Chemical Coordination and Integration — Class 11 Biology NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 11 Biology chapter "Chemical Coordination and Integration" — 8 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 11 Biology chapter "Chemical Coordination and Integration" — 8 important questions with detailed answers f…
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NCERT Solutions for Class 11 Biology — Chemical Coordination and Integration. Step-by-step answers to all 8 textbook questions from this chapter, written for CBSE board preparation and free to use.
Chemical Coordination and Integration — All 8 Questions Solved
Q1. Define hormones. What are their characteristics?
Hormones are chemical messengers secreted by endocrine glands into bloodstream.
Characteristics:
- Secreted in small amounts; highly potent
- Act on distant target cells via specific receptors
- Effects are long-lasting and slow compared to nerves
- Coordinate and regulate physiological processes
- Maintain homeostasis
- Cannot be recycled; degraded after use
Q2. What is the hypothalamic-pituitary axis? Explain with an example.
Hypothalamic-pituitary axis controls major endocrine functions via feedback loops.
Structure:
- Hypothalamus secretes releasing hormones to anterior pituitary
- Anterior pituitary releases tropic hormones affecting other glands
- Example: TRH from hypothalamus → TSH from pituitary → T3/T4 from thyroid
- High T3/T4 inhibits further TRH and TSH (negative feedback)
- Posterior pituitary stores hormones made by hypothalamus (ADH, oxytocin)
Q3. Name the hormones secreted by the anterior pituitary and their functions.
Anterior pituitary hormones:
- Growth hormone: stimulates growth; lipolysis; protein synthesis
- TSH: stimulates thyroid to secrete T3/T4
- ACTH: stimulates adrenal cortex to secrete cortisol
- FSH: stimulates gamete production in gonads
- LH: triggers ovulation in females; testosterone production in males
- Prolactin: stimulates milk production; decreases after weaning
Q4. What are thyroid hormones and their effects?
Thyroid hormones: T3 (triiodothyronine) and T4 (thyroxine); both contain iodine.
Effects:
- Increase basal metabolic rate
- Increase heat production
- Promote growth and development
- Increase oxygen consumption
- Stimulate nervous system activity
- Essential for proper physical and mental development
Deficiency: cretinism in infants; myxedema in adults
Excess: symptoms of hyperthyroidism
Q5. What is the role of parathyroid hormone and calcitonin in calcium homeostasis?
Parathyroid hormone (PTH):
- Secreted when blood Ca2+ is low
- Increases renal reabsorption of Ca2+
- Stimulates osteoclasts to release Ca2+ from bones
- Increases intestinal Ca2+ absorption
Calcitonin (from thyroid):
- Secreted when blood Ca2+ is high
- Inhibits osteoclasts; stimulates osteoblasts
- Increases Ca2+ deposition in bones
- Both hormones maintain blood Ca2+ at 9-10 mg/100 mL
Q6. Explain the effects of epinephrine during the fight-or-flight response.
Epinephrine (adrenaline) secreted by adrenal medulla during stress:
- Increases heart rate and force of contraction
- Constricts blood vessels in skin and gut; dilates in muscles
- Increases blood glucose via glycogenolysis
- Increases oxygen supply to muscles
- Dilates bronchi for increased respiration
- Increases blood pressure
- Pupil dilation; heightened awareness
- Prepares body for emergency response
Q7. What is diabetes mellitus? Describe its two main types.
Diabetes mellitus is disorder of glucose homeostasis due to insulin deficiency or resistance.
Type 1 (Insulin-dependent):
- Autoimmune destruction of pancreatic beta cells
- Little to no insulin production
- Develops in childhood/young adults
- Requires insulin injections
Type 2 (Non-insulin dependent):
- Insulin resistance in tissues
- Pancreas produces insulin but cells don't respond
- Associated with obesity; develops later in life
- Managed with diet, exercise, oral medications
Q8. What are the effects of cortisol during stress?
Cortisol (glucocorticoid) secreted by adrenal cortex during chronic stress:
- Increases blood glucose via gluconeogenesis
- Increases blood pressure
- Suppresses immune response
- Anti-inflammatory effects
- Increases lipolysis; mobilizes fatty acids
- Decreases protein synthesis
- Increases anxiety and alertness
- Prolonged elevation can cause immunosuppression and muscle wasting
Chemical Coordination and Integration — Practice MCQs with Answers
Attempt these 20 multiple-choice questions after working through the solutions above. Each carries the correct option and the reasoning behind it, so a wrong answer tells you which idea to revisit.
MCQ 1. Which of the following endocrine glands is often referred to as the 'master gland' due to its extensive control over other endocrine glands?
- A. Thyroid gland
- B. Adrenal gland
- C. Pituitary gland
- D. Pancreas
Answer: C. Pituitary gland — The pituitary gland secretes several hormones that regulate the functions of other endocrine glands, earning it the title 'master gland'.
MCQ 2. The posterior pituitary gland is responsible for the storage and release of which two hormones?
- A. Growth Hormone (GH) and Prolactin (PRL)
- B. Oxytocin and Vasopressin (ADH)
- C. Thyroid Stimulating Hormone (TSH) and Adrenocorticotropic Hormone (ACTH)
- D. Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH)
Answer: B. Oxytocin and Vasopressin (ADH) — The posterior pituitary does not synthesize hormones but stores and releases oxytocin and vasopressin (ADH), which are synthesized by the hypothalamus.
MCQ 3. Deficiency of which hormone leads to 'diabetes insipidus'?
- A. Insulin
- B. Glucagon
- C. Vasopressin (ADH)
- D. Thyroxine
Answer: C. Vasopressin (ADH) — Diabetes insipidus is caused by the hyposecretion of vasopressin (Anti-diuretic Hormone), leading to excessive water loss through urine.
MCQ 4. Which hormone regulates the sleep-wake cycle in humans?
- A. Thyroxine
- B. Melatonin
- C. Cortisol
- D. Adrenaline
Answer: B. Melatonin — Melatonin, secreted by the pineal gland, plays a crucial role in regulating the 24-hour diurnal rhythm of our body, including the sleep-wake cycle.
MCQ 5. Exophthalmic goitre is a form of hyperthyroidism characterized by:
- A. Enlargement of the thyroid gland
- B. Protrusion of eyeballs
- C. Increased basal metabolic rate
- D. All of the above
Answer: D. All of the above — Exophthalmic goitre (Grave's disease) is a type of hyperthyroidism causing an enlarged thyroid gland, bulging eyes (exophthalmos), and an elevated metabolic rate.
MCQ 6. Which hormone is responsible for lowering blood calcium levels?
- A. Parathyroid Hormone (PTH)
- B. Calcitonin
- C. Thyroxine
- D. Aldosterone
Answer: B. Calcitonin — Calcitonin, secreted by the thyroid gland, acts to decrease blood calcium levels by suppressing bone resorption and increasing calcium excretion by the kidneys.
MCQ 7. A sudden fall in parathyroid hormone (PTH) levels can lead to:
- A. Osteoporosis
- B. Hypercalcemia
- C. Tetany
- D. Kidney stones
Answer: C. Tetany — Hyposecretion of PTH leads to a decrease in blood calcium levels (hypocalcemia), which can cause muscle cramps and sustained muscle contractions known as tetany.
MCQ 8. The thymus gland primarily plays a role in:
- A. Regulating blood glucose
- B. Maturation of T-lymphocytes
- C. Secreting digestive enzymes
- D. Controlling mineral metabolism
Answer: B. Maturation of T-lymphocytes — The thymus gland secretes thymosins, which play a major role in the differentiation and maturation of T-lymphocytes, thereby contributing to cell-mediated immunity.
MCQ 9. 'Fight or flight' response is primarily mediated by hormones from which gland?
- A. Thyroid gland
- B. Adrenal medulla
- C. Pancreas
- D. Gonads
Answer: B. Adrenal medulla — The adrenal medulla secretes adrenaline (epinephrine) and noradrenaline (norepinephrine), which are rapidly released during stress and are responsible for the 'fight or flight' response.
MCQ 10. Glucocorticoids are secreted by which part of the adrenal gland?
- A. Adrenal medulla
- B. Adrenal cortex
- C. Zona glomerulosa
- D. Zona reticularis
Answer: B. Adrenal cortex — The adrenal cortex secretes glucocorticoids (e.g., cortisol) and mineralocorticoids (e.g., aldosterone), while the adrenal medulla secretes catecholamines.
MCQ 11. Which of the following conditions is associated with the hypersecretion of cortisol?
- A. Addison's disease
- B. Grave's disease
- C. Cushing's syndrome
- D. Diabetes mellitus
Answer: C. Cushing's syndrome — Cushing's syndrome results from prolonged exposure to high levels of cortisol, often due to hypersecretion by the adrenal cortex.
MCQ 12. Insulin is secreted by which cells of the pancreas?
- A. Alpha cells
- B. Beta cells
- C. Delta cells
- D. F cells
Answer: B. Beta cells — Insulin is secreted by the beta cells of the islets of Langerhans in the pancreas, and it helps lower blood glucose levels.
MCQ 13. Which hormone increases blood glucose levels by promoting glycogenolysis and gluconeogenesis?
- A. Insulin
- B. Glucagon
- C. Somatostatin
- D. Gastrin
Answer: B. Glucagon — Glucagon, secreted by alpha cells of the pancreas, primarily acts on the liver to increase blood glucose levels through glycogenolysis and gluconeogenesis.
MCQ 14. Steroid hormones typically exert their effects by:
- A. Binding to receptors on the cell surface
- B. Activating secondary messenger systems
- C. Entering the cell and binding to intracellular receptors
- D. Directly stimulating the release of other hormones
Answer: C. Entering the cell and binding to intracellular receptors — Steroid hormones are lipid-soluble and can easily pass through the cell membrane to bind with intracellular receptors, forming a hormone-receptor complex that regulates gene expression.
MCQ 15. Which of the following is NOT a peptide hormone?
- A. Insulin
- B. Glucagon
- C. Thyroxine
- D. Oxytocin
Answer: C. Thyroxine — Thyroxine is an iodinated derivative of an amino acid (tyrosine), whereas insulin, glucagon, and oxytocin are peptide hormones.
MCQ 16. Gonadotropins (LH and FSH) are secreted by which part of the pituitary gland?
- A. Posterior pituitary
- B. Anterior pituitary
- C. Pars intermedia
- D. Hypothalamus
Answer: B. Anterior pituitary — Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) are gonadotropins secreted by the anterior pituitary gland, regulating gonadal activity.
MCQ 17. The primary function of growth hormone (GH) in the body is to:
- A. Regulate blood sugar
- B. Stimulate protein synthesis and bone growth
- C. Control fluid balance
- D. Influence immune response
Answer: B. Stimulate protein synthesis and bone growth — Growth hormone (GH) promotes growth by stimulating protein synthesis, cell division, and bone elongation.
MCQ 18. Acromegaly is a condition caused by:
- A. Hyposecretion of GH in adults
- B. Hypersecretion of GH in adults
- C. Hyposecretion of GH in children
- D. Hypersecretion of TSH in adults
Answer: B. Hypersecretion of GH in adults — Acromegaly results from the hypersecretion of growth hormone (GH) in adults, leading to abnormal growth, especially of the face, hands, and feet.
MCQ 19. Which mineral is essential for the synthesis of thyroid hormones?
- A. Calcium
- B. Iron
- C. Iodine
- D. Sodium
Answer: C. Iodine — Iodine is a crucial component required for the synthesis of thyroid hormones (Thyroxine and Triiodothyronine) by the thyroid gland.
MCQ 20. The hormone that primarily maintains sodium and water balance in the body is:
- A. Cortisol
- B. Aldosterone
- C. Adrenaline
- D. Calcitonin
Answer: B. Aldosterone — Aldosterone, a mineralocorticoid from the adrenal cortex, regulates electrolyte balance by promoting reabsorption of sodium and water and excretion of potassium in the renal tubules.
How to Use These Solutions
Attempt each question yourself first and only then compare with the worked answer. Marks in the CBSE board exam are awarded for the METHOD as much as the final result, so reproduce the steps rather than memorising the last line. Where a solution states a law, a formula or a definition, learn that wording — examiners look for it.
Related practice for this chapter: chapter MCQs, previous-year questions, revision notes and sample papers.