6.6 Hormones, homeostasis and reproduction Understanding: -Insulin and glucagon are secreted by alpha and beta cells in the pancreas to control blood glucose concentration -Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature -Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite -Melatonin is secreted by the pineal gland to control circadian rhythms -A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone -Testosterone causes prenatal development of male genitalia -Estrogen and progesterone cause prenatal development of female reproductive organs and female secondary sexual characteristics during puberty -The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones Applications: -Causes and treatment of type I and type II diabetes -Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease -Causes of jet lag and use of melatonin to alleviate it -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 -William Harvey’s investigation of sexual reproduction in deer Skills: -Annotate diagrams of the male and female reproductive system to show names of structures and their functions 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

Blood Glucose Concentration Pancreas responds to changes in blood glucose Set point = 5mmolL Large deviation = insulin or glucagon hormones

Two Roles 1.Exocrine tissue = digestive enzymes 2.Endocrine tissue (Islets of Langerhans) = secrete hormones Endocrine (secrete into bloodstream) Exocrine (secrete outside of bloodstream)

Endocrine tissue Islets of Langerhans Alpha cells: Blood glucose falls Synthesize and secrete glucagon Stimulates break down of glycogen into glucose Released into blood to increase concentration

Endocrine tissue Islets of Langerhans Beta cells: When blood glucose rises Synthesize and secrete insulin Stimulate uptake of glucose Glucose converted to glycogen Blood glucose reduced

Research Cause and treatment of type I and type II diabetes -What is diabetes? -What is type I diabetes? -Treatment? -What is type II diabetes? -Treatment? -Which foods should people with each type of diabetes avoid or eat?

HormoneThyroxinLeptinMelatonin Secreted by RoleInclude details about using leptin on obese patients and why it failed Include details about using melatonin to alleviate jet lag

HormoneThyroxinLeptinMelatonin Secreted byThyroid gland in neck Cells in adipose tissue (fat storage cells) Pineal gland in brain RoleRegulates body’s metabolic rate and help control body temperature Targets most metabolically active: liver, muscle, brain Acts on hypothalamus to inhibit appetite – reduces food intake Tested on mice – inject with leptin = treat obesity May have become resistant to leptin Control circadian rhythms Increase melatonin in the evening and reduced in the morning Controls the sleep wake cycle Causes drowsiness Take when sleep should be started

Sex determination in males Human reproduction: Sperm cell fuses with egg cell Embryonic gonads develop that could become male or female Depends on presence of absence of one gene: SRY gene located on the Y chromosome Present = testes Absent = ovaries

Testosterone Testes develop from week 8 Testosterone is secreted until week 15 Causes male genitalia to develop At puberty – testosterone increases again stimulating sperm production, hair growth, deepening of voice…

Sex determination in females No SRY gene = ovaries Estrogen and progesterone from mother Not over powered by testosterone, therefore female reproductive organs form During puberty estrogen and progesterone increase causing enlargement of breasts, growth of hair…

Male Testes Scrotum Epididymus Sperm Duct Seminal vesicle and prostate gland Urethra Penis

Female Ovary Oviduct Uterus Cervix Vagina Vulva

Menstrual Cycle Occurs from puberty until menopause (apart from during pregnancies) Each cycle gives the chance of pregnancy Two phases: 1.Follicular phase 2.Luteal phase

Follicular Phase Follicles develop in the ovaries Each follicle has an egg inside that start to develop Lining of the uterus is repaired and thickens Most developed follicle breaks open and releases the egg Other follicles degenerate

Luteal Phase Wall of follicle that has released the egg = corpus luteum Uterus continues to develop to prepare for implantation of an embryo No fertilisation = corpus luteum in ovary breaks down, uterus lining breaks down and is shed

Four hormones in menstrual cycle Draw a diagram to show the rise and fall of the following hormones during the menstrual cycle -FSH -LH -Progesterone -Estrogen Summarise the role of each hormone in the cycle

Research IVF -What is it? -What does a woman need to do in IVF? -Why do people choose to do IVF? -What are the different stages of IVF? William Harvey -What was his research? -What did his tests with deer involve? -What were his findings?