The substance diffusing into circulation from sympathetic nerve terminals when they are active. The term was introduced by W.B. Cannon, who thought that this substance differed from the mediator produced by the nerve ending (now known to be incorrect); the mediator itself (norepinephrine) diffuses into circulation. SYN: sympathetic hormone.
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sym·pa·thin 'sim-pə-thən n a substance (as norepinephrine) that is secreted by sympathetic nerve endings and acts as a chemical mediator
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n.
the name given by early physiologists to the substances released from sympathetic nerve endings, now known to be a mixture of adrenaline and noradrenaline.
Medical dictionary. 2011.