6.6 Hormones, homeostasis and reproduction

1. 6.6 Hormones, homeostasis and reproduction Thyroxin is a hormone produced by the thyroid gland. It's key role is in controlling the metabolism of cells. If affects almost every physiological process in the body including growth and development. Most hormones affect more than one target tissue in more than one way. https://commons.wikimedia.org/wiki/File:Thyroid_system.svg https://commons.wikimedia.org/wiki/File:%28S%29-Triiodthyronine_Structural_Formulae_V2.svg

2. 6.6 • Essential idea: Hormones are used when signals need to be widely distributed.

3. Introduction: • Animal hormones are usually secreted by organs specialized for their production and transported through the circulatory system to a very specific target tissue • Overall function of the endocrine system: guide growth, regulate metabolism, and maintain general homeostasis

4. Homeostasis • maintaining a “steady state” • Maintenance of the conditions of the tissue fluid bathing the cells at a relatively constant level (blood pH, temperature, CO2 concentration, blood glucose concentration, and water balance are all regulated by humans)

5. Usually achieved by negative feedback – a change in the level of an internal factor causes effectors to restore the internal environment to its original level (returns level back to set point) • Ex. An increase in body temperature causes the body to lose more heat and vice versa

6. Occasionally positive feedback is used, such as in childbirth – oxytocin is released, contractions occur, stimulate more release of oxytocin and therefore more contractions (moves level away from set point)

7. Ability of mammals to maintain a stable internal environment makes them independent of changing external conditions and enables them to exploit a wide range of habitats • Ex. Maintenance of internal body temperature

8. Mammals have two types of glands: • Exocrine glands have ducts and produce secretions that are released outside the body or into digestive system

9. Endocrine glands do not have ducts and release hormones into the bloodstream

10. The Endocrine System • Key endocrine glands: • : Controls pituitary and other glands; connects nervous & endocrine system • : Makes hormones that control other glands • : releases melatonin, which is involved in rhythmic activities, such as daily sleep-wake cycles • : Makes thyroxin to control metabolism • : Makes thymosin to help white blood cells mature • : Makes adrenalin to prepare body for emergencies • : Makes insulin and glucagon to control blood glucose levels • Female gonads – • Male gonads - 1 3 2 4 5 6 7 8 Controls secondary sex characteristics; makes testosterone in men and progesterone in females 9

11. 6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration. • Control of Blood Glucose Concentrations • Glucose is transported in solution in the blood plasma • Maintenance of glucose at steady levels is vital • Normal blood glucose concentration is about 90-100 mg of glucose per 100 cm3 of blood • Two interactive hormones control blood glucose concentrations (both are produced by the pancreas) • Insulin – compensates for glucose levels that are too high • Glucagon – compensates for glucose levels that are too low

12. 6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration. • Insulin • Secreted by special cells called • When blood glucose concentrations , more insulin is secreted by the pancreas which results in: • An increase in the • An increase in the • An increase in the

13. 6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration. • Glucagon • Secreted by the • When blood glucose concentrations , the alpha cells secrete glucagon which results in: • Glucagon

16. 6.6.A1 Causes and treatment of Type I and Type II diabetes. • SYMPTOMS: Constant thirst and hunger and excessive urination • Sometimes called juvenile or early onset diabetes • CAUSE: • TREATMENT:

17. 6.6.A1 Causes and treatment of Type I and Type II diabetes. • SYMPTOMS: Constant thirst and hunger and excessive urination • Sometimes called adult or late onset diabetes • CAUSE: ;There is also a – this type of diabetes tends to run in families; Insulin receptors on the cell membranes of the target cells fail to respond to insulin • TREATMENT: (small frequent meals, low sugar content, starchy food should have a low glycemc index – slow to digest, high fiber food) and

18. “Glycemic index and glycemic load offer information about how foods affect blood sugar and insulin. The lower a food’s glycemic index or glycemic load, the less it affects blood sugar and insulin levels.” Click the link to view a list of common foods: http://www.health.harvard.edu/healthy-eating/glycemic_index_and_glycemic_load_for_100_foods

19. 6.6.U2 Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature. Thyroxin • Produced by: • Targets: • Effects: Iodine https://commons.wikimedia.org/wiki/File:T3-3D-vdW.png

20. 6.6.U3 Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite. Leptin Produced by: (fat storage cells) Targets: Effects: https://commons.wikimedia.org/wiki/File:Fatmouse.jpg https://commons.wikimedia.org/wiki/File:Leptin.png

21. 6.6.A2 Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease. Leptin treatment for obesity 1949 Scientists discovered the ob/ob or obese mouse. It is a mutant mouse that eats excessively and becomes profoundly obese. It was found that obese mice possess two recessive alleles and consequently do not produce any leptin. Obese mice treated with leptin saw large losses of weight • Clinical trials were carried out to see if the effect was similar in humans, but trials failed: • Most people have naturally high levels of leptin • If linked to leptin, obesity in people is due to resistance of the appetite control center to leptin • Very few patients in the clinical trial experienced significant weight loss • Many patients experienced side-effects such as skin irritations https://commons.wikimedia.org/wiki/File:Fatmouse.jpg

22. 6.6.U4 Melatonin is secreted by the pineal gland to control circadian rhythms. AND 6.6.A3 Causes of jet lag and use of melatonin to alleviate it. Melatonin Produced by: Targets: Effects: Jet lag is a condition caused by travelling rapidly between time zones. Symptoms often experienced are sleep disturbance, headaches, fatigue, and irritability. Symptoms usually fade after a few days. Jet lag is caused by the pineal gland continuing to set a circadian rhythm for the point of origin rather than the current time zone. Taking melatonin close to the sleep time of the destination can alleviate symptoms. https://commons.wikimedia.org/wiki/File:Melatonin_molecule_ball.png http://www.nhs.uk/Livewell/travelhealth/PublishingImages/sb10065516i-001_jet-lag_377x171.jpg

23. 6.6.U5 A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone. Sex determination Humans have 23 pairs of chromosomes in diploid somatic cells (n=2). 22 pairs of these are autosomes, which are homologous pairs. One pair is the sex chromosomes. XX gives the female gender, XY gives male. SRY The X chromosome is much larger than the Y. X carries many genes in the non-homologous region which are not present on Y. The presence and expression of the SRY gene on Y leads to male development. Chromosome images from Wikipedia: http://en.wikipedia.org/wiki/Y_chromosome

24. 6.6.U5 A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone. Sex determination In embryos the first appearance of the gonads is essentially the same in the two sexes. Gonads could become either ovaries or testes. If present, the SRY gene encodes for a protein known as testis determining factor (TDF). TDF is a DNA binding protein which acts as a transcription factor promoting the expression of other genes. In the presence of TDF the gonads become testis. In the absence of TDF the gonads become ovaries and the developing fetus becomes female. SRY

25. 6.6.U6 Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty. Testosterone The testes develop from the embryonic gonads when the embryo is becoming a fetus. The testes secrete testosterone which causes the male genitalia to develop. • At puberty the secretion of testosterone increases, causing: • The primary sexual characteristic of sperm production in the testes • Development of secondary sexual characteristics such as enlargement of the penis, growth of pubic hair and deepening of the voice http://schoolbag.info/biology/concepts/188.html

26. 6.6.U7 Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. • In the absence of fetal testosterone and the presence of maternal estrogen and progesterone, female reproductive organs develop (ovaries develop from the embryonic gonads) due to: • Estrogen and progesterone • No testosterone Estrogen and progesterone Estrogen and progesterone are present. At first they are secreted by the mother’s ovaries and later by her placenta. • At puberty the secretion of estrogen and progesterone increases, causing: • Primary sexual characteristic of egg release • Development of female secondary sexual characteristics such as enlargement of the breasts and growth of pubic hair http://schoolbag.info/biology/concepts/188.html

27. 6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.

28. 6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.

29. 6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. Click on the animation above to watch the animated graph form (APBI Schools.org.uk) http://goo.gl/eCNcH

30. 6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. • Hormonal control of female reproductive system • At puberty, FSH and LH (made by pituitary gland) stimulate the ovaries to produce estrogen and progesterone. This starts menstrual cycle. • Estrogen stimulates development of secondary sex characteristics (pubic and underarm hair, broadening of pelvis, development of breasts, distribution of fat, changes in voice)

31. 6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. • Human Menstrual Cycle • Averages every 28 days • 1st day of menstruation is day one of cycle • Days 1-5: lining is sloughed off (lining is thin)

32. 6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. • Events during the 1st half of the cycle (approximately days 1-14): • Menstruation – • Pituitary releases (only 1 will complete maturation); also • Estrogen stimulates • Estrogen stimulates the ; (around the middle of the cycle – about day 14) • Estrogen inhibits the (negative feedback)

33. 6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. • Events during the 2nd half of the cycle (days 15-28) • After ovulation, ; continues to release estrogen and also progesterone • Progesterone promotes (also inhibits production of FSH and LH – negative feedback) • If no fertilization occurs ,

34. *Meiosis II is completed if fertilization occurs

36. 6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. More Menstrual Cycle Animations Video and doctors’ advice from NHS UK: http://www.nhs.uk/Video/Pages/Menstrualcycleanimation.aspx http://course.zju.edu.cn/532/study/theory/2/Genital%20system/Menstrual%20cycle.swf • How does the contraceptive pill work? • this site has a good comparison of the regular menstrual cycle and the cycle with the influence of contraceptive pills. • http://www.pbs.org/wgbh/amex/pill/sfeature/sf_cycle.swf Edited from: http://www.slideshare.net/gurustip/reproduction-core

37. Hormonal control of pregnancy • Once fertilized, egg immediately becomes impermeable to other sperm cells – membrane changes consistency • Fertilized egg forms the zygote • Cell division occurs as zygote travels down oviduct to uterus and it implants in the wall of the uterus 8-10 days after fertilization

38. After implantation – fertilized egg forms embryo, umbilical cord (vessels connect baby and mother), and placenta (formed from embryonic and uterine tissues; blood systems of baby and mother come in close contact but never actually mix; exchange occurs between circulatory systems)

39. Fertilized egg , which • Eventually

40. 5 weeks ~1 cm long 14 weeks ~6 cm long 20 weeks ~30 cm at end of 24 weeks

42. IVF is . On the right is a special x-ray called a hydrosalpingogram. A dye is infused through the cervix into the uterus and from there it flows through the fallopian tubes and into the pelvic cavity. This woman is all clear, you can see the swirls of dye coming out the ends of her tubes Dye in the pelvic cavity Uterus Fallopian tube filled with dye Tube administering dye via vagina http://commons.wikimedia.org/wiki/File:Hysterosalpingogram.jpg

43. Other causes of infertility: • Female: • Ova not maturing or being released • Abnormality in uterus prevents implantation • Antibodies in cervical mucus impair sperm • Male • Unable to achieve an erection or normal ejaculation • Low sperm count or sperm are abnormal with low motility • Blocked vas deferens Two tailed sperm, unable to swim http://goo.gl/XqAOk

44. Introduction to In vitro fertilisation (IVF) http://www.sumanasinc.com/webcontent/animations/content/invitrofertilization.html Edited from: http://www.slideshare.net/gurustip/reproduction-core

45. 6.6.A4 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. Hormonal treatments involved in IVF Down-regulation is the first step in IVF is the shutting down of the menstrual cycle, by . The process takes about two weeks and allows better control of superovulation. Down-regulation is done with a drug, commonly in the form of a nasal spray. Next superovulation . (the developing egg and their surrounding cells). After about 14 days, an . Approximately 36 hours later, under a general anesthetic, follicles (typically 8 – 12) . Prepared eggs (removed from the follicles) are combined with sperm in sterile conditions. Successfully fertilized eggs are then incubated before implantation. For approximately two weeks before implantation the , usually in the form of a suppository, to aid implantation. This treatment is continued until pregnancy test, and if positive, until 12 weeks of gestation. As the natural success rate of implantation is around 40% usually two or three blastocysts (growing fertilized egg) are implanted. As a consequence the chances of IVF treatment leading to multiple pregnancies are high. http://hopefulmum.co.nz/wp-content/uploads/2015/05/IVF.jpg

46. 6.6.A5 William Harvey’s investigation of sexual reproduction in deer. William Harvey’s investigation of sexual reproduction ‘seed and soil’ theory of Aristotle states that the male produces a seedwhich forms an egg when mixed with menstrual blood. The egg then develops into a fetus inside the mother. Harvey studied animal reproduction, particularly in chickens and deer. He dissected female deer after mating to observe changes in the sexual organs and found none. Harvey came to understand that menstrual blood did not contribute to the formation of a fetus (true), putting Aristotle's idea to rest. He also questioned the direct role of semen in reproduction (false). https://commons.wikimedia.org/wiki/File:Fawn_and_mother.jpg

47. 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. (1.8) William Harvey’s investigation of sexual reproduction His findings, both true and false, are based on a misinterpretation of insufficient data. His biggest problem was that without microscopes (invented 17 years after his death) that sperm, eggs and embryos are too small to observe. https://commons.wikimedia.org/wiki/File:Fawn_and_mother.jpg