1. Topic 6.6: Homoeostasis

7. Secreted by the thyroid gland . Regulates metabolic rate
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

8. Click for animation

10. Secreted by the adipose tissue cells. Acts on the hypothalamus
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.

11. Spot the mouse treated with Leptin blockers.
Leptin and Obesity: should GM Leptin be made available as a treatment for obesity?

12. Secreted by the pineal gland . Helps control circadian rhythms.
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?