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The Nervous System
Central Nervous System
Peripheral Nervous SystemSomatic Nervous System
Autonomic Nervous System
DIV IS IONS OF NERVOU S
SYSTEM
The Central Nervous
System
(CNS)Consists of the brain and spinal cord
Regulates body functions
Interprets information sent by the
peripheral nervous system (PNS ) and
then sends stimuli back to the PNS
Peripheral Nervous System
Somatic NS acts on skeletal muscles
to produce locomotion & respiration
Autonomic NS visceral system;
controls and regulates functioning of the
heart, respiratory system, digestive
system & glands
Sympathetic nervous system
Parasympathetic nervous system
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Features of Autonomic Nervous System
2 neuron system
Synaptic transmission
Synapse - space between neurons or between
neuron and its target organ
Presence of Ganglion/ganglia
Ganglia collection of nerve cell bodies outside
CNS
Comparison of SNS and PSNS
SYMPATHETIC PARASYMPATHETIC
Origin of
fibers
Thoracolumbar Craniosacral
Length of
fiber
Preganglionic: short
Postganglionic:long
Long
Short
Receptors Alpha, beta,
dopamine
Muscarinic,
Nicotinic
NT NE, EPI, dopamine Acetylcholine
Responses
General
Fight, flight, fright Rest and digest
Receptors
1. Nicotinic receptors are located on thecell bodies of all postganglionicneurons of the PSNS and SNS (&adrenal medulla)
2. Muscarinic receptors are located in allorgans regulated by the PSNS
3. Adrenergic receptors are located in allorgans regulated by SNS except sweatglands
Neurotransmitters
1. All preganglionic neurons of the PSNS andSNS release ACh as their transmitter.
2. All postganglionic neurons of the PSNSrelease ACh as their transmitter.
3. Most postganglionic neurons of the SNSrelease NE
4. EPI is the principal transmitter released by
adrenal medulla5. All motor neurons to skeletal muscles
realese ACh as their transmitter
The Sympathetic NS
Fight or flight response the bear
prepares the body for stress by
increasing metabolism, diverting blood to
larger muscles and increasing cardiacand respiratory functions
The Parasympathetic NS
Rest and digest response increases
digestion, absorption and slows
metabolism to save energy the pig
SNS vs. PNS Effects on Tissues
SNS Effects
Dilates pupils
Relaxes smooth
muscles of the GIT
Dilates bronchioles
Increases heart rate
Constrict blood
vessel
Relaxes bladder &
uterine muscle
PNS Effects
Constricts pupils
Increases peristalsis
Constricts
bronchioles &
increases secretions
Decreases heart
rate
Dilates blood
vessels
Increases salivation
Sympathetic Nervous System
Also called theadrenergic system (adrenaline)
The neurotransmitter isnorepinephrine Drugs thatmimicthe effects of norepinephrine are the
adrenergics, sympathomimeticsor ad renomim etics
Because they initiate a response they are calledadrenergicagonists
Drugs whichblock the SNS are calledsympatholyticsor adrenolytics, anti-adrenergicsand thealpha andbeta adrenergicblockers; because they b lock aresponse, they areadrenergicantagonists
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Parasympathetic Nervous System
Also called the cholinergic system
The neurotransmitter is acetylcholine
Parasympathomimetics , cholinomimetics andcholinergics stimulate the PNS
Called cholinergic agonists because theyinitiate a cholinergic response
Parasympatholytics, anticholinergics andcholinergic blocking drugs inhibit the PNS;
called cholinergic antagonists because theyblock a response
Comparison of SNS & PNS Drugs
Sympathetic
Response the bear
Agonist
Sympathomimetics
Adrenergic drugs
Antagonist
Sympatholytics
Adrenergic blockers
Parasympathetic
Response the pig
Agonist
Parasympathomimetic
Cholinergic drugs
Antagonist
Parasympatholytic
Anticholinergic drugs
Cholinergic blockers
Functions of Peripheral Adrenergic Receptor
Alpha 1 Eye Mydriasis
Arterioles Constriction
Sex organ, male EjaculationBladder neck, prostatic capsule Contraction
Alpha 2 Presynaptic nerve terminal Blocks NE release
Beta 1 Heart +Inotropic,Chronotr
opic, dromotropic
Kidney Renin release
Beta 2 Arterioles Dilation
Bronchi Dilation
Uterus Relaxation
Liver Glycogenolysis
Adrenergic Drugs: Review
Act on adrenergic receptor sites on the cells ofsmooth muscles
Adrenergic receptorsAlpha1 vasoconstriction; increases cardiac
contraction; mydriasis, bladder neck and prostaticcapsule contraction
Alpha2 inhibits norepinephrine, dilates bloodvessels; decreases GIT tone & motility
Beta1 increases rate & force of cardiac contraction;increases renal secretion of renin, increasing BP
Beta2 dilates bronchioles ; glycogenolysis;increases skeletal muscle blood flow; GIT/uterinerelaxation
Catecholamines
The chemical structures of a substance,
either endogenous or synthetic, that can
produce a sympathomimetic response
Endogenous
Dopamine, epinephrine & norepinephrine
Synthetic
isoproterenol, dobutamine
Indications of Adrenergic Drugs
Emergency drugs inotropic drugs, vasopressors
Cardiac arrest, hypotension, heart failure
Asthma, URT congestion bronchodilation,vasoconstriction
Allergies, bleeding vasoconstriction Hypoglycemia glucogenolysis
Obstetric use stops premature labor
Eye disorders causes pupil dilation
Not for patients with glaucoma
Used with local anesthetics vasoconstriction
Alpha and beta adrenergic agonists
Dobutamine
Dopamine
Ephedrine
Epinephrine
Metaraminol
Norepinephrine
Adrenergic Drug: Epinephrine
Epinephrine (Adrenaline Cl) acts indirectly bystimulating release of norepinephrine whichacts directly on adrenergic receptor sites
Can be given IV, IM, topical, inhalation or SQ
Used to fight anaphylaxis ; rapid onset of actionPotent inotropic drug ; may reduce renal
perfusionNurses must monitor vital signs carefully
and watch for rapid heart rate, dizzinessand increased blood pressure; ECGmonitoring
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Beta specific adrenergicadrenergic agonists
Albuterol
Bitolterol
Isoetharine
Isoproterenol
Salmeterol
Terbutaline
Metaproterenol
Isoproterenol HCl (Isuprel)
Bronchodilation & increase in heart rate
Can cause severe tachycardia
Often used to treat asthma
Albuterol (Proventil, Ventolin)
Produces rapid bronchodilation
Used to treat bronchospasms
SE: tachycardia, tremors, restlessness,
nervousness
Caution : taken with mono amineoxidase inhibitors (MAOI), may cause
hypertensive crisis
Alpha specific adrenergic agonists
Clonidine
Midrodrine
Phenylephrine
Clonidine (Catapres) &Methyldopa (Aldomet)
Alpha2 adrenergic drugs
Treats hypertension by regulating /
inhibiting the release of norepinephrine
May cause cardiovascular depression by
stimulating alpha2 receptors in the CNS
SE: tachycardia, palpitations,
dysrrhythmia, n/v, urinary difficulty,
tremors, dizziness
Nursing Responsibilities
Frequent VS monitoring
Check urinary output , bladder distention
Check for IV infiltration. Norepinephrine & dopaminemay cause tissue necrosis . Antidote is Phentolaminemesylate (Regitine)
Take with food to prevent N/V.
Monitor labs may increase glucose level Glycogenolysis
Read OTC labels: cold medicines, diet pills
Rebound nasal congestion may occur.
DO NOT give to nursing mothers.
Adrenergic Blockers
Blocks the effects of neurotransmitters
Alpha blockers cause a decrease in blood
pressure, orthostatic hypotensionBeta blockers decrease heart rate and force of
cardiac contraction, cause bronchoconstriction
Used in HTN, PVD, Raynaud s disease,
dysrhythmias
Monitor HR, BP
Use with caution in patients with COPD
Adrenergic Blockers
Alpha 1 blockers
Prazosin HCl (Minipress), Doxazosin HCl (Cardura),Terazosin HCl (Hytrin)
Alpha 1, Beta 1 & 2 blockersCarvedilol (Coreg), Labetalol (Trandate)
Beta 1 blockers
Metoprolol tartrate (Lopressor), Atenolol (Tenormin)
Beta 1 & 2 blockers
Propanolol (Inderal), Nadolol (Corgard)
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Nursing Responsibilities
VS monitoring; ECG for baseline
Assess for respiratory problems
Observe for and prevent orthostatic
hypotension
Advise clients to avoid abruptly stopping
a beta -blocker & to monitor blood sugarDose -related changes in male sexual
function may occur
Cholinergic Drugs
Cholinergic stimulants, cholinergic agonists,parasympathomimetics - they mimic acetylcholine
Stimulate the PNS. Major action is to stimulate bladderand GI tone, constrict pupils (miosis) and increaseneuromuscular transmissions to receptor sites
Acetylcholine (ACh) neurotansmitter located at theganglions and parasympathetic nerve endings
Two cholinergic receptors:
Muscarinic receptors stimulate smooth muscle(eye, GIT, urinary system) and slow heart rate
Nicotinic receptors - affect skeletal muscle
Acetylcholine (ACh) &Cholinesterase (ChE)
Acetylcholine (ACh) - neurotransmitter
Cholinesterase (ChE) promotes breakdown
of ACh
Cholinesterase destroys acetylcholine.More cholinesterase, less acetylcholine
available.
Inhibit cholinesterase, more acetylcholineavailable.
Direct -acting Cholinergics
Bethanecol (Urecholine ) increases
urination
Metoclopramide HCl (Reglan) treats
gastro -esophageal reflux disease
(GERD) by increasing gastric emptyingtime
Pilocarpine causes miosis; used in
treating glaucoma
Bethanechol Cl (Urecholine)
Treats urinary retention and abdominal distention ;promotes micturition and increases peristalsis in theGIT
Poorly absorbed in the GIT. Given on empty stomach.
Voiding occurs 30 minutes 1 hrs after poadministration and 15 minutes after SC
SE: N/V, hypotension, bradycardia ,
diarrhea, salivation, sweating, flushing,
frequent urination, rash, miosis, blurred vision
Contraindication: intestinal or urinary tract obstruction,asthma
Reversible Cholinesterase Inhibitors
Produces miosis to treat glaucoma
Increases muscle strength in myasthenia
gravisNeostigmine (Prostigmine ), Pyridostigmine bromide
(Mestinon ), Edrophonium Cl (Tensilon )
CAUTION : bradycardia , asthma, PUD,
hyperthyroidism
CONTRAINDICATION: intestinal / urinary tract
obstruction
Nursing Responsibilities
Assess urine output, bowel & breath sounds
Assess for asthma, PUD, urinary & intestinalobstruction
Monitor BP, pulse orthostatic hypotension
Give 1 hour ac or 2 hours pc
Check serum lipase, amylase
Cholinergic overdose: sweating, salivation,flush, abdominal cramps
Antidote: Atropine sulfate (0.6mg)
Anticholinergics
Parasympatholytics, cholinergic blockingagents
They inhibit the actions of acetylcholine
Major responses are to decrease GI motilityand salivation , to dilate pupils and to increasepulse rate; may cause decreased bladdercontraction
Used to treat the early stages of Parkinson sdisease and to decrease tremors and rigidity &to decrease salivation and drooling
CONTRAINDICATION: Glaucoma
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Atropine sulfate
Derived from the belladonna plant
Vagolytic inhibits vagal stiumulation
Used as a pre -op med, anti -spasmodic,treatment of bradycardia; for mydriasis &cycloplegia
Give IV undiluted or with 10 cc sterile water at0.6 mg/min
SE: dry mouth, decreased perspiration, blurred
vision, tachycardia, constipation, urinaryretention
Anticholinergic Drugs
Belladona
Hyoscyamine sulfate
Scopolamine hydrobromide
Patch used for prevention of n/v amongadults with motion sickness
Antiparkinson - AnticholinergicDrugs
Used to treat the early stages of Parkinson sdisease and to decrease tremors and rigidity &
to decrease salivation and drooling
Used in the treatment of pseudoparkinsonismin psychotropic drugs
Trihexyphenidyl HCl (Artane)
Biperiden HCl (Akineton)
Benztropine mesylate (Cogentin)
Nursing Responsibilities
Assess PR, UO, bowel sounds
Encourage void before taking medication
Maintain adequate fluid intake
Encourage to eat foods high in fiber
Encourage activity. Avoid hot environment.
Oral care. Ice chips. Hard candy.
Avoid caffeine, alcohol, cigarettes, aspirinbefore bedtime
Safety precautions drowsiness is common