Autonomic Nervous System 1. Function of the Autonomic Nervous System 2.
The Autonomic Nervous System (Ch 13). Two Major Divisions of the Nervous System Central Nervous...
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Transcript of The Autonomic Nervous System (Ch 13). Two Major Divisions of the Nervous System Central Nervous...
The Autonomic Nervous System (Ch 13)
Two Major Divisions of the Nervous System
Central Nervous System (CNS) Brain and spinal cord
Peripheral Nervous System all nervous tissue outside the CNS, including
sensory and motor neurons
Basic Functions of the Nervous System
Recognizing changes in Internal environment External environment
Processing and integrating environmental changes
Reacting to environmental changes by producing and action or response
Figure 13.1 Functional divisions of the peripheral nervous system.
Divisions of the Peripheral Nervous System
Somatic nervous system Voluntary control over skeletal muscles
Autonomic nervous system Involuntary control over smooth and cardiac muscle
and glands
Autonomic Nervous System:Sympathetic Nervous System
Activated under stressFight-or-flight responseReady the body for an immediate response
to a potential threat
Autonomic Nervous System: Parasympathetic Nervous System
Activated under nonstressful conditionsRest-and-digest responseDigestive processes promoted, heart rate
and blood pressure decline
Autonomic Nervous System: Sympathetic and Parasympathetic Divisions
Branches produce mostly opposite effectsHomeostasis – proper balance of the two
branches achieved by changing one or both branches
Branches do not always produce opposite effects
Figure 13.2 Effects of the sympathetic and parasympathetic nervous systems. Source: Biology Guide to the Natural World, 2nd ed (p. 558) by David Krogh, 2002 Upper Saddle River, NJ, Prentice Hall. Reprinted by permission.
Synaptic Transmission
Synapse – juncture of neuronsConnection of two neurons outside CNS –
ganglionic synapse Preganglionic neuron Postganglionic neuron
Many drugs affect autonomic function by altering neurotransmitter activity at the second synapse
Five Mechanisms by Which Drugs Can Affect Synaptic Transmission
1. Affect the synthesis of the neurotransmitter in the presynaptic nerve
2. Prevent storage of the neurotransmitter in vesicles within the presynaptic nerve
3. Influence release of the neurotransmitter from the presynaptic nerve
4. Prevent the normal destruction or reuptake of the neurotransmitter
5. Bind to the receptor site on the postsynaptic target tissue
Drugs Not Given to Correct Autonomic Nervous System
System is relatively free of diseaseDrugs used to stimulate or inhibit target
organs of the autonomic nervous system
Figure 13.3 Basic structure of the autonomic pathway.
Figure 13.4 Receptors in the autonomic nervous system: (a) sympathetic division; (b) parasympathetic division
Primary Neurotransmitters of Autonomic Nervous System
Norepinephrine (NE)Acetylcholine (Ach)
Norepinephrine
Released by most postganglionic nervesClass of agents called natural
catecholamines, all involved in neurotransmission
Adrenergic receptors - receptors at the ends of postganglionic sympathetic neurons
Two Types of Adrenergic Receptors
Alpha-receptors and Beta-receptorsHugely important to pharmacologyDrugs are selective and activate only one
type of adrenergic receptor, whereas others affect all receptor subtypes
Alpha1-adrenergic Receptors
In all sympathetic target organs except heart
Response Constriction of blood vessels Dilation of pupils
Alpha2-adrenergic Receptors
At presynaptic adrenergic neuron terminalsActivation inhibits release of
norepinephrine
Beta1-adrenergic Receptors
In heart and kidneysResponse
Activation increases heart rate and force of contraction of heart.
Increases release of renin
Beta2-adrenergic Receptors
In all sympathetic target organs except the heart
Inhibit smooth muscle
Prototype Drug: Phenylephrine (Neo-Synephrine)
Prototype Drug: Phenylephrine (Neo-Synephrine)
Norepinephrine (NE) is synthesized
In the nerve terminalRequires the amino acids phenylalanine and
tyrosineConversion of dopamine to norepinephrineNE in nerve terminal may be returned to
vesicles for future use, or destroyed enzymatically by monoamine oxidase
Adrenal Medulla
Anatomic and physiologic arrangement much different from rest of sympathetic branch
Other types of adrenergic receptors
Dopamine serves a larger role as a neurotransmitter
Acetylcholine
Released by cholinergic nervesTwo types cholinergic receptors
Muscarinic receptors Nicotinic receptors
Nicotinic Receptors
In sympathetic and parasympathetic divisions at the ganglionic synapse
Response Stimulate smooth muscle Stimulate gland secretion
Muscarinic Receptors
In parasympathetic target organs except the heart Response
Stimulate smooth muscle Stimulate gland secretion
In heart: decreased heart rate and force of contraction
Physiology of Acetylcholine
Affords several mechanisms by which drugs may act
Synthesized in presynaptic nerve terminal from choline and acetyl coenzyme A
Ach in the synaptic cleft is rapidly destroyed by the enzyme acetylcholinesterase (AchE)
Classification and Naming of Autonomic Drugs
Based on four possible actions of sympathetic and parasympathetic nervous systems
Stimulate sympathetic nervous system Adrenergic agents or sympathomimetics
Inhibit sympathetic nervous system Adrenergic-blocking agents, adrenergic antagonists,
or sympatholytics
Classification and Naming of Autonomic Drugs (cont'd)
Stimulate parasympathetic nervous system Cholinergic agents or parasympathomimetics
Inhibit parasympathetic nervous system Cholinergic-blocking agents, anticholinergics,
parasympatholytics, or muscarinic blockers
One of Four Drug Classes is Most Important to Learn
If the fight-or-flight actions of the sympathomimetics are learned, the other three groups can be deduced
Mastering the actions and terminology of autonomic drugs early will pay dividends later
Role of Nurse
Monitor patient’s conditionProvide education on drug therapyNote adverse effects of drug therapyIdentify possible interactionsIdentify contraindications of drug therapy
Sympathomimetic
Monitor vital signs, urinary and cardiac output as appropriate
Monitor breathing patternsObserve patient’s responsiveness to lightMonitor for rhinorrhea and epistaxis
Nursing Process Focus: Patients Receiving Adrenergic (Sympathomimetic Therapy)
Nursing Process Focus: Patients Receiving Adrenergic (Sympathomimetic Therapy)
Nursing Process Focus: Patients Receiving Adrenergic (Sympathomimetic Therapy)
Nursing Process Focus: Patients Receiving Adrenergic (Sympathomimetic Therapy)
Anticholinergics
Monitor for signs of anticholinergic crisisReport changes in heart rate, blood
pressure, or development of dysrhythmiasProvide comfort measures for dry mouth
Anticholinergic (cont'd)
Minimize exposure to heat or cold or strenuous exercise
Monitor intake and outputMonitor patient for abdominal distension,
and auscultate for bowel sounds
Nursing Process Focus: Patients Receiving Anticholinergic Therapy
Nursing Process Focus: Patients Receiving Anticholinergic Therapy
Nursing Process Focus: Patients Receiving Anticholinergic Therapy
Nursing Process Focus: Patients Receiving Anticholinergic Therapy
Adrenergic Blockers
Monitor urinary hesitancy, incomplete bladder emptying, interrupted urinary stream
Monitor vital signs, level of consciousness, and mood
Monitor for dizziness, drowsiness, or light-headedness
Observe for side effectsMonitor cardiac output
Nursing Process Focus: Patients Receiving Adrenergic-Blocker Therapy
Nursing Process Focus: Patients Receiving Adrenergic-Blocker Therapy
Nursing Process Focus: Patients Receiving Adrenergic-Blocker Therapy
Nursing Process Focus: Patients Receiving Adrenergic-Blocker Therapy
Parasympathomimetics
Monitor for adverse effectsMonitor liver enzymesCalculate and monitor dosesAssess and monitor for appropriate self-care
administration
Direct Acting
Monitor intake and output ratioMonitor for blurred visionMonitor for orthostatic hypotension
Cholinesterase Inhibitors
Monitor muscle strength and neuromuscular status
Monitor ptosis, diplopia, and chewingSchedule medication around mealtimesSchedule activities to avoid fatigueMonitor for muscle weakness
Nursing Process Focus: Patients Receiving Parasymptathomimetic Therapy
Nursing Process Focus: Patients Receiving Parasymptathomimetic Therapy
Nursing Process Focus: Patients Receiving Parasymptathomimetic Therapy
Nursing Process Focus: Patients Receiving Parasymptathomimetic Therapy
Nursing Process Focus: Patients Receiving Parasymptathomimetic Therapy
Adrenergic Agents (Sympathomimetics)
Prototype drug: phenylephrine (Neo-Synephrine) Mechanism of action: to stimulate the sympathetic
nervous system directly/indirectly produce many of the same responses as the
anticholinergics
Adrenergic Agents (Sympathomimetics) (cont'd)
Primary use: depends on receptors activated Alpha1-receptors: nasal congestion, hypotension,
dilation of pupils for eye examination Alpha2-receptors: hypertension Beta1-receptors: cardiac arrest, heart failure, shock Beta2-receptors: asthma and premature-labor
contractions
Adrenergic Agents (Sympathomimetics) (cont'd)
Adverse effects: tachycardia, hypertension, dysrhythmias, CNS excitation and seizures, dry mouth, nausea and vomiting, anorexia
Adrenergic-Blocking Agents
Prototype drug: prazosin (Minipress)Mechanism of action: to inhibit the
sympathetic nervous systemPrimary use: hypertension, dysrhythmias,
angina, heart failure, benign prostatic hypertrophy, narrow-angle glaucoma
Adverse effects: dizziness, drowsiness, headache, loss of energy and strength, palpitations, dry mouth
Prototype Drug: Prazosin (Minipress)
Adrenergic-Blocking Agents
Primary use of beta blockers is in the treatment of hypertension
Beta-adrenergic antagonists have several other important therapeutic applications angina pectoris Migranes Heart failure
Cholinergic Agents (Parasympathomimetic)
Prototype drug: bethanechol (Urecholine)Mechanism of action: to activate the
parasympathetic nervous system directly/indirectly, induce rest/digest response
Uses: glaucoma, urinary retention, myasthenia gravis, Alzheimer’s disease
Adverse effects: profuse salivation, sweating increased muscle tone, urinary frequency, bradycardia
Prototype Drug: Bethanechol (Duvoid,Urecholine)
Cholinergic Agents (Parasympathomimetic)
Divided into two classes direct acting
bind to cholinergic receptors to produce the rest-and-digest response
indirect acting inhibit the action of AchE
High potential for serious adverse effects
Cholinergic-Blocking Agents
Prototype drug: atropine (Atropair, Atropisol)Mechanism of action: to inhibit the
parasympathetic nervous systemPrimary use: peptic ulcers, irritable bowel
syndrome, mydriasis and cycloplegia during eye examination, bradycardia, preanesthetic, asthma
Adverse effects: tachycardia, CNS stimulation, urinary retention, dry mouth, dry eyes, decreased sweating, photophobia
Prototype Drug: Atropine (Atro-Pen, Atropair,Atropisol)
Prototype Drug: Atropine (Atro-Pen, Atropair,Atropisol)
Drugs Affecting the Autonomic Nervous System
Assessment Potential nursing diagnoses Reason for drug Monitoring vital signs Doing complete health history
Drugs Affecting the Autonomic Nervous System (cont'd)
Cautions and contraindications for drug Allergies Drug history Possible drug interactions Evaluating lab findings Assess for therapeutics effect Watch for adverse effects
Drugs Affecting the Autonomic Nervous System (cont'd)
Nursing Diagnosis Knowledge deficient, related to drug therapy Risk for injury, related to side effect of drug therapy Disturbed sleep pattern
Drugs Affecting the Autonomic Nervous System (cont'd)
Planning Patient will exhibit therapeutic outcome based on
specific drug Patient will demonstrate an understanding of drug’s
activity Patient will accurately describe drug side effects
and precautions Patient will demonstrate proper administration
technique
Drugs Affecting the Autonomic Nervous System (cont'd)
Implementation Administration of drug Observing for adverse effects Patient education/discharge planning Providing additional information as needed to
encourage compliance Doing home-health visits
Drugs Affecting the Autonomic Nervous System (cont'd)
Evaluation Evaluating effectiveness of drug therapy Confirming that patient goals and expected
outcomes have been met
NCLEX-RN ReviewQuestion 1
1. Following administration of an adrenergic (sympathomimetic) drug, the nurse would
assess for which adverse drug effects?
1. Insomnia, nervousness, and hypertension 2. Nausea, vomiting, and hypotension 3. Nervousness, drowsiness, and dyspnea 4. Bronchial dilation, hypotension, and
bradycardia
NCLEX-RN ReviewQuestion 1 – Rationale
Rationale: Adrenergic agonists stimulate the sympathetic nervous system and produce symptoms of the fight-or-flight response. Nausea, vomiting, nervousness, bronchial dilation, and hypertension are potential adverse reactions related to the use of adrenergic agonists. Hypotension is a potential adverse reaction related to the use of adrenergic antagonists.
NCLEX-RN ReviewQuestion 2
2. Adrenergic-blocking (antagonist) drugs may include all of the following adverse reactions except:
1. Bronchodilation 2. Tachycardia 3. Edema 4. Heart failure
NCLEX-RN ReviewQuestion 2 – Rationale
Rationale: Potential adverse reactions associated with the use of adrenergic antagonists include tachycardia, edema, and heart failure. Bronchodilation is associated with the use of adrenergic agonists.
Cognitive Level: AnalysisNursing Process: Assessment Patient Need: Physiological Integrity
NCLEX-RN ReviewQuestion 3
3. Elderly patients taking bethanechol (Urecholine) need to be assessed more frequently because of which of the following side effects?
1. Diaphoresis 2. Hypertension 3. Dizziness 4. Urinary retention
NCLEX-RN ReviewQuestion 3 – Rationale
Rationale: The nurse should monitor elderly patients for episodes of dizziness caused by CNS stimulation from the parasympathomimetic. Diaphoresis and dizziness are potential side effects related to the use of bethanechol. Bethanechol is used to treat nonobstructive urinary retention.
Cognitive Level: ApplicationNursing Process: ImplementationPatient Need: Physiological Integrity
NCLEX-RN ReviewQuestion 4
4. The patient taking benztropine (Cogentin) should be assessed for:
1. Heartburn 2. Constipation 3. Hypothermia 4. Increased gastric motility
NCLEX-RN ReviewQuestion 4 – Rationale
Rationale: Anticholinergic medications slow intestinal motility; therefore, constipation is a potential side effect. Heartburn and hypothermia are not associated with the use of benztropine.
Cognitive Level: ApplicationNursing Process: AssessmentPatient Need: Physiological Integrity
NCLEX-RN ReviewQuestion 5
5. The patient taking tacrine (Cognex) should be observant for which of the following adverse effects that may signal a possible overdose has occurred?
1. Excessive sweating, salivation, and drooling2. Extreme constipation 3. Hypertension and tachycardia 4. Excessively dry eyes and reddened sclera
NCLEX-RN ReviewQuestion 5 – Rationale
Rationale: Overdosage of parasympathomimetics (cholinesterase inhibitors) may produce excessive sweating, drooling, dyspnea, or excessive fatigue. These symptoms should be promptly reported.
Cognitive Level: ComprehensionNursing Process: AssessmentPatient Need: Physiological Integrity