• Your brain on sex

• Oxytocin
• Vasopressin
• Melatonin
• Adrenocorticotropic hormone (ACTH)

• Oxytocin
• Vasopressin
• Melatonin
• Adrenocorticotropic hormone (ACTH)

• Midbrain.
• Sympathetic nervous system.
• Adrenal medulla.
• Hypothalamus.

• Midbrain.
• Sympathetic nervous system.
• Adrenal medulla.
• Hypothalamus.

• Organizing effects
  • Influence sexual development
• Activating effects
  • Influence sexual behavior
• But sexuality in humans is complex

• Promiscuity (both -> multiple)
• Polyandry (female -> multiple males)
• Polygyny (male -> multiple females)
• Monogamy

• Primates: 1/2 promiscuous (e.g., chimps); 1/3 polygynous (e.g., gorillas)

• outward signs of estrous (i.e. higher body temperature, breast swelling, sugar cravings, etc.) less obvious
• copulate throughout the reproductive cycle, not just at estrous
• after ejaculation/orgasm in males and females, oxytocin release has sedative effect
• sex in multiple positions
• couples live in large social groups

• large relative size of testes, ejaculate volume, and sperm count vs. most primates;
• spend more time in copulation & copulate with greater frequency than other primates

• Biology isn’t "destiny""
• “Natural” doesn’t mean morally right
• Human behavior shaped by biology AND culture

http://www.thevisualmd.com/read_videoguide.php?id_url=1033607627

• Before orgasm
  • Amygdala, fusiform gyrus deactivation
• During orgasm
  • Cerebellar activation
  • Lateral orbitofrontal cortex deactivates
  • Deactivation of amygdala, hippocampus
  • Periaqueductal grey (PAG) activates in men

Consistent with previous findings (14, 15), our analysis of the structure of the human brain, which included most regions of gray and white matter, as well as measures of connectivity, revealed many nondimorphic group-level sex/gender differences in brain structure. There was extensive overlap of the distributions of females and males for all brain regions and connections assessed, irrespective of the type of sample, measure, or analysis (including analysis of absolute brain volumes)…

(Joel et al. 2015)

This extensive overlap undermines any attempt to distinguish between a “male” and a “female” form for specific brain features…

(Joel et al. 2015)

Sex differences are of high scientific and societal interest because of their prominence in behavior of humans and nonhuman species. This work is highly significant because it studies a very large population of 949 youths (8–22 y, 428 males and 521 females) using the diffusion-based structural connectome of the brain, identifying novel sex differences. The results establish that male brains are optimized for intrahemispheric and female brains for interhemispheric communication…

(Ingalhalikar et al. 2014)

The developmental trajectories of males and females separate at a young age, demonstrating wide differences during adolescence and adulthood. The observations suggest that male brains are structured to facilitate connectivity between perception and coordinated action, whereas female brains are designed to facilitate communication between analytical and intuitive processing modes.

(Ingalhalikar et al. 2014)

• Sexually dimorphic nucleus of the hypothalamus
  • Dimorphic means two forms
• Males >> females
• Controls male sexual behavior

• Sleep and circadian rhythms