Sex on the Brain by Dr Jack Lewis

Hypothalamus’s PVN (red) prepares the body for sex by sending a torrent of electrical messages along neurons within the spinal cord which ultimately releases a cocktail of neurotransmitters into the genitals. In both men and women this leads to vasocongestion whereby the genitals become engorged with blood – leading to an erection in men and lubrication, increase in vaginal depth and diameter in women.

Lust, Love & Long-Term Bonding by Dr Jack

Behaviours associated with lust, love and long-term bonding developed through evolution of separate but overlapping brain systems. Lust encourages coitus on a relatively indiscriminate basis: ensuring that genes are passed on to the next generation. Love involves a sexual preference for an individual considered in some way superior to the competition. And long-term bonding encourages fulfilment of parenting duties.