1. The Endocrine System

2. Function The endocrine system produces chemicals that control many of the body’s daily activities. The endocrine system also regulates long-term changes such as growth and development

3. Hormones The chemical product of an endocrine gland is called a hormone. Hormones turn on, turn off, speed up or slow down the activities of organs and tissues. Hormones are chemical messengers secreted directly into the blood by the endocrine glands.

4. What causes the release of hormones? Nerve impulses from the brain. For example, you see a deadly knife-edged pendulum. Nerve impulses from your eyes travel to the brain. The brain interprets the message and sends an impulse to the adrenal glands. The adrenal glands then secrete the hormone adrenaline to the bloodstream. Adrenaline makes your heart rate and breathing increase.

5. Hormone action Hormones usually cause a long-lasting effect. For example, when adrenaline reaches your heart, it makes the heart beat more rapidly. The heart continues to race until the amount of adrenaline in the blood drops to a normal level.

6. Target cells When a hormone enters the bloodstream, it affects some organs but not others. A hormone interacts only with specific target cells. Target cells recognize the chemical structure of a hormone. Like a key that will only open one lock, hormones travel through the blood stream until they find the “lock” – or particular cell type – that they fit.

7. Functions of the endocrine glands The endocrine glands include the hypothalamus, pituitary, thyroid, parathyroid, adrenal, thymus and pancreas. They also include the ovaries in females and testes in males.

8. Hypothalamus: links the nervous system and endocrine system. The nerve messages that control sleep, hunger and other basic body processes come from the hypothalamus. The hypothalamus also produces hormones that control other endocrine glands and organs. Pituitary gland: Communicates with the hypothalamus to control many body activities. The hormones it produces regulate growth, blood pressure and water balance.

9. Thyroid gland (C): Controls the release of energy from food molecules. Parathyroid glands (G): Regulate the amount of calcium in the blood. Thymus gland (D): Hormones from this gland help the immune system develop during childhood. Adrenal Glands (E): These glands release several hormones. Adrenaline triggers the body’s response to emergency situations. Other hormones affect salt and water balance in the kidneys and sugar in the blood. Pancreas (H): Produces insulin and glucagon., which control the level of glucose in the blood.

10. Ovaries: Release estrogen and progesterone. These hormones are responsible for the changes in a female’s body and for egg development Testes: Release testosterone, which controls changes in a males body and regulate sperm production.

11. Negative Feedback The endocrine system works like a thermostat. When a hormone’s level fall below the requirement, the system “kicks in”. Once normal levels are achieved, the system “feeds-back” the information, which shuts down he release of that hormone