ANS Flashcards
Where are preganglionic and postganglionic neurons of SNS located?
Preganglionic: T1-L2/L3, intermediolateral horn of grey matter
Postganglionic: Paravertebral chains, prevertebral ganglia
Are preganglionic vs. postganglionic neurons myelinated or unmyelinated?
Preganglionic- myelinated
Postganglionic- unmyelinated
Where are PSNS preganglionic neurons and postganglionic neurons located?
Preganglionic: Cranial (CN 3,7,9,10) Sacral (S2-4)
Postganglionic: target organs, also ganglia in head and neck
Does SNS or PSNS have long preganglionic neurons and short postganglionic neurons?
PSNS
SNS has short pre and long post
Most organs are innervated by SNS and PSNS.
What are the innervations for the exceptions? (sweat glands, ciliary muscle of the eye, bronchial smooth muscle, and blood vessels)
SNS: sweat glands and blood vessels (muscarinic receptors present)
PSNS: ciliary muscle of the eye and bronchial smooth muscle (B2 receptors present)
Ach binds to _____ receptors, what are the types?
Epi, NE, and dopamine bind to _______ receptors, what are the types?
ACh binds to cholinergic receptors, which are nicotinic (ligand gated) or muscarinic (g-protein coupled)
Epi, NE, and dopamine bind to adrenergic receptors, which are alpha 1-2 and beta 1-3 (**NE does NOT stimulate beta-2)
The adrenal medulla releases ____% epi and _____% norepi
80% epi, 20% norepi
What receptors activate G-alpha-Q? What is the effect?
Alpha-1, M1, and M3
Increased calcium -> contraction/vasoconstriction
What receptors activate G-alpha-I? What are the effects?
Alpha-2, M2
Inhibits adenylate cyclase which DECREASES cAMP (post synaptic) -> contraction!
Presynaptic increases K conductance
What receptors activate G-alpha-S? What are the effects?
Beta 1,2,3
S=Stimulate the activation of adenylate cyclase increasing cAMP
Vasodilates, increases HR and contractility
Alpha-1 effects?
Vascular smooth muscle CONTRACTION Iris contracts, pupil dilates Pilomotor smooth muscle erects hair Prostate/uterus contraction Heart increases force of contraction (not as mjuch as beta-1) Think of Phenylephrine!
Alpha-2 effects?
Platelets aggregate
Presynaptic inhibition of adrenergic/cholinergic transmitter release (decrease BP/HR)
Presynaptic/CNS vasodilation, postsynaptic vasoconstriction
GI relaxation
CNS sedation and analgesia (via decreased SNS outflow from brain stem)
Think of Clonidine!
Beta-1 effects?
Heart- increase force and rate of contraction
Kidney- stimulate renin release (this will increase BP)
Beta-2 effects?
Respiratory, uterine, vascular, GI, GU- relaxation
Mast cells- decrease histamine release
Skeletal muscle- dilation, uptake of K, increased speed of contraction
Liver- glycogenolysis
Pancreas- increase insulin secretion (so you can use the glucose)
Adrenergic nerve- increase release of NE
Beta-3 effects?
Activates lipolysis, thermogenesis
worry about athrosclerosis
D-1 effects?
Smooth muscle- (postsynaptic) dilates renal, mesenteric, coronary, and cerebral blood vessels (decreased afterload)
D-2 effects?
Nerve endings- (presynaptic) modulates transmitter release, increases N/V
All sympathomimetics are derivatives of what?
Beta-phenylethylamine
An amine side chain, hydroxyl group on 3,4 carbons of benzene ring (catechol)
Thus the name catecholamine
Sympathomimetics: MOA
Activation of G-protein couple receptor directly (drug binds to receptor) or indirectly (drug increase NE release from SNS nerves activating the receptor)
G-protein will have downstream effects, usually effecting the amount of intracellular Ca
How are catecholamines vs. non-catecholamines metabolized?
Catecholamines: Reuptake (neuronal, extraneuronal), MAO, COMT, lungs
Non-catecholamines: MAO, urinary excretion
**If someone is on MAOI’s, this will increase the availability of neurotransmitters in the CNS/PNS
What is the selectivity of Phenylephrine vs. Clonidine?
Phenylephrine α1>α2»»>β
Clonidine α2>α1»»>β
These are alpha agonists
What is the selectivity of Norepinephrine vs. Epinephrine?
Norepinephrine* α1=α2; β1»»»>β2
*B2 not innervated
Epinephrine α1=α2; β1=β2
These are mixed alpha/beta agonists
What is the selectivity of Dobutamine, Isoproterenol, and Terbutaline/albuterol?
Dobutamine β1>β2»»α
Isoproterenol β1=β2»»α
Terbutaline/albuterol β2»β1»»α
These are beta-agonists
What is the selectivity of Dopamine vs. Fenoldopam?
Dopamine D1=D2»β»α
Fenoldopam D1»D2
These are dopamine agonists
Epinephrine: route, onset, duration?
Route: subq or IV
Onset: subq 5-10 min, IV 1-2 min
Duration: 5-10 min
Epinephrine: indications?
Bronchial asthma Acute allergic reaction Electromechanical dissociation V fib unresponsive to defib Infusion to increase myocardial contractility (low dose)
Epinephrine dosing?
Resuscitation: bolus dose 10 mcg/kg IV (can start w 2-8 mcg/kg)
Beta-2: 1-2 mcg/min IV
Beta-1: 4-5 mcg/min IV
Alpha and Beta: 10-20 mcg/min IV (over 20 is alpha)
CV effects of Epinephrine?
With moderate doses, SBP increases (B1, A1), DBP decreases (B2), MAP stays the same
α1 - vasoconstriction - ↑ BP, ↑ CVP, ↑ Cardiac work
α2 - negative feedback - ↓ BP
β1 - increased contractility, HR, CO – ↑ BP
β2 - peripheral vasodilation - ↓ BP
Cerebral effects of Epinephrine?
Minimal vasoconstriction of arterioles in cerebral vasculature (increase CBF), coronary vasculature, and pulmonary vasculature
Ocular effects of Epinephrine?
Alpha-1-mydriasis
Alpha 1/2- increase humoral outflow
Beta 1- increase production of aqueous humor (inc intraoccular pressure)
Respiratory effects of Epinephrine?
B2- dilate bronchial tree, decrease release of histamine
A1- reduce mucosal secretion-decongestion
(Note: beta blockers do the OPPOSITE which is why asthmatics can’t handle them)
GI effects of Epinephrine?
A2- decreased secretions
A/B2- decreased peristalsis
A1- blood flow reduced even if BP normal
GU effects of Epinephrine?
A1- renal blood flow REDUCED, contract urethral sphincter
B1-kidney increases renin release
B2- decreases UO, inhibits labor
The kidneys take a big hit! Consider giving a vasodilator
Metabolic effects of Epinephrine?
B2- Increased liver glycogenolysis and insulin release
B3- lipolysis
A2- minorly opposes B2, inhibits insulin release
End result: BG goes up
Prep and dosage of norepinephrine (Levophed)?
For hypotension: 4-16 mcg/min
Mix in 5% glucose solution (to prevent oxidation)
What are the effects of norepinephrine?
Potent alpha and beta-1, but minimal beta-2, leading to intense vasoconstriction (increased BP/MAP), baroreceptors are activated decreasing HR/respiration
Decreased venous return/CO/HR, preload is going up
Bottom line: good for shock/hemorrhaging, but will do a lot of damage if the problem isn’t fixed
How does dopamine work? What is the dose?
Works on all adrenergic receptors (a,b,d) D1 dominates ("renal dose" for peeing more, misleading) 1-3 mcg/kg/min B1 dominates 3-10 mcg/kg/min Alpha dominates over 10 mcg/kg/min
Why is dopamine not as useful with depleted catecholamine stores?
Increases endogenous norepinephrine release
If dopamine PIV infiltrates, dangerous
Inhibitory at carotid bodies, pt may have altered response to hypoxia
Increased intraocular pressure
Yup
Isoproterenol: what are the effects?
B1 and B2 agonists
Increases HR and contractility, decreases SVR
(inc SBP, dec DBP, dec MAP)
Who do you NOT give isoproterenol to?
Someone with a high HR, we decrease O2 delivery and increase demand, therefore setting them up for an MI