Chemical Coordination and Integration

The neural system provides quick, point-to-point coordination, while the endocrine system provides slower but long-lasting chemical coordination through hormones. Hormones are non-nutrient chemicals that act as intercellular messengers and are produced in trace amounts. The hypothalamus makes releasing and inhibiting hormones and controls the pituitary. The anterior pituitary secretes growth hormone, prolactin, TSH, ACTH, LH and FSH, and the posterior pituitary releases oxytocin and vasopressin. You will also study the pineal gland (melatonin), thyroid (thyroxine and thyrocalcitonin), parathyroid (parathyroid hormone), thymus (thymosins), adrenal glands, and the pancreas with its islets of Langerhans. You will learn how insulin and glucagon maintain blood glucose, how adrenaline prepares the body for emergencies, and how the adrenal cortex secretes glucocorticoids and mineralocorticoids such as aldosterone. You will also learn how the testis and ovary produce sex hormones. The chapter covers hormones of the heart (atrial natriuretic factor), kidney (erythropoietin) and gastrointestinal tract (gastrin, secretin, CCK and GIP), and disorders like gigantism, Addison's disease and diabetes. It ends with how hormones act through membrane-bound or intracellular receptors and second messengers.

Detailed Worksheet: Chemical Coordination and Integration Section A - Definitions (10 marks) 1. What are hormones? How do they differ from enzymes? (2 marks) 2. Why is the hypothalamus called the link between the neural and endocrine systems? (2 marks) 3. What is diabetes insipidus? Which hormone deficiency causes it? (2 marks) 4. What is atrial natriuretic factor? State its function. (2 marks) 5. What is a second messenger? Give an example. (2 marks) Section B - Calculations and Applications (15 marks) 6. The pancreas of an adult weighs about 80 g and the islets of Langerhans form about 1-2% of it. Calculate the mass of endocrine tissue for 1.5%. If there are about 15 lakh islets, calculate the average mass of one islet in micrograms. (3 marks) 7. A person's fasting blood glucose rises from 90 mg/dL to 220 mg/dL after a sugary meal and falls back within 3 hours. Explain the role of insulin and glucagon in this response. Calculate the average rate of fall in mg/dL per hour if the level returns to 90 mg/dL in 2.5 hours from its peak. (3 marks) 8. A person lacking ADH may pass up to 20 litres of dilute urine daily, compared to a normal 1.5 litres. Calculate how many times more urine is produced. Name the disorder and explain why it occurs. (3 marks) 9. An adult needs about 150 micrograms of iodine daily. Iodised salt contains 15 mg of iodine per kg of salt at consumption. Calculate the salt needed per day to meet the requirement. Which disorder is prevented by iodine? (3 marks) 10. Match each hormone to its gland and one function: melatonin, thymosin, aldosterone, relaxin, erythropoietin, cholecystokinin. (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram showing the location of the major endocrine glands in the human body. (4 marks) 12. Draw a diagram showing the relationship between the hypothalamus and the anterior and posterior pituitary. (3 marks) 13. Draw diagrams showing the mechanism of action of a protein hormone and a steroid hormone. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Explain the role of the hypothalamus and pituitary in regulating other endocrine glands, with a feedback loop example such as TSH and thyroxine. (5 marks) 15. Why is adrenaline called the emergency hormone? Explain the 'fight or flight' responses it causes, and compare the hormones of the adrenal medulla and cortex. (5 marks) 16. Explain the effects of hypersecretion and hyposecretion of growth hormone and thyroid hormones, with the disorders they cause. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw diagrams neatly with labels. Show calculations with units.