AUTONOMIC NERVOUS SYSTEM

INTRODUCTION

•      PURPOSE

–   Maintain stable internal environment by coordinating, adjusting, and regulating the body’s visceral activity

•   examples include:  digestion, body temperature, heart rate

•   Primary Function - Maintain homeostasis

 

DIVISIONS

•      PARASYMPATHETIC

–   Cranio-sacral System

–   Conserve and Restore Energy

•      SYMPATHETIC

–   Thoraco-lumbar System

–   Prepares body for stress and emergency

–   Also non-stress regulation

NEUROFIBER ANATOMY

•      Pre-ganglionic and post-ganglionic fibers

•      Neurotransmitter vesicles

•      Junctional Spaces

•      Receptors

PARASYMPATHETIC FIBER

•      Post-ganglionic neurotransmitter:  acetylcholine

•      Receptor Site:  Muscarinic

•      Activity Stopped by acetylcholine esterase

SYMPATHETIC FIBER

•      Post-ganglionic neurotransmitter:  norepinephrine (catecholamine)

•      Receptor Site:  alpha, beta 1 and beta 2

•      Activity stopped by:

–   Reuptake (primary mechanism)

–   Mono amine oxidase

 

 

Neurohormonal Transmission

•      Acetylcholine

–   Released by all pre-ganglionic fibers (stimulates nicotinic receptors)

–   Post-ganglionic parasympathetic fibers (stimulates muscarinic receptors)

•      Norepinephrine

–   Post-ganglionic sympathetic fibers (stimulates alpha, beta 1 and beta 2 receptors)

PARASYMPATHETIC EFFECTS

•      EYES

–   Miosis (pupil constriction)

–   Lacrimation (tear secretion)

–   Accommodate for near vision

–   Decreased intra-ocular pressure

•      DIGESTIVE

–   Saliva Secretion

–   Stomach acid secretion

–   Peristalsis

PARASYMPATHETIC EFFECTS

•      Decrease heart rate

•      Bronchial Constriction (asthmatics)

•      Enhances Urination

–   Bladder contraction

–   Sphincter relaxation

PARASYMPATHOMIMETIC AGENTS

•      Bethanechol - stimulates GI motility and bladder

 

•      Pilocarpine - ophthalmic - lowers intra-ocular pressure

PARASYMPATHOMIMETIC AGENTS

•      Contraindications

–   Asthma

–   Cardiac insufficiency

–   Peptic Ulcer

 

–   Eye drops may still be used with precaution

ACETYLCHOLINE ESTERASE INHIBITORS

•      Blocks acetylcholine esterase enzyme from breaking down acetylcholine

 

•      Pharmacology will be similar to parasympathomimetic agents, just mechanism of action differs

Edrophonium

•      Short acting - reversible

 

•      Diagnose myasthenia gravis

INTERMEDIATE ACTING REVERSIBLE AGENTS

•      Neostigmine and Pyridostigmine

–   Treatment of myasthenia gravis

•      Physostigmine

–   Ophthalmic agent - lower intra-ocular pressure

•      Donepezil, Galantamine, Rivastigmine

–   Temporarily lessen symptoms of Alzheimer’s Disease

LONG ACTING IRREVERSIBLE AGENTS

•      Echothiophate and Isofluorphate

–   Organophosphate toxic agents

–   Must use precaution when administering by placing pressure on the corner of the eye

–   Only utilized as an ophthalmic agent

ANTICHOLINERGICS

•      Blocks muscarinic receptor so that acetylcholine cannot bind and stimulate

 

•      Eye

–   Dry eye

–   Accommodate for far vision

–   Mydriasis - dilate pupil

–   Increased intra-ocular pressure

ANTICHOLINERGIC

•      DIGESTION

–   Decreased saliva production

–   Decreased acid production

–   Decreased peristalsis

•      INCREASED HEART RATE

•      URINARY RETENTION - especially in BPH

•      BRONCHODILATION (asthmatics)

ANTICHOLINERGIC ORDER OF SENSITIVITY

•      Secretory (saliva, sweat, stomach acid)

•      Eye

•      Heart

•      GI Motility

THERAPEUTIC USE

•      NATURAL ALKALOIDS

–   Prior to procedure (decrease aspiration)

–   Sinus Bradycardia

–   Motion Sickness

–   GI Cramping

•      ANTISPASMODIC

•      MYDRIATIC AND CYCLOPLEGIC - ophthalmic exam

ANTICHOLINERGIC CONTRAINDICATIONS

•      Myasthenia gravis

•      Narrow angle glaucoma

•      Unstable cardiovascular system

•      Intestinal atony

SYMPATHETIC (ADRENERGIC)

•      ALPHA

–   Vasoconstriction

–   Stimulate sweat and salivary gland

–   Decrease intra-ocular pressure

•      BETA 1

–   Increase heart rate and force of contraction

•      BETA 2

–   Bronchodilation, Smooth muscle relaxation

EPINEPHRINE

•      ALPHA - decrease IOP

–   Prolong action of local anesthetics and decrease bleeding

–   Increase blood pressure in shock

•      BETA 1

–   Increase blood pressure in shock

•      BETA 2

–   Relieve bronchospasm

LEVARTERENOL

•      ALPHA

–   VERY STRONG VASOCONSTRICTION

–   REVERSED BY ALPHA BLOCKER

•      BETA 1

–   Increases blood pressure in shock

ISOPROTERENOL

•      BETA 1

–   Increase blood pressure

•      BETA 2

–   Bronchodilation

DOPAMINE

•      DOPAMINE

–   Renal Artery Dilation

•      BETA 1

–   Increase blood pressure

•      ALPHA

–   Very strong vasoconstriction (dose rate dependent)

DOBUTAMINE

•      BETA 1

–   Cardiogenic shock

BRONCHODILATORS

•      BETA 2 STIMULATION

•      BETA 1 SPILL OVER

–   best avoided by giving via inhaled route and utilizing a beta 2 specific agent (e.g. albuterol)

ALPHA STIMULANTS

•      OPHTHALMIC DECONGESTANT

 

•      NASAL DECONGESTANT

–   Oral products may also increase blood pressure

–   Topical nasal sprays should not be used for more than 3 days

ALPHA BLOCKING AGENTS

•      PHEOCHROMOCYTOMA

 

•      REVERSE ALPHA PROPERTIES OF LEVARTERENOL

–   phentolamine

BETA BLOCKERS

•      Utilized to block beta 1 receptors

•      All will have beta 2 spillover, some more than others

•      Use

–   arrhythmia (tachycardia)

–   Hypertension (decrease renin release)

–   angina

–   post-myocardial infarction

–   migraine

BETA BLOCKER CAUTION

•      ASTHMA - use beta 1 specific

•      INSULIN DEPENDENT DIABETIC - masks symptoms of hypoglycemia

•      PERIPHERAL VASCULAR DISEASE

SUMMARY COMPARISON

•      Parasympathetic

 

•      Acetylcholine esterase inhibitors

 

•      Alpha/Beta Blockers

•      Sympathetic

 

•      Anticholinergics