (agonists).

Sympatholytics

Drugs that antagonize the sympathetic nervous system (receptor blockers).

Alpha-adrenergic agonists (sympathomimetics)

Activate alpha receptors; cause alpha-1–mediated vasoconstriction and alpha-2 negative feedback to reduce NE release.

Nonselective beta-adrenergic agonists

Stimulate both beta-1 and beta-2 receptors; produce cardiac stimulation and bronchodilation; examples include epinephrine and isoproterenol.

Selective beta-2 adrenergic agonists

Stimulate beta-2 receptors causing bronchodilation and relaxation of certain smooth muscles; examples include albuterol, terbutaline, formoterol, salmeterol, levalbuterol.

Adrenergic neuronal blocking drugs

Drugs that interfere with synthesis or release of NE, thereby decreasing sympathetic activity; examples include methyldopa, reserpine, guanethidine.

Methyldopa

Interferes with NE synthesis and forms a false transmitter (alpha-methyl-NE) to reduce sympathetic tone.

Reserpine and Guanethidine

Reserpine depletes NE stores; Guanethidine prevents NE release and depletes vesicular NE.

Alpha-adrenergic blocking drugs

Blockade of alpha receptors; used to treat hypertension, benign prostatic hyperplasia, pheochromocytoma, and peripheral vascular conditions.

Common adverse effects of alpha-blockers

Pupil constriction, nasal congestion, increased GI activity, and reflex tachycardia when blood pressure falls.

Representative alpha-adrenergic drugs (hypotension and decongestion uses)

Examples include midodrine and norepinephrine for hypotension; phenylephrine, naphazoline, oxymetazoline, pseudoephedrine, tetrahydrozoline, and xylometazoline for decongestion.

Beta-adrenergic blocking drugs (beta-blockers)

Block beta receptors to reduce heart rate/contractility and blood pressure; used for cardiovascular conditions.

Nonselective beta-blockers

Blockade of both beta-1 and beta-2 receptors; examples include propranolol, nadolol, pindolol, timolol; also includes carvedilol and labetalol as additional agents.

Selective beta-1 blockers

Blockade primarily at beta-1 receptors (heart); examples include acebutolol, atenolol, esmolol, metoprolol, nebivolol, etc.

Indications for beta-blockers

Angina pectoris, hypertension, chronic heart failure, cardiac arrhythmias, post-myocardial infarction prevention, glaucoma, migraine, supraventricular tachycardia.

Adverse effects of beta-blockers

Bradycardia, congestive heart failure, cardiac arrest, bronchoconstriction (esp. nonselective blocks in asthma/COPD); CNS disturbances for lipophilic agents.

Dopamine (Intropin) in beta/adrenoceptor pharmacology

Nonselective beta-1 and alpha effects; used in circulatory shock; causes vasodilation and increased renal blood flow at receptor-specific doses; higher doses cause vasoconstriction.

Epinephrine (adrenaline) clinical use

Nonselective alpha and beta agonist used in anaphylaxis and acute allergic reactions; also acts as bronchodilator/inotropic/vasopressor depending on dose.

Isoproterenol

Nonselective beta-adrenergic agonist (beta-1 and beta-2) used as a cardiac stimulant when indicated; parenteral administration.

Beta-adrenergic blocking drugs: key categories

Nonselective blockers (affect both beta-1 and beta-2) and selective beta-1 blockers (beta-1–selective) with distinct clinical uses and side-effect profiles.