6.6 Hormones, homeostasis and reproduction Hormones are used when signals need to be widely distributed.

Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.

Application: Causes and treatment of Type I and Type II diabetes.

Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature. Q: Why do we iodize our salt?

Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite. Application: Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease.

Melatonin is secreted by the pineal gland to control circadian rhythms. Q: Define circadian rhythm. Q: Explain how levels of melatonin are related to the sleep-wake cycle. Application: Causes of jet lag and use of melatonin to alleviate it.

Q: List three secondary sex characteristics of males. A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone. Q: What combinations of chromosomes are connected to males and females? Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty. Q: About when could you determine if a baby was a male? Justify your answer. Q: List three secondary sex characteristics of males.

Skill: Annotate diagrams of the male and female reproductive system to show names of structures and their functions. Testis – produce sperm and testosterone Scrotum – keep testis below body temperature Epididymis – store sperm until ejaculation Sperm duct – transfer sperm during ejaculation Seminal vesicle and prostate gland – secrete fluids added to sperm to make semen Urethra – transfer semen during ejaculation and urine during urination Penis – penetrate vagina for ejaculation of semen near the cervix

Q: List three secondary sex characteristics of females. Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. Q: List three secondary sex characteristics of females.

Skill: Annotate diagrams of the male and female reproductive system to show names of structures and their functions. Ovary – produce eggs, estrogen, and progesterone Oviduct – collect eggs at ovulation, provide a site for fertilization then move the embryo to uterus Uterus – provides the needs of the embryo and then fetus during pregnancy Cervix – protect fetus during pregnancy and then dilate to provide a birth canal Vagina – stimulate penis to cause ejaculation and provide a birth canal Vulva – protect internal parts of female reproductive system

The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. The roles of FSH, LH, estrogen and progesterone in the menstrual cycle are expected. Q: Explain the functions of each of the four hormones listed above. (Do not talk about concentrations at this point)

Application: The use in IVF of drugs to suspend the normal secretion of hormones, followed by the use of artificial doses of hormones to induce superovulation and establish a pregnancy.

Application: William Harvey’s investigation of sexual reproduction in deer. Nature of science: Developments in scientific research follow improvements in apparatus—William Harvey was hampered in his observational research into reproduction by lack of equipment. The microscope was invented 17 years after his death.