The nervous system is divided into central and peripheral components Central Nervous System Brain Spinal Cord

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1 1 Unit 12 Autonomic Nervous System 2 Divisions The nervous system is divided into central and peripheral components Central Nervous System Brain Spinal Cord Peripheral Nervous System Somatic Autonomic 3 4 Structural Division PNS Sensory Recognize changes to the environment Motor Respond to changes by moving muscles or secreting chemicals 5 Structural Division PNS Somatic Voluntary control over skeletal muscle Autonomic Involuntary control sympathetic and parasympathetic branches 6 Subsystems Sympathetic Fight or flight response Times of stress Parasympathetic Rest and digest Non-stressful situations 7 Figure 8.2 Effects of the sympathetic and parasympathetic nervous systems Source: Pearson Education/PH College 1

2 8 Autonomic Nervous System Involuntary Control Smooth Muscle Cardiac Muscle Glands Branches Sympathetic Parasympathetic Almost all organs and glands receive nerves from both branches 9 The Neuron Functional cell of the nervous system Transmits information Throughout nervous system To muscle and glands 10 Synapse Synapses are common sites of drug action Area at the end of the neuron Synaptic cleft Space between neurons Nerve impulses must cross to reach next neuron Presynaptic Neuron Before the synapse Generates original impulse Postsynaptic Neuron On other side of synapse Waiting to Receive impulse 11 Figure 8.3 A nerve impulse travels along the presynaptic neuron, bridges the synaptic cleft, and reaches the receptors in the postsynaptic neuron. There, the impulse is regenerated. 12 Neurotransmitters Chemicals released by presynaptic neurons into synaptic cleft Attach to receptors on postsynaptic neurons Regenerate nerve impulse Acetylcholine and norepinephrine are the two primary neurotransmitters in the ANS 13 Important Neurotransmitters Norepinephrine (adrenergic) Released by sympathetic nerves at synapse with organs Acetylcholine (cholenergic) Released by all presynaptic neurons at synapse with ganglia 14 Cholinergic Receptors Nicotinic 2

3 Found in ganglia and skeletal muscle Muscarinic End of postsynaptic neurons in parasympathetic nervous system 15 Adrenergic Receptors 1 Norepinephrine alpha 1 All sympathetic target organs Except the heart alpha 2 Presynaptic adrenergic neuron terminals 2 beta1 Heart Kidney beta 2 All sympathetic target organs Except the heart 16 Figure 8.4 Norepinephrine (NE) receptors are adrenergic receptors (α and β) in the sympathetic pathway. Acetylcholine (Ach) receptors in the ganglia and skeletal muscles (not shown here) are called nicotinic. Ach receptors at the ends of postganglionic neurons in the parasympathetic pathway are called muscarinic Autonomic drugs are classified according to the receptors they stimulate or block 19 Four Actions Stimulation of sympathetic nervous system Sympathomimetics or adrenergic agents Stimulation of parasympathetic nervous system Parasympathomimetics or cholinergic agents Inhibition of sympathetic nervous system Adrenergic blockers or sympatholytics Inhibition of parasympathetic nervous system Anticholinergics or cholinergic blockers Parasympathomimetics have few therapeutic uses because of their numerous adverse effects 3

4 22 Direct-Acting Parasympathomimetics Used only in the clinical setting Serious adverse effects Reduce intraocular pressure in glaucoma Stimulate smooth muscle in bowel and urinary tract after anesthesia 23 Indirect-Acting Parasympathomimetics Acetylcholinesterase inhibitors Facilitate effects of acetylcholine Same effects as direct-acting agents 24 Uses Affect acetylcholine receptors in skeletal muscles Use with myasthenia gravis Stimulate skeletal muscle contractions Temporarily restore muscle strength Examples pyridostigmine (Mestinon) Neostigmine (Prostigmin) 25 Adverse Effects Increased salivation Increased sweating Muscle twitching Involuntary defecation and urination Confusion Convulsions Anticholinergic Drug Actions Anticholinergics are used to dry secretions and to treat asthma Opposite of the parasympathetic nervous division Mimic fight-or-flight response Block muscarinic receptors 28 Therapeutic Uses for Anticholinergic Agents Dilation of pupils Increase heart rate Drying of secretions Dilation of bronchi 29 Adverse Effects Limit Their Usefulness 4

5 Tachycardia Urinary retention in men with prostate disorders Sympathomimetics Primarily used for their effects on the heart, bronchial tree, and nasal passages Produce same effects as anticholinergics Mimic sympathetic nervous system Stimulate alpha and beta receptors Actions more specific Wider therapeutic uses 32 Sympathomimetics Affect Alpha and Beta Receptors Heart Bronchial tree Nasal passages 33 Selective Sympathomimetics Stimulate Certain Adrenergic-Subreceptors Alpha1 receptors Located in nasal passages Dry nasal secretions Beta1 receptors 34 Selective Sympathomimetics Located in the heart Increase heart rate Increase force of contractions Beta2 receptors Located in the bronchi Bronchodilation 35 Nonselective Sympathomimetics Stimulate All adrenergic receptors Epinephrine Used in cardiac arrest and asthma Alpha1 and beta2 receptors Pseudoephedrine Oral nasal decongestant 36 Nonselective Sympathomimetics Stimulate Beta1 and beta2 receptors 5

6 Isoproterenol Increases rate, force, and conduction speed of heart More autonomic-related side effects Adrenergic Blockers Primarily used to treat hypertension Most widely prescribed class of autonomic drugs Inhibit sympathetic nervous system Produce same response as parasympathomimetics Most widely used class of autonomic drugs Used to treat hypertension 40 Adrenergic Blockers Alpha1 Blockers Relax vascular smooth muscle Causes vasodilation Decreases blood pressure Treat hypertension Doxazosin (Cardura) 41 Adrenergic Blockers Beta1 Blockers Beta1 receptors found only in heart Slow heart rate and lower blood pressure Cardioselective Atenolol (Tenormin) 42 Adrenergic Blockers Some Beta Blockers Block Both Beta1 and Beta2 Receptors Nonselective Used to treat Hypertension 43 Adrenergic Blockers Angina Cardiac arrhythmias More side effects Propranolol (Inderal) 6

7 44 45 Review The nurse recognizes that which of the following drugs is contraindicated in patients with glaucoma? 46 Review Alpha1-adrenergic blockers cause what to occur in the body? 47 Review How would a person who is engaging in stressful or energetic activity benefit from the sympathetic effects of bronchodilation, slowed GI motility, and pupil dilation? 48 Review Why do the sympathomimetics produce many of the same symptoms as the anticholinergics? 49 Review Both parasympathomimetics and adrenergic blockers produce similar actions. Why are the adrenergic blockers used to treat hypertension, but the parasympathomimetics not used for this purpose? 7