The Endocrine System
In IGCSE biology curriculum, endocrine glands make hormones which are released directly into the blood. These hormones are carried around the body in the blood to the target organs that they affect. The target organs are often a long way from the endocrine glands that secreted the hormone. Hormones act as chemical co-ordinators. The hormones secreted by the endocrine glands co-ordinate and control a wide range of bodily functions.
- Antidiuretiic hormone (ADH) is secreted by the pituitary gland and it controls the content of the water in the blood by its effects on the kidneys
- Insulin and Glyugaon are secreted by the pancreas and lower and rainse the glucose levels.
- Adrenaline is secreted by the adrenal glands and prepares the body for stressful or physically active situations (the fight or flight response)
- Oestogen is secreted by the ovaries and controls the development of female secondary sexual characteristics
- Progesterone is secreted in the ovaries and regulates the menstrual cycle
- Testosterone is secretes by the testes and controls the development of male secondary characteristics and is involved in sperm production
Adrenaline
There are few important points of adrenaline in IGCSE biology curriculum, they are:
- Increases breathing rate and depth to get more oxygen into your blood and removes excess carbon dioxide
- Increases heart rate and volume sending more oxygen to the muscles for respiration
- Blood is diverted from the digestive systems to the muscles
- Glycogen in the liver is converted to glucose in the blood
- Mental awareness and speed of reactions increase
- Body hair stands up on end
Insulin and Glucagon
Blood glucose levels are kept at 4-6mmol/l by insulin and glucagon. In IGCSE biology, after a meal, blood sugar levels go up. Insulin is produced by your pancreas and lets your cells take in some of this glucose. It lets your liver cells store glucose as glycogen. As blood sugar levels start to drop, insulin levels drop and glucagon levels rise. Glycogen is converted back to glucose by the negative feedback system involving the pancreas in the hormones insulin and glucagon.
End of this topic!
Drafted by Gina (Biology)