Class 8, Science, Chapter-7, Lecture-2, Hormone (Notes)
HORMONE:
A chemical substance produced in the body which controls and regulates activities of specific tissue or organ of a living organism is termed as hormone.
ENDOCRINE SYSTEM:
The collection of ductless glands that produce hormones to control and regulate activities of various tissues or organs of a living organism is called endocrine system.
CHARACTERISTICS OF HORMONES:
- They are specific chemical messengers
- They are secreted by endocrine glands
- They are poured directly into the blood and carried by blood circulation
- They act on specific tissue or organs called target organ.
LIST OF ENDOCRINE GLANDS AND HORMONES RELEASED:
Endocrine gland | Hormone released | Role |
1. Pineal | Melatonin | Regulates Sleep Cycle. |
2. Hypothalamus | Tropic Hormone | Regulates Endocrine System |
3. Pituitary | Growth Hormone, Gonadotropic Hormone Thyroid Stimulating Hormone (TSH) | Controls Growth Controls secretion of sex hormones Stimulates the thyroid to release thyroxin |
4. Thyroid | Thyroxin | Regulates Basic Metabolism |
5. Parathyroid | Parathyroid Hormone | Regulates amount of Phosphorus and Calcium |
6. Thymus | Thymosin | Activates Immune System |
7. Adrenal | Aldosterone Adrenalin | Regulates salt balance of body. Helps to adjust to stress during anger, embarrassment or depression (“Fright, Fight or Flight” action) |
8. Pancreas | Insulin Glucagon | Reduces sugar level Increases sugar level |
9. Ovary | Estrogen and Progesterone | Regulates Female sex organs |
10. Testes | Testosterone | Regulates Male sex organ |
METAMORPHOSIS:
The biological process of transformation from larva or tadpole to an adult is called metamorphosis.
Hormones involved in Metamorphosis:
- Insect Hormones in insects
- Thyroxine in amphibian
SEXUALLY TRANSMITTED DISEASES:
An infectious disease which is spread from an infected person to a healthy person by sexual contact is called sexually transmitted disease (STD).
Examples of STD:
- Bacterial Infections - Gonorrhoea, Syphilis
- Viral Infections - Warts, AIDS
Symptom of STD: Burning sensation at urination and urethral discharge
Prevention from STD: Use of condom during sex.
Mode of Transmission of AIDS:
- From infected mother’s milk to child
- Through sharing of syringes or Shaving blades
- Blood transfusion from infected person
- Sexual contact with infected person