<Li> Blood - borne stimuli, including leptin, ghrelin, angiotensin, insulin, pituitary hormones, cytokines, plasma concentrations of glucose and osmolarity etc . </Li> <Li> Invading microorganisms by increasing body temperature, resetting the body's thermostat upward . </Li> <P> Olfactory stimuli are important for sexual reproduction and neuroendocrine function in many species . For instance if a pregnant mouse is exposed to the urine of a' strange' male during a critical period after coitus then the pregnancy fails (the Bruce effect). Thus, during coitus, a female mouse forms a precise' olfactory memory' of her partner that persists for several days . Pheromonal cues aid synchronization of oestrus in many species; in women, synchronized menstruation may also arise from pheromonal cues, although the role of pheromones in humans is disputed . </P> <P> Peptide hormones have important influences upon the hypothalamus, and to do so they must pass through the blood--brain barrier . The hypothalamus is bounded in part by specialized brain regions that lack an effective blood--brain barrier; the capillary endothelium at these sites is fenestrated to allow free passage of even large proteins and other molecules . Some of these sites are the sites of neurosecretion - the neurohypophysis and the median eminence . However, others are sites at which the brain samples the composition of the blood . Two of these sites, the SFO (subfornical organ) and the OVLT (organum vasculosum of the lamina terminalis) are so - called circumventricular organs, where neurons are in intimate contact with both blood and CSF . These structures are densely vascularized, and contain osmoreceptive and sodium - receptive neurons that control drinking, vasopressin release, sodium excretion, and sodium appetite . They also contain neurons with receptors for angiotensin, atrial natriuretic factor, endothelin and relaxin, each of which important in the regulation of fluid and electrolyte balance . Neurons in the OVLT and SFO project to the supraoptic nucleus and paraventricular nucleus, and also to preoptic hypothalamic areas . The circumventricular organs may also be the site of action of interleukins to elicit both fever and ACTH secretion, via effects on paraventricular neurons . </P>

The part of the cns that contains the hypothalamus is which of the following