Chemical Coordination and Integration Class 11 Notes CBSE Biology Chapter 22 [Free PDF Download]

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. The gland that acts as biological clock in our body is pineal gland. The secretion of 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 human body. Name the glands which is absent in male and the one absent in female.  

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 pituitary gland is MSH i.e., Melanocyte Stimulating Hormone.

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 stimulate 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 second messenger in the mechanism of protein hormone action?

Ans. Secondary messenger help in regulating the metabolism of cell. There are some hormones that cannot enter the cell and bind to membrane bound receptors. When these hormones bind to the receptors, they stimulate the release of secondary messenger which help in bringing out the desired biochemical change.

9.  Draw a well labelled diagram of thyroid gland.

Ans.

10. Define the following:

i. Exocrine gland

ii. Endocrine gland

Ans. (i) Exocrine gland are the glands that have ducts and they pour their secretion on 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.Corpus luteum is a temporary endocrine gland which is formed in the ovary from the remnants of Graafian follicle after the ovulation. It produces a hormone called progesterone which is important for 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, gastrointestinal tract also produces 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 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 are 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 regulates 24 hours 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, deaf. 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 parathyroid called parathyroid hormone. It has the following effects:

(i) Maintenance of proper calcium and phosphate level 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, increases alertness, sweating, etc.           

The 3 layers of 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, 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 decreases blood glucose levels. So, it is known as a hypoglycemic hormone. Prolonged hyperglycemia causes diabetes mellitus.

Testes

The location of 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 mustaches, 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 hormones.

Progesterone Helps in:

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

(ii) placentation.

(iii) development of breast 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

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 that 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 activity levels of the target tissue. The binding of hormones to hormone-receptor 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. 

CBSE Class 11 Biology Revision Notes Chapter 22 - Chemical Coordination and Integration

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NCERT Class 11 Revision Notes Biology Chapter 22

Control and coordination are done by the neural system and the endocrine system together in animals. The endocrine system is necessary to coordinate the functions when the nerve fibres do not innervate every cell of the body.

Endocrine Glands

• They are the ductless glands. Their secretion is directly released into the blood, sent to specific target organs to start a particular metabolic change.

• They also secrete chemicals which are called hormones.

• Hormones are non-nutrient chemicals that are produced in trace amounts and serve as intracellular messengers.

Human Endocrine System

In humans, the endocrine glands and hormone-producing cells are situated in different parts of our body. The kidney, liver, Gastrointestinal tract, and heart also release a very small quantity of hormones to regulate and coordinate the function of respective organs.

Hypothalamus contains many groups of neurosecretory cells called nuclei that produce hormones. These regulate the secretion and synthesis of pituitary hormones.

It Produces Two Types of Hormones:

• These hormones reach the anterior pituitary through the portal circulatory system and control its function.

• It also controls the posterior pituitary.

Pituitary Gland is available in sella turcica, a bony cavity. It is connected to the hypothalamus with a stalk.

• The overgrowth of the body due to the excess of growth hormone leads to gigantism, and low secretion leads to stunted growth known as dwarfism.

• The growth of the mammary gland and production of milk is stimulated by prolactin.

• TSH also stimulates the production and release of thyroid hormone.

• LH and FSH stimulate gonads. The LH in males stimulates the synthesis and secretion of androgen hormone from the testis in the male body. The LH in females induces the ovulation of a fully mature ovum from the ovary.

• The contraction of the uterus during childbirth and milk ejection from mammary glands is controlled by oxytocin.

• The absorption of water and electrolyte in the kidney is stimulated by vasopressin.

• MSH works on the melanocytes and controls skin pigmentation.

The Pineal Gland - Is present on the forebrain's dorsal side and gives out melatonin hormone to regulate the body's diurnal rhythm like the water cycle, sleep, and body temperature.

Thyroid Gland - It consists of two lobes on either side of the trachea, which is connected by the isthmus.

The thyroid gland is made up of stromal and follicles tissues:

• Iodine is required for the synthesis of thyroid hormones. The deficiency of iodine can result in hypothyroidism (Goitre). Hypothyroidism may also result in stunted growth of the baby and mental retardation in the baby during pregnancy. 

• Thyroid hormones control the basal metabolic rate. These hormones support the process of red blood cell formation. They regulate the metabolism of proteins, carbohydrates, and fats. Thyrocalcitonin hormone also regulates calcium levels in the blood.

Parathyroid Gland - It is found on the backside of the thyroid gland. It also secretes peptide hormone, which is called parathyroid hormone (PTH). PTH controls the calcium ion concentration present in the blood. It aids in the reabsorption of calcium from digestive tracts and renal tubules.

Thymus - It is found on the dorsal side of the heart and the aorta. This gland secretes peptide hormone thymosins that aids in the differentiation of T-Lymphocytes for cell-mediated immunity. It also helps to produce the antibodies to provide humoral immunity.

Adrenal Gland - It is found on the anterior part of each of the kidney, which is composed of two types of tissues - outside adrenal cortex and central adrenal medulla. The adrenal medulla releases adrenaline and noradrenaline hormone, which are called catecholamines. These hormones are also known as an emergency hormone. It also helps in increasing alertness, pupillary dilation, heartbeat, rate of respiration, glycogenolysis, sweating.

While the adrenal cortex releases glucocorticoids and mineralocorticoids, Gluconeogenesis is stimulated by Glucocorticoids. The water and electrolyte contents of the body are controlled by Mineralocorticoids.

Pancreas - It acts as both exocrine and endocrine glands. The endocrine pancreas contains “Islets of Langerhans,” which include the α-cells and β-cells. The α-cells secrete glucagon while the β-cells secrete insulin. Both hormones are used for maintaining blood sugar levels.

• Glucagon is a type of peptide hormone that stimulates glycogenolysis leading to increased blood sugar (hyperglycemia).

• Insulin is a type of peptide hormone that acts as a regulator in glucose homeostasis. It stimulates increased movement of glucose from the blood to hepatocytes and adipocytes, which leads to a decreased level of blood glucose (hypoglycemia).

Testis - It performs double functions, which are as a primary sex organ and also as an endocrine gland. Leydig cells or interstitial cells or Leydig cells produce androgen, testosterone, which controls the spermatogenesis and the maturation of primary sex organs.

Ovary - It produces two groups of steroid hormones, namely Estrogen and Progesterone. The Estrogen is secreted by growing ovarian follicles. The ruptured ovum called corpus luteum secretes progesterone after ovulation. Estrogen secretes a wide range of actions like the development of growing ovarian follicles, growth of female secondary sex organs, and regulation of female sexual behaviour.

The pregnancy is regulated by progesterone.

The Hormones of Heart, Kidney, and Gastrointestinal Tract

• The atrial wall of the heart secretes a type of peptide hormone called atrial natriuretic factor (ANF), which results in decreases in blood pressure.

• The juxtaglomerular cells of the kidney secrets the erythropoietin hormone, which triggers erythropoiesis.

• Gastrointestinal tract release four main peptide hormones:

1. The secretion of hydrochloric acid and pepsinogen is stimulated by gastrin.

2. Secretin works on the exocrine pancreas and triggers the secretion of bicarbonate ions and water.

3. The secretion of bile juice and pancreatic enzymes is stimulated by Cholecystokinin (CCK).

4. The gastric secretion and motility are inhibited by Gastric inhibitory peptide (GIP).

Mechanism of Hormone Action

• The hormone can lead to their effects on target tissues after binding to a specific protein called hormone receptors located in the target tissue.

• The binding of hormones to receptors results in the hormone-receptor complex formation, which leads to a change in the target tissue.

Hormones are Grouped Based on Their Chemical Nature:

1. Peptide, Polypeptide, and Protein Hormones - Insulin, hypothalamic hormones, glucagon, a pituitary hormone. 

2. Steroids - Testosterone, cortisol, Progesterone.

3. Iodothyronines - These are also called thyroid hormones.

4. Amino Acid Derivatives - Which are also called epinephrine.

The hormones that bind with membrane-bound receptors normally do not go to the target cells but produce a second messenger, which further regulates cellular metabolism.

The hormones (steroid hormones) that interact with intracellular receptors mostly control the chromosome function or gene expression by interaction with hormone-receptor complexes with the genome. These biochemical actions lead to physiological and developmental consequences.