Fig. 1

Sex differences in peripheral influences on the central nervous system. The CNS is embedded in a sexually differentiated body that is embedded in an environment, which may interact with the body in a manner that varies by sex . This diagram represents interactions between the central nervous system and sex differences elsewhere in the body that are discussed in this paper; other interactions undoubtedly occur. Solid arrows indicate a sex influence from one organ on another. Dashed arrows indicate an influence inferred from circumstantial evidence, but not yet demonstrated. Black arrows indicate neural communication; red arrows indicate humoral communication. “XX XY” indicates organs in which sex chromosome complement has a demonstrated effect; in most cases, it is not known whether the effect is mediated within that organ or indirectly via effects on other organs. The small colored circles in the upper right are the many species of microorganisms living commensally in our gut or on our skin