BIOLOGY CLASS NOTES FOR CBSE Chapter 22. Chemical Coordination 01. Introduction Human body consists of two independent integrating systems, i.e. nervous system and endocrine system. The nervous system plays an important role in maintaining the physical coordination among various organ systems through nerve stimulation. But, its response is short-lived. Moreover, cellular functions need to be continuously regulated. Hence, comes the need of endocrine system. This system regulates its functions through chemical messengers called hormones. These hormones are released directly in the blood stream to reach every cell of the body and regulates its functions. The study of endocrine glands and their secretions (hormones) is called endocrinology. This discipline of study was founded by WH Bayliss and EH Starling.
02. Hormones These are non-nutrient chemical messengers which act as intracellular messengers and are produced in trace amounts. The term ‘Hormone’ was coined by Starling in 1950. According to the classical definition, a hormone is a chemical produced by the endocrine glands, released into the blood and transported to far located target tissue organs.
03. Chemical Nature of Hormones Their chemical nature depends on these molecules. The molecules and hormones derived from them are (i) Iodothyronines Thyroxine secreted from thyroid glands is an iodination thyronine. (ii) Amines These are amino acid derivatives, Like melatonin (from pineal gland) and catecholamines, adrenaline and noradrenaline (from tyrosine in adrenal medulla. (iii) Peptides Hypothalamic hormones, such as TRH, GRH, GIH, Intermediates (MSH); hormones of posterior lobes of pituitary, such as ADH, oxytocin, ACTH of anterior pituitary and calcitonin of thyroid gland belong the his category. (iv) Proteins Hormones of pancreas like insulin and glucagon; hormones of gastrointestinal tract like PTH (parathyroid hormone); female hormones like relaxin, hCG are proteinaceous in nature.
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(v)
Steroids These are derived from cholesterol. They are hormones of adrenal cortex like aldosterone, cortisol, sex corticoids and hormones of gonads like, testosterone, oestrogen, progesterone.
04. Human Endocrine System The endocrine system consists of various endocrine glands, which are widely separated from each other with no direct anatomical links. The endocrine glands present in our body are discussed below
05. Hypothalamus Position The basal part of forebrain (diencephalon) represents hypothalamus. Origin It originates from embryonic ectoderm. Structure It is made up of neurosecretory cells called hypothalamic nuclei. These produce hormones that regulate the synthesis and secretion of pituitary gland hormones. Hypothalamus produces following two types of hormone (i) Releasing or Trophic hormones These stimulate the secretion of pituitary hormones. For example, a hypothalamic hormones called Gonadotrophin Releasing Hormone (GnRH) Stimulates the synthesis and release of gonadotrophins from the pituitary gland. (ii) Inhibiting hormones These inhibit the secretion of pituitary hormones. For example, somatostatin from the hypothalamus inhibits the release of growth hormone from the pituitary.
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(iii) All these hormones originate from hypothalamic neurons, pass through axons and are released from their nerve endings. The hypothalamic hormones reach the anterior pituitary region through hypophysial portal circulation. The posterior pituitary is directly regulated by hypothalamus through their nerve pathway.
Some hypothalamic hormones and pituitary response Hypothalamic hormones Thyrotropin- Releasing Hormone (TRH) Adrenocorticotropin Releasing Hormone (ARH) Luteinizing Hormone-Releasing Hormone (LH-RH) Follicle Stimulating Hormone- Releasing Hormone (FSH-RH) Growth Hormone-Releasing Hormone (GH-RH)
Response of pituitary Secretes Thyroid Stimulating Hormone (TSH) Secretes Adrenocorticotropin Hormone (ACTH) Secretes Luteinizing Hormone(LH)
Secretes Follicle Stimulating Hormone (FSH) Secretes Growth Hormone (GH) or Somatotropic Hormone (STH) Growth Hormone-Releasing inhibits secretion of Inhibiting Hormone or Growth Hormone (GH) Somatostatin (SRH or GH-IH) Prolactin-Releasing Secretes Luteotropic Hormone (P-RH) Hormone (LTH) or Prolactin Hormone (PH) Prolactin- Inhibiting Inhibits secretion of Hormone (P-IH) prolactin Melanocyte Stimulating Secretes Melanocyte Hormone- Releasing Stimulating Hormone Hormone (MSH-RH) (MSH) Melanocyte Stimulating Inhibits or secretes Hormone –inhibiting Melanocyte Stimulating Hormone (MSH-IH) Hormone (MSH)
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Target organ Thyroid
Adrenal cortex
Ovary/Testis
Ovary/Testis
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Most tissues
Mammary glands
Skin pigment cells
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CLASS NOTES FOR CBSE – 22. Chemical Coordination
06. Pituitary Glands (Hypophysis Cerebri) The pituitary or master gland acts as a regulating unit of hormonal system. It regulates activity of most of the other endocrine glands. Position It is the smallest and most protected gland of the body. It lies in the bony cavity called hypophysial fossa or sella turcica of the sphenoid bone. This gland is attached to hypothalamus by a stalk like infundibulum. Origin The gland has dual origins, i.e. from embryonic buccal cavity (anterior part) and diencephalon (posterior part) of brain. Structure Pituitary gland is a small pink-coloured gland with a diameter of about 1-1.5 cm and weight 0.5 gm. Morphologically, pituitary has three parts. i.e. Pars dorsalis (anterior lobe), Pars intermedia (intermediate lobe) and Pars nervosa (posterior lobe). It is functionally divided into two parts, i.e. adenohypophysis and neurohypophysis.
07. Adenohypophysis Anterior and intermediate lobes are collectively known as adenohypophysis. It develops from Rathke’s pouch, i.e. a diverticulum of buccal cavity. (i) Pars dorsalis It consists of two types of cells, i.e. chromophobes and chromophils. Chromophil cells are of two types, i.e. acidophils and basophils. The hormones secreted by pars distalis region of adenohypophysis are called trophic hormones. These are as follows (a) GH or STH (Growth or Somatotropin Hormone) It is a globulin protein made up of 188 amino acids secreted by specialised acidophilic cells. It stimulates body growth by increasing protein, fat and carbohydrate metabolism. It affects cells that undergo growth. Hyposecretion of this hormone causes dwarfism (midgets) during the skeletal growth period. If the deficiency of GH occurs after puberty, then it causes acromicria It is a condition in which the person has normal body and intelligence but small bands, feet and face. Hypersecretion of GH can cause gigantism characterised by excessive growth of bones along with the enlargement of internal organs. If hypersecretion occurs after puberty then the individual suffers from acromegaly which is characterised by enlarged bands, feet, jaws, nose and ears in a normal person. (b) Gonadotropic hormones These are hormones that stimulate gonadal activity and are produced by basophilic cells. These are Ÿ FSH (Follicle Stimulating Hormone) It is a hormones when released in females helps in growth of ovarian follicles till ovulation and when released in males helps in development of seminiferous tubules and maintenance of spermatogenesis
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LH (Luteinizing Hormone) This hormones is also called Interstitial Cells Stimulating Hormones (ICSH) in males. It stimulates the development of interstitial cells or Leydig cells in testes and is also concerned with androgens in males. In females, it affects growing follicles in ovary by stimulating the release of progesterone and oestrogen. Follicle Stimulating Hormone, ICSH and LH are made up of nearly 204 amino acids each. (c) Prolactin (PRL) It is a non-tropic hormone produced by acidophilic cells. It was previously called Luteotropic Hormone (LH). It contain 198 amino acid. This hormone stimulates, the mammary glands for lactation (milk production). It also has a direct effect on the breasts immediately after parturition. (d) ACTH (Adrenocorticotropic Hormone) It is secreted by the basophilic (corticotropic) cells of anterior pituitary. It is a 39 amino acid polypeptide. It stimulates secretion of hormones from adrenal cortex, e.g. cortisol. It also increase the concentration of cholesterol and steroids within the gland. Ÿ Cushing’s disease Hypersecretion of ACTH results into this disease which is characterised by obesity of trunk but not limbs, skin pigmentation, excessive hair, demineralisation of bones and loss of function. (e) ATSH (Thyroid Stimulating Hormone) It is a glycoproteinacesous hormone secreted by special basophilic cells. This hormone promotes growth and proper functioning of thyroid gland by stimulating synthesis and secretion of thyroxine. (f) LPH (Lipotropin or Lipolytic Hormone) This hormone is in the form of a complex with I, II and - lipotropins. It stimulates fatty acid liberation from adipose tissue. Its hyposecretion causes obesity and hypersecretion causes thinness. (ii) Pars intermedia It develops from upper surface of Rathke’s pouch. This lobe contains prismatic cells having granules. These produce Melanocyte Stimulating Hormone (MSH). MSH stimulates synthesis and dispersal of melanin pigment in skin of fishes, amphibians and some reptiles, it cause change in colour of skin by a phenomenon known as metachrosis.
08. Neurohypophysis The neurohypophysis is formed by the posterior lobe (Pars nervosa) of pituitary gland. Its called pituicytes. These cells do not produce any hormone. The hormones are produced by the axons of neurons of hypothalamus. This lobe stores and secrete these hormones. They are (i) Oxytocin It is a small peptide hormone (nanopeptide). It initiates vigorous uterine contractions in females at the time of childbirth, thus also called birth hormone. It also causes milk secretion from mammary glands and stimulates adenohypophysis to secrete LTH/prolactin. Pitocin is a synthetic oxytocin which is often given to induce labor.
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(ii)
Vasopressin or Pitressin or ADH (Antidiuretic Hormone) It causes contraction of blood vessels and raises blood pressure. It also aids in reabsorption of water from glomerular filtrate in nephrons of kidney resulting in production of concentrated urine. Disease caused by abnormal secretion of ADH include Diabetes insipidus is a disease caused by the hyposecretion of ADH. It leads to a condition of reduced water absorption. Thus, the urine becomes diluted (diuresis), without sugar or glucose.
09. Thyroid Gland Origin It is the largest endocrine gland that develops from the endoderm of embryo. Position Thyroid gland is situated in the base of neck between the trachea and larynx at the level of fifth, sixth and seventh cervical and first thoracic vertebra. Structure Thyroid is larger in females. It consists of two lobes, on either sides of trachea below larynx. These two lobes are connects to each other by a narrow structure called isthmus. The thyroid gland is composed of follicles and stromal tissues. These follicles consist of cuboidal epithelial cells. The follicles are considered as the functional units of thyroid. An iodised colloidal substance thyroglobulin is filled in the cavity of these follicles. The stroma also contains specialised small cells called Parafollicular or ‘C’ cells. These follicles synthesise mainly two hormones known as tetraiodothyronin or thyroxin (T4)and triiodothyroxin or T3. A horThese hormones can be described as (i) Thyroxine (T4) and triiodothyronine (T3) Both these hormones are named so, because they contain four and three iodine respectively. T3 is secreted in smaller amount but, it is more potent than T4. T4 hormone is lipolytic, catabolic in nature. T3 hormones is mainly concerned with thermoregulation in the body. T3 and T4 hormones have similar effects, hence they are collectively known as Thyroid hormone (TH).mone called Thyrocalcitonin (TCT) is secreted by ‘C’ cells in small quantities. Diseases caused by abnormal thyroid hormones secretion are (a) Hyperthyroidism (Thyrotoxicosis) It is caused when the body tissues gets exposed to excessive levels of T3 and T4. Ÿ Exophthalmic goitre (Grave’s disease) In this enlargement of thyroid gland takes place. Thus, thyroid secretion increase. It leads to protrusion of the eyeballs, increased basal metabolic rate and weight loss. Ÿ Toxic nodular goitre (Plummer’s disease) In this type of hyperthyroidism, there occurs an increased body metabolic rate. (b) Hypothyroidism The insufficient secretion of thyroid hormones causes hypothyroidism. it causes following diseases Ÿ Cretinism It is seen in children. These children have retarded physical, mental and sexual growth. They show disproportionately short limbs, a large protruding tongue, coarse dry skin, poor abdominal muscle tone and an umbilical hernia. Such a dwarf child is called cretin.
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(ii)
Myxoedema (Gull’s disease) This condition is common in adults and five times more common in females than males. The deficiency of thyroid hormones occurs after normal mental and physical development is complete. It result in an abnormally low fat and protein metabolism. In these individuals less energy and heat production is seen by muscles during exercise. Mental and physical processes become slower, skin becomes coarse, the hair lacks lustre, becomes brittle and tends to fall out. Ÿ Simple goitre In this condition, there is enlargement of the thyroid gland and deficient secretion of thyroid hormones inspite of excess TRH and TSH. It is caused due to the deficiency of iodine in diet. Sometimes, the extra thyroid tissue is able to maintain normal hormone level but if not. myxoedema develops. Calcitonin (TCT) It is a hypocalcemic and hyperphosphatemic hormone. It is proteinaceous in nature with 32 amino acids. This is secreted by the C-cells (Parafollicular cells) in the thyroid gland. These receptors of calcitonin are found in osteoclasts, kidney and regions of brain. It acts bone and the kidneys to reduce the blood calcium level. It reduces the reabsorption of calcium form bones and inhibits reabsorption of calcium by the renal (tubules. Its effect is opposite to that of paratormone (parathyroid PTH), the hormone secreted by the parathyroid glands.
10. Parathyroid Gland Origin This gland develops from the endoderm of the embryo. Position It is present as four small pouches, two of each are embedded in the posterior surface of each lobe of thyroid gland. Structure It develops as epithelial buds from third and fourth paris of pharyngeal pouches. the two types of cells present in parathyroid gland are (i) Chief cells or Principal cells These cells contain prominent Golgi apparatus, endoplasmic reticulum and secretory granules. They are involved in the synthesis and secretion hormone. (ii) Oxyphil cells or Eosinophils. These cells contain oxyphil granules and large number of mitochondria in cytoplasm. Their function is unknown, although few scientists consider them as degenerated chief cells. The hormone secreted by parathyroid gland is Parathormone (PTH) or Collip’s hormone It is a linear polypeptide with about 84 amino acids. PTH acts directly on bone to increase bone dissolution demineralisation mobilise Ca2+ ions in to blood. it is a hypercalcemic and hypophosphatemic hormone. Disorders associated with PTH are (i) Hyperparathyroidism Excess secretion of parathormone (PTH, usually by benign tumours of the gland, causes reabsorption of calcium form bones and raised the blood calcium level. The effects may lead to formation of renal calculi complicated by pyelonephritis (inflammation of kidney) and renal failure, muscle weakness, general fatigue, calcification of soft tissue, osteoporosis, etc.
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(ii)
Hypoparathyroidism PTH deficiency causes abnormal low level of ionised calcium in the blood. This reduces absorption of calcium from the small intestine and reabsorption from the bones. Hypoparathyroidism may also lead to parathyroid tetany. It is a disease characterised by increased excitability of nerves and muscles, causing cramps, contraction of larynx, face, hand and feet.
11. Adrenal Glands Origin These glands develops from two separate embryological tissues, i.e. ectoderm (medulla region) and mesoderm (cortex region). Position There are two adrenal glands, situated on the upper side of each kidney enclosed within the renal fascia. Structure These glands are about 4 cm long and 3 cm thick. Internally, the gland is differentiated into two parts adrenal cortex and adrenal medulla.
12. Adrenal Cortex It is the external part of the adrenal gland. It is divided into three layers as follows (i) Zone glomerulosa (outermost) (ii) Zone fasciculata (middle) (iii) Zone reticularis (innermost) The adrenal cortex secretes over 20 steroid hormones, commonly called corticoids. (i) Mineralocorticoids : These are released from zone glomerulosa. These functions to regulate the electrolyte balance in the body fluid specially sodium (Na+), e.g. Aldosterone. The amount of aldosterone secreted in the blood is influenced by the sodium level in blood. if there is a fall in the sodium blood level, more aldosterone is secreted and more sodium is reabsorbed. (ii) The diseases caused due to abnormal aldosterone level are (a) Hypersecretion of mineralocorticoids (Aldosteronism or Conn’s syndrome) It is characterised by increased sodium and decreased potassium level in blood plasma, high blood pressure and increased blood volume. (b) Hyposecretion of mineralocorticoids (Addison’s disease) it is characterised by dark bronze colour pigmentation of skin, low blood sugar, excretion of sodium in urine, vomiting, weakness, low blood pressure and diarrhoea. (iii) Glucocorticoids : These are released from zone fasciculata and include cortisol, cortisone and corticosterone. Cortisol is the most potent glucocorticoid in the body. As the name suggests glucocorticoids are involved in earbohydrate metabolism, as it helps to convert glycogen into glucose. These are also involved in protein and fat metabolism, i.e. proteolysis and lipolysis respectively. Cortisol maintains cardiovascular system as wall as the kidney functions. It produces anti-inflammatory responses and helps to suppress the immune system therefore it is given during transplantation surgery. It can also stimulate the production of RBCs. Cortisol is often called life-saving hormone, as it serves to maintain the body in living condition.
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(a) Hypersecretion of glucocorticoids (Cushing’s syndrome) It is caused by the hypersecretion of cortisol. It is characterised by high blood sugar, obesity, wasting of limb muscles, high sodium and potassium level in blood, excessive hair growth in males, musculinisation in females. (b) Hyposecretion of glucocorticoids secretion of cortisol causes diminished gluconeogenesis, low blood glucose (hypoglycemia) muscle weakness, abdominal pain and restlessness. (iv) Sexcorticoids These are released from zone reticularis. These are sex hormones, i.e. androgens and oestrogens. These hormones are produce in small amount and believed to have little significance. These hormones are secreted as DHEA (Dehydroxy Epiandrosterone - a precursor of both testosterone and oestrogens). These hormones help in development of secondary sexual characters in males and females. Hypersecretion of androgens can lead to Adrenal virilism. It leads to appearance of male characteristics in females like heavy/coarse voice, beard and mustaches.
Adrenal medulla (Suprarenal gland) The adrenal medulla is completely surrounding by the cortex. It consists of specialised cells called chromaffin cells. These are modified postganglionic cells of sympathetic nervous system. Adrenal medulla is stimulated by chromaffin cells to produce two hormones, i.e. adrenalin or epinephrine and noradrenaline or norepinephrine. These are commonly called catecholamines. These hormones are called emergency hormones as they are associated with initiating fight or flight response in the body. When the body is under stress, homeostasis is disturbed. Adrenaline and noradrenaline are rapidly secreted in response to that stress to restore balance. These hormones increase alertness, dilation of pupil, piloerection (raisin of hairs), sweating, etc. Both these hormones increase heartbeat, strength of heart contraction and increased rate of respiration.
13. Pancreas Origin It is endodermal in origin. Position It is present on the backside of stomach in abdominal cavity. Structure It is a heterocrine gland which acts as both exocrine and endocrine gland. Pancreas in about 15 cm in length, 2.5 cm in width and 85 gms in weight and lies close to the duodenum. Its exocrine part occurs as acini which secrete about 500-1000 mL of pancreatic juice everyday. The endocrine part consists of cells that form islets of Langerhans. The three main types of cells in islets of Langerhans are cells, -cells and - cells, which produce endocrine secretions, i.e. insulin, glucagon and somatostatin. (i) Insulin : It is a peptide hormone secreted by - cells and it plays a major role in the regulation of glucose homeostasis. Insulin acts mainly on hepatocytes and adipocytes cells. Insulin enhance oxidation of glucose causing the blood sugar level. to fall. It also promotes protein synthesis, fat synthesis and inhibits synthesis of ketone bodies.
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It stimulates the conversion of glucose to glycogen (glycogenesis) in the target cells, Secretion of insulin is stimulated by the increase in blood glucose, amino acid levels and gastrointestinal hormones. Hyposecretion of insulin result in the presence of excess glucose in blood. This condition is known as hyperglycemia. Prolonged hyperglycemia leads to a complex disorder called diabetes mellitus. Diabetes mellitus causes following effects (a) Raised blood polyuria Glycosuria refers to excess of sugar in urine. Polyuria refers to production of excess urine. hyperglycemic hormone. (iii) Somatostatin It is polypeptide hormone with 14 amino acid residues and a disulfide (S-S) bond. It plays an important role in the regulation of secretions of islets of Langerhans cells. It is released by (delta) cells of islet of Langerhans. Its effect is to inhibit the secretion of both glucagon and insulin. Thymus gland : Origin This is endodermal in origin. It has developed from the epithelium of the outer part of third gill pouch or epithelium of gill cleft. Position It is a lobular structure present in between pericardium and upper part of sternum. Structure It is covered from outside by a capsule of loose connective tissue. It possesses a dense perished cortex and a loose central medulla on the inner side. The outer cortex consists of densely packed thymocytes (T-lymphocytes lineage). The medulla consists of epithelial cells, few lymphocytes and macrophages. The nest of epithelial cells of thymus is called Pineal gland : Origin It develops from the ectoderm of the embryo. Position The pineal gland (epiphysis) is located on the dorsal side of forebrain. Structure It is a stalked, small, rounded, reddish−brown gland which resembles a pine cone. Its weight is about 150 mg and length is about 10 mm. It consists of pineal cells and supporting gland cells. The pineal gland secretes following three hormones (i) Melatonin It is a derivative of amino acid tryptophan. It targets melanophore cells of skin. It has antagonistic action to Melanocyte Stimulating Hormone (MSH) secreted by the pars intermedia of pituitary. Melatonin plays very important role in the regulation of a biological clock. It controls sleep−wake cycle, body temperature, etc. In addition, melatonin also influence metabolism, pigmentation on skin, the menstrual cycle as well as defence capability. (ii) Serotonin It is a biogenic amine hormone (5−Hydroxy tryptamine) which acts as a vasoconstrictor to increase blood pressure. (iii) Adrenoglomerulotropin It stimulates the zone glomerulosa of adrenal cortex to secrete aldosterone. In man, the pineal gland starts calcifying at the time of puberty. Such calcium deposits are called brain sand. Its presence may indicate increased secretory activity. (ii)
Gonads Origin These are sex glands the develop from the mesoderm of the embryo. The main function of the gonads is to produce gametes. These are mixed glands. i.e. they are both exocrine and endocrine in function.
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Testis Position In man, a pair of testis is present in the scrotal sac (outside abdomen). Testes produces sperms as wall as sex hormones. Structure Testis is composed of seminiferous tubules and interstitial tissue. The Leydig cells or interstitial cells which are present in the intertubular spaces produce a group of hormones called androgens mainly testosterone. Male sex hormone androgens are steroid hormones produced under the control of ICSH (LH) of anterior pituitary Dihydrosterone In the active form of testosterone. It is produced at the age of 10−13 years, i.e. at the beginning of puberty. At this time, testosterone initiates development of male secondary sex organs (seminal vesicles, prostate gland, scrotum and penis), external male sex characters (beard, moustaches, masculine voice, body hair), growth in body tissue, broadening of shoulders, aggressiveness, growth of muscles, increased sebaceous gland activity, etc.
Ovary Position Ovary is a paired structure located in the abdomen in females. It is the primary female sex organ which produces one ovum during each menstrual cycle. Structure Ovary is composed of ovarian follicles and stromal tissues. After ovulation, the ruptured follicle is converted to a structure called corpus luteum. The two important female sex hormones, secreted by ovaries are oestrogen and progesterone. These are steroid hormones. In addition to these, some other female sex hormone are also there, i.e. relaxin hCG, HPL and inhinbin/actin. (i) Oestrogen It is secreted by the ovarian follicles and influenced by FSH, (a secretion of anterior pituitary). It is the main female sex hormone. It initiates the development of female secondary sex organs like vagina, duct system of mammary glands, uterus, Fallopian tubes and accessory female sex characters like breasts, high pitch voice and development of female body pattern and onset of menstrual cycle. (ii) Progesterone It is secreted mainly by the corpus luteum under the influence of LH of anterior pituitary It causes temporary changes in endometrial lining of uterus (secretory phase of menstrual cycle) for receiving egg. This hormone basically supports pregnancy. (iii) Relaxin It is secreted by corpus luteum during the end of gestation period. It helps in loosening of pelvic ligaments, softening and relaxing of uterus and eases the process of parturition. (iv) Human Chorionic Gonadotropin (hCG) It is secreted by the placenta for maintaining corpus luteum. Its presence in urine indicates pregnancy. (v) Human Somatomammotropin (hCS) Human Placental Lactogenic (HPL) Hormone. It is produced by the placenta and prepares mammary glands to secreted milk. (vi) Inhibin/Activin It is produced by corpus luteum, placenta and testes. It can inhibit or activate gonadotropic activity of pituitary gland and hypophysis.
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CBSE Pattern Exercise (1) (Q 1 to 3) One Mark 1. Which cells of testis secrete the male sex hormone? 2. What is the function of Leydig’s cells? 3. Name two organs, which are made up of mixed tissues. (Q 4 to 6) Two Marks 4. Why is oxytocin called ‘birth hormone’? 5. Name the gland the secrets vasopressin. What are its two principal actions? 6. What is the function of pineal gland? (Q 7 to 8) Three Marks 7. Name the inhibiting hormone released by hypothalamus. 8. What is the endocrine control in the ‘fight and fight’ response? Explain. (Q 9 to 10) Five Marks 9. Write the differences between the vitamins and hormones. 10. What is the role FHS, LH and estrogen in female reproductive cycle?
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ANSWER Q1 Male sex hormone (testosterone) is secreted from the leydig cells which are found around the seminiferous tubules of the testes. Q2 Leydig cells or interstitial cells of testes secrete testosterone hormone. It stimulates the development of external male sex characters such as beard, moustasche and low pitch voice in man. It stimulates the formation of sperms in testes. Q3 The two organs, which are made up of mixed tissues are pancreas and gonads. Q4 Oxytocin causes the contraction of smooth muscles of uterus during child birth. So it is called birth hormone. Q5 It is secreted by posterior part of the pituitary gland (formerly) called hypophysis). Function: Osmoregulation, water reabsorption of blood vessel, rise in blood pressure. Q6 The pineal gland secretes a hormone, melatonin. It reduces the reproductive activity and may also delay the sexual development in an individual. Q7 GHH- Growth Hormone Inhibiting Hormone. PIH- Prolactin Inhibiting Hormone. MIH- Melanocyte Stimulating Hormone Inhibiting Hormone. Q8 Physiological charges in the human body occur in response to a perceived threat, including secretion of glucose, endorphins and hormone as well as elevation of heart rate, metabolism, blood pressure, breathing and muscle tension. There are two adrenals at the top of each kidney. Hormone secreted by adrenal medulla help the body of an individual in handling emergency situation. Adrenaline is known as emergency hormone and is secreted in proportion to the stimulus through the central nervous system. The hormone mobilizes the source of the body to enable it to cope with emergencies, i.e. the fight and fight response to fear.
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Q9 (i)
Vitamins Carried in the food.
(ii)
Used up during the process.
Hormones Carried by blood. Consumed during the metabolic reaction. (iii) Produced by an endocrine gland. (i) (ii)
(iii) Obtained from food. (iv) May be organic acid, acid amide, amine, ester, alcohol or steroid. (v) Act coenzymes. (vi) Causes deficiency diseases when in less amounts.
(iv) Glycoprotein, steroid or polypeptide. (v) Act as stimulating substance. (vi) Causes hormonal disorders and diseases when excess.
Q10 FSH is a follicle stimulating hormone. It is secreted by anterior pituitary gland (adeno-hypophysis). Liquid filled follicle (graffian follicle) gradually enlarges enlarges so as to from th surface of ovary and finally bursts, releasing the oocyte in the funnel of uterine tube (ovulation). LH is the lutenizing hormone. It is related to the development of corpus luteum and progesterone secretion. Estrogen-Menstrual cycle (at the end of female reproductive cycle) is regulated by the action of hormones estrogen and progesterone on the uterine tissue. Estrogen stimulates the growth of myometrium. Estrogen is secreted by graffian follicle. Progesterone is secreted by corpus luteum and the placenta. It promotes the development of mammary glands during pregnancy and protects the uterus from contraction. Progesterone prevents the abortion. This hormone prepares the uterus to receive the egg. It increases the size of breasts and regulates menstrual cycle.
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