NCERT Solutions for Class 11 Biology Chapter 19 (2025-2026)

Coordination in multicellular organisms is achieved through two systems: the nervous system and the endocrine system. Chapter 19 of Class 11 Biology, Chemical Coordination and Integration, explores how hormones secreted by endocrine glands regulate and coordinate various physiological processes in the body. The chapter explains the structure and functions of major endocrine glands including the hypothalamus, pituitary, pineal, thyroid, parathyroid, thymus, adrenal, pancreas, and gonads. It examines the mechanism of hormone action, feedback mechanisms that regulate hormone secretion, and the role of hormones in growth, metabolism, reproduction, and stress response. The chapter also covers common disorders associated with hypo- and hyper-secretion of hormones. This chapter is part of the comprehensive NCERT Solutions Class 11 Biology series, which covers all chapters in detail.

The NCERT Solutions for Chemical Coordination and Integration provided here offer detailed, step-by-step explanations for all textbook questions, helping students strengthen their conceptual understanding, clear doubts effectively, and prepare efficiently for both school exams and competitive tests like NEET.

NCERT Solutions for Class 11 Biology Chapter 19 - All Exercise Questions

Chemical Coordination and Integration
Easy
Q.
Define the following:
(a) Exocrine gland
(b) Endocrine gland
(c) Hormone
Chemical Coordination and Integration
Easy
Q.
Diagrammatically indicate the location of the various endocrine glands in our body.
Chemical Coordination and Integration
Difficult
Q.
List the hormones secreted by the following:
(a) Hypothalamus
(b) Pituitary
(c) Thyroid
(d) Parathyroid
(e) Adrenal
(f) Pancreas
(g) Testis
(h) Ovary
(i) Thymus
(j) Atrium
(k) Kidney
(l) G-I Tract
Chemical Coordination and Integration
Easy
Q.
Fill in the blanks:
Chemical Coordination and Integration
Difficult
Q.
Write short notes on the functions of the following hormones:
(a) Parathyroid hormone (PTH)
(b) Thyroid hormones
(c) Thymosins
(d) Androgens
(e) Estrogens
(f) Insulin and Glucagon
Chemical Coordination and Integration
Easy
Q.
Give example(s) of:
(a) Hyperglycemic hormone and hypoglycemic hormone
(b) Hypercalcemic hormone
(c) Gonadotrophic hormones
(d) Progestational hormone
(e) Blood pressure lowering hormone
(f) Androgens and estrogens
Chemical Coordination and Integration
Easy
Q.
Which hormonal deficiency is responsible for the following?
(a) Diabetes mellitus  
(b) Goitre   
(c) Cretinism
 
Chemical Coordination and Integration
Difficult
Q.
Briefly mention the mechanism of action of FSH.
Chemical Coordination and Integration
Easy
Q.
Match the following:
Column I
Column II
(a) T4 
 (i) Hypothalamus
(b) PTH
 (ii) Thyroid
(c) GnRH
 (iii) Pituitary
(d) LH
(iv) Parathyroid

Download the PDF of NCERT Solutions for Class 11 Biology Chapter 19 –Chemical Coordination and Integration

Class 11 Chapter 19 Biology Questions & Answers -Chemical Coordination and Integration

Q1. Define the following:
(a) Exocrine gland
(b) Endocrine gland
(c) Hormone

Solution: .

(a) Exocrine gland: The glands which secrete their products via a duct are called exocrine glands. Examples: sweat glands, salivary glands, mammary glands and liver.

(b) Endocrine gland: The glands that do not secrete their products (hormones) via any duct, but directly secrete them into the bloodstream or into its surrounding tissues are known as endocrine glands. Examples: adrenal gland, pituitary gland and thyroid glands.

(c) Hormone: The secretions of endocrine glands that perform their function at a distant location, away from the location of their origin by travelling through the bloodstream are called hormones. They can also diffuse to their neighbouring tissues.

Current scientific definition defines hormones as “Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.”  Example: thyroid hormone, follicle stimulating hormone, testosterone.

 

Q2.Diagrammatically indicate the location of the various endocrine glands in our body.
Solution: Diagrammatic representation of the location of various endocrine glands in our body:

 

Q3. List the hormones secreted by the following:
(a) Hypothalamus
(b) Pituitary
(c) Thyroid
(d) Parathyroid
(e) Adrenal
(f) Pancreas
(g) Testis
(h) Ovary
(i) Thymus
(j) Atrium
(k) Kidney
(l) G-I Tract

Solution:

(a) Hypothalamus: Two types of hormones are secreted by hypothalamus:

(i) Releasing hormones: Gonadotropin releasing hormone, thyrotrophin releasing hormone, somatotrophin releasing hormone and adrenocorticotrophic hormone

(ii) Inhibiting hormones: Somatostatin, growth- inhibiting hormone and melanocyte-stimulating hormone

(b) Pituitary: List of hormones secreted by two different parts of the pituitary gland:

(i)  Hormones secreted by Adenohypophysis: Growth hormone (GH), prolactin, thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH), melanocyte stimulating hormone (MSH) and follicle stimulating hormone (FSH)

(ii) Hormones secreted by Neurohypophysis: Oxytocin and vasopressin

(c) Thyroid: Thyroxin (T4), triiodothyronine (T3) and thyrocalcitonin

(d) Parathyroid: Parathyroid hormone (PTH)

(e) Adrenal: List of hormones secreted by adrenal gland:

  • Corticoid hormones are secreted by adrenal cortex. Corticoids are further divided into

-glucocorticoid (hormone secreted is cortisol)

-mineralocorticoid (hormone secreted is aldosterone).

  • Catecholamines are secreted by adrenal medulla. It secretes adrenaline (also called epinephrine) and noradrenaline (also called norepinephrine).

(f) Pancreas: Insulin and glucagon

(g) Testis: Testosterone

(h) Ovary: Estrogen and progesterone

(i) Thymus: Thymosins

(j) Atrium: Atrial natriuretic hormone (ANH)

(k) Kidney: Erythropoietin

(l) G-I Tract: Gastrin, secretin, cholecystokinin and gastric inhibitory peptide (GIP, also known as glucose-dependent insulinotropic peptide).

 

Q4. Fill in the blanks:

Solution:

 

Write short notes on the functions of the following hormones:

(a) Parathyroid hormone (PTH)
(b) Thyroid hormones
(c) Thymosins
(d) Androgens
(e) Estrogens
(f) Insulin and Glucagon

Solution:

(a) Parathyroid hormone (PTH): Parathyroid hormone is a peptide hormone and secreted by parathyroid glands. It plays a significant role in:

  • Calcium homeostasis in the body. It increases the calcium level in blood. It also stimulates calcium absorption from digested food and reabsorption of Ca++ by renal tubules.
  • It stimulates the dissolution and demineralisation of bones.

(b) Thyroid hormones: Thyroxine (T4), tri-iodothyronine (T3) and thyrocalcitonin are collectively called as thyroid hormones. Iodine is essential for an adequate rate of thyroid hormone synthesis. Low level of thyroid hormones (hypothyroidism) results in enlargement of the thyroid gland, commonly called goitre. Excessive synthesis of thyroid hormones is called hyperthyroidism which is also harmful to the body. Thyroid hormones are essential for many physiological processes.

  • They play an important role in maintaining normal basal metabolic rate (BMR).
  • They control the metabolism of carbohydrates, proteins and fats.
  • They also help in red blood cell (RBCs) formation and regulating blood calcium levels.
  • They also influence water and electrolytes balance.

(c) Thymosins: It is a peptide hormone and secreted by the thymus. Its functions are:

  • Differentiation of T-lymphocytes which are essential for cell-mediated immunity.
  • Promotes antibody production which provides humoral immunity.

(d) Androgens: Androgens are a group of hormones. Main androgen hormone is testosterone hormone. Androgens are secreted by leydig cells of testes. The main functions of androgens are:

  • It stimulates the development of male secondary sex characteristics.
  • It is required for the development, maturation and functions of the male accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate gland, urethra, etc.
  • It stimulates spermatogenesis (formation of spermatozoa) and influence male sexual behaviour (libido).

(e) Estrogens: Estrogen is a steroid hormone produced by the ovaries. The main functions of estrogen are:

  • It stimulates the development of female secondary sex organs.
  • It helps in the development of ovarian follicles and mammary glands.
  • It also regulates female sexual behaviour.

(f) Insulin and Glucagon: Functions of Insulin and glucagon:

  • Insulin stimulates uptake of excess glucose and its utilisation by liver cells by the process of glycogenesis. In glycogenesis, excess glucose is converted into its polymer glycogen and stored in the liver cells. Deficiency of insulin results in a disease, called diabetes mellitus.
  • Glucagon acts in just the opposite manner. In case of low glucose level in blood, it stimulates the breakdown of glycogen and release of glucose in the bloodstream. It also stimulates the synthesis of glucose from non-carbohydrate substrates like pyruvate, lactate, glycerol, etc., by the process of gluconeogenesis.

 

Q6 Give example(s) of:

(a) Hyperglycemic hormone and hypoglycemic hormone
(b) Hypercalcemic hormone
(c) Gonadotrophic hormones
(d) Progestational hormone
(e) Blood pressure lowering hormone
(f) Androgens and estrogens

Solution: 

(a) Hyperglycemic hormone and hypoglycemic hormone: Hyperglycemic hormone- Glucagon, Hypoglycemic hormone- Insulin

(b) Hypercalcemic hormone: Parathyroid hormone

(c) Gonadotrophic hormones: Luteinising hormone, follicle-stimulating hormone

(d) Progestational hormone: Progesterone

(e) Blood pressure lowering hormone: Atrial natriuretic factor (ANF)

(f) Androgens and estrogens:  Androgen- Testosterone, Estrogen- Estradiol

 

Q7. Which hormonal deficiency is responsible for the following?

(a) Diabetes mellitus  
(b) Goitre   
(c) Cretinis

Solution:

(a) Diabetes mellitus: Diabetes mellitus is caused by deficiency of insulin. It is also caused when insulin becomes non-responsive to blood glucose level.

(b) Goitre: Goitre is the enlargement of thyroid glands and happens due to the deficiency of thyroid hormones.

(c) Cretinism: It is caused by low level of thyroid during pregnancy that results in the stunted growth of baby.

Q8. Briefly mention the mechanism of action of FSH.
Solution:  Follicle Stimulating Hormone (FSH) is synthesised and secreted by the anterior lobe of the pituitary gland. FSH, being a glycoprotein, is insoluble in lipid thus, cannot enter the target cells. So, these glycoproteins first bind with the specific receptor molecules, that are found on the surface of a cell membrane, form a hormone-receptor complex and activate the cellular system to perform functions.

Mechanism of Action: After the release of FSH from the site of production, it reaches the ovary, uterus or testis and binds to FSH receptor, present at the plasma membrane of these organs. FHS receptor is a transmembrane G-protein coupled receptor protein. The binding of FSH to receptor generates second messengers (cAMP). Secondary messengers start several biochemical changes inside these organs and carry out many important functions.

Functions:

  • In the ovary, it results in follicular development.
  • In the uterus, it is involved in the development of secretory endometrium during the luteal phase.
  • In the males, the FSH is responsible for spermatogenesis.

 

Q9.Match the following:

Column I
Column II
(a) T4
 (i) Hypothalamus
(b) PTH
 (ii) Thyroid
(c) GnRH
 (iii) Pituitary
(d) LH
(iv) Parathyroid

Solution: 

Column I Column II
(a) T4
(ii) Thyroid
(b) PTH
(iv) Parathyroid
(c) GnRH
 (i) Hypothalamus
(d) LH
(iii) Pituitary

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NCERT Solutions for Class 11 Biology Chapter 19 – FAQs

1. What is the difference between endocrine glands and exocrine glands?

Endocrine glands are ductless glands that secrete hormones directly into the bloodstream, which then carry these hormones to target organs (e.g., pituitary, thyroid, adrenal glands). Exocrine glands have ducts through which they release their secretions to specific locations or body surfaces (e.g., salivary glands, sweat glands, sebaceous glands). Hormones from endocrine glands have widespread effects throughout the body, while exocrine secretions act locally.

2. What is the role of the hypothalamus in the endocrine system?

The hypothalamus acts as the link between the nervous system and the endocrine system. It regulates the pituitary gland by secreting releasing hormones (which stimulate pituitary hormone secretion) and inhibiting hormones (which suppress pituitary hormone secretion). The hypothalamus also produces hormones like oxytocin and vasopressin (ADH), which are stored and released by the posterior pituitary. It controls various functions including body temperature, hunger, thirst, sleep, and circadian rhythms through hormonal regulation.

3. What are the major hormones secreted by the pancreas and their functions?

The pancreas functions as both an endocrine and exocrine gland. As an endocrine gland, it secretes two main hormones from the Islets of Langerhans:

(i) Insulin - secreted by beta cells, it lowers blood glucose levels by promoting glucose uptake by cells, glycogenesis (glucose to glycogen conversion), and lipogenesis, and

(ii) Glucagon - secreted by alpha cells, it raises blood glucose levels by promoting glycogenolysis (glycogen breakdown) and gluconeogenesis (glucose formation from non-carbohydrates). These hormones work antagonistically to maintain blood glucose homeostasis.

 

Q.1 Define Glomerular Filtration Rate (GFR).

Ans-

Glomerular Filtration Rate (GFR) is the amount of filtrate formed by the kidneys per minute. It is measured in ml/min. In a healthy person, GFR is approximately 125 ml/min that is equal to 180 litres per day.

Q.2 Explain the autoregulatory mechanism of GFR.

Ans-

Kidneys maintain a uniform Glomerular Filtration Rate (GFR) with the help of the autoregulatory mechanism. Kidneys have a microscopic structure called juxta glomerular apparatus (JGA) located between an afferent arteriole and distal convoluted tube of the same nephron that is required for this auto-regulation. Whenever there is a fall in glomerular blood flow/glomerular blood pressure/GFR, cells of juxta glomerular apparatus release a hormone called renin which converts angiotensinogen in the blood to angiotensin I and further to angiotensin II.

  • Angiotensin II is a strong vasoconstrictor. It increases the glomerular blood pressure and blood flow and thereby, increases the GFR.
  • Angiotensin II also activates the release of Aldosterone which causes reabsorption of Na+ and water from the distal parts of the tubule. This also causes an increase in blood pressure and GFR.

Q.3 Indicate whether the following statements are true or false:
(a) Micturition is carried out by a reflex.
(b) ADH helps in water elimination, making the urine hypotonic.
(c) Protein-free fluid is filtered from blood plasma into the Bowman’s capsule.
(d) Henle’s loop plays an important role in concentrating the urine.
(e) Glucose is actively reabsorbed in the proximal convoluted tubule.

Ans-

(a) True

(b) False

(c) True

(d) True

(e) True

Q.4 Give a brief account of the counter current mechanism.

Ans-

The transport of substances facilitated by a special arrangement of Henle’s loop of nephron and vasa recta is called counter current mechanism.

When fluid flows in these two tubes which are anti-parallel to each other, it forms a counter current. This helps mammals to produce concentrated urine. There are two counter current systems in human kidneys-

  • Henle’s loop consists of ascending and descending limbs. Fluid flows in the two limbs in opposite directions making a counter current system.
  • Second counter current system is made by vasa recta. Blood flows in the two limbs of vasa recta in anti-parallel direction.

Henle’s loop and vasa recta are positioned next to each other. Descending limb of Henle’s loop is anti-parallel to ascending limb of vasa recta and ascending limb of Henle’s loop is anti-parallel to descending limb of vasa recta. Counter current system and proximity of the loops help to increase the osmolarity (solute concentration) in inner medullary interstitium i.e. from 300mOsmolL-1 in the cortex to about 1200mOsmolL-1 in the inner medulla. Increased solute concentration in medullary interstitium causes water to come out of collecting duct making the urine concentrated. This system has the ability to concentrate urine upto four times depending upon the need.

Q.5 Describe the role of liver, lungs and skin in excretion.

Ans-

In addition to kidneys, liver, lungs and skin also play an important role in excretion of waste materials from the body.

Liver: It is the largest gland of the human body. Liver converts toxic ammonia into less toxic urea; thus carry out the detoxification role. It helps in the excretion of bile containing substances like bilirubin, biliverdin which are produced by the decomposition of haemoglobin pigment. Then bilirubin, biliverdin, urea along with other waste like cholesterol, degraded steroid hormones, vitamins and drugs are excreted by the liver. Finally, these substances are thrown out of the body along with digestive wastes.

Role of Lungs: Lungs diffuse out a large amount of gaseous waste like CO2 (18 litres/day) as part of normal respiration along with the significant quantity of water.

Role of Skin: Skin contains sweat and sebaceous glands which help in the excretion of many substances. The sweat produced by sweat glands secrete NaCl, small amounts of urea, lactic acid, etc., along with water. Sebaceous glands help in excretion by elimination of certain sterols, hydrocarbons and waxes through sebum.

Q.6 Explain micturition.

Ans-

Micturition is the process of releasing of urine from urinary bladder. Urine formed by kidney is carried to urinary bladder where it is stored. When urinary bladder is filled with urine, it exerts the pressure on bladder wall. Pressure activates receptors present in bladder wall that send signals to central nervous system (CNS). The CNS sends the signal for the contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincter causing the release of urine.

An adult human excretes about 1 to 1.5 litres of urine per day. The urine is light yellow coloured watery fluid which is slightly acidic with a characteristic odour.

Q.7 Match the items of column I with those of column II:

Q.8 What is meant by the term osmoregulation?

Ans-

Osmoregulation is a process by which organisms maintain homeostasis of water content in their body. It protects body fluids from becoming too dilute or too concentrated. For example, large amount of water goes into the nephrons from blood during the process of glomerular filtration. This water is reabsorbed by medullary interstitium and transferred again to blood in vasa recta thus, maintaining water homeostasis in blood.

Q.9 Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic. Why?

Ans-

Terrestrial animals are generally either ureotelic or uricotelic because it is an adaptation to conserve water. In these animals, water soluble ammonia is converted into less soluble urea and uric acid. These are then filtered by the kidney and excreted out with urine. This requires minimum water; thus the animal conserves water.

Ans-10 What is the significance of juxta glomerular apparatus (JGA) in kidney function?

Ans-

Kidneys have a microscopic structure called juxta glomerular apparatus (JGA) between an afferent arteriole and distal convoluted tubule of the same nephron that is required for the maintenance of uniform Glomerular Filtration Rate (GFR). Whenever there is a fall in GFR, cells of juxta glomerular apparatus release a hormone called renin which travels into the bloodstream of glomerulus where it converts angiotensinogen into angiotensin I. Angiotensin I further gets converted to angiotensin II. Angiotensin helps in constriction of smooth muscle cells of the blood vessel that increases the blood pressure. Increased blood pressure results in an increase in glomerular filtration rate. Angiotensin also stimulates the secretion of aldosterone from adrenal glands. Aldosterone increases the absorption of sodium ions and water which increases blood pressure and brings the GFR back to normal. Thus, juxta glomerular apparatus plays a complex regulatory role in the functioning of the kidney.

Q.11 Name the following:
(a) A chordate animal having flame cells as excretory structures
(b) Cortical portions projecting between the medullary pyramids in the human kidney
(c) A loop of capillary running parallel to Henle’s loop

Ans-

(a) Amphioxus
(b) Columns of Bertini
(c) Vasa recta

Q.12 Fill in the gaps:
(a) Ascending limb of Henle’s loop is _______ to water whereas the descending limb is _______ to it.
(b) Reabsorption of water from distal parts of the tubules is facilitated by hormone _______.
(c) Dialysis fluid contains all the constituents as in plasma except _______.
(d) A healthy adult human excretes (on an average) _______ gm of urea/day.

Ans-

(a) Ascending limb of Henle’s loop is impermeable to water whereas the descending limb is permeable to it.

(b) Reabsorption of water from distal parts of the tubules is facilitated by hormone antidiuretic hormone or vasopressin.

(c) Dialysis fluid contains all the constituents as in plasma except the nitrogenous waste.

(d) A healthy adult human excretes (on an average) 25-30 gm of urea/day.

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