(Stress hormone)

Energy burned in combating stress

Sodium uptake (luminal epithelia)

Blood pressure elevation

► Antiinflammatory effects

Cell death t

^ prolonged

Reduced immune function Stress induced diabetes Elevated blood pressure

FIGURE 10-7 Pathways activated by stress. Abbreviations: +, stimulates; —, inhibits; CRH, corticotropic releasing hormone; ACTH, adrenocorticotropic hormone; /3-LTH, /3-lipotropin; GR, glucocorticoid receptor; PRL, prolactin; ACh, acetylcholine; *, ACTH is a growth factor for cells of the adrenal cortex, especially the zona fasciculata cells; **, Cortisol is also released through a rhythmic pathway under the control of a serotonergic neuron. In this 24-hr biorhythm, Cortisol secretion is highest in the morning; thus, Cortisol is secreted by an endogenous pathway that does not rely on stress. The secretion of Cortisol can be increased greatly by stress, as shown here through the humoral pathway, whereas the secretion of aldosterone is largely a stress response.

When the organism becomes immobile or passive, the adrenocortical axis is preferentially activated. This is discussed in detail by Henry (1993).

The catecholamines will be considered in-depth in Chapter 11, but are presented in outline form here because stress reactions involve both glucocorticoids and catecholamines. Figure 10-7 shows three pathways, including a dual pathway responding to stress: the neural pathway and the humoral pathway generating Cortisol. It is important to emphasize that these two pathways are sometimes operating together, but they can also be dissociated especially when the individual is confronted with an emotionally stressful situation and copes on different levels. This concept is elaborated in Figure 10-8. The sympathetic adre-nomedullary pathway is activated when a fight or flight response is issued to a specific challenge. On the other hand, the humoral pathway, ending in Cortisol release from the adrenal gland, is operative when the individual becomes immobile, passive, and depressed

Threat to control

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