CBSE Class 11 Biology Revision Notes Chapter 22

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

Class 11 Biology Chapter 22 Chemical Coordination and Integration involve various topics such as the endocrine glands, the pituitary glands, hormones secreted from various glands, their functions, the target organs and many more. Students can refer to the Chapter 22 Biology Class 11 notes by Extramarks for a thorough and better understanding of the concepts covered in this chapter and also clarify their doubts.

Access Class 11 Biology Chapter 22- Chemical Coordination and Integration

Endocrine Glands

The secretions from endocrine glands are called hormones, and the endocrine glands are ductless glands. Hormones do not take part in the reactions of the body, rather they stimulate metabolic reactions. They are intercellular messengers and are the un-nutritious chemicals produced in small amounts.

Human Endocrine System

There are many endocrine glands located in the different parts of the body -the pituitary, pineal, thymus, parathyroid, adrenal, thyroid and gonads. Hormones are also produced by the kidney, liver and gastrointestinal tract.

The Hypothalamus

The hypothalamus is situated at the base of the forebrain. The nuclei are the group of secretory cells present in the hypothalamus which produce the hormones. A balance is maintained through this. The secretion of pituitary hormones is controlled and regulated by hormones secreted by the hypothalamus. The hormones of the hypothalamus are of two kinds:

• The releasing hormones
• The inhibiting hormones

The gonadotropin-releasing hormones stimulate the release of gonadotropins from the pituitary. The portal circulatory system helps these hormones to reach the pituitary gland.

The Pituitary Gland

The pituitary gland is situated in the cavity known as Sella turcica. This cavity is attached to the hypothalamus with the help of a stalk. It has two divisions. They are adenohypophysis or anterior pituitary and neurohypophysis or posterior pituitary. The adenohypophysis secretes the adrenocorticotropic hormone, growth hormone, thyroid-stimulating hormone, prolactin, follicle-stimulating hormone, melanocyte-stimulating hormone, and luteinizing hormone. The neurohypophysis releases vasopressin and oxytocin.  

The Pineal Gland

The pineal gland is situated on the dorsal side of the forebrain. This gland secretes the melatonin hormone, which regulates the 24 hours rhythm in the body. For example, the body temperature, sleep-walking cycle, etc. It is also associated with controlling metabolism, pigmentation, menstrual cycle and defence capability.

Thyroid Gland

On either side of and anterior to the trachea, the thyroid glands are situated. The isthmus connects the bilobed gland. Stromal tissues are the thyroid follicles binder together by the connective tissue. The lobules of the thyroid gland are made of these and the follicles. The thyroid follicles are made up of follicular cells that produce two hormones; they are tetraiodothyronine or thyroxine (T4) and triiodothyronine (T3). Iodine is an essential element required for the synthesis of thyroid hormones. The deficiency of iodine in the body can cause hypothyroidism called Goitre. 

Hypothyroidism affects the growth of a baby during pregnancy. It also affects the baby’s mental condition. It might lead to the baby having a low intelligence quotient, abnormal skin and deafness. Hypothyroidism in adult women can cause irregular menstrual cycles. Hyperthyroidism is a condition caused by the excessive secretion of thyroid hormone. Exophthalmic goitre, which is the enlargement of the thyroid gland, the protrusion of eyeballs, the increase in basal metabolic rate, and weight loss, is a form of hyperthyroidism. It is also referred to as Graves’ disease.

Parathyroid Gland

There are four parathyroid glands in a human being. They are one superior and one inferior situated behind each upper and lower pole of the thyroid. The parathyroid gland secretes a peptide hormone which is known as parathyroid hormone. It has many effects some of which are given below.

1. It maintains the level of calcium and phosphate in the blood.
2. It plays a significant role in bone formation.
3. It excretes calcium and phosphate.
4. It has effects on the intestinal absorption of calcium, phosphate and Vitamin D.

Thymus

The thymus in the human body is located in between the lungs behind the sternum. They play a significant role in the development of the immune system. Thymosin is the hormone secreted by this gland that participates in cell-mediated immunity. It also has its part in the production of antibodies.

Adrenal Gland

It is a pair of glands situated in the anterior part of the kidney. The adrenal gland is made up of two types of tissues: the outer adrenal cortex and the inner medulla. The adrenal medulla produces two types of hormones: adrenaline and noradrenaline. Adrenaline is also known as the emergency hormone because it is secreted during times of fear, fight, or flight. It gets us alert, increases sweating and dilates the pupil.

There are three layers of the adrenal cortex. They are,

• Zona reticularis (inner layer)
• Zona fasciculata (middle layer)
• Zona glomerulosa (outer layer)

The hormones secreted by the adrenal cortex are known as corticoids. The corticoids participating in carbohydrate metabolism are called glucocorticoids. Their function is to stimulate proteolysis, lipolysis and gluconeogenesis. It includes cortisol and cortisone. Cortisol is responsible for 95% of glucocorticoid activity. It supports anti-inflammatory reactions and oppresses the immune system. Mineralocorticoids are corticoids that assist in regulating the level of water and electrolyte balance. The vital hormone of the mineralocorticoids is aldosterone. It assists in reabsorbing the sodium ions and water and the excretion of potassium and phosphate ions.

Pancreas

The pancreas is a dual gland since it has both endocrine and exocrine functions. The islets of Langerhans, which are composed of two types of cells, alpha cells and beta cells, are situated in the endocrine part. Glucagon hormones are secreted by alpha cells, and insulin is secreted by beta cells. Normal blood glucose is maintained by glucagon, which increases blood glucose levels and promotes gluconeogenesis. Therefore, glucagon is a hyperglycemic hormone.

The glucose levels in our bodies are also regulated by insulin. It decreases blood glucose levels by enhancing cellular glucose uptake. Therefore, it is a hypoglycemic hormone. Hyperglycemia for a long period can cause diabetes mellitus.

Testes

The testis is situated in the scrotal sac outside the abdominal cavity. They are endocrine in function and are the primary sex organ. The testis consists of the seminiferous tubules and interstitial cells. The hormone testosterone is secreted by the interstitial cells or Leydig cells. The functions of this hormone are to regulate spermatogenesis, the development of beards and mustaches, as well as the maturation of male accessory sex organs.

Ovary

The pair of ovaries are situated in the lower pelvic region of the abdominal cavity. In females, it is one of the primary sex organs. They are mainly associated with the production of ova or eggs. The ovaries secrete two hormones; they are oestrogen and progesterone.

Estrogen Helps in:

• The development of the accessory sex organs
• The development of the mammary glands that produce milk
• The menstrual cycle in females
• The process of ovulating
• The water balance is done by increasing the water content and thickening the skin.

Progesterone is also called the pregnancy hormone since it is responsible for changes during pregnancy.

Progesterone Helps in:

• The enhancement of the blood supply in the wall of the uterus
• The placentation procedure
• The development of breasts during the time of pregnancy
• The assistance of premenstrual changes in the uterus
• The promotion or retention of water and sodium salts by influencing kidney functions.

Hormones of Kidney, Gastrointestinal Tract, and Kidney

The atrial natriuretic factor (ANF) is a hormone secreted by the wall of the heart. It decreases the blood pressure in the body and gets released when the blood pressure level increases. Erythropoietin is the hormone secreted by the kidney cells. It assists in the promotion of the RBC production. The gastrointestinal tract secretes gastrin, secretin, cholecystokinin and gastric inhibitory peptides. 

Mechanism of Hormone Action

The work of the various hormones is to control and balance the activity levels of the target tissue. The attachment of hormones to the hormone-receptor produces their effects on the target tissues. Biochemical changes will be further seen within the target tissue as a result of the formation of the hormone-receptor complex. The interaction of hormones with the membrane receptors and intracellular receptors will take place. Steroid receptors are intracellular, and the peptide hormones bind to the membrane receptors.

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

Chemical Coordination and Integration is a very important chapter and is composed of many essential topics. To comprehend all the topics well, students of Class 11 are suggested to follow the important questions in the chapter, and the Chapter 22 Biology Class 11 notes are available at Extramarks’ official website.

Class 11th Biology Notes

Students can download the Class 11 Biology Chapter 22 notes from the official website of Extramarks. The notes are prepared by subject experts and specialists who hold years of experience in their respective fields. They draft the notes in a manner that is suitable to all categories of students and gives the best learning experience. 

NCERT Class 11 Revision Notes Biology Chapter 22

The neural and endocrine systems promote control and coordination in animals. When the nerve fibres do not innervate the cells of the body, the endocrine system plays a significant role. 

Endocrine Glands

• Endocrine glands are the ductless glands, and whatever they secret gets directly released into the blood. Then they are sent to specific target organs to initiate the particular metabolic change.
• They secrete chemicals known as hormones.
• Hormones act as intracellular messengers produced in trace amounts. They are non-nutrient chemicals.

Human Endocrine System

In the human body, the endocrine glands and the hormone-producing glands are located in different parts of the body. A very small amount of hormones are released by the kidney, liver, gastrointestinal tract, and also heart. They regulate and coordinate the various functions of their respective organs. Hypothalamus consists of many groups of neurosecretory cells. It is called nuclei, and it produces hormones to regulate the secretion and the synthesis of the pituitary gland.

It Produces Two Types of Hormones:

• These hormones control the functions of the anterior pituitary by reaching it through the portal circulatory system.
• It also has its control on the posterior pituitary. The pituitary gland is located in the sella turcica and is connected to the hypothalamus through a stalk.
• Gigantism is a condition that occurs due to excessive growth hormone present in the body. Dwarfism is a condition caused due to the deficiency of growth hormones in the body.
• The TSH stimulates the release of thyroid hormone.
• The LH and FSH stimulate gonads. The LH stimulates the synthesis and the secretion of androgen hormone from the testis in males. LH induces ovulation of a completely mature ovum in females.
• Oxytocin controls the milk ejection and the contractions of the uterus during childbirth.
• Vasopressin stimulates the absorption of water and electrolyte in the kidney.
• MSH controls skin pigmentation and works on the melanocytes. The pineal gland gives out melatonin hormone to regulate the body’s rhythm. It is situated on the dorsal side of the forebrain.
• The thyroid gland is composed of stromal and follicle tissues. It has two lobes connected by the isthmus.
• Thyroid hormones are synthesised with the help of iodine. The deficiency of iodine results in hypothyroidism (Goitre). It may cause retardation in a baby during pregnancy.
• The thyroid hormones control the basal metabolic rate. They support the formation of RCBs and also manage the metabolism of proteins, carbohydrates, and fats. 
• The calcium level in blood is regulated by thyrocalcitonin.

The parathyroid gland is situated on the backside of the thyroid gland, and it secretes the peptide hormone. It is also called the parathyroid hormone (PTH). It regulates the calcium ion concentration in the blood.

The thymus secretes a peptide hormone called Thymosin. The thymus is located on the dorsal side of the heart and aorta. Thymosin is associated with producing antibodies to provide immunity.

An adrenal gland is located on the anterior part of the kidneys. It comprises two types of tissues, the outer adrenal cortex and the central adrenal medulla. The adrenaline and noradrenaline are released by the adrenal medulla, collectively known as catecholamines. They are known as emergency hormones. The adrenal cortex releases glucocorticoids and mineralocorticoids.

The pancreas is both an exocrine and an endocrine gland. The endocrine part consists of the Islets of Langerhans that further include the alpha and beta cells. The alpha cells secrete the glucagon, and the beta cells secrete the insulin.

Mechanism of Hormone Action

• The hormones can only perform their effects on the target tissue after getting attached to a specific protein known as hormone receptors that are located in the target tissue.
• Hormone receptor complex formation results from this attachment of the hormones, which further leads to changes in the target tissue.

Hormones are Grouped Based on Their Chemical Nature:

• Peptide, Polypeptide, and Protein Hormones: Insulin, hypothalamic hormones, glucagon, a pituitary hormone.

• Steroids: Testosterone, cortisol, progesterone.

• Iodothyronines: Also called thyroid hormones.
• Amino acid derivatives: Also called epinephrine.

The hormones binding with the membrane-bound receptors generally do not go to the target cells. Instead, they produce a second messenger that regulates cellular metabolism. The steroid hormones that interact with intracellular receptors control the function of the chromosome or gene expression mostly by interacting with hormone-receptor complexes with the genome. All these biochemical actions affect and lead to developmental and physiological consequences.