Endocrine Glands Class 10 ICSE — Selina Chapter 10

Endocrine glands class 10 ICSE explains how the body coordinates its activities through chemical signals. This Selina Biology chapter covers the four syllabus glands — adrenal, pancreas, thyroid and pituitary — along with their hormones, actions and disorders. The feedback mechanism that keeps hormone levels stable is also covered. Each section below follows the book’s order. Browse more Class 10 Biology chapters on the biology hub, or see the full book collection.

ICSE Class 10 Biology Selina Concise Chapter 10 Endocrine Glands PDF

What is inside Chapter 10

13 pages · 5 sections · 54 exercise questions

• PROGRESS CHECK: 2 questions
• PROGRESS CHECK: 9 questions
• PROGRESS CHECK: 5 questions
• PROGRESS CHECK: 3 questions
• REVIEW QUESTIONS: 35 questions

10.1 NEED FOR THE REGULATION OF BODY ACTIVITIES

Your body runs thousands of processes at once. Each must happen at the right time and in the correct sequence. Gastric juice, bile and pancreatic juice, for example, should enter the food canal only when food is present. The nervous system handles part of this regulation. Chemical regulators called hormones handle the rest. The word hormone comes from ‘horma’, meaning to stir up, to excite, or to put into action.

Hormones are secretions from specific cells or glands. Blood carries them to all parts of the body, but they act only on specific target organs or cells. Most come from endocrine glands — ‘endo’ means inside, ‘crine’ means separate. These ductless glands pour secretions directly into blood, not through ducts. Some organs with other primary functions also produce hormones, such as the stomach and duodenum.

Table 10.1 in the book lists seven differences between hormonal and nervous control:

The endocrine system is the group of glands and glandular cells that work together for chemical coordination. These glands activate one another and function as one system. The nervous system, covered in the Selina Chapter 9 page, handles the other half of this coordination. The official CISCE website publishes the current class 10 Biology syllabus.

10.2 GENERAL PROPERTIES OF HORMONES

Hormones share eight general properties that define how they behave in the body:

1. They are secreted directly into blood, not lymph.
2. They regulate processes by chemical means, affecting enzyme systems.
3. They act on target organs usually away from their source.
4. Hormones from one species usually show similar influence in other species.
5. They are produced in tiny quantities yet are biologically very active.
6. Chemically, they are peptides (like insulin), amines (like adrenaline) or steroids (like testosterone).
7. Both excess and deficiency cause serious consequences.
8. They are not stored in the body and are excreted.

Point 5 deserves attention. One part of adrenaline in hundreds of millions of parts of blood still produces an effect. Think of one drop of ink in a large water tank. The hormone acts even at that dilution.

The formal definition ties these properties together. A hormone is a secretion from a glandular part of the body, poured into blood, acting on target organs or cells of the same individual. It brings about coordination between distant parts of the body.

The Progress Check after this section has 2 questions. They test these properties and the definition directly.

10.3 ENDOCRINE GLANDS

Seven principal endocrine glands exist, but the syllabus covers only four: adrenal, pancreas, thyroid and pituitary. Parathyroid, thymus and gonads are mentioned but not required.

1. Adrenal glands

Each adrenal gland caps a kidney, with a central medulla and a peripheral cortex. The medulla secretes adrenaline, the emergency hormone for fight or flight. Table 10.2 lists its effects. The heart beats faster with rising blood pressure. Breathing deepens. Skin arterioles constrict, so the person turns pale. Digestive arterioles constrict, causing a dry mouth. Muscles tense. The liver converts glycogen to glucose. Fat deposits release fatty acids.

The cortex secretes cortisone, mineralocorticoids for \mathrm{Na^+} and \mathrm{K^+} balance, and glucocorticoids for carbohydrate, protein and fat metabolism. Undersecretion causes Addison’s disease with loss of energy and skin pigmentation. Oversecretion causes Cushing’s syndrome with obesity and high blood sugar. Cortex overgrowth can cause adrenal virilism in women.

2. Pancreas

The pancreas is both a duct gland and a ductless gland. Its Islets of Langerhans contain beta cells making insulin, alpha cells making glucagon, and delta cells making somatostatin, which is not in the syllabus. Insulin lowers blood sugar by promoting glucose uptake and storing extra glucose as glycogen.

The book highlights a common mistake: do not say ‘insulin converts glucose to glycogen’. The corrected statement is that insulin enables cells to absorb glucose and use it or convert it into glycogen. Insulin shortage causes diabetes mellitus; excess causes hypoglycaemia and possible brain coma. Glucagon raises blood sugar by breaking down liver glycogen into glucose.

3. Thyroid

The butterfly-shaped thyroid sits below the larynx, its lobes joined by an isthmus. It secretes thyroxine, which regulates basal metabolism. Hypothyroidism causes simple goitre from iodine deficiency, cretinism in children, and myxoedema in adults. Iodised salt prevents goitre. Hyperthyroidism causes exophthalmic goitre with protruding eyes and raised metabolism.

4. Pituitary

The pea-sized pituitary below the hypothalamus is the master gland. Anterior hormones include GH, TSH, gonadotropic hormones and ACTH. GH deficiency causes dwarfism; excess causes gigantism in childhood and acromegaly in adults. Posterior hormones include vasopressin (ADH) and oxytocin. ADH deficiency causes diabetes insipidus. Gonadotropic hormones regulate the testes and ovaries, which the reproductive system chapter covers.

To recall anterior hormones, use the mnemonic ‘Great Teachers Always Feed Little Puppies’ — GH, TSH, ACTH, FSH, LH, Prolactin.

Patient scenario — match the symptoms to the gland, hormone and disorder. A 45-year-old man has a swollen neck, protruding eyes and a racing pulse, yet he loses weight despite eating normally. The gland is the thyroid, the hormone is thyroxine, and the disorder is exophthalmic goitre from oversecretion.

10.4 CONTROL OF HORMONAL SECRETIONS [Feedback mechanism]

The body keeps hormone levels within a normal range through feedback. The book describes it as commands: ‘Too much, slow down’ or ‘Too little, speed up’.

Negative feedback reverses a change. When a level rises above normal, a message tells the system to decrease it. When it falls below normal, a message tells the system to increase it. This restores the normal state. Most feedback in the body is negative.

Blood sugar is the classic example. After a meal, blood sugar rises. The body releases insulin, which lowers it back toward normal. Between meals, blood sugar falls. The body releases glucagon, which raises it. Each response opposes the change.

Positive feedback is rare. It amplifies the change instead of reversing it. Uterine contractions during childbirth are the example. Each contraction signals the next to continue, not to stop. This continues until delivery is complete.

Both feedback types appear as diagrams in the book. The general scheme shows how messages travel between the source and the target. For negative feedback, the message reverses the direction. For positive feedback, it continues in the same direction.

10.5 THE HORMONES AT A GLANCE

Table 10.4 in the book consolidates the four glands, their hormones, principal actions and disorders. The table below is the chapter’s master summary, paraphrased from the book. For each gland, learn three things: the hormone it secretes, what that hormone does, and what happens when it is under or over produced.

The table shows a clear pattern. Each hormone has a specific job. When its level is wrong, the body shows characteristic disorders. Memorising the gland-hormone-disorder trio is the core of this chapter. The somatostatin row from the book is omitted here because the syllabus excludes it.

What to practise from this chapter

• Progress Check after Section 10.2 — 2 questions on the general properties of hormones.
• Progress Check within the adrenal and pancreas parts of Section 10.3 — 9 questions on islet cells, insulin action, adrenaline effects and cortical hormones.
• Progress Check within the thyroid part of Section 10.3 — 5 questions on gland location, thyroxine disorders and adrenaline responses.
• Progress Check after Section 10.3 — 3 questions on pituitary size, lobes, GH disorders and hormone abbreviations.
• Review Questions at the end of the chapter — 35 questions split into parts A to E: multiple choice, very short answer, short answer, long answer, and structured or application or skill type.

Frequently asked questions

Why is the pituitary gland called the master gland?

It controls practically all other endocrine glands. It secretes TSH, which activates the thyroid. ACTH regulates the adrenal cortex. Gonadotropic hormones regulate the testes and ovaries. Its hormones direct the activity of much of the endocrine system.

What is the difference between diabetes mellitus and diabetes insipidus?

Diabetes mellitus comes from insulin shortage, with sugar in the urine. Diabetes insipidus comes from ADH deficiency, with no sugar in the urine. ‘Mellitus’ means honey; ‘insipid’ means tasteless. Here is a side by side comparison:

Why is insulin given by injection and not as an oral medicine?

Insulin is a peptide hormone. Digestive enzymes in the stomach and intestine would break it down if swallowed. Injection delivers it directly into the blood. The book notes that giving insulin is not a cure. It only supplies the hormone the pancreas is not producing.

What causes simple goitre and how can it be prevented?

Simple goitre is an enlarged thyroid, visible as a neck swelling. It comes from insufficient iodine in food. Iodine is the active ingredient in thyroxine production. Using iodised salt prevents it. This matters most in regions where soil and food lack iodine.

What happens if growth hormone is secreted in excess during adulthood?

Excess GH in adulthood causes acromegaly. The bones of the face, especially the jaws, grow extra. Hands and feet enlarge. The person develops a large nose and thick lips. This differs from gigantism, which happens when excess GH acts during childhood.

Reference: ICSE Class 10 Biology textbook material, chapter 10: Endocrine Glands — CISCE-aligned.

More from this book

• Chapter 2: Structure of Chromosomes Cell Cycle and Cell Division
• Chapter 3: Genetics Some Basic Fundamentals
• Chapter 4: Absorption By Roots the Processes Involved
• Chapter 5: Transpiration
• Chapter 6: Photosynthesis
• Chapter 7: The Circulatory System
• Chapter 8: The Excretory System
• Chapter 9: The Nervous System
• Chapter 11: The Reproductive System
• Chapter 12: Population
• Chapter 13: Aids to Health
• Chapter 14: Health Organisations
• Chapter 15: Pollution