CBSE · Class 10 · Science · Control and CoordinationExplain the mechanism of chemical coordination in animals with special emphasis on the endocrine system. Discuss the role of any four major endocrine glands and their respective hormones in maintaining physiological balance in the human body.

Mechanism of Chemical Coordination in Animals and Endocrine System

\nIn animals, control and coordination are achieved not only through the nervous system but also via a chemical coordination system mediated by hormones. Hormones are chemical messengers secreted by specialized glands known as endocrine glands (ductless glands). These chemicals are released directly into the blood stream and transported to target organs to regulate various physiological processes, growth, and metabolism. \nHere is the detailed role of four major endocrine glands and their respective hormones in the human body:

• 1. Thyroid Gland and Thyroxine:

  • Located in the neck region, the thyroid gland produces the hormone thyroxine.
  • Thyroxine regulates carbohydrate, fat, and protein metabolism in the body to provide the best balance for growth.
  • Iodine is essential for the synthesis of thyroxine. Deficiency of iodine in the diet leads to a disease called goiter, characterized by swollen neck.

• 2. Pancreas and Insulin:

  • The pancreas acts as both an exocrine and endocrine gland. Its endocrine part (Islets of Langerhans) secretes insulin.
  • Insulin plays a vital role in lowering blood glucose levels by promoting the uptake of glucose into body cells and its conversion into glycogen in the liver.
  • Deficiency of insulin causes diabetes mellitus, resulting in high sugar levels in the blood and frequent urination.

• 3. Adrenal Gland and Adrenaline:

  • Situated above the kidneys, the adrenal glands secrete adrenaline (the emergency hormone).
  • During stress, fear, or anger, adrenaline is rapidly released into the blood. It increases heart rate, breathing rate, and blood supply to muscles while diverting blood away from the digestive system, preparing the body to 'fight or flight'.

• 4. Pituitary Gland and Growth Hormone:

  • Often called the 'master gland', the pituitary gland is located at the base of the brain and secretes several hormones, including Growth Hormone (GH).
  • Growth hormone regulates normal growth and development of the body. Over-secretion leads to gigantism (abnormal tallness), while under-secretion results in dwarfism (stunted growth). \nThrough these hormones, the endocrine system ensures slow, long-lasting, and coordinated control over the entire body.