Chapter 33 Agents Affecting the Autonomic Nervous System

Autonomic Nervous System Includes two neurotransmitters ◦ Norepinephrine and acetylcholine Two branches 1.Sympathetic  Adrenergic  “Fight or flight” 2.Parasympathetic  Cholinergic  “Rest and digest” 2

Sympathetic Nervous System (SNS) Stimulates vital organs ◦ Suppresses nonvital body functions ◦ Signs of stimulation of the SNS  Pupil dilation  Bronchiole dilation  Increased rate and force of contraction  Blood vessel dilation in muscle tissue  Increased breakdown of glycogen to glucose 3

Sympathetic nervous system receptors ◦ Alpha  Found in smooth muscle tissue of peripheral blood vessels and in the sphincters of the gastrointestinal and genitourinary system; respond to norepinephrine ◦ Beta  Found mainly in the heart, lungs, and brain, respond to epinephrine 4

Alpha Receptors Alpha 1 - Primarily in the smooth muscle tissue of peripheral blood vessels and the sphincters of the GI and genitourinary (GU) tracts - When stimulated, smooth muscle contracts Anorexiants: dextroamphetamine (Dexedrine), methamphetamine (Desoxyn) 5

Alpha Receptors Alpha 2 - Functions as “controllers” of neurotransmitter release - When stimulated, release of neurotransmitters from the presynaptic neurons are decreased 6

Beta Receptors Beta 1 - Primarily in the heart and fatty tissue - When stimulated, rapid heart rate, more forceful heart contraction, and the breakdown of stored fat to fatty acids occurs 7

Beta Receptors Beta 2 ◦ Primarily in bronchial smooth muscle and the walls of blood vessels ◦ produces bronchodilation when stimulated by adrenergic drugs albuterol, epinephrine, terbutaline When stimulated, bronchial muscles relax and diameter of airways increases 8

Adrenergic Receptors produces increased contractility, increased heart rate, and AV and sinoatrial (SA) node conduction when stimulated by adrenergic drugs ◦ dobutamine, dopamine, and norepinephrine 9

Parasympathetic Nervous System (PNS) One neurotransmitter ◦ Acetylcholine Conserves energy Promotes nutrient use 10

Drugs Affecting the ANS Sympathomimetic: adrenergic drugs ◦ Stimulate the system: “fight-or- flight” Sympatholytic: adrenergic blocking drugs ◦ Block alpha and beta receptors 11

Drugs Affecting the ANS Parasympathomimetic: cholinergic drugs ◦ Mimic the PNS Parasympatholytic: anticholinergic drugs ◦ Block acetylcholine receptors 12

Sympathomimetics (Adrenergics) Mimic the action of the sympathetic nervous system Neurotransmitters norepinephrine, epinephrine, and dopamine (catecholamines) 13

Sympathomimetics (Adrenergics) Catecholamine receptor sites are where adrenergics bind and produce their response at locations throughout the body 14

Geriatric Considerations for Adrenergics More sensitive to the effects of adrenergics Must be monitored for excessive cardiac and CNS stimulation Signs and symptoms to watch for include: - chest pain - palpitations - blurred vision - headache - seizures - hallucinations Notify provider immediately for these symptoms 15

Sympatholytics (Adrenergic Blockers) Block or inhibit the responses of adrenergic neurotransmitters at the alpha and beta receptor sites 16

Alpha-adrenergic Blockers Inhibits the response at the alpha receptors Causes vasodilation and decreases blood pressure Used to treat migraine headaches, hypertension, and peripheral vascular diseases (promotes blood flow to vasoconstricted areas) 17

Alpha-adrenergic Blockers Adverse effects can include hypotension, dizziness, and ejaculation suppression Commonly used alpha blockers are ergotamine tartrate (for migraines), and tolamine and prazosin (for hypertension) 18

Beta-adrenergic Blockers Blocks the beta receptor sites in the heart Decreases pulse rate and controls angina pectoris Decreases firing rate in the SA node and conduction velocity in the AV node and therefore, treats dysrhythmias 19

Beta-adrenergic Blockers They also decrease blood pressure and cause bronchoconstriction Use with caution in patients with asthma and COPD Some common drugs are propranolol, metoprolol, and atenolol 20

Adrenergic Blockers Treat ◦ Hypertension ◦ Migraine headache Side effects/adverse effects ◦ Hypotension ◦ Dizziness 21

Adrenergic Blockers: Geriatric Considerations Increase sensitivity to adrenergic drugs ◦ Monitor for:  Chest pain  Palpitations  Blurred vision  Headache  Seizures  Hallucinations 22

Cholinergics Stimulate the PNS Treat ◦ Conditions with poor muscular contraction ◦ Neurogenic bladder ◦ Glaucoma ◦ Cardiac arrhythmias 23

Cholinergics: Geriatric Considerations Increase sensitivity to cholinergic drugs Monitor for: ◦ Diarrhea ◦ Increased bronchoconstriction ◦ Increased bronchial secretions ◦ Increased lacrimation ◦ Blurred vision 24

Anticholinergics Action ◦ Decrease gastrointestinal and respiratory secretions ◦ Dilate bronchioles ◦ Dilate pupils Treat ◦ Nausea ◦ Urinary incontinence ◦ Overactive bladder 25

Anticholinergics: Geriatric Considerations Increase sensitivity to anticholinergic drugs ◦ Hyperthermia ◦ Urinary retention ◦ Decreased appetite 26