Sympathetic-adrenal-medullary system

Two major neuro-endocrine systems have been associated with stress. The first one is associated with acute stressful states such as fear, anger and excitement (Amkraut and Solomon 1975) and is called the sympathetic-adrenal-medullary system (SAM). SAM activation has been associated with action proneness and raised effort and it has also been described as the fight or flight system . It is activated when the organism is challenged in its control of the environment, and is accompanied by the release of catecholamines (epinephrine and norepinephrine) into the bloodstream. Catecholamine output is increased in response to a challenge to perform well (Frankenhaeuser et al. 1980 Lundberg and Frankenhaeuser 1980). 

Psychological stress may influence the immune system by activation of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic-adrenal-medullary axis (SAM). The well-described innervation of primary and secondary lymphoid tissues by the autonomic nervous system also has been implicated in stress-related modulation of the immune response. These pathways operate by producing biological mediators that interact with and affect cellular components of the immune system.13... 

The sympathetic adrenal medullary (SAM) system with the secretion of the catecholamines epinephrine and norepinephrine (or adrenaline and noradrenaline) has been of particular interest in the study of stress. 

Two PNS neurotransmitters, acetylchohne and norepinephrine, have particular chnical importance. Both are synthesized and stored primarily in the nerve terminals until released by a nerve impulse. It should be noted, to avoid confusion, that in the United States the transmitter in the sympathetic nervous system is referred to as norepinephrine and the major adrenal medullary hormone is referred to as epinephrine. In Europe and most of the world these two substances are called noradrenaline and adrenaline, respectively. 

General activation of the sympathetic system during stress, fear, or anxiety is accompanied by increased secretion of adrenal medullary hormones, which consist primarily of epinephrine in the human. The secretory activity of the adrenal medulla is regulated by the CNS. 

Sympathetic Nervous Function, Disorders of Adrenal Medullary Function, and Genetic Disorders of Catecholamine Systems... 

The hormones of (he adrenal glands are essential for survival. The adrenal cortex is the source of the two important steroid hormones, aldosterone and cortisol (Fig. 1). The adrenal medulla is embryologically and histologically distinct from the cortex anil is part of the sympathetic nervous system. Medullary cells synthesize, store and secrete adrenaline, along with noradrenaline and dopamine. The adrenal medullary hormones arc discussed further on pages 126-127. 

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