6.6 homeostasis and hormones
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Hormones and Homoeostasis
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Transcript of 6.6 homeostasis and hormones
Hormones and Homoeostasis
6.6• Insulin and glucagon are secreted by β and α cells of the pancreas
respectively 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.• Testosterone causes pre-natal development of male genitalia and both
sperm production and development of male secondary sexual characteristics during puberty.
• Oestrogen and progesterone cause pre-natal 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.
Thyroxin: Key Points• Secreted by the thyroid gland .• Regulates metabolic rate• Helps control body temperature.
Correct functioning of the thyroid requires IODINE in the diet.Lack of dietary iodine causes GOITRE
Lack of thyroxin causes:• lack of energy• Depression• Weight gain despite appetite
loss• Feeling cold
Leptin: Key Points• Secreted by the adipose tissue cells.• Acts on the hypothalamus• Inhibits appetite
Leptin is a protein hormone that targets the appetite centre of the hypothalamus.
Food intake triggers Leptin secretion which in turn inhibits appetite which reduces food intake.This is an example of negative feedback.
Spot the mouse treated with Leptin blockers.
Leptin and Obesity: should GM Leptin be made available as a treatment for obesity?
Melatonin: Key Points• Secreted by the pineal gland .• Helps control circadian rhythms.
High levels of MELATONIN cause feeling of drowsiness and promote sleep.Falling melatonin levels encourage waking at the end of the night.Melatonin also promotes a drop in core temperature and probably causes the night time body temperature drop.
Melatonin is sometimes advertised as a treatment for Jet Lag why do you think it might work?
Functions of OestrogenOestrogen and progesterone cause pre-natal 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.
Complete Q16 from the workbook.
Text pages 162-3 and complete Q 20 in the workbook
William Harvey and Sexual Reproduction“Omne vivum ex ovo” All life comes from the egg.
• In 1651 he asserted that all life developed from the egg
• Harvey was right in some ways but was limited by his observations as the microscope was not invented until 17 years after his death.
Further information:
Three of the best sites for IB-specific Biology information. The top link takes you to the PPT by Stephen Taylor
There are a whole series of videos in this channel
