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last updated:

April 9, 2021
  

[Brain Image]    

PSY 340 Brain and Behavior

Class 23: Sex and Hormones

   

  

March 17, 2005: The human X chromosome has been fully decoded and the results published in the journal, Nature. The "X" chromosome, one of the two sex chromosomes, is a DNA sequence of ca. 1.5 million base-pairs  ca. 154 million base-pairs coding for ca. 800 proteins in every cell in the human body (vs. ca. 59 million base-pairs in the "Y" chromosome coding for ca. 70 proteins). The sexes are differentiated by the presence of two X chromosomes in females and an X and Y chromosome in males.

 
How are women and men different over and above the obvious physical differences?

Are there real differences between the sexes? If so, why?



[Sexual
            Differentiation]A. Becoming male or female (that is, sexual differentiation)

Development in males
Development in females

Actions of
            HormonesHormones: Androgens & Estrogens

steroid
                hormones

B. Organizing Effects of Sex Hormones

Organizing Effects -> Causes permanent structural differences to develop gradually in the body. Usually happens during "sensitive" periods in development of the fetus and newborn infant. However, sex hormones also have organizing effects at puberty, e.g. development of female breasts or male facial hair.

Activating Effects -> Causes temporary behavior to occur over seconds, minutes, hours, or days following exposure to hormone(s). Some such effects can be emotional arousal during pregnancy, aggressive behaviors, heightened sexual receptivity, etc.

We have already seen the organizing effect of sex hormones above in the initial development of the sexual organs. What about the continuing organizing effects during pregnancy?


   1. Sex Differences in the Hypothalamus

SDN
        POA AH
Males
Females

   2. Sex Differences in Childhood Behavior

C. Activating Effects of Sex Hormones in Humans

1. Sexual Behavior in Humans

In males

[menstrual cycle]In females: the menstrual cycle

  Interactive effects of hypothalamus and pituitary gland

Sex Hormones & Nonsexual Characteristics

Male-Femail Brain Connectivity

D. Parental Behavior

Rat Pups[Pups]1. Behavior in Mammals

2. Human Parental Caregiving (this is not in text but required)



References

Armstrong, K. (2019, February). Janet Shibley Hyde sinks stereotypes with data. APS Observer. Retrieved from https://www.psychologicalscience.org/observer/janet-shibley-hyde-sinks-stereotypes-with-data

Daniel, S., Balalian, A. A., Insel, B. J. et al. (2020) Prenatal and early childhood exposure to phthalates and childhood behavior at age 7 years. Environment International, 143. https://doi.org/10.1016/j.envint.2020.105894

Dickerson, L. M., Mazyck, P. J., & Hunter, M. H. (2003, April 15). Premenstrual syndrome [Online]. American Family Physician, 67, 1743-1752.

Feldman, R. (2007). Parent-infant synchrony: Biological foundations and developmental options. Current Directions in Psychological Science, 16(6), 340-345.

Feldman, R. (2015). The adaptive parental brain: Implications for children’s social development. Trends in Neurosciences, 38(6), 387-399.

Feldman, R. (2016). The neurobiology of mammalian parenting and the biosocial context of human caregiving. Hormones and Behavior, 77, 3-17. doi: 10.1016/j.yhbeh.2015.10.001

Gorski, R. (1986). Sexual differentiation of the brain: A model for drug-induced alterations of the reproductive system. Environmental Health Perspectives, 70, 163-175.

Hofman, M. A., & Swaab, D. F. (1989). The sexually dimorphic nucleus of the preoptic area in the human brain: a comparative morphometric study. Journal of Anatomy, 164, 55-72.

Joel, D., et al (2015) Sex beyond the genitalia: The human brain mosaic. PNAS, 112(50), 15468-15473. doi: 10.1073/pnas.1509654112

KiM, P., Strathearn, L, & Swain, J. E. (2016) The maternal brain and its plasticity in humans. Hormones and Behavior, 77, 113-123 doi: 10.1016/j.yhbeh.2015.08.001

Lee, D.-W., Kim, M.-S., Lim, Y.-H, Lee, N., & Hong, Y.-C. (2018) Prenatal and postnatal exposure to di-(2-ethylhexyl) phthalate and neurodevelopmental outcomes: A systematic review and meta-analysis. Environmental Research, 167, 588-566.

Lilienfeld, S. O., Sauvigné, K. C., Lynn, S. J., Cautlin, R. L., Latzman, R. D., & Waldman, I D. (2015). Fifty psychological and psychiatric terms to avoid: A list of inaccurate, misleading, misued, ambiguous, and logically confused words and phrases. Frontiers in Psychology, 6, Artlcle 1100. doi: 10.3389/fpsyg.2015.01100

Kimura, D. (2002, May 12). Sex differences in the brain [Online] Scientific American [No longer available online]

Montejo, A. L., Montejo, L., & Navarro-Cremades, F. (2015). Sexual side-effects of antidepressant and antipsychotic drugs. Current Opinion in Psychiatry, 28, 418-423. doi: 10.1097/YCO.0000000000000198

Ritchie, S. J., Cox, S. R., ... & Deary, I. J. (2017). Sex differences in the adult human brain: Evidence from 5,216 UK Biobank participants. Retrieved from bioRxiv. http://dx.doi.org/10.1101/123729

Swaab, D. F., & Fliers, E. (1985). A sexually dimorphic nucleus in the human brain. Science, 228(4703), 1112-1115. https://dx.doi.org/10.1126/science.3992248

Swan, S. H. & Colino, S. (2020). Count down: How our modern world is altering male and female reproductive development, threatening sperm counts, and imperiling the future of the human race. New York, NY: Scribner.

Swan, S. H., Liu, F., et al. (2009) Prenatal phthalate exposure and reduced masculine play in boys. International Journal of Andrology, 33(2), 259-269. https://10.1111/j.1365-2605.2009.01019.x

 
This page was first posted March 20, 2005.