Cognitive stimuli (stress) activate (the alarm phase of the stress reaction) the direct pathway of the sympathetic nervous system "brain-adrenal medulla" with production of catecholamines (adrelanin and noradrenaline, dopamine).
Cognitive or non-cognitive stimuli (physical agents, bacteria, viruses, toxins, etc.) induce the production of CRH (corticotropin realizing hormone) by the hypothalamus and the immune system (lymphocytes). CRH, in turn, can stimulate the release of ACTH (adrenocoticotropic hormone) from iysis and IL-1 (interleukin-1) from macrophages. IL-1, in turn, can cause an increase in CRH production from the hypothalamus and ACTH from iysis or B lymphocytes (HPA Hypotalamus-Pituitary-Adrenal axis reaction in the resistance phase of the stress reaction). The glucocorticoids, produced by the adrenals, stimulated by the ACTH, and the parasympathetic nervous system "switch off" everything (exhaustion phase of the stress reaction).
