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Ch 5 Sex Hormones.docx

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Psychology 2075
Corey Isaacs

Sex Hormones 10/25/2012 10:33:00 AM Chapter 5 Sex Hormones  Prenatal period – the time from conception to birth  Hypothalamus – a small region of the brain that is important in regulating many body functions, including the functioning of the sex hormones  Pituitary gland – also known as the master gland, a small endocrine gland located on the lower side of the brain below the hypothalamus o Important in regulating levels of sex hormones  Hormones – chemical substances secreted by the endocrine glands into the bloodstream o Androgens – the group of male sex hormones o Testosterone – a hormone secreted by the testes in the male, and also present in lower levels in females o Estrogens – the group of female sex hormones o Progesterone – a female sex hormone secreted by the ovaries  Gonads – testes and ovaries  Sex hormone system in males o The pituitary produces several hormones, two important ones include:  Follicle-stimulating hormone (FSH) – stimulates the follicle development in females and sperm production in males  Luteinizing hormone (LH) – regulates estrogen secretion and ovum development in the female and testosterone in the male  Gonadotropin-releasing hormone – secreted by the hypothalamus to regulate the pituitary’s secretion of FSH and LH o HPG axis – hypothalamus-pituitary-gonad axis, the negative feedback loop that regulates sex hormone production o Inhibin – a substance secreted by the testes and ovaries that regulates FSH levels (produced by Sertoli cells)  Sex hormones in females o Levels of estrogen and progesterone fluctuate according to the phases of the menstrual cycle o Operates along a similar negative feedback loop as males – hypothalamus, pituitary and ovaries o Prolactin – simulates production of milk by the mammary gland after a woman has given birth, produced by the pituitary o Oxytocin – stimulates ejection of that milk from the nipple, also produced by the pituitary  The menstrual cycle o Humans have menstrual cycles while other species of mammals have estrous cycles, differences include:  Estrous cycles don’t involve much bleeding, only slight spotting  Ovulation only occurs while the animal is in heat, or while they have slight spotting, where the menstrual cycle occurs between periods of menstruation  Animals can only engage in sexual activity when they are in heat o Phases of the menstrual cycle  Follicular phase (proliferative phase) – beginning just after menstruation, during which an egg matures in preparation for menstruation  Ovulation – release of an egg from the ovaries  Luteal phase (secretory phase) – after releasing the egg, the follicle turns into a glandular mass of cells (corpus luteum)  Menstruation – shedding of the inner lining of the uterus, the endometrium o Length and time of the cycle  Anywhere from 20 to 36 days is considered normal with an average of about 28 days  There is enormous variation from woman to woman  Four phases and timing:  Menstruation – days 1 to 4/5  Follicular phase – day 5 to 13  Ovulation – occurs day 14  Luteal phase – day 15 to the end of the cycle  Luteal phase is fairly constant from woman to woman  The day from ovulation to menstruation is always 14 days o Mittelschmerz – middle pain, when a woman can feel herself ovulate o Anovulatory cycle – absence of ovulation, it does not occur in every cycle o Menstrual problems:  Dysmenorrhea – painful menstruation, caused by:  Prostaglandins – chemicals secreted by the uterus that cause the uterine muscles to contract  Endometriosis – a condition in which the endometrium grows abnormally outside the uterus
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