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; neutralizes acidic conditions inside vagina 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

Q: Explain the functions of each of the four hormones listed above. 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. FSH stimulates development of the follicle, stimulates secretion of estrogen Estrogen stimulates repair and thickening of the uterine wall LH stimulates completion of meiosis in developing egg, development of follicle into corpus luteum Progesterone promotes thickening and maintenance of endometrium, inhibits FSH and LH secretion

What is going on in the uterus at these times? Uterine walls are “empty” Endometrium is building up, and up and up… Menstruation (endometrium is shed)

What is going on in the ovaries at these times? Follicle turns into corpus luteum Ovulation Follicle matures Corpus luteum disappears Follicle appears What hormone does the follicle make? Estrogen What hormone does the corpus luteum make? Progesterone

At what time is a female most fertile? Why? Right before and after ovulation a female is most fertile. It is at this time that she has released a “fresh” egg, and afterwards the egg dies. Therefore, right before and after menstruation is when she is least fertile. Most fertile

Male Female Pituitary Gland Vas Deferens Progesterone to the… to the… Sperm cells start here and travel from… Which stands for Contains a gland called the function Which makes a 2 hormones called… to the… Pituitary Gland Which stands for function These 2 hormones stimulate the ovary to make a structure that will eventually release an egg; this structure is called a. to the… makes a hormone called Vas Deferens function to the… The egg is eventually released; this is called Which causes the uterus to build the function to the… The leftover follicle changes into a structure called the function Which causes the uterus to maintain the to the… It makes a hormone called Progesterone function to the… If the egg is fertilized, then the endometrium becomes the If the egg is not fertilized, then there is a decrease in the level of the hormone function Ejaculation happens, and sperm first enters the female’s and then travels through the female’s cervix, uterus, and fallopian tube to find an egg Which will produce the hormone This causes the endometrium to die; it will be pushed out by contractions of the and provide nutrients to the embryo for about 9 months until the uterus contracts, pushing the fetus out through the and will exit through the vagina in a process called

Male Female Brain Testicle FSH Pituitary Gland LH Epididymis Follicle Sperm cells start here and travel from… Spermatogenesis happens here Which stands for Contains a gland called the Testicle Which makes a 2 hormones called… FSH Follicle stimulating hormone function to the… Pituitary Gland Which stands for LH Luteinizing hormone Sperm matures here and is stored until ejaculation Epididymis function These 2 hormones stimulate the ovary to make a structure that will eventually release an egg; this structure is called a. to the… Sperm travels through this tube during ejacultion Follicle makes a hormone called Estrogen Vas Deferens function to the… The egg is eventually released; this is called Which causes the uterus to build the Adds fructose (a sugar for sperm food) and mucus (to lubricate sperm) Seminal vesicle function Ovulation Endometrium to the… Adds fluids that neutralize the acids in the vagina, to help the sperm survive Prostate The leftover follicle changes into a structure called the function Which causes the uterus to maintain the to the… It makes a hormone called A duct shared between urine and sperm Corpus Luteum Progesterone Urethra function to the… If the egg is fertilized, then the endometrium becomes the If the egg is not fertilized, then there is a decrease in the level of the hormone Enters the vagina, delivering the sperm and semen Penis function Placenta Progesterone Ejaculation happens, and sperm first enters the female’s and then travels through the female’s cervix, uterus, and fallopian tube to find an egg This causes the endometrium to die; it will be pushed out by contractions of the Which will produce the hormone Progesterone Uterus Vagina and provide nutrients to the embryo for about 9 months until the uterus contracts, pushing the fetus out through the and will exit through the vagina in a process called Vagina Menstruation

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.