Final answer:
The brain regulates sexual behavior primarily through neurotransmitters, with the endocrine system and specifically the hypothalamus and pituitary gland playing major roles. Sex hormones like testosterone and estrogen, secreted from the gonads, are also crucial in controlling sexual functions and behaviors.
Step-by-step explanation:
In humans and animals, the brain controls and regulates sexual behavior chiefly through neurotransmitters. The endocrine system plays a significant role in this process, with the hypothalamus acting as a link between the nervous system and the endocrine system. The hypothalamus regulates the secretion of hormones from the pituitary gland, which in turn controls the release of other hormones, including sex hormones like testosterone and estrogen from the gonads. These sex hormones are responsible for controlling sexual motivation and behavior.
Testosterone is the primary male sex hormone influencing the development of male secondary sexual characteristics and sperm production. Estrogen, along with progesterone in females, controls the development of female secondary sexual characteristics and is involved in reproductive cycles. Both hormones contribute to sexual behavior and motivation but the involvement of various neurotransmitters and their interaction with the hormones make the regulation of sexual behavior in humans and animals a complex system.