Hormones & Endocrine System

• Hormones — chemical messengers secreted by endocrine glands into blood.
• Major glands — pituitary, thyroid, adrenal, pancreas, gonads.
• Feedback control — e.g. insulin and blood glucose.
• Compare nervous (fast, localised) vs hormonal (slow, widespread, long-lasting).
• Iodine needed for thyroxine; diabetes — insulin deficiency.

1. Pituitary — master gland; growth hormone; TSH etc.
2. Thyroid — thyroxine regulates metabolism; goitre if iodine deficient.
3. Adrenal — adrenaline (fight-or-flight); increases heart rate, blood flow to muscles.
4. Pancreas — insulin (lowers blood glucose); glucagon raises it.
5. Diabetes mellitus — insufficient insulin → high blood sugar; treated with insulin injections.
6. Testes — testosterone; ovaries — oestrogen, progesterone.
7. Nervous vs endocrine — speed, duration, pathway differ.
8. Feedback — high glucose → insulin release → glucose stored as glycogen → level falls.
9. Dwarfism/gigantism — growth hormone imbalance in childhood.
10. NCERT table — gland, hormone, function (must memorise main entries).

Role of insulin when blood glucose rises after meal

Step 1 — Carbohydrate digestion raises blood glucose.
Step 2 — Pancreatic β-cells secrete **insulin** into blood.
Step 3 — Insulin helps cells uptake glucose; liver stores glycogen.
Step 4 — Blood glucose returns to normal (feedback).
Step 5 — Without insulin (Type 1 diabetes) → hyperglycaemia, glucose in urine.
Conclusion: insulin maintains blood sugar homeostasis.

• Confusing insulin (lowers glucose) with glucagon (raises).
• Misconception: hormones work only in adults (growth hormone in children).
• Thinking adrenaline slows heart (it speeds heart for emergency).
• Forgetting iodised salt prevents goitre.
• Mixing endocrine (ductless) with exocrine (pancreatic digestive enzymes via duct).

• Name hormone from thyroid and its function.
• What gland secretes insulin?
• Compare nervous and hormonal control (one difference).
• Why is iodine important in diet?

Open the Practice tab for graded questions on Hormones & Endocrine System.