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SECRET BEHIND THE CHEMISTRY OF CELL

NATIONAL ANTHEM Jana Gana Mana Adhinayaka Jay He Bharata Bhagya Vidhata Panjab Sindhu Gujarat Maratha Dravida Utkala Banga Vindhya Himachal Yamuna Ganga Uchchala Jaladhi Taranga Tava Subha Name Jaage Tave Subha Aashish Mange Gaahe Tava Jay Gaatha Jana Gana Mangal Daayak Jay He Bharat Bhagya Vidhata Jaya he Jaya he Jaya he Jaya hey



CONSTITUTION OF INDIA PART IVA FUNDAMENTAL DUTIES ARTICLE 51 A Fundamental duties.—It shall be the duty of every citizen of India— (a) to abide by the Constitution and respect its ideals and institutions, the National Flag and the National Anthem; (b) to cherish and follow the noble ideals which inspired our national struggle for freedom; (c) to uphold and protect the sovereignty, unity and integrity of India; (d) to defend the country and render national service when called upon to do so; (e) to promote harmony and the spirit of common brotherhood amongst all the people of India transcending religious, linguistic and regional or sectional diversities; to renounce practices derogatory to the dignity of women (f) to value and preserve the rich heritage of our composite culture; (g) to protect and improve the natural environment including forests, lakes, rivers and wild life, and to have compassion for living creatures (h) to develop the scientific temper, humanism and the spirit of inquiry and reform (i) to safeguard public property and to abjure violence (j) to strive towards excellence in all spheres of individual and collective activity so that the nation constantly rises to higher levels of endeavour and achievement (k) who is a parent or guardian to provide opportunities for education to his child or, as the case may be, ward between the age of six and fourteen years.

PREFACE Our body is a chemical storehouse. These chemicals play a major role in various physiological functions. One among them is hormones. Hormones involves in numerous activities that takes place in our body. Hormones are chemical messengers that involves in cellular activities. It is secreted by endocrine glands. This textual material presents ideas about endocrine glands in man and its secretions, its action and various hormonal disorders. Go ahead, thinking, asking questions, approaching ideas critically and quizzing with teachers and friends. Make studying a joyful experience.

OBJECTIVES  To understand the endocrine system  To familiarize the endocrine glands in man  To analyze the hormonal action  To identify hormonal disorders

CONTENTS 1) ENDOCRINOLOGY 2) ENDOCRINE SYSTEM 3) MECHANISM OF ACTION OF HORMONES 4) HORMONE DISORDERS 5) BIBLIOGRAPHY

CHAPTER - 1 ENDOCRINOLOGY Do you have this kind of doubt in your mind? What may be the reason for this? Have you heard about hormones? Do they play any role in our body functions?

1.1.ENDOCRINE SYSTEM The endocrine system is one of the body’s coordinating systems, the other being nervous system. It is an organ system that controls and coordinates all activities in the body. Endocrine system regulates relatively slow processes such as metabolic activities of the body. The endocrine system includes endocrine glands and their secretions called hormones. Hormones are chemical messengers that regulate cellular activities. Endocrine glands do not have particular ducts to carry hormones to various tissues. Hence they are known as ductless glands. Hormones are transported through blood. The organs influenced by the hormones are called target organs. 1.2. HORMONES Hormones are extra cellular signaling molecules secreted by endocrine system.

1.2.1 FEATURES OF HORMONES  Hormones are usually relatively small molecules and are  Hormones are secreted in very small quantities  Hormones are secreted from endocrine glands transported in blood to target organs  Each hormone has high specificity in its activity  Many hormones have a very short life in the body 1.2.2. CLASSIFICATION OF HORMONES Hormones fall into four different chemical classes; i. Amine Hormones o The amine hormones are nitrogen containing derivatives of the amino acids tyrosine and tryptophan o E.g., Hormones of thyroid and adrenal medulla ii. Steroid Hormones o Steroid hormones are molecules chemically related to cholesterol. Cholesterol is the precursor of all steroid hormones. o E.g., Hormones of adrenal cortex and gonads

iii. Peptide Hormones o Peptide hormones may contain a few amino acids to 100 or more amino acids. o E.g., Insulin, Glucagon, Vasopressin iv. Glycoproteins o These are composed of polypeptides significantly longer than 100 amino acids to which are attached carbohydrates. o E.g., Follicle stimulating hormone(FSH), Luteinizing hormone (LH) All hormones may be classified into two categories, based on their solubility in fats. Lipophilic hormones are fat soluble (Non – polar). These include the steroid hormones and thyroxine. Lyophobic hormones are water soluble (Polar). All hormones other than lipophilic hormones are lipophobic hormones.

SUMMARY Endocrine system is an organ system that controls and coordinates all activities in the body. This system consists of endocrine glands and their secretions called secretions. Hormones are chemical messengers that regulate cellular activities. EXERCISES 1.What is endocrinology? 2.What are hormones? 3.How hormones are classified? 4.Differentiate lipophilic and lipophobic hormones. 5.What are the unique features of a hormone?

CHAPTER - 2 ENDOCRINE SYSTEM The main endocrine glands in man are pituitary, thyroid, parathyroid, pancreas adrenals and gonads. In females, placenta functions as an endocrine organ. Endocrine cells are scattered throughout gastrointestinal mucosa. Endocrine function is also attributed to the heart and kidney and neurosecretory cells in the central nervous system. FIG:1.1 ENDOCRINE SYSTEM IN MAN The major endocrine glands are; 1) HYPOTHALAMUS Hypothalamus is part of the brain located beneath the thalamus. The major role of hypothalamus is to control the activity of pituitary

gland. The secretions of hypothalamus are transported to the pituitary. The special neurosecretory cells of the hypothalamus secretes hormones oxytoxin and vasopressin. The posterior lobe of the pituitary stores these hormones and release into blood when necessary. FIG:1.2 HYPOTHALAMUS Table 1.1 showing the hormones produced by hypothalamus HORMONES FUNCTIONS Oxytoxin  Facilitates child birth by stimulating the contraction Vasopressin of smooth muscles in the uterus  Facilitates lactation  Helps in the reabsorption of water from the kidney Table 1.1

2) PITUITARY GLAND Pituitary gland lies in a pocket of the bone at the base of the brain, just below the hypothalamus. The pituitary gland produces hormones responsible for growth. The anterior lobe of the pituitary gland produces hormones which regulate the functions of other endocrine glands. These are tropic hormones. Hence, the pituitary gland has great significance in the endocrine system. FIG 1.3. PITUITARY GLAND

Table 1.2 showing the hormones produced by the anterior lobe of pituitary gland. HORMONES FUNCTIONS Thyroid Stimulating Stimulates the activity of Hormone (TSH) thyroid gland Adreno Cortico Tropic Stimulates the activity of Hormone (ACTH) adrenal cortex Gonado Tropic Hormone Stimulates the activity of ( GTH) testes in males and ovaries in females Growth Hormone (GH) Promotes the growth of the body Prolactin Production of milk 3) THYROID GLAND The thyroid gland is situated on either side of trachea, just below the larynx. It consists of two lobes connected by a narrow isthmus. The hormones secreted by thyroid gland controls metabolic activities. The hormones secreted by thyroid gland are thyroxine and calcitonin.

Fig; 1.4 Thyroid gland Table 1.3 shows hormones produced by thyroid gland HORMONES FUNCTION Thyroxine  Stimulate the rate of cellular metabolism  Promotes excessive elimination of water through urine  Calcitonin  Reduce the calcium level in blood 4) PARATHYROID GLAND Parathyroid gland are two pairs of very small glands, one pair on each side of the dorsal surface of the thyroid. They secrete the hormone parathormone. It play an important role in the regulation of blood calcium levels. The hormone promotes the

absorption of calcium and other ions from the intestinal lumen. 5) PANCREAS Pancreas is both exocrine and endocrine. The hormones secreted by pancreas are glucagon and insulin. Glucagon promotes breakdown of liver glycogen and release of glucose into the blood. Insulin promotes lowering of blood glucose level. FIG: 1.5. PANCREAS

6) ADRENAL GLANDS Adrenal glands lie atop the kidneys, one on each kidney. Each gland is a pyramidal structure with two distinct parts- an outer cortex and inner medulla. Adrenal cortex produces mineralocorticoids, glucocorticoids and gonocorticoids. Adrenal medulla secretes epinephrine and norepinephrine. FIG; 1.6: ADRENAL GLANDS 7) GONADS The gonads, the primary reproductive organs, are the paired testes in males and the ovaries in the female. Mature gonads produce germ cells and synthesis and release sex hormones

FIG; 1.7: GONADS Testes secretes testosterone and androstenedione. Ovaries produce oestrogen and progestrone 8) PLACENTA Placenta is a tissue that joins the embryo to the wall of mother’s uterus through which nutrients and wastes are exchanged. It produces female sex hormones. 9) PINEAL GLAND It is a small endocrine gland in the roof of third ventricle of brain. It secretes melatonin.

EXERCISES 1) What is endocrine system? 2) What are hormones? 3) Which are the endocrine glands? 4) Which hormones are secreted from hypothalamus? 5) What is the role of glucagon?

CHAPTER- 3 MECHANISM OF ACTION OF HORMONES Minute amounts of hormone can bring about an effect on the target tissue. This is achieved by a step by step amplification of the original signal. Starting with a small amount of the initial signal, the cascade will produce a final response that is amplified thousands of times. For a hormone to have an effect on a specific target organ and not on other organs, the responding cells must have specific receptor sites (hormone receptors) that interact with the hormones Since the hormones travel in the blood, they are able to reach practically all tissues. But the selective response depends upon the presence on (or in) the target cells of specific receptors for those hormones. A hormone receptor is a receptor protein on the surface of a cell or in its interior that binds to a specific hormone. The hormones bind their corresponding receptors

and change the configuration of the receptors to elicit the response. The steroid hormone receptors and the receptors for thyroid hormones are proteins that are located inside the target cells. Because these hormones are lipid soluble, they readily pass through the plasma membrane and bind their specific receptors inside the cells. Hormones are lipophobic and hence cannot cross the plasma membrane to reach the target sites. The peptide hormone receptors, therefore, are the proteins located on the plasma membrane of the target cell. A hormone binds the specific receptor to form a hormone receptor Complex that in turn elicit a response internally. Glycoprotein hormone receptors functions as receptors for the pituitary hormones thyrotropin, FSH receptor and lutropin.

Steroid hormone response Many lipids soluble hormones diffuses across the plasma membrane and interact with receptors in the cytosol or nucleus. Steroid hormones such as (progesterone, testosterone) and tyrosine are good examples. These lipophilic molecules can easily pass through lipid bilayer of the cell membrane. After entering the cell cytoplasm the steroid hormones in react with their specific steroid receptors. The hormone receptor Complex then enter the nucleus and act as a transcription factor. The hormone receptor Complex has a high affinity for DNA. By binding to a specific sequence of DNA, it is possible to switch a particular gene on or off. If the gene is switched on, the transcription product (RNA) exit the nucleus and it may be translated to a specific protein. This protein in terms performs a biological task.

FIG: 1.1. MECHANISM OF STEROID HORMONE SIGNAL TRANSDUCTION G protein coupled pathway (Peptide hormone pathway) The peptide hormones such as glucagon, vasopressin etc. bind the cell extra cellular domain of the membrane bound G protein coupled receptor. This includes conformational change in the receptor that allows the cytosolic

domain of the receptor to bind a G protein. The G protein consisting of three subunits, can bind GTP to get itself activated. The activated G protein then undergoes dissociation, so that a sub unit is separated, which carries the signal to a new target, the effector. An induced receptor can activate a number of G protein molecules, providing a means of signal amplification. The activated effector undergoes conformational change that leads to the production of the second messenger. The second messenger in turn activates one or more cellular responses. The ultimate response is the activation of kinases, which in turn phosphorylate a regulatory protein. The phosphorylated protein produces the biological response. For example, glucagon causes the activation of phosphorylase that finally results in the breakdown of glycogen to glucose.

FIG; 1.2. MECHANISM OF G PROTEIN COUPLED SIGNAL TRANDUCTION Another system of second messenger pathway of hormone action involves IP 3 (inositol triphosphate) and Calcium. Hormones like epinephrine bind to a different type of G protein and activate another membrane bound enzyme called phospholipase. This enzyme convert membrane bound phospholipids into inositol triphosphate which in turn function as a second messenger. IP 3 bind to its receptors on endoplasmic reticulum and stimulate it to release the stored calcium into the cytosol. The calcium then binds to a protein called calmodulin. The calcium /calmodulin complex activate other intracellular proteins, Ultimately producing the effects of the hormone.

FIG; 1.3. MECHANISM OF IP3- Ca SIGNAL TRANSDUCTION Hormonal control of reproductive cycles Reproductive cycle is a common phenomenon exhibited by sexually reproducing animals. In mammals the reproductive cycles are much more distinct than in other vertebrates. In some mammals there is a brief period of intense sexual activity at one particular season of the Year and then a long period during which there is no sexual activity. A brief period of pronounced sexual activity in males is known as rutting season. This period always corresponds in time with the female period of strong mating urge which is known as the period of heat or oestrus. Most of the female mammals accept the male in copulation only during oestrus period. Such cyclic and rhythmic changes in the sexual behaviour of the female mammals constitute the reproductive cycles. Although the reproductive cycles are basically similar there are slightly different among non- primate and primate mammals. The

reproductive cycle in non-primate female is called oestrus cycle while that in primate female mammal is known as menstrual cycle. Menstrual cycle In primates including humans, reproductive cycles begin in females at the time of puberty. These sexual cycles occur at two levels in the reproductive system. The cyclic changes which occur in the ovary are collectively known as ovarian cycle and those which occur in the uterus are referred to as uterine cycle or menstrual cycle. The ovarian cycle and uterine cycle go hand in hand and occur in an inter related manner. Ovarian cycle is a monthly series of events associated with the maturation and release of ovum whereas the uterine cycle is a series of changes in the uterine wall of a non pregnant individual.

Hormones and child birth Several factors are responsible for the onset of parturition. The high concentration of estradiol in the blood increase of uterine irritation. It enhances the tendency of the uterus to contract under slight provocation. The Oxytocin released from the posterior lobe of pituitary also cause the rhythmic contraction of the uterus during the time of parturition. The total duration of parturition is about 18 hours. Another hormone involved in parturition is relaxin. It is produced by both Corpus luteum and placenta towards the end of pregnancy. It stimulates relaxation of pelvic ligaments and helps dialate the uterine cervix to facilitate delivery. Hormonal control of lactation Lactation is a unique feature of mammals. The secretion of milk by the breasts or mammary glands is termed as lactation. Mammary glands are modified sebaceous glands. Prolactin is

the single major hormone that initiates and maintains milk secretion by mammary glands after child birth.

EXERCISES 1) How hormones acted on target cells? 2) What is G protein coupled pathway? 3) What is the role of prolactin? 4) How hormones affect in reproduction? 5) What is oestrus cycle?

CHAPTER – 4 HORMONAL DISORDERS Hormones are extra cellular signaling molecules that control many diverse physiological functions like metabolism, growth, reproduction, osmoregulation, circulation. Normal secretions and release of hormones ensure the proper functioning of the body. Both hypo activity and hyper activity of the endocrine glands result in malfunctioning of the body systems. Such abnormal conditions of the body developed in response to hypo secretion or hyper secretion of hormones are called hormonal disorders. Some of the common hormonal disorders are described below: 1) DWARFISM Dwarfism occurs when an individual is abnormally short in stature resulting from slow growth. In dwarfism, adult height is usually less than 4 feet 10 inches. Two type of dwarfism are there.

2) GIGANTISM Over production of growth hormone in children result in gigantism characterized by growth of over growth of bones. This is caused by occasional hyperactivity of the growth hormone producing cells of the anterior pituitary and sometimes by the development of acidophilic tumors in the glands. In adults, over secretion of growth hormones results in acromegaly characterized by abnormal and disproportionate growth of the bones of the head, hands and feet. 3) DIABETES INSIPIDUS Diabetes insipidus is a condition in which there is a deficiency of the production of vasopressin. Deficiency of vasopressin result in diuresis. Urine volume can

exceed 15 litre per day. Excretion of large amount of urine causes dehydration and increased the concentration of sodium chloride in the extracellular fluid 4) GOITRE An enlargement of the thyroid gland is called goitre. If there is an iodine deficiency, the thyroid cannot make sufficient hormone. 5) DIABETES MELLITUS A collection of abnormalities caused by insulin deficiency is called diabetes mellitus. Deficiency of insulin results in a rapid decrease in the cellular uptake and oxidation of glucose. PLANT HORMONES Plant hormones control and coordinates life activities in plants. These are also called plant growth regulators.



EXERCISES 1) Differentiate dwarfism and gigantism. 2) Which condition is caused by deficiency of insulin? 3) Differentiate the types of goiter.

BIBLIOGRAPHY 1) Barker, Llewellys franklin. Endocrinology and metabolism.1992 2) Gregory, Jennie. A B C of the endocrines. 1997 3) Rolleston, Sir Humphry Davy. Endocrines organs in health and diseases. 1976. Oxford univ. press London 4) Gregory.J. Evolution of endocrinology. 1939. 19:213 – 15 5) Goldzieher, Max A. The endocrine glands. 1987 6) SCERT Textbook standard 10