BIOPSYCH MOD 7

• Sexual differentiation

  Begins with the chromosomes. A female has an XX chromosome pattern and males have an XY
• Early prenatal development

  Males and females start with the same anatomy. Both have Müllerian ducts (precursors to female internal structures) and Wolffian ducts (precursors to male internal structures)
• SRY (sex-determining region on the Y chromosome) gene


  A gene on the Y chromosome responsible for causing the primitive gonads in males to become testes
• Testes


  Sperm-producing organs which produce androgens (male hormone)
• Wolffian ducts


  Precursors of the male reproductive organs that develop into seminal vesicles (sac-like structures that store semen) and the vas deferens (a duct from the testes into the penis) after testosterone exposure during prenatal development
• Müllerian inhibiting hormone (MIH)


  Peptide hormone that degenerates the Müllerian ducts in males
• Testosterone


  Results in the development of the penis and scrotum
• Genetic females (XX)


  More estrogen than androgens are produced and primitive gonads become ovaries (egg-producing organs), her Wolffian ducts degenerate, and her Müllerian ducts develop and mature as long as she is not exposed to large amounts of testosterone
• Steroid hormones


  Like estrogen, contain four carbon rings and are derived from cholesterol. Steroid hormones exert their effects in three ways: 1) They can bind to membrane receptors like protein or peptide hormones, 2) They can enter cells and activate certain kinds of proteins in the cytoplasm, 3) They can bind to chromosomes where they activate or inactivate specific genes
• Androgens


  Chemicals that promote the development of typically masculine features (like facial hair)
• Estrogens


  Chemicals that promote typically female features (like breast development)
• Testosterone


  The most widely known androgen
• Estradiol


  The most prominent type of estrogen. Levels are higher in women than men
• Progesterone


  Another predominantly female hormone. prepares the uterus implantation of a fertilized ovum and promotes the maintenance of pregnancy
• Organizing effects of sex hormones


  Occur mostly during a sensitive stage of development and determine whether the brain and body develop as male or female
• Activating effects of sex hormones


  Are more temporary and happen only while the hormone is present. Activating effects can occur at any time in life
• Sensitive period


  Time early in prenatal development during which a particular event has a long-lasting effect. For example, testosterone controls the development of external genitalia in humans during the third and fourth months of pregnancy
• A genetic male will develop the anatomy and behavior of a female if he is castrated, lacks androgen receptors, or is exposed to substances that block testosterone effects
• Alpha-fetoprotein


  A protein that binds with estrogen and keeps it from entering cells during the early sensitive period (this process prevents females from becoming masculinized by their own estrogen)
• In the medial preoptic area


  Both testosterone itself and estradiol increase the production of a chemical called prostaglandin E2, which leads to an increase in microglia, dendritic spines, and synapses. These expansions make later male sexual behavior possible
• In part of the ventromedial hypothalamus


  Estradiol activates an enzyme called PI3 kinase that increases the release of glutamate from presynaptic neurons, and therefore causes postsynaptic neurons to increase their dendritic branching. This contributes to aggressive and sexual behavior as well as feeding
• Oxytocin


  Stimulates contractions of the uterus during delivery of a baby, and it stimulates the mammary gland to release milk. Sexual pleasure also releases oxytocin, especially at orgasm
• Impotence

  Inability to have an erection (this is usually not caused by low testosterone levels in the body). Impotence can be treated by increasing blood circulation in the penis and hypothalamus
• Women's Estradiol and Related Hormones

  • Menstrual cycle: A periodic variation in hormones and fertility over the course of about 28 days. At the end of the menstrual period, the anterior pituitary releases follicle-stimulating hormone (FSH) that promotes the growth of a follicle in the ovary. Toward the middle of the menstrual cycle, the follicle produces increasing amounts of estradiol (a type of estrogen); this leads to an increased release of FSH and luteinizing hormone (LH) from the anterior pituitary. FSH and LH cause the follicle to release an ovum. Progesterone is released from the remnant of the follicle and prepares the uterus for implantation of a fertilized ovum. At the end of the menstrual cycle, the levels of LH, FSH, estradiol, and progesterone all decline. If the ovum is fertilized, the levels of estradiol and progesterone increase throughout pregnancy. Birth-control pills, such as the combination pill (which contains both estrogen and progesterone), prevent the surge of FSH and LH that would release an ovum. The estrogen-progesterone combination also makes it harder for a sperm to reach the egg and for an egg to be implanted in the uterus
• Periovulatory period

  Midway point of the menstrual cycle when sexual interest increases, possibly due to high estrogen levels
• The hormones associated with fertility move women's mate preferences toward men who look and act more masculine. They also make a woman feel and act sexier (although this might be subconscious)
• Effects of Sex Hormones on Nonsexual Characteristics

  • Well-documented gender difference in ability to recognize facial expressions of emotion. Women receiving testosterone injections became less accurate at recognizing facial expressions of anger. Increased testosterone decreased women's ability to infer a person's mood from watching their eyes
• Prolactin

  Necessary for milk production. Enables mother to eat more than usual. Responsible for some maternal behavior
• Vasopressin

  Hormone synthesized by the hypothalamus. Secreted by the posterior pituitary gland. Associated with social behavior in many species. Facilitates olfactory recognition
• Correlation exists between father's hormones and level of interaction with their child. Fathers with lowest testosterone and prolactin levels spent most time playing with and caring for child
• Later stages of maternal behavior in rodents are not dependent on hormones. Rat mothers have shown tendencies to adopt and nurture baby rats after a few days of being in their presence (after she has become familiar with their smell, as the babies' pheromone elicit an aggressive reaction)
• In humans, hormonal changes are not necessary for parental behavior; hence, the successful adoption of children
• Evolutionary Interpretations of Mating Behavior


  People vary in frequency of sexual behavior, preferred types of sexual activity, and sexual orientation. Evolutionary explanations are controversial in explaining mating behavior
• Darwin's theory of evolution


  Individuals whose genes help them survive and reproduce will pass on more of their genes to future generations
• Olfactory recognition


  • Facilitates olfactory recognition
• Father's hormones


  Level of interaction with their child
• Fathers with lowest testosterone and prolactin levels spent most time playing with and caring for child
• Later stages of maternal behavior in rodents are not dependent on hormones
• Rat mothers have shown tendencies to adopt and nurture baby rats after a few days of being in their presence (after she has become familiar with their smell, as the babies' pheromone elicit an aggressive reaction)
• Mating behavior


  Frequency of sexual behavior, preferred types of sexual activity, and sexual orientation