1. 6.6: Hormones, homeostasis & reproduction

2. Negative feedback Homeostasis – maintain constant internal environment Using the nervous and endocrine system to monitor the body. Any increase or decrease causes the body to respond and so the body returns to normal. E.g. thermoregulation, blood glucose level, This is called negative feedback.

4. Blood glucose concentration Usually between 4-8 millimoles per dm 3 1. Pancreas monitors blood/glucose concentration 2. Hormone messages sent to target organs when levels increase/decrease blood glucose level (insulin & glucagon) 3. Target organ responds This is another example of negative feedback

6. Initial high blood glucose levelInitial low blood glucose level Beta cells in pancreatic islets produce insulin Insulin stimulates liver to absorb glucose (converted to glycogen) Granules of glycogen stored in cytoplasm Other cells absorb glucose to use in respiration Blood glucose levels lowers Alpha cells in pancreatic islets produce glucagon Glucagon stimulates liver to breakdown glycogen into glucose Glucose released into blood Blood glucose level increases

7. Diabetes Type IType II Childhood Beta cells do not produce insulin Autoimmune disease Insulin injections Cannot be controlled by diet After childhood Cells insensitive to insulin Usually no need for injections Low carbohydrate diet can control

8. Thyroxin Produced by the thyroid gland Regulates metabolic rate & temperature Contains 4 atoms of iodine Iodine deficiency can cause hypothyroidism aka thyroxin deficiency. Symptoms listed page 332.

9. Leptin A protein hormone Secreted by adipose tissue (fat storage cells) Inhibits appetite Appetite is controlled by the hypothalamus, therefore the target organ for leptin is the brain.

10. Melatonin Secreted by pineal gland Controls circadian rhythm (24 hour cycle) Suprachiasmatic nuclei (SCN) in hypothalamus control circadian rhythm Control the secretion of melatonin Melatonin = sleep to wake cycle

12. Sex determination in males XY – male The SRY gene develops testes and is located on the Y chromosome. SRY codes for a DNA-binding protein called TDF (testis determining factor). TDF also stimulates the expression of other genes that contribute towards testis development.

13. Testosterone Male sex hormone Causes prenatal development of genetalia, sperm production as well as the development of secondary male characteristics during puberty (deepening voice, pubic hair etc.)

15. Sex determination in females Oestrogen & progesterone cause prenatal development of female reproductive organs and secondary female characteristics during puberty. XX (no SRY gene)

17. TestisProduce sperm and testosterone ScrotumHold testes at lower than core body temperature EpididymisStore sperm until ejaculation Sperm ductTransfer sperm during ejaculation Seminal vesicle & prostate glandSecrete semen (sperm, alkaline, proteins & fructose) UrethraTransfer semen during ejaculation and urine during urination PenisPenetrate the vagina for ejaculation of semen near the cervix

18. OvaryProduce eggs, estrogen & progesterone OviductCollect eggs at ovulation, provide site for fertilization then move the embryo to the uterus UterusProvide needs for embryo/foetus during pregnancy CervixProtect foetus during pregnancy, dilates to provide a birth canal VaginaStimulate penis to cause ejaculation and provide a birth canal VulvaProtect internal parts of the female reproductive system

19. Menstrual cycle http://www.abpischools.org.uk/page/modules/hormon es/horm4.cfm?coSiteNavigation_allTopic=1

20. William Harvey As well as developing theories regarding blood/circulation Harvey was also interested in inheritance and the process of reproduction. Harvey tested Aristoles theory of ‘seed and soil’ by dissecting recently mated female deer to observe the uterus. He only found evidence of a fietus several months after mating, therefore Aristotle could not be correct.