Chemical Coordination And Integration Class 11 Notes: CBSE Biology Chapter 19

Section–A (1 Mark Questions)

1. Define hormones.

Ans. Hormones are defined as non-nutrient chemicals which act as intracellular messengers and are produced in trace amounts.

2. Name the gland that functions as a biological clock in our body. Name its one secretion.

Ans. he gland that acts as a biological clock in our body is the pineal gland. The secretion of the pineal gland is melatonin. 

3. What are gonadotropins?

Ans. Gonadotropins are the gonads stimulating hormones produced by the anterior pituitary gland. There are two gonadotropins produced are: LH – Luteinizing Hormone and FSH- Follicle Stimulating Hormone. 

4. There are many endocrine glands in the human body. Name the glands that are absent in males and the ones absent in females.  

Ans. In males, ovaries are absent and in females, testes are absent.

5. Name the only hormone secreted by pars intermedia of the pituitary gland.

Ans. The hormone secreted by pars intermedia of the pituitary gland is MSH i.e., Melanocyte Stimulating Hormon.

Section–B (2 Mark Questions)

6.  What is erythropoiesis? Which hormone stimulates it?

Ans. Erythropoiesis is the process of formation of red blood cells. Erythropoietin is the hormone that stimulates erythropoiesis. 

7. Which hormonal deficiency is responsible for the following:

i. Diabetes mellitus

ii. Goitre

iii. Diabetes insipidus

iv. Addison’s disease

Ans. (i) Insulin

 (ii) Thyroxine

(iii) Aldosterone

(iv) Mineralocorticoid 

8. What is the role of the second messenger in the mechanism of protein hormone action?

Ans. Secondary messenger helps in regulating the metabolism of cells. Some hormones cannot enter the cell and bind to membrane-bound receptors. When these hormones bind to the receptors, they stimulate the release of secondary messengers which helps in bringing out the desired biochemical change.

9.  Draw a well-labelled diagram of the thyroid gland.

Ans.

10. Define the following:

i. Exocrine gland

ii. Endocrine gland

Ans. (i) Exocrine glands are the glands that have ducts and they pour their secretion on the epithelial surface directly or through ducts.    

 (ii) Endocrine glands are the glands that lack ducts and are hence called ductless glands. Their secretions are called hormones which are poured directly into blood and lymph.  

                                            

11. What is corpus luteum? How does it function as an endocrine gland?

Ans. The Corpus luteum is a temporary endocrine gland that is formed in the ovary from the remnants of the Graafian follicle after ovulation. It produces a hormone called progesterone which is important for the maintenance of pregnancy.

Endocrine Glands

Endocrine glands are ductless glands. Their secretions are referred to as hormones. Hormones have been defined as non-nutrient chemicals which are produced in small amounts and are intracellular messengers. Hormones only stimulate metabolic reactions, they do not take part in such reactions.

Human Endocrine System

The location of the endocrine glands is in different parts of the human body. Different endocrine glands are the pituitary, pineal, thyroid, parathyroid, thymus, adrenal, and gonads. The kidney, liver, and gastrointestinal tract also produce some hormones.

The Hypothalamus

The location of the hypothalamus is at the base of the forebrain. The group of secretory cells present in the hypothalamus is known as nuclei that produce hormones. This regulates the synthesis and secretion of pituitary hormones are regulated by the hormones secreted by the hypothalamus. The hormones produced by from the hypothalamus are of two types-

(i) the releasing hormones 

(ii) the inhibiting hormones. 

For example, the gonadotropin-releasing hormone stimulates the release of gonadotropins from the pituitary. These hormones reach the pituitary gland with the assistance of the portal circulatory system. 

The Pituitary Gland

The location of the pituitary gland is in the cavity known as sella turcica which is attached to the hypothalamus via a stalk. It has two divisions as adenohypophysis or anterior pituitary and neurohypophysis or posterior pituitary. Hormones such as adrenocorticotropic hormone, growth hormone, thyroid-stimulating hormone melanocyte-stimulating hormone, prolactin, follicle-stimulating hormone, and luteinizing hormone are secreted by the adenohypophysis. The release of Vasopressin and oxytocin is by neurohypophysis.

The Pineal Gland

The location of the pineal gland is on the dorsal side of the forebrain. The pineal gland secretes the melatonin hormone. The melatonin hormone regulate the 24-hour rhythm in the body like body temperature, sleep-wake cycle etc. Along with the sleep-wake cycle, melatonin also controls:

(i) metabolism

(ii) pigmentation

(iii) menstrual cycle

(iv) defense capability

Thyroid Gland

Thyroid glands are located on either side of and anterior to the trachea. An isthmus connects the bilobed gland. The lobules of the thyroid gland are made up of follicles and thyroid follicles bound together by connective tissue are called stromal tissues. Thyroid follicles are composed of follicular cells that produce two hormones- tetraiodothyronine or thyroxine (T4) and triiodothyronine (T3). A vital element required for thyroid hormone synthesis is Iodine. Deficiency of iodine will lead to hypothyroidism, called Goitre. During pregnancy, hypothyroidism affects the growth of the baby, its mental condition also gets affected. There will be a low intelligence quotient, abnormal skin, and deafness. For adult women, there will be an irregular menstrual cycle in hypothyroidism. Another condition is when there is an increase in the secretion of thyroid hormone, it will be called hyperthyroidism. A form of hyperthyroidism is Exophthalmic goiter which is an enlargement of the thyroid gland, protrusion of the eyeballs, increased basal metabolic rate, and weight loss also referred to as Graves’ disease. 

Parathyroid Gland

Normally, there are four parathyroid glands in the human being, one superior and one inferior located immediately behind each upper and lower pole of the thyroid. A peptide hormone is secreted by a parathyroid called parathyroid hormone. It has the following effects:

(i) Maintenance of proper calcium and phosphate levels in blood.

(ii) Role in bone formation.

(iii) Excretion of calcium and phosphate.

(iv) Effect on intestinal absorption of calcium, phosphate, and vitamin D.

Thymus

The location of the thymus is in between the lungs behind the sternum. An important role is played by them in the development of the immune system. The hormone secreted by this gland is called thymosin. It participates in cell-mediated immunity. It also

participates in the production of antibodies.

Adrenal gland

It is a pair of glands located in the anterior part of the kidney. It is composed of two types of tissues- the outer adrenal cortex and the inner medulla. The adrenal medulla produces two hormones known as adrenaline and noradrenaline. Adrenaline is also known as an emergency hormone as it is secreted at the time of fear, fight, or flight. Adrenaline dilates the pupil and increases alertness, sweating, etc.           

The 3 layers of the adrenal cortex are- 

(i) zona reticularis (inner layer),

(ii) zona fasciculata (middle layer), and 

(iii) zona glomerulosa (outer layer). 

Hormones of the adrenal cortex are commonly known as corticoids. Corticoids which participate in carbohydrate metabolism are referred to as glucocorticoids. They stimulate proteolysis, lipolysis, and gluconeogenesis. The glucocorticoid includes cortisol and cortisone in which cortisol accounts for 95% of glucocorticoid activity which helps in anti-inflammatory reactions and suppresses the immune system.

Corticoids that help in regulating the level of water and electrolyte balance are referred to as mineralocorticoids. Aldosterone is the main hormone of mineralocorticoids. It helps in the reabsorption of sodium ions and water and the excretion of potassium and phosphate ions.

Pancreas

The pancreas is considered to be a dual gland, i.e., it is endocrine as well as exocrine in function. The endocrine part of the pancreas consists of islets of Langerhans that are mainly made up of two types of cells- alpha cells and beta cells. Alpha cells secrete hormones known as glucagon whereas beta cells secrete insulin. Glucagon maintains normal blood glucose. It increases blood glucose levels. It also promotes gluconeogenesis. So, glucagon is a hyperglycemic hormone.

Insulin also regulates glucose levels in our bodies. It enhances cellular glucose uptake thus decreasing blood glucose levels. So, it is known as a hypoglycemic hormone. Prolonged hyperglycemia causes diabetes mellitus.

Testes

The location of the testes is in the scrotal sacs present outside the abdominal cavity. They are the primary sex organ as well as endocrine in function. The testis includes seminiferous tubules and interstitial cells. Interstitial cells or Leydig cells secrete hormones known as testosterone. This hormone regulates spermatogenesis, the development of beards and moustaches, as well as the maturation of male accessory sex organs.

Ovary

The paired ovaries lie in the lower pelvic region of the abdominal cavity. It is one of the primary sex organs. Ovaries are mainly concerned with the production of ova or eggs and they also secrete two hormones, known as estrogen and progesterone.

Estrogen Helps in:

(i) development of accessory sex organs.

(ii) development of mammary glands.

(iii) menstrual cycle.

(iv) ovulation.

(v) water balance, by increasing water content and thickness of the skin.

Progesterone is responsible for changes during pregnancy hence, called pregnancy hormone.

Progesterone Helps in:

(i) enhancing the blood supply of the wall of the uterus.

(ii) placentation.

(iii) development of breasts during pregnancy.

(iv) helps in premenstrual changes in the uterus.

(v) also helps in the promotion of retention of water and sodium salts by affecting kidney functions.

Hormones of Kidney, Gastrointestinal Tract, and Kidney

The heart wall secretes a hormone referred to as atrial natriuretic factor (ANF) which decreases the blood pressure. ANF is released when blood pressure increases. 

The hormone secreted by kidney cells is called erythropoietin which helps in the promotion of  RBC formation. 

Gastrin, Secretin, Cholecystokinin, and Gastric inhibitory peptides are secreted by the gastrointestinal tract.

Mechanism of Hormone Action

The function of different hormones is to control and regulate the activity levels of the target tissue. The binding of hormones to hormone receptors produces their effects on target tissues. The hormone-receptor complex formed will result in certain biochemical changes within the target tissue. There will be the interaction of hormones with the membrane receptors as well as intracellular receptors. Steroid receptors are generally intracellular in nature whereas peptide hormones generally bind to membrane receptors. 

5 Important Topics of Biology Class 11 Chapter 19 You Shouldn’t Miss!

Importance of Biology Class 11 Chapter 19 Chemical Coordination and Integration Notes

• Chemical Coordination And Integration Class 11 Notes are essential for simplifying complex topics related to the body's hormonal regulation. 

• These notes help students understand how various endocrine glands and hormones work together to maintain homeostasis, control growth, and manage metabolism. 

• By using Class 11 Biology Chapter 19 Notes, students can quickly revise key concepts and prepare for exams with confidence. 

• The clear diagrams and summaries make it easier to grasp the important details of hormonal coordination, making the subject more approachable.

• Chemical Coordination And Integration Notes break down difficult concepts like feedback mechanisms, the role of the hypothalamus and pituitary gland, and the mechanism of hormone action into easy-to-understand explanations.

Tips for Learning the Class 11 Biology Chapter 19 Chemical Coordination And Integration 

• Focus on the Endocrine Glands: Understand the location and function of each endocrine gland, such as the thyroid, adrenal, and pituitary glands.

• Understand Hormonal Functions: Learn how different hormones regulate various processes like growth, metabolism, and stress response.

• Use Diagrams: Study diagrams that show the endocrine glands and their target organs to visualise the hormone pathways.

• Revise Feedback Mechanisms: Focus on positive and negative feedback loops that regulate hormone production and balance in the body.

• Practice Questions: Regularly solve questions related to hormone action and the role of glands to reinforce your understanding.

Conclusion

Chemical Coordination And Integration Class 11 Notes provide a clear understanding of how hormones regulate various body functions. These notes explain the role of endocrine glands, feedback mechanisms, and the action of hormones in a simple, easy-to-understand way. With the help of diagrams and summaries, students can quickly grasp complex topics like hormonal control of growth and metabolism. Class 11 Chemical Coordination And Integration Notes make learning more manageable and help students prepare effectively for their CBSE exams by focusing on key concepts and detailed explanations.

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