Title: Reproductive behavior: Sexuality and physiology
1 Reproductive behavior Sexuality and physiology
Neuromodulators or autacoids
Hormones act on receptors
Amino acid-based hormones
Peptides and polypeptide proteins
Steroids from cholesterol
3 Sex hormones
Sex hormones are steroids
In addition to acting on surface receptors steroids are fat-soluble and can enter cells to bind with internal receptors even in the nucleus
Secreted by gonads and adrenal cortex triggered by hypothalamus via the pituitary
4 Estrogens and androgens
Gonads and adrenal cortex of both genders secrete both The difference is in the relative amounts
Testosterone and estradiol
Anterior pituitary Gonadotropins and ACTH
Posterior pituitary ADH and oxytocin
5 Hypothalamic control
Hypothalamus controls posterior pituitary through neurohormones released from axon terminals in PP
Hypothalamus controls anterior pituitary through releasing hormones secreted into a portal vein system.
6 Sexual effects of hormones
7 Hormones in sexual development
Primordial gonads or fetal gonadal anlage are hermaphroditic Medulla becomes testes cortex becomes ovaries.
SRY gene on Y chromosome causes H-Y antigen to be synthesized leading to development of medulla.
8 Reproductive tracts
Mullerian and Wolffian tissue develop under hormonal control
Testosterone triggers Wolffian development MIS inhibits Mullerian development
Mullerian tissue develops by default unless MIS is present
9 Other differentiation effects
The external genitals develop in two different pathways from the same tissue influenced by testosterone
Some brain structures develop different sizes or activity levels
Hypothalamus corpus callosum anterior commissure thalamus planum temporale
Temporal lobe and limbic system (more active in men) cingulate gyrus (more active in women)
10 Brain effects of hormones
During early development testosterone affects the hypothalamus by turning off the cycling pattern of gonadotropin release.
Testosterone acts on brain cells only after it is aromatized inside cells to estradiol which then masculinizes the cells.
11 More on brain effects
Estradiol in the mothers blood is kept from the rat fetus by being bound by alpha fetoprotein in humans by the placental barrier.
Synthetic estrogens like DES can cross the placental barrier causing some masculinization in female children.
12 Sexual effects of hormones
13 Behavioral effects of hormones
In animal studies perinatal testosterone treatment and ovariectomy leads to masculine sexual patterns (mounting) when testosterone is added at maturity.
When injected with progesterone and estradiol they showed less female sexual response (lordosis).
14 Sexual effects of hormones
15 Hormones and puberty
Timing by the hypothalamus SCN
Anterior pituitary and growth hormone
Gonadotropic and adrenocorticotropic hormones trigger greater increases in either androgens or estrogens but both are secreted in increased amounts by both genders eg. androstenedione
16 Exceptional development
Androgen Insensitivity Syndrome
No receptors for androgens
Insufficient cortisol to inhibit adrenal androgen
17 Sexual effects of hormones
18 Hormones and adults
Male sexual capacity and behavior relate to testosterone levels
Castration reduces sex drive and potency
Replacement testosterone increases sex drive and potency in men with a testosterone deficiency castrati and elderly
Healthy males are unaffected by additional testosterone. They already have plenty.
19 Sexual hormones in adult females
Sexual hormones do control the estrus cycle which is related to sexual activity and the menstrual cycle which is not.
Ovariectomy does not reduce sex drive if the consequent lack of lubrication is compensated.
Sexual interest appears to be controlled by testosterone.
20 Other hormone effects
Social-cognitive functioning (Macrae et al. 2002)
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