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Autonomic Nervous System

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Physiology 3120
Tom Stavraky

Human Physiology Monday, November 30, 2009 “ANS II” Autonomic Nervous System • Isoproterenol = manufactured adrenergic agonist • Goal of drug companies is to manufacture specific agonists/antagonists to specific receptors and receptor subtypes  Alpha-adrenergic receptors can be excitatory (vasodilation) or inhibitory (iris dilation, intestinal relaxation)  Beta-adrenergic receptors can be excitatory (heart acceleration) or inhibitory (bronchodilatation) • Adrenal medulla secretes nor/epinephrine (80% epi; has a greater effect on heart because heart has beta receptors, which respond to epinephrine much more strongly than norepi) • Anaphylactic shock  2 classic symptoms  Decrease in blood pressure (can lead to breathing)  Bronchial constriction (trouble breathing)  These effects are controlled by beta receptors, which are more responsive to epi, so give epi to counter anaphylactic shock • Sympathetic/parasympathetic “tone”  Basal rate of neuron discharge (about 1 AP per few seconds; can reach about 20 APs/sec); much lower “tone” than those of the somatic NS  Allows a single system to increase & decrease activity of stimulated organ  For arterioles, increased discharge causes vasoconstriction, and decreased discharge causes vasodilation • Enteric nervous system  Arose early in evolution  Two neural plexuses that are contained within the wall of the gut  Has reflex arcs that control gastric motor & secretory activity  Complex activity; multiple behavioural states (i.e. activity is different during eating & fasting)  Can function by itself, but is “tuned up” or regulated by the ANS  Synaptic structure  Some connections resemble the NMJ, but has many varicosities (i.e. think of a snake who’s eaten a bunch of golf balls) from which transmitters are released  Adrenergic varicosities • NE often associated with ATP; ATP acts on a purinergic receptor, and produces
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