sympathetic nervous system (adrenergic) Flashcards
the sympathetic nervous system (adrenergic) is stimulated by…
physical or emotional stress
physiological responses when the SNS is activated include
- increased HR, arterial blood pressure, and cardiac output
- increased blood glucose (breakdown of muscle glycogen prn)
- increased mental activity/clear thinking
- pupil dilation
- increased rate of cellular metabolism
- increased blood flow to brain, heart, and skeletal muscle
- relaxation of smooth muscle of urinary bladder
what are the 3 primary adrenergic neurotransmitters
- norepinephrine
- epinephrine (adrenaline)
- dopamine
norepinephrine, epinephrine, and dopamine are all…
endogenous “catecholamines”
define catecholamines
- neurotransmitters when they are produced in the sympathetic nervous system and brain, and circulating hormones when synthesized in the adrenal medulla
- can produce a sympathomimetic response
describe sympathomimetic
mimics the sympathetic system
where is norepinephrine synthesized?
adrenergic nerve endings (released when nerve endings are stimulated)
describe the action of norepinephrine
- intense/brief/most → reuptake for reuse
- does its job quickly in the sympathetic nervous system, then gets put away for later
what drugs prevent the reuptake of norepinephrine
cocaine and tricyclic antidepressants
what enzymes assist with reuptake and metabolism of norepinephrine and epinephrine
- monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) metabolize remaining portion in tissue and bloodstream (via liver)
- effects of epinephrine last longer
what is required in the diet to produce norepinephrine?
- tyrosine
- found in dairy, cheese, beef, soybeans, nuts, and eggs
where is epinephrine produced?
produced by both adrenal glands and a small number or neurons in the medulla oblongata where it acts as a neurotransmitter involved in regulating visceral functions (e.g. respiration)
describe how epinephrine is an important emergency medication
- strengthens myocardial contraction and used in the treatment of anaphylaxis
- in anaphylaxis (narrowing of the airway) it causes veins to constrict (pump more blood) and relaxes the respiratory muscles
where is dopamine found and how does it act?
- found in brain, blood vessels of the kidneys, and other viscera
- acts on the BP and HR
- pleasure/rewards system and attention/problem solving in frontal lobe
- affects are dose dependent
low dose dopamine is used to treat…
- acute renal failure
- increases renal blood flow
what is a higher dose of dopamine used for?
increase blood pressure
dopamine can be used to treat:
- hypotension
- shock
- myocardial infarction
- trauma
- renal failure
where are Alpha1 receptors located
located primarily in smooth muscle in blood vessels, GI and GU tracts
what happens when Alpha1 receptors are stimulated
- production of muscle contraction / vasoconstriction / mydriasis (dilated pupils)
- gastrointestinal/bladder sphincter contraction (urinary retention)
-
what happens when Alpha1 receptors are inhibited
- relax vascular smooth muscle / cause vasodilation
- decrease BP and treat BPH
where are alpha2 receptors located
located in the brain and pancreatic B cells
what happens when alpha2 receptors are stimulated
- inhibits norepinephrine → have antiadrenergic effect
- inhibits insulin release
what happens when alpha2 receptors are inhibited?
- stimulates norepinephrine - have adrenergic effect
- stimulates insulin release
where are beta1 receptors located
primarily in cardiac cells
what happens when beta1 receptors are stimulated
increase HR and force of contraction
what happens when beta1 receptors are inhibited
- decrease HR and force of contraction
- “beta adrenergic blockers” (BP medication) work to lower BP and control heart rate by blocking these receptors
beta adrenergic blockers are used in the treatment of…
- HTN
- dysrhythmias
- HF
- MI
- narrow angle glaucoma
where are beta2 receptors located
located primarily in smooth muscle of the lungs/skeletal/detrusor and uterine muscles
what happens when beta2 receptors are stimulated
relaxation of smooth muscles of the lungs = bronchodilation
what happens when beta2 receptors are inhibited
bronchoconstriction
what receptor is the site of action for respiratory and asthma medications
beta2 receptors
name the adrenergic drug classifications
- adrenergic
- sympathomimetic / adrenergic agonist
- sympatholytic / adrenergic antagonist
- adrenergic blocker
- alpha 1 and 2 receptor (selective vs nonselective)
- beta 1 and 2 receptor (selective vs nonselective)
what drugs mimic the effect of norepinephrine
- sympathomimetics
- adrenergic agonists
what drugs block the effects of norepinephrine
- sympatholytics
- adrenergic blockers AKA adrenergic antagonists
sympathomimetic treatment based on receptor site activation
Alpha1
Tx of nasal congestion, hypotension, cause dilation of pupils (for glaucoma)
sympathomimetic treatment based on receptor site activation
alpha2
Tx of hypertension (inhibits norepinephrine, decreases BP)
sympathomimetic treatment based on receptor site activation
Beta1
tx of cardiac arrest, HF, shock
sympathomimetic treatment based on receptor site activation
beta2
tx of asthma and premature labor contractions
explain the difference between selective and nonselective medications
selective medications
- act on a specific receptor site
- induces the normally occurring action of the receptor site
- less side effects
nonselective medications
- act on more than one type of receptor site
- more broad range of effects
- more side effects
Describe phenylephrine
- stimulates A1 to constrict
- increases BP
- common in allergy, decongestant preparations bc it constricts nasal vessels to decrease congestion
what should you monitor when giving low dose dopamine
urine output (bc its a renal dose)
what should you monitor when giving a high dose of dopamine
monitor BP (bc its a cardiac dose)
what receptors does norepinephrine stimulate
A1, A2, and B1
what should you be concerned about when a pt is hypertensive and is given an epi pen
epi pens are nonselective and can cause BP issues when used with hypertension
what is epinephrine used for
- allergic reaction/anaphylaxis
- ACLS medication
describe midodrine
- alpha adrenergic agonist
- for treatment of orthostatic hypotension
describe albuterol
- selective B2 adrenergic agonist
- bronchodilation
describe isoproterenol
-nonselective B1 and B2 adrenergic agonist
- increased HR (B1) and bronchodilation (B2)
- not safe for pts with tachycardia or hypertension
name some side effects of sympathomimetics
- tachycardia, dysrhythmias, chest pain
- HTN
- CNS excitement, nervousness, restlessness
- dry mouth
- N/V
- HA
- dysuria
what are some nursing concerns related to the sympathomimetic side effect…
tachycardia, dysrhythmias, CP
- VS
- telemetry
- nitrates (med that treats CP - potent vasodilators)
what are some nursing concerns related to the sympathomimetic side effect…
HTN
- VS
- low sodium diet
- renal function
- fluid intake
what are some nursing concerns related to the sympathomimetic side effect…
CNS excitement, nervousness, restlessness
relaxation techniques
what are some nursing concerns related to the sympathomimetic side effect…
dry mouth
- fluid provision
- oral hygiene
- ice chips
what are some nursing concerns related to the sympathomimetic side effect…
nausea and vomiting
- ginger ale
- antiemetic
- fluid volume status (careful of dehydration)
what are some nursing concerns related to the sympathomimetic side effect…
headache
- lighting
- quiet environment
- pain meds
what are some nursing concerns related to the sympathomimetic side effect…
dysuria
- I&O
- urine assessment
- increase fluids to flush (if not on fluid restriction)
what are some contraindications/cautions r/t sympathomimetics
- pheochromocytoma
- tachy-arrhythmias
- CV disease/PVD
- thyroid disease
- hypovolemia
- renal or hepatic impairment
- drug interactions
describe pheochromocytoma
a rare neoplasm that secrets catecholamines and is usually found in the adrenal medulla
what are the signs/symptoms and treatment of pheochromocytoma
- Sx: HTN, headache, heart palpitations, sweating
- Tx: medication and often times surgery
describe tachy-arrhythmias
fast, irregular heart rhythms
how can thyroid disease contraindicate sympathomimetics
- hyperthyroid
- the thyroid hormone increases target cell responsiveness to catecholamines
how can hypovolemia contraindicate sympthaomimetics
vasoconstrict a vascular system with no blood volume
what types of drugs do sympathomimetics interact with
- TCAs: impairs reuptake of norepinephrine
- MAOIs: inhibits liver metabolism or norepi/epi
- herbals
- OTCs
