*Corresponding author e-mail: ruudbuiis@gmail.com The hypothalamus integrates information from the brain and the body; this activity is essential for survival of the individual (adaptation to the environment) and the species (reproduction). As a result, countless functions are regulated by neuroendocrine and autonomic hypothalamic processes in concert with the appropriate behaviour that is mediated by neuronal influences on other brain areas. Within the hypothalamus de suprachiasmatic nucleus (SCN) imposes its rhythm onto the body via three different routes of communication: l.Via the secretion of hormones; 2. via the parasympathetic and 3.via the sympathetic autonomous nervous system. The SCN uses separate connections via either the sympathetic or via the parasympathetic system not only to prepare the body for the coming change in activity cycle but also to prepare the body and its organs for the hormones that are associated with such change. Herein the SCN is essential to prepare the body for the coming activity and inactivity period by determining the set point of various physiological variables. The hypothesis for our present work is that in view of the role of the SCN in determining these physiological day-night levels the SCN also needs to be informed about the accurate values of these variables. Apart from light, activity and melatonin little is known about the information that is provided to the SCN in order to execute its functions. In this presentation attention will be paid not only to the mechanisms the SCN is using to organize the set point in hormones, glucose, heart rate and temperature but also in how the SCN receives back information about these physiological variables. For example the role of the circumventricular organs in passing circulating information to the SCN will be discussed. In addition the role of the nucleus Tractus Solitarius (NTS) in providing visceral sensory information to the SCN and the role of the SCN in controlling cardiovascular functions is discussed in relation with the post-mortem finding that the activity of the SCN is diminished in people who had a long history of hypertension. Support: CONACyT 79797, DGAPA PAPIIT IN215308-3 UNAM, Mexico Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil
Buijs et al. (Thu,) studied this question.