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.

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TL;DR: Free step-by-step NCERT solutions for Class 11 Biology chapter "Chemical Coordination and Integration" — 8 important questions with detailed answers f…

Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated Jul 23, 2026

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Key Questions Covered:

Define hormones. What are their characteristics?
What is the hypothalamic-pituitary axis? Explain with an example.
Name the hormones secreted by the anterior pituitary and their functions.
What are thyroid hormones and their effects?
What is the role of parathyroid hormone and calcitonin in calcium homeostasis?
Explain the effects of epinephrine during the fight-or-flight response.
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
Define hormones. What are their characteristics?	✓ Solved
What is the hypothalamic-pituitary axis? Explain with an …	✓ Solved
Name the hormones secreted by the anterior pituitary and …	✓ Solved
What are thyroid hormones and their effects?	✓ Solved
What is the role of parathyroid hormone and calcitonin in…	✓ Solved
Explain the effects of epinephrine during the fight-or-fl…	✓ Solved

Showing 6 of 8 questions

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

Showing 6 of 8 questions. Visit the full page for complete solutions.