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Autonomic nervous system
• motor system for smooth muscle and glands
• contrasted with somatic system innervating striated (skeletal) muscle
• Autonomic has preganglionic and postganglionic output
Anatomy & Pharmacology
• Parasympathetic, cranio-sacral • ACh (nicotinic and muscarinic) • ganglion near target • Sympathetic, thoraco-lumbar • ACh (nicotinic) then NE • ganglion near spinal cord
Adrenergic
• For NE (adrenergic), all receptors are G-protein-coupled-receptors
• Alpha (vasoconstriction) phenylephrine (Neosynephrine, nasal decongestant) is agonist
• Beta-1 in heart, why beta blockers like propranalol were given for high blood pressure
• Beta-2 bronchioles, why asthma inhalers had epinephrine
Push-Pull vs Unique
• Many targets are "push-pull" like heart • Some are unique like arterioles
(sympathetic only) • -- close in peripheral vascular beds
(make hands cold) • open in muscle (hyperemia).
anatomy
• sympathetic output from lateral horn neuron • -> white ramus -> sympathetic ganglion • -> gray ramus • Simpler for parasympathetic • from brain stem nucleus or lateral horn in
sacral cord • ->parasympathetic ganglion called enteric for
gut.
Enteric nervous system
• Contribution of neural network (plexus) • to circular and longitudinal muscles to
mediate peristalsis. • Parasympathetic allows digestion, • sympathetic puts it on hold. • Atropine blocks muscarinic synapses and is
in anti-diarrhea medications to slow motility.
Beautiful women
• Atropine muscarinic antagonist • Atropa belladonna (beautiful woman) • [deadly nightshade] • SLIDE (Hess, Scientific American, Nov.
1975, p.111) • Women are more beautiful with dilated
pupils
Heart as an example
• Automaticity at SA and AV nodes • (spread from myocardial cell to next
myocardial cell). • Sympathetic speeds heart, • parasympathetic (via vagus, X) slows, • relaxed heart rate is slower than
automatic rate.
Male sexual function
• Furchgott, Ignarro, Mura 1998 Nobel • parasympathetic dilates arterioles in
corpus cavernosum for erection • Sympathetic contributes to ejaculation. • This is too simple
More
• adrenergic (via alpha 1 receptors) contracts smooth muscle,
• cholinergic (via muscarinic receptors) inhibits adrenergic-induced-contraction (resulting in relaxation)
• more than cholinergic and adrenergic, a little mentioned autonomic component, the NANC (nonadrenergic noncholinergic) system, mediates relaxation.
Nitric oxide
• Nitric Oxide (NO) • endothelial nitric oxide synthase (eNOS), • unusual in that it diffuses across
"postsynaptic" membrane • affects guanylyl cyclase (GC) involved in
making cGMP • NO = endothelial derived relaxation factor
(EDRF)
More
• mediator of parasympathetic nervous system's dilation of arterioles in corpus cavernosum.
• Viagra (sildenafil) inhibits the PDE that breaks down cGMP
More
• 2003 Something's gotta give, Jack Nicholson • Viagra contraindicated w/ nitroglycerine. • (also listed in advertisements for ED (erectile
dysfunction) medications because of interaction and resulting low blood pressure)
• People take nitroglycerine for angina (chest pain), and it releases NO (nitric oxide) and relaxes the coronary arteries