08 - Autonomic Nervous System 1, Cholinergic System Flashcards
The ANS is the part of the nervous system that regulates ______ muscle, _____ and _____ function.
cardiac/smooth
visceral
gland
The ANS controls _____ functions and reflexes
involuntary
The ANS influences homeostasis of every tissue and organ system using
only 3 substances
The sympathetic nervous system is also known as the
adrenergic system (adrenaline = epinephrine)
The parasympathetic nervous system is also known as the
cholinergic system (acetylcholine)
The principle site of organization of the CNS is found in the
brainstem and hypothalamus
The _____ is the main nerve of the CNS. It transmots sensory input from the ____ and ____ organs
Vagus (CN X)
throracic, abdominal
HR, BP, GI, temp, hunger, thirst, osmolarity, and gland secretions are regulated by the
CNS
Emotional responses (blushing, fainting, anxiety) are controlled by the CNS in the
cortex
limbic system
The peripheral nervous system is the ______ component of the CNS
efferent (motor)
What is the difference between autonomic and somatic nerves?
Autonomic - two neuron unit: 1. myelinated neuron from CNS to ganglion, 2. unmyelinated neuron from ganglion to target organ
Somatic - single myelinated axon with cell body in spinal cord
Both SNS and PNS are
tonically active - have baseline activity that can increase or decrease -> more than one way to accomplish effect
The SNS is also known as the
thoraco-lumbar system
In the SNS, ____ preganglionic fibers originate from the spinal cord at ______ and synapse at the
short
T1-L3
paravertebral sympathetic ganglionic chain
The preganglionic fibers of the SNS can synapse with the postganglionic neuron at the _____ or
same level
course of and down the ganglionic chain and synapse at another level
The paravertebral sympathetic ganglionic chain is
paired
The sympathetic collateral ganglia are
unpaired
Examples of the sympathetic collateral ganglia
celiac plexus
inferior mesenteric plexus
Special paired ganglia of the SNS are formed at _____. Examples?
T1-T4
Superior cervical, middle cervical, stellate
SNS ganglia are closer to the _____ than the
spinal cord
target organ
Some preganglionic fibers of the SNS go directly to _____ where ______ take the place of postganglionic neurons
adrenal gland
adrenal chromaffin cells
Adrenal stimulation releases ____ epi and ____ NE into circulation
80%
20%
Postganglionic fibers of the SNS originate at the sympathetic ganglion and synapse at effector tissues. They travel within
spinal nerves
Postganglionic fibers of the SNS outnumber preganglionic fibers by
20-30:1
Concurrent stimulation of many organs at once = mass sympathetic discharge
Postganglionic fibers of the SNS release ______ at the effector tissues. Exceptions are the
NE
sweat glands - Ach
adrenal medulla - NE + Epi
CNS neurotransmitter
Dopamine
Synthesized/stored in postganglionic neurons and adrenal medulla
Norepinephrine
Synthesized/stored in adrenal medulla
Epinephrine
Phenylalanine -> Tyrosine -*-> DOPA -> DA -> NE -> Epi
- represents
tyrosine hydroxylase - the rate limiting step
NE causes _____ at the point of tyrosine hydroxylase
negative feedback
Almost all endogenous NE undergoes ____ into the presynaptic terminal and is metabolized by
reuptake monoamine oxidase (MAO)
Reuptake of NE is inhibited by
tricyclic antidepressants (TCA) cocaine
Circulating catecholamines (NE + Epi) are metabolized in the ______ by
liver and kidneys
Catechol-O-methyltransferase (COMT)
What is the metabolite of NE and epi? It is used in the diagnosis of
Vanillylmandelic acid
Pheochromocytoma
Systemic catecholamines ____ cross the blood brain barrier
do NOT
Sympathomimetics are
drugs that act like catecholamines but have a different structure
The PNS is also known as the ______. Preganglionic fibers originate in
cranio-sacral system
bainstem or sacral segments (S2-S4) of the spinal cord
The Vagus Nerve (CN X) accounts for ____ of all parasympathetic fibers
> 75%
PNS ganglia are near the
target organ
Unlike the SNS, there is ______ of pre to post ganglionic fibers in the PNS
little divergence (1:1) PNS effects are more discrete and localized
What is released at the effector tissues of the PNS?
Ach
How long does it take Ach to be removed by acetylcholinesterase?
<1 msec
What are the two types of cholinergic receptors?
Nicotinic and muscarinic
but both respond to Ach
Nicotinic (n-Ach-r) receptors are found on cell bodies of
all postganglionic neurons
within ganglia of both SNS and PNS
Ach (nicotine) excites
the PNS and SNS
A low dose of Ach ->
adrenal medulla -> Epi, NE -> HTN, tachy
A high dose of Ach ->
ganglionic blocker -> hypotension, weakness
Ach in the NMJ is blocked by
nondepolarizing neuromuscular blocking agents
Muscarinic (m-Ach-r) receptors are found on
cell membranes of effector tissues
Ach (muscarine) will ______ and be ________, depending on the target tissue
mimic the PNS
excitatory or inhibitory
Stimulation of muscarinic receptors on the presynaptic membrane of the SNS nerve terminals
inhibits the release of NE
Anticholinergic drugs act specifically at the
muscarinic receptor
What is a prototype muscarinic blocker that causes sympathomimetic activity?
Atropine
Anticholinergic drugs are ______ that competitively bind to _______ and block activity by Ach
aromatic acid esters
muscarinic receptors
CV effects of anticholinergics
reversing brady due to vagal reflexes
transient slowing of HR at low doses
block vagal activity in SA node
facilitate conduction through AV node
Pulmonary effects of anticholinergics
relaxation of bronchial smooth muscle
Ophthalmic effects of anticholinergics
mydriasis (pupillary dilation)
GU effects of anticholinergics
urinary retention
Which anticholinergic is the first choice for bradyarrhthmias? It has the side effect of
atropine
tachycardia
Why should atropine be used with caution in CAD?
It causes an increased O2 demand
The inhaled derivative of atropine is called ________. It has minimal systemic absorption due to its
ipratropium (atrovent)
quaternary ammonium structure
Does atropine cross the BBB? It can cause
Yes
memory deficits, CNS excitement
central anticholinergic syndrome
usually minimal effect
Central anticholinergic syndrome caused by atropine can be treated with
physostigmine (also crosses the BBB)
What is an antisialagogue?
a substance that prevents the production of saliva
Which anticholinergic is the strongest antisialagogue?
scopalamine
Which anticholinergic is a good premedication for antisialagogue?
Glycopyrrolate
Atropine should be used with CAUTION in
narrow angle glaucoma
benign prostate hyperplasia (BPH)
Usual adult dose of atropine
0.4-.06 mg IV
1-2 mg/kg for total vagal blockade
Duration of action for atropine?
30 min
Scopalamine has ____ CNS effects than atropine
greater: sedation, amnesia
Which anticholinergic is an antiemetic?
scopolamine (patch commonly used for PONV)
Scopalamine should be used with CAUTION in
closed angle glaucoma
Why doesn’t glyco cause CNS/ophthalmic activity?
It does not cross the BBB due to its charged quaternary ammonium structure
Atropine and scopolamine are tertiary amines
The concentration and dose of glycopyrrolate is
half of atropine
Duration of action of glyco?
2-4 hours
Adrenergic receptors are subdivided into
alpha and beta and DA (dopaminergic)
Which adrenergic receptor is the most abundant? Where are they found?
a1
only found on post synaptic membrane
smooth muscles of coronary arteries, skin, uterus, intestines, renal/splanchnic beds
a1 receptors are _____ and cause
excitatory
increased intracellular Ca++
The effect of a1 receptors
vasoconstriction and GI relaxation
cardiac contractility
a2 receptors are ___ that cause
inhibitory
decrease in cAMP
Presynaptic effects of a2 receptors
inhibit NE release -> reduce sympathetic outflow; vasodilation; sedation
Postsynaptic effects of a2 receptors
arterial/venous vasoconstriction, platelet aggrgation, inhibiton of insulin release and gut motility, inhibition of ADH
b receptors cause
increased cAMP
b1 receptors are only
postsynaptic
b1 receptors are found mostly in the ____, causing
heart
increased HR and contractility
renin release
coronary dilation
How does the affinity for epi compare with NE in b1 receptores?
Equal
b2 receptors are primarily ____ and tend to be
postsynaptic
inhibitory
b2 receptors cause
vasodilation
brochodilation
renal vessel relaxation
b2 receptor affinity is greater for
Epi than NE
It is stimulated by circulating epi instead of direct sympathetic activity
Cardiac effects of b2 receptors
increased HR and contractility
Presynaptic b2 receptors cause
accelerated NE release
vasoconstriction
The resting HR of a person who has had a heart transplant is
90-100 bpm
Pt with heart transplants cannot respond to drugs that _____ because
block the parasympathetic system
connections are severed during the transplant
Heart transplant patients do not have
baseline parasympathetic innervation and therefore lack vagal tone
Patients who have had heart transplants need to have adequate intravascular volume because
they lack normal tachycardia and contractility response to hypotension/hypovolemia
What drugs can treat bradycardia in pt with heart transplant?
Isoproterenol and glucagon
They directly affect the heart
Epi/NE may have _______ in pt with heart transplant
exaggerated beta mimetic effects on HR
Increased BP will _____ reflex slowing of HR in pt with heart transplant
not lead to