Autonomic Nervous System Flashcards
What part of the autonomic NS responds to stress?
Sympathetic nervous system
What part of the ANS sustains homeostasis during periods of rest?
Parasympathetic nervous system
What part of the autonomic nervous system increases CO, bronchiolar dilation, and dilated pupils?
Sympathetic nervous system
The sympathetic nervous system comes from this region of the spinal cord.
Thoracolumbar region
The parasympathetic nervous system exits what part of the nervous system?
level of the brain, or sacral spinal cord
Blood vessels are directly innervated by ____ NS, but NOT directly innervated by ____ NS.
sympathetic; parasympathetic
The adrenal medulla acts just like a ____ ganglion because it is innervated by preganglionic fiber and the adrenal medulla releases compounds directly into the blood stream.
Sympathetic ganglion
Sympathetic physiology does what to heart rate, contractility, CO, blood pressure, blood flow to muscles, respiration, pupil size, blood glucose?
Increases it all!!!
What part of ANS has very short postganglionic fibers?
PSNS
Parasympathetic physiology does what to heart rate, pupil size, peristalsis and GI secretions, glucose stoarge in liver, and urinary bladder activity (micturition)?
PSNS decreases heart rate and pupil size; and increases peristalsis/GI secretions, glucose storage in liver, and micturition.
What NT do cholinergic synapses use?
Acetylcholine
Adrenergic receptors use what NT?
Norepinephrine
Sympathetic outflow uses what two kind of synapses?
1st = cholinergic; 2nd = adrenergic
Parasympathetic outflow uses what two kind of synapses?
Both are cholinergic
Describe neurohumoral transmission:
Presynaptic terminal depolarizes –> opens voltage gated Ca2+ channels –> calcium enters presynaptic terminal –> calcium allows vesicles to fuse with presynaptic membrane –> NT gets dumped into the cleft –> NTs bind to corresponding receptors on the postsynaptic membrane
List three catecholamines:
Norepinephrine; Dopamine; Epinephrine
How does epinephrine get synthesized (start from beginning)
Phenylalanine –> tyrosine –> DOPA –> dopamine –> norepinephrine –> epinephrine
What role does alpha-methylparatyrosine play in the synthesis of catecholamines?
It faciliatates the making of DOPA from tyrosine. Without it, concentrations of dopamine AND NE would go down.
List the NTs that bind to alpha receptors, ordered preferentially.
Epi > norepi»_space; isoproterenol; (very high affinity for Epi and NE)
List the NTs that bind to beta receptors, ordered preferentially.
Isoproterenol > epi > NE (very low affinity for NE)
Because alpha receptors have a high affinity for NE and beta receptors have a low affinity for NE; NE is mostly a/an _____ agonist (beta or alpha)?
Alpha agonist (however also beta in the heart)
Because Epi can bind well with alpha and beta receptors; epi is considered a _____ agonist.
mixed agonist
What is the most efficient way to get NE out of the cleft?
Take it back up into the presynapti terminal –> usually repackaged back into granules and can be recycled in this way
What is MAO (monoamine oxidase)?
Enzyme that breaks down NTs to terminate adrenergic transmission.
What will cocaine do to adrenergic transmission?
Cocaine will inhibit neuronal uptake of NE back into presynaptic terminal –> cocaine will increase NE
What will reserpine do to adrenergic transmission?
Reserpine will inhibit the uptake of NE back into these granules (it can still be taken back up into presynaptic terminals, but stays in cytoplasm) –> decreases NE because it won’t be taken back up into granules which are needed for NE to be secreted into the cleft
Monoamine oxidase inhibitors increases or decreases NE in the cleft?
Increases NE in the cleft.
Adrenergic Receptors –> alpha 1s
These are excitatory and result in contraction of vascular smooth muscle, stimulate iris dilator muscle, stimulate GI sphincters and bladder sphincters. The end result is vasoconstriction, mydriasis, sphincter constriction.
Alpha 1 adrenergic receptor NTs:
Epi > norepi»_space; isoproteronol
Adrenergic Receptors –> alpha 2s
These are presynaptic and inhibit NE release.
Adrenergic receptors –> beta-1s
Excitatory to the heart, resulting in increased cardiac function. Inhibitory to detrusor muscle, resulting in relaxation of the bladder. These receptors are positive ionotropes, chornotrops and create faster cardiac implusles.
Adrenergic receptors –> beta-1 NTs:
Iso > epi > NE
Adrenergic receptors –> beta-2s
Inhibitory –> resulting in relaxation and dilation.
Affects vascular smooth muscle, bronchiolar smooth muscle, and GI smooth muscle.
These receptors are also presynaptic - modulates NE release (stimulatory). The end result of adrenergic receptors are bronchodilation, blood vessel dilation, and GI smooth muscle relaxation.
Adrenergic Pharmacology = ____ Pharmacology
Sympathetic nervous system
Sympathomimetics
evoke responses similar to Epi and NE to increase sympathoadrenal discharge; activate (directly or indirectly) adrenergic receptors on effector cells (smooth muscle); many are chemically similar to endogenous compounds (catechoalmines and noncatecholamines)
Antiadrenergics
block effects of sympathetic NS on the body
_____ are direct-acting sympathomimetic amines that activate receptors whether or not presynaptic terminal is present.
Catecholamines
Dobutamine works on what adrenergic receptor, and has _____ cardioselectivity.
Beta-1; ionotropic
Isoproteronol is a ___ agonist and is a synthetic.
beta
NE is an alpha agonist that stimulates a presser response. What is a pressor response?
vasoconstriction/increase in blood pressure
Isoproterenol is mostly a ___ agonist.
beta
Effects of NE via IV
Remember that NE is an alpha agonist. It will cause global vasoconstriction and increase peripheral resistance. There is a large increase in blood pressure - this tells the brain to tell the heart to decrease HR; and this decrease in HR will override the increase in HR due to NE itself. You may also see increase in contractility int he heart.
Does NE change cardiac output?
NO, but it has a huge effect on vasculature
Effects of Epi via IV
Remember that epinephrine is a mixed agonist working on alpha receptors and beta receptors. Epi binds to central alpha receptors to cause vasoconstriction viscerally, increasing peripheral blood flow to muscles. Blood pressure increases. Contractility increases, HR increases and CO increases.
Why does CO increase with epinephrine but not norepinephrine?
The baroreceptors don’t override epinehprine’s increase in blood pressure because it is not as high as with norepinephrine, which is a strict alpha agonist.
Effect of isoproterenol
Remember that isoproterenol is a beta agonist. It will result in an increase in blood flow to both the muscles and viscera. Resistance and blood pressure falls (depressor effect). Increases HR and CO.
Effects of Catecholamines on Blood pressure: Epi vs NE
NE –> body wide vasoconstriction leading to increased BP;
Epi –> BP increases with vasocinstrition and myocardial stimulation; however a small constant infusion can lead to regional vasodilation (beta mediated) and decreased blood pressure; tachydardia due to acting on beta-1s; you can get a depressor response following a pressor response due to activation of beta-2s
Effects of catecholamines on vascular smooth muscle: cutaneous, mucosal, renal, and mesenteric arteries:
vasoconstriction - alpha receptors
Effects of catecholamines on vascular smooth muscle: in skeletal muscle? NE vs Epi
NE = constriction (alpha); Small amount of epi = dilation (beta2); large amount of epi = constriction (alpha); Isoproterenol = dilation
Effects of catecholamines on vascular smooth muscle: coronary arteries
dilation (beta receptors predominate
Effects of catecholamines on vascular smooth muscle: cerebral arteries
these arteries act independently of peripheral stimulation
Effects of Catechoalmines: Myocardium
Increased function; beta1s –> increased contractile force, increased rate, increased work and oxygen sometimes; often get bradycardia (decreased HR) during peak pressor response because of baroreceptor reflex which will inhibit sympathetics