Control and Coordination | Class 10 Science Notes

6.3 HORMONES IN ANIMALS

In animals, chemical coordination is achieved through hormones, which are chemical messengers secreted by endocrine glands. Hormones regulate physiological processes such as growth, metabolism, reproduction, and stress responses. For example, adrenaline is secreted by the adrenal glands during stressful situations, preparing the body for 'fight or flight' by increasing heart rate, breathing rate, and diverting blood flow to muscles. Hormones are transported through the bloodstream to target organs where they elicit specific responses. The endocrine system works alongside the nervous system to provide control and coordination. Important endocrine glands include the pituitary, thyroid, adrenal, pancreas, testes, and ovaries. The pituitary gland secretes growth hormone, regulating overall body growth. The thyroid gland produces thyroxin, which controls metabolism. The pancreas secretes insulin to regulate blood sugar levels. Testosterone and oestrogen regulate sexual development and reproduction. Hormone secretion is regulated by feedback mechanisms to maintain balance. For example, insulin secretion increases when blood sugar rises and decreases when it falls. Hormonal coordination ensures that complex bodily functions are integrated and maintained for survival and development.

📊 Diagram: Figure 6.7 Endocrine glands in human beings (a) male, (b) female

🧪 Activity: Activity 6.3: Identifying endocrine glands in the human body and discussing their functions.

🔗 Connection: This section leads to understanding specific hormones and their functions, summarized in the next table and section.