Chemical Coordination and Integration PDF

Chemical Coordination 22 and Integration NCERT Motes 22.0 Introduction The neural system provides apoint-to-point rapid coordination among organs. The neural coordinator is fast...

Chemical Coordination 22 and Integration NCERT Motes 22.0 Introduction The neural system provides apoint-to-point rapid coordination among organs. The neural coordinator is fast but short-lived. The nerve fibres do not innervate all cells of the body and the cellular functoS need to be continuously regulated; so aspecial kind of coordination and regulation has to be providet This function is carried out by hormones. The neural system and the endocrine system jointy coordinate and regulate the physiological functions in the body. 22.1 Endocrine Glands and Hormones Endocrine glands lack ducts, so they are called ductless glands. Their secretions are caled hormones. The classical definition of hormone is a chemical produced by endocrine glands and releaset into the blood and transported to a istantly located target organ. According to current scentt definition: Hormones are non-nutrient chemicals which act as intercellular messengerS and are produced in trace amounts. The new definition covers a number of new molecUES ll addition to the hormones secreted by the endocrine gland. Invertebrates possess very simple enoui systems with few hormones. They have a large number of chemicals that act as hormones and provu coordination. particular region Exocrine qland is a gland that pours its secretion on the surface or into a + by means of ducts for performing a metabolic activity, e.g., sebaceous glands, Sweatglands salivary glands, intestinal glands. endocrineregions, Heterocrine gland (mixed gland) is a gland that has both exocrine and theirsecretion the former pouring their secretion through ducts while the latter pouring directly into bloodlymph. Properties of Hormones blood. and (0) They have low molecular weight. (i1) They are soluble in waterconcentration. (ii) They have no cumulative effect. (iv) They can act in very low slowly or quickly.todisorde's (v) They are non-antigenic. (VI) They may act leads (vii) Hormone controlled reactions are not reversible. (vii) Their excess or deficiency (ix) They do not provide energy or building materials. (activefom n ’ Insulin (x) Hormones are produced in inactive form called prohormones. E.g. Proinsulin site of synthesis (xi) They are also called messenger because the site of effect is different from the  645 ChemicalCoordination and Integration Biology| HD 22Human Endocrine System comprises of the endocrine glands and hormone Hypothalamus Pineal system endocrine ) The tissues or cells,located in different parts of our body. P1tuitary producingdiffused glands in our body are hypothalamus, pituitary, pineal, Theendocrine thymus and gonads (testis in Thyroid and thyroid, adrenal, pancreas, parathyroid, parathyroid males and ovary in females). There are some other organs that also gastrointestinal tract, liver, kidney, heart. -Thymus produce hormones e.g., The study of endocrine glands and role of their secretions is + called endocrinology. -Pancreas Anerson who specialises in endocrine glands is known as -Adrenal an endocrinologist. Hypothalamus Ovary Testis ,his the basal part of diencephalon, fore brain and it requlates a wide (in female) (in male) soectrum of body tunctions. It is Considered as supreme commander of endocrine system. It Contains several groups of neurosecretory cells rled nucdei which produce hormones. These hormones regulate the Fig.: Location of endocrine glands svnthesis and secretion of pituitary hormones. Hypothalamus serves as an anatomical connection between neural system and endocrine system. Ihe hormones secreted by hypothalamus are of two types, the releasing hormones (which stimulates secretion of pituitary hormones) and the inhibiting hormones (which inhibit secretions of pituitary hormones). For example a hypothalamic hormone called Gonadotrophin releasing hormone (GnRH) stimulates the pituitary synthesis and release of gonadotrophins. On the other hand, somatostatin from the hypothalamus inhibits the release of growth hormone from the pituitary. These hormones originating in the hypothalamic neurons, pass through axons and are released from their nerve endings. Various other hormones secreted by hypothalamus are : Thyrotropin releasing hormone (TRH or TSH-RH), Adrenocorticotropin releasing hormone (ARH or ACTH-RH), Somatotropin releasing hormone or growth hormone- releasing hormone (SRH or GH-RH), Prolactin releasing hormone or luteotrophic or lactogenic hormone releasing hormone (PRH, LTH-RH), Prolactin inhitbiting hormone and Melanocyte stimulating hormone and melanocyte inhibiting hormone (MSH and MIH). These hormones reach the pituitary gland through a portal circulatory system and regulate the hormones secreted by anterior and middle lobes of pituitary. The posterior pituitary is under the direct neural regulation of hypothalamus. Pituitary Gland Hypothalamus Hypothalamic Ihe pituitary gland is a small pea shaped gland located in a bony cavity called neurons sella turcica. It is attached to hypothalamus by a stalk. Pituitary is often Called master endocrine aland because it secretes a number of hormones, Which regulate and control the activity of other endocrine glands. is divided anatomically into two parts : adenohypophysis and neurohypophysis..Adenohypophysis consists oftwo portions: pars distalis ond pars intermedia. The pars distalis region of pituitary, commonly called Portal circulation anterior pituitary. produces growth hormone (GH),. prolactin (PRL), thyroid stimulating hormone hormone (TSH), adrenocorticotrophic hormone (ACTH), Posterior pituitary Parlusteinintermedia ising secretes(LH)onlyandonefollicle stimulating hormone (FSH). hormone called melanocyte stimulating Anterior horwithmonepars (MSH). However, humans, the intermedia almost in pars is merged distalis. Neurohypophysis or pars nervosa also known as posterior pituitary Fig.: Diagrammatic representation of pituitary and its relation with hypothalamus pituitary, stores and releases stwo hormones called oxytocin and vasopressin. These hohormones are actually synthesised by the hypothalamus and are transported axonally to neurohypophysis. Ihe fol owing table summarises various hormones of pituitary glands, their functions and consequences of their over 0f under secretion 646 WtG Objective NCERT at you Table : Pituitary hormones, their functions and effects tng Hormones from anterior lobe (adenohypophysis) of pituitary 1. Growth hormone (GH) or Stimulates growth by stimulating protein Somatotrophic hormone (STH) synthesis. and acromegaly Hypersecretion ggantn 2 Hyposecretion :dwarfism Thyroid stimulating hormone (TSH) Stimulates thyroid secretion. 3 Adrenocorticotropic hormone (ACTH) Stimulates the production of steroid hormones called glucocorticoids from adrenal cortex. 4 Gonadotropic hormones 0 Follicle stimulating hormone Stimulates gamete production, secretion of sex (FSH) hormones, developnent of follicles, () Interstitial cell-stimulating Stimulates the Leyd1g's cells of testis and hormone (iCSH) or Luteinising induces secretion of testosterone. hormone (LH) Induces ovulation of fully matured graafian follicles and maintenance of corpus luteum in female 5 Luteotropic hormone (LTH) or Stimulates the growth ot mammary glands and Prolactin lactation. Hormone from middle lobe (pars intermedia) of pituitary 6 Melanocyte stimulating hormone Controls dispersal of melanophores in skin in Hypersecretion: (MSH) vertebrates, in man it is doubtful. hyperpigmentation Hormones from posterior lobe (neurohypophysis) of pituitary 7 Oxytocin Stimulates milk ejection from mammary glands; (Acts on smooth muscle of our body) causes contraction of uterus at the time of child birth 8 Antidiuretic hormone or ADH Stimulates reabsorption of water and Hyposecretion: diabetes (Vasopressin) electrolytes by the distal tubules and there by insipidus (Acts mainly at the kidney) reduce loss of water through urine (diuresis). Stimulates contraction of smooth muscles, blood vessels and causes rise in blood pressure. Simmonds' disease is commonly due to degeneration of anterior lobe of the pituitary gland, resulting in dy ard + wrinkled skin of face and premature ageing. Pineal Gland The pineal gland is located on the dorsal side of forebrain. Pineal gland secretes a hormone called melatonin. Melatoni maintainn; plays a key role in the regulation of a 24-hour (diurnal) rhythm of our body. For example, it helpsin the normal thythms of sleep-wake cycle, body temperature. Apart from this, melatonin also influences metabols caled pigmentation, the menstrual cycle as well as our defence capability. Due to its location, pineal glands isalso epiphysis cerebri. tactor Melatonin is antagonistic to that of MSH secreted by pars intermedia of pituitary. It is aninhibitory + for sexual maturation and excitement i.e., it opposes SSH and LH Serotonin a neurotransmitter found in other locations in the brain,hormones. is also found in the pinealgland.  647 /ChemicalI Coordination and Integration Biology ThyroidGland one of fthe largest endocrine qlands and is Thyroidglandis pos1tioned onthe neck just belowthe larynx and has two Vocal side of trachea Cord Iobes, one on either lobes.are interConnectedI with athin flap of connective Itstwocalled isthmus The thyroid gland iS composed of Thyrod tissue and stromal Itissues. Each thyroid folliceis thyroid follicles Irachea Parattyrod composed offcubical epithelium anddfilled witha homogenous glands material called colloid. Small amount of loose connective the gland. Besides Scontaining biood (al tissueforms stroma of Fig : Diagtammatic VIew of the positiun of thyrod and small cdusters of specialised capillaries,ithe stroma contains cells. parathyroid glands (a) ventral side (b) dorsal side parafollicular cells or 'C' Thyroid gland secretes three hormones Thyroxine, tri- Thycod follicles iodothyronineand thyrocalcitonin (TCT), Thyroxine (T.) and tri-iodothyronine (1) are secreted by thyroid follicular follkcola epithei colls. lodine is essential for the normal rate of hormone (ollod svnthesis in the thyroid. Both are iodinated forms of an amino arid tyrosine. I, is more active and potent than I, gets converted into T, by removal of one iodine atom in the liver kidneys and some tissues. Thyrocalcitonin (Calcium lowering hormone) is secreted by Fig.: 1S of ttiyroud glard C-cells of the thyroid gland. It is secreted in response to high hlood calcium level. It suppresses release of calcium ions from the bones and lowers the calcium level in blood Functions of thyroid hormones (0) Requlate the metabolic rate of the body and maintain BMR (basal metabolic rate). () Requlate growth of body tissues and development of mentalfaculties (i) Stimulate tissue differentiation (eg., promote metamorphosis of tadpoles into adult frogs). (iv) Support the process of red blood cellformation. (v) Regulate carbohydrates, proteins and fats metabolism. Disorders of thyroid gland Hyperthyroidism: ExCessive secretion of thyroid hormones results in Grave's disease or exophthalmic goitre characterised by bulging eyes due to fluid accumulation, loss of weight, nervousness and rapid heart beat. Hypothyroidism : Deficiency of thyroid hormones causes cretinism in infants. Symptoms are retarded growtrh, undeveloped sex organ, mental retardation. Myxoedema or gull's disease is caused by deficiency of thyroxine in aduits. It is characterised by puffy appearance due to fat accumulatiorn in subcutaneous tissue, lack of alertness, slow heart beat,etc. Simple goitre (iodine deficiency goitre) is the enlargement of thyroid gland, may lead to cretinism or myxoedema. It is caused due to dietary deficiency of iodine. Parathyroicd Gland numans, four parathyroid glands are present on the back side of the thyroid gland, one par each in the two lobes of the thyroid gland. rarathyroid glands consist of two types of cells: chief cells (smal) and oxyphil cells (large). The chiefcells secrete a Reptde hornone called parathormone or Collip's hormone which regulates calcium and phosphate balance between n odand other tissues. The secretion of PTH is regulated by the circulating levels of calium ions. Parathyroid hormone ncreases the Cal- levels in the blood. PTH acts on bones and stimuiates the process of bone resorption. This is C5 dissolution or demineralisation. PTHalso stimulates reabsorption of Ca'' by the renal tubules and increases dbsorption from the digested food. Along with TCT, it plays a significant role in calcium balance in the body.  wtG Objective NCERT at 648 your high level of PTH may lead to the development of a blood Persistent excess production of to as hyperparathyroidism. It may be associated with the development of osteoporosis (destruction of with increased incidence of fractures), kidney stones, osteitis fibrosa cystica (means normal bone calcium, refere, by cysts and fibrous tissue). concentration of calcium ions in the blood and tissues due 10 Hyposecretion of parathormone lowers convusexcrieotinsonis excitability of nerves and muscles, causing cramps Sustained increases in urine. This(tetany) of calcium contractions the of the muscles of larynx, face, hands and feet are produced. This disorterand known as parathyroid tetany. Thymus The thymus is located between lunas behind the sternum on the ventral side of aorta. It is asoft, pinkish,, bilobed mass t lymphoid tissue. At birth, it is a prominent gland but it gradually atrophies in the adult. Thymus plays a major role in the which stimulates the of immune system, It secretes the peptide hormones named thymosins development and differentiation ofTlymphocytes, which provide cell-mediated immunity, thus, increasing resistance to intectior It also hastens attainment of sexual maturity, In addition, thymosins also promote production of antibodies to provge development humoral immunity. Thymus is degenerated in old individuals resulting in a decreased production of thymosins, As; result, the immune responses of old persons become weak. Adrenal gland Adrenal cortex Hassall's corpuscles are spherical or oval bodies present in the thymus. They are phagocytic in function. Adrenal Glands Adrenal glands are paired structures (conical, yellowish bodies) located on the top of kidneys. These are also called as glands Adrenal medulla of emergency. The gland is composed of twotypes of tissues. Kidney The centrally located tissue is called the adrenal medulla, and (a) (b) Fig.: Diagrammatic representation of (a) Adrenal gland abo# outside this lies the adrenal cortex. kidney (b) Section showing two parts of adrenal gland Adrenal gland has two parts Adrenal Cortex Adrenal Medulla It is derived from the mesoderm of the embryo. It develops from the neuroectoderm of the embryo. It is divided into three layers: The adrenal medulla secretes two hormones: nor (0) Zona glomerulosa is the outer zone that epinephrine (noradrenaline) and epinephrine lies just below the capsule. It secretes hormones (adrenaline) which are commonly called called mineralocorticoids,that affect mineral catecholamines. Nor-epinephrine and epinephrine homeostasis. are derived from the arino acid tyrosine. Adrenal medulla consists of chromaffin cels. (i) Zona fasciculata is the middle and widest These cells are modified postganglionic cels of zone and consists of cells arranged in long, straight columns which secrete glucocorticoids Sympathetic nervous system and are connected because they regulate glucose homeostasis. With pre-ganglionic motor fibres of sympathetic (ii) Zona reticularis is the inner zone and consists nervous system. Sympathetic nervous system and adrenal of cells arranged in branching cords which medulla function as an inteqrated system Calilu secrete gonadocorticoids or sex corticojds. sympathetico-adrenal system. Corticoids The adrenal cortex secretes many hormones, commonly called as corticoids. minera Mineralocorticoids: They maintain water and electrolyte balance and blood volume in the body by requlatingSodiumleve metabolism. The major mineralocorticoid is aldosterone, commonly called salt-retaining hormone. increased Low/ urina in body stimulates release of aldosterone. it causes retention of sodium and water from the kidney ano  Chemical Coordination and Integration Biology| 649 excretionoff potassium and phosphate ions. Thus, aldosterone helos in the maintenance of oSmotic pressure and blood pressure. electrolytes, body fluid volume, Glucocorticoids : They affect carbohydrate metabolism however, they also They alsostimulate gluconeogenesis, lipolysis and proteolysis; and inhibit cellularaffect uptakemetabol1sm of proteins and utlisation fats. andacids. of amino Glucocorticoids include three main hormones cortisol, corticosterone and cortisone. Of the three, cortisol is the most abundant. Cortisol oroduces anti-inflammatory reactions and suppresses the immune Cortisol is also involved in maintaining the cardio-vascular system as wel as the kidney functions. Cortisol is response. used for treatment of allergy as it suppresses synthesis ofiantibodies by inhibiting production of lymphocytes in the lymphoid tissues. It stimulates the RBC production. Under stressconditions our body secretes cortisol. That is why it is also known as stress Sexcorticoids: These include both male and female sex hormones. hormone. Androgens are important for development of male also stimulate the development of male secondary sexual characters. female secondary sexual characters Estrogen controls the development of Catecholamines The adrenal medulla secretes two hormones adrenaline and noradrenaline, commonly called as catecholamines. Catecholamines also stimulate the breakdown of glycogen resulting in an increased concentration of glucose in blood. Inaddition, they also stimulate the breakdown of lipids and proteins. Nor.epinephrine (Noradrenaline) - It regulates the blood pressure under normal condition. It causes constriction of essentially all the blo0d vessels of the body. It causes increased activity of the heart, inhibition of gastrointestinal tract, dilation of the pupils of the eyes, etc. Epinephrine (Adrenaline) - It is secreted at the time of emergency hence, also called emergency hormone. It causes the same effects as those caused by nor-epinephrine but with minor differences. Epinephrine has a greater effect on cardiac activity than nor-epinephrine. It causes only weak constriction of the blood vessels of the muscles in comparison with amuch stronger constriction that results from nor-epinephrine. ofadrenal cortex Disorders Addison's disease Cushing's syndrome Caused due to deficiency of mineralocorticoids and gluCOCorticoids. Caused by excess of cortisol. It is characterised by high blood sugar, Its symptoms include low blood sugar, low plasma Na, high appearance of sugar in the urine, rise in plasma Nat,fall in plasma plasma K*t, increased urinary Na*, nausea, vomiting, diarrhoea, etc K*,rise in blood volume, high blood pressure, etc Conn's syndrome Adrenal virilism Caused due to excessive production Gynaecomastia of aldosterone. Its symptoms include a Appearance of male characters in female Development of enlarged mammary is called virilism. Excessive production of glands (breasts) in the males, due to high plasma Nat, low plasma K*, rise male sexcorticoids (androgens) produces excessive secretion of estrogens in males. in blood volume, high blood pressure male secondary sexual characters like beard, Decreased testosterone may also lead to and polyurea. moustache, hoarse voice in woman. gynaecomastia. Pancreas rancreas is a composite gland which acts as both exocrine and endocrine gland. The endocrine pancreas consists of 'Islets Or Langerhans'.There are about 1 to 2 million Islets of Langerhans in a normal human pancreas representing only 1 to