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Lecture 6

Lecture 6 - Sexual Behaviour

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Ayesha Khan

PSY290H5S – Introduction to Physiological Psychology Lecture 6 – July 31, 2013 Sexual Behaviour Outline: - Hormones - Genes and the Gonads - Hormones and sexual development - Puberty - Hormones and sexual behaviour - Sexual orientation 3 Major Classes of Hormones - Steroid - Peptide - Amino Acid Types of Steroid Hormones - Adrenal Cortical Hormones - Sex Hormones o Testosterone o Estradiol o Progesterone More on Steroid Hormones - Synthesized from cholesterol - Synthesis primarily occurs in the gonads o Also in the adrenal glands - All steroid hormones are found in both males and females o Amounts vary between the sexes o Amounts also vary within each sex Steroid Hormone Synthesis PSY290H5S – Introduction to Physiological Psychology Lecture 6 – July 31, 2013 Hormone Regulation - Hypothalamic-Pituitary Gonadal (HPG) Axis - Primary location: in the brain through the HPG axis G HPG Axis - Hypothalamus releases hormones, which releases hormones - GnRH = Gonadotropin releasing hormone o Example of a peptide hormone - When it is released from hypothalamus, it travels to the anterior pituitary - LH = leutenizing hormone - FSH – Follicle Stimulating Hormone - Example of protein hormones - Travel from the pituitary gland and released into the blood stream - FEMALES: o FSH: promotes the development of the follicle (egg) o LH: Regulates the menstrual cycle - MALES: o FSH: stimulates sperm production o LH: stimulates testosterone production Steroid Hormone Regulation - Negative feedback is the most common type of regulatory mechanism o Example: thermostat in a home - the brain detects the level and monitors the levels of different hormones - Positive feedback where the presence of estrodile will cause the hypothalamus and pituitary to release o more - Circulating hormones provide feedback to the hypothalamus and pituitary gland o After GnRH, LH and FSH production - Anabolic Steroids o Synthetic versions of testosterone used to build tissue and promote muscle growth  Therapeutic Uses: Osteoporosis, weight loss in cancer or AIDS patients, anemia o If overuse of anabolic steroids: PSY290H5S – Introduction to Physiological Psychology Lecture 6 – July 31, 2013  Testicles can shrink due to the glands detecting hormones in the system, they will reduce their production o Question: How can anabolic steroids alter the HPG axis? o Other health effects: MEN:  Breast development  Balding  Cancer (prostate, liver, and kidney) WOMEN  Heart disease  Cancer (Liver and kidney)  Depression  Body and facial hair growth Genes and the Gonads Genes and the Gonads - Y chromosome was only detected in the 1900s; before they thought that the x chromosome determined the sex - What is it about the Y chromosome that is critical for the development of the male gonads? o Found in most mammals and even in some insects and plants o So we are not unique in terms of the pairing o Sex-determining region Y (SRY) gene that is important that is found on the short “arm” of the chromosome - We have this SRY gene, that is critical to development male characteristics o It was producing a protein called the testis-determining factor o Develops approx. around 6 weeks in he utero o It will have an activational affect of other genes o Later leads to testis development - When there is no SRY, things progress and we have ovary development - How does this lead to male/female sex organs? Differentiation of Sex Organs - Representation of reproductive organs and a fetus - This fetus is undifferentiated at the moment - There are two systems: o Wolddlan duct o Mullerian duct - Male (XY) o In a couple of weeks, it will move the system to have the Wolffian duct to produce testis o SRY and TDG - Female (XX) PSY290H5S – Introduction to Physiological Psychology Lecture 6 – July 31, 2013 o There is no promotion of the WOlffian system and goes to the mullerian system o You have the development of the overies o No SRY/TDF Sex Chromosome Abnormalities - Turner Syndrome (XO) o 1 out of 2,500 births (0.04%) o Normal female external genitalia but ovaries develop abnormally o Normal intelligence, deficits in spatial relationships and memory - Klinefelter Syndrome (XXY) o 1.79 out of 1,000 male births (0.179%) o Male with reduced fertility  Because they do have the Y chromosome, it does the have SRY o Require hormone treatment at puberty to develop secondary sex characteristics and inhibit female characteristics o Normal intelligence but social awkwardness, delayed or reduced verbal skills - XYY o 1 out of 1,000 male births (0.1%) o Subtle physical and behavioral correlates o Controversial association with antisocial behavior o Does not create a “super male” Hormones and Sexual Development Hormones and Development - The presence of androgens and other hormones are critical for the development of male sexual organs - These sergers of testosterome are critical for the development of male reproductive system - Only occurs in males, and not in femals - After this, hormonal activity goes “very quiet” PSY290H5S – Introduction to Physiological Psychology Lecture 6 – July 31, 2013 - The presence of androgens and other hormones are critical for the development of male sexual organs o Testosterone: Promotes the Wolffian system o 5-alpha-dihydrotestosterone: Must be recognized for male external genitalia o Anti-Müllerian Hormone: Initiates the degeneration of the Müllerian system - In females, the development of sexual organs is based on the absence of androgens Differentiation of Sex Organs - Males (XY) o 6 weeks you have TDF o Around 8-12 weeks, you start to have a serge of hormones - Females (XX) o Malarian system develop, and without additional hormones, goes to the female tract Hormones and Development - Following sex organ differentiation, sexual differentiation of the brain happens o Permanent - Thought of as organizing effects of sex steroid - Differences in male/female behaviour can be observed very early in life PSY290H5S – Introduction to Physiological Psychology Lecture 6 – July 31, 2013 o First day of life, girls prefer looking at human faces, boys prefer mechanical mobiles (Connelan et al. 2000) o During the first year, girls will choose dolls while boys will choose toy- cars and balls - Increased levels of testosterone is the main mechanism responsible for gender identity and sexual orientation o Several sexually dimorphic structures o Example: Sexually dimorphic nucleus of the preoptic area (SDN-POA)
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