ENDOCRINE SYSTEM RAVI P. AGRAHARI (Science & Technology)
Endocrine system is a system of isolated glandsthat pour their secretions directly into venousblood or lymph for passage to different bodyorgans in order to control their functioning,metabolism, cell permeability, growthdifferentiation and stress condition.A gland is a structure which secretes a specificchemical substance or substances. Like othercommunication networks, endocrine systemcontains transmitters, singles and receivers thatare called, respectively hormone producing cells,hormones and receptors.
Nervous System Endocrine system1 Electrical and chemical Chemical transmission transmission (never impulses (hormones) through blood system and chemicals across synapses)2 Rapid transmission and Slower transmission and response relatively slow action (adrenaline an exception)3 Often short term Often long term changes4 Pathway is specific (through Pathway is not specific (blood nerve cells) around whole body), target is specific.5 Responses often very localized. Response may be widespread. eg. eg. On muscle Growth.
Types of glands on the basis of presence or absence of ducts1. Exocrine glands – Those which drain out their secretion duct.Eg. Liver, gastric glands, intestinal glands etc.2. Endocrine glands (holocrine glands) – Those glands whichlack which lack duct and discharge their secretion (mainly calledhormones) directly into the blood stream. Due to absence of ductthey are also called ductless gland.3. Heterocrine glands – Those glands which have dual functiondue to possession of both exocrine as well as endocrine region.They secrete hormone in association with other substances fortheir respective function. Eg. ovary testes, pancreas.
Mechanisms controlling release of hormones1. Presence of specific metabolite in the bloodEg. Excess glucose in the blood causes the release of insulin fromthe pancreas which lowers the blood glucose level.2. Presence of another hormone in the bloodEg. Stimulation hormones released from the anterior pituitarygland cause the release of other hormones from other glands inthe body.3. Stimulation by neurons from the autonomic nervoussystemEg. Adrenaline and noradrenaline are released from the cells ofadrenal medulla by the arrival of nerve impulse in situations ofanxiety, stress and danger.
Properties of hormonesThe hormones have the following properties: 1. They have low molecular weight 2. They are soluble in water and blood 3. They have no cumulative effect 4. They can act in very low concentration 5. They are non-antigenic 6. They are organic catalysts 7. They may act slowly or quickly 8. Hormone controlled reactions are not reversible 9. Hormones are produced in inactive form called prohormones. . eg. Proinsulin→Insulin (active form) 10. It is also called messenger because it has effect at a sitedifferent from the site different from the site where it is made.
Hormones1. All hormones are synthesized in the animal body itself.2. Hormones are circulated in blood Completely used up inmetabolism3. They may accelerate or retard the specific.4. Hormone controlled reactions are not reversibleEnzymes1. All enzyme are proteins2. Enzyme are mostly used locally Catalyze metabolic reactionand are reusable.3. Enzyme speed up the reaction.4. Enzyme controlled reactions are reversible.
BIOCHEMICAL CLASSIFICATION OF HORMONE1. Biogenic amines or phenolic or amino acid derivative-Thyroxine, adrenaline, noradrenaline2. Proteinaceous or polypeptide - Hypothalamic hormones,ACTH, GH, vasopressin, oxytocin,parathormone, calcitonisn, MSH3. Glycoproteinaceous - Thyrotropin, FSH, LH4. Steroids - Sex hormones and adrenocorticoids.5.Fatty acids - Prostaglandins.
hypothalamic – pituitary system is a direct proof of coordination between thehormonal and nervous system. It regulates mostof physiological activities of body and maintains homeostasis inside the body.
Thyroid GlandThyroxin - It stimulates oxygen consumption by metabolic active tissues (except testes, uterus, lymph nodes, spleen, anterior pituitary) and increases metabolic rate. - Helps to regulate tissue growth and development. - It increases the oxidation of glucose in tissues. - It increases the rate of metamorphosis in amphibians. In its absence or presence of thiourea (antithyroid substance), tadpoles remains in larva stage indefinitely. - It maintains nervous and muscular tonus. - It also has metabolic effects on protein synthesis and lipid metabolism. As metabolism is increased to meet the demand for substrate associated with the increase rate of O2 consumption. For this it increases glucose absorption (from GI tract), glycogenolysis, gluconeogenesis and glucose oxidation, lipolysis and protein synthesis and degradation.
Hyposecretion Cretinism Disorder of children and infants (called cretin). Hence called childhood hypothyroidism. Characterized by decreased TRH and TSH; dwarfism (stunted growth with peculiar infantile expressions), mental retardation; decreased BMR, blood pressure, heart rate, body temperature; delayed puberty; pigeon chest, protruding tongue etc. Myxoedema Also called gull’s diseases Occurs in adults Characterized by puffy appearance due to subcutaneous accumulation of fat, low BMR, heart rate and body temperature, lack of alertness, retarded sexuality, growth etc. Simple goitre Occurs due to deficiency of iodine, hence less thyroxine production Also called endemic goitre because it occurs in northern hilly areas where soils and ground water is deficient of iodine Characterized by enlarged thyroid gland which brings about a swelling in the neck region.
Hashimoto’s disease Also called autommunea thyroiditsis thyroiditis due to sensitization of their own thyroid proteins called thyroglobuliiiin. It occurs in middle aged females. Characterized by the iodine deficiency and atrophy of the thyroid gland due to antibodies produced in response to thyroid antigens. Hence it is known as wuicide of thyroid gland. Discovered by Japanese surgeon Hakaru Hashimoto.Hypersecretion Grave’s disease Over activity of gland produces a swelling in the necl region called as goitre. Also called exophthalmic goitre as the eyes appear as if they are coming out of their sockets Characterized by enlarged thyroid gland; increased BMR, heart rate, pulse rate, cardiac output, body temperature; protrution of eyes or exophthalmia; physical and mental restlessness, insomnia and nervouseness etc.
Parathoid glandParatharmone Regulate calcium and phosphate level in blood Increases the rate of calcium absorption from intestine in children to elevate blood level of calcium Retards bone dissolution (osteoclastic action) and stimulates excretion of calcium in urine It affects the growth of bones, membrane permeability, nerve functioning and the muscular activity of body. Hyposecretion : Causes : parathyroid tetany Since calcium is reqired for blood clotting, nerve and mucle functioning, so low level of calcium (parathoromone) lead tetany Characterized by decreased serum Ca and increased serum phosphate and decreased urinary phosphate muscle spasm, twitching, contraction of muscles of face, hands, feets etc., and increase deneuroexcitation. Hypersecretion : Causes : osteitis fibrosa cystica Osteitis fibrosa cystica means normal bones is replaced by cysts and fibrous tissues Destruction of bone starts (osteoporosis) Increased level of calcium is deposited in various parts of body to bring about calcification of soft tissues Produces stones in kidneys and ureters causing renal insufficiency.
What are the Adrenal Glands?• The adrenal glands are endocrine glands that produce hormones. A hormone is a chemical messenger. Each hormone influences specific organs or tissues, thus regulating a certain body process.• The adrenal glands are shaped like a boomerang and located on top of each kidney. The adrenal glands are about the size of the end of your thumb.• The adrenal glands produce hormones that affect almost every system in your body. When the adrenal glands fail to work properly, serious diseases and disorders can develop.• One of the hormones that the adrenal glands secretes is called adrenaline. Adrenaline produces a sudden and remarkable burst of energy.
Outer and Inner layer The adrenal glands consists of two portions: the inner core (medulla) and the outer layer (cortex).• The inner core of the adrenal gland produces hormones called catecholamines. The 2 most important catecholamines are: adrenaline and noradrenaline. Physical and emotional stress usually trigger their release. When secreted into the bloodstream, adrenaline and noradrenaline increase heart rate and blood pressure. Adrenaline often produces a sudden and remarkable burst of energy.• The outer layer of the adrenal gland produces hormones called corticosteroids. There are three types of corticosteroids.Sex Hormones. – Male androgens and female estrogens. – They affect sexual development and reproduction. – Sex hormones are also produced in larger amounts in the testicles and ovaries.Glucocorticoids – Hormones that aid in the conversion of starchy foods into glycogen. – An important glucocorticoid is cortisol. Cortisol helps regulate the immune system, helps maintain proper blood pressure and blood volume, and helps the body deal with physical stress.Mineralocorticoids – Control the bodys content of the minerals sodium and potassium
Adrenaline1. Amine hormone2. Secreted by adrenal medulla on stimulation by sympathethicnervous system for meeting an emergency or stress condition, likeinjury, pain, fear, accident, grief, fall in blood pressure etc. hencecalled emergency hormone.3. It increases blood pressure, BMR4. Acts as vasodilator5. Increases respiration rate6. Increases sugar level in blood by stimulating gycogenolysis inliver and skeletal muscles7. Slows down peristalsis8. Lipolysis in adipose tissue to increase level of fatty acids inblood.9. Hyper secretion of adrenaline causes hypertension, high levelof sugar in the blood and urine, high metabolic rate, nervousnessand sweating etc
Nor-adrenaline1. Amino hormone2. More or less it resembles adrenaline in its biologicaleffects excepts that it operates during normal state,exercise3. It has lesser effect on cardiac activity and producesgreater constriction of vessels in muscles (i.e. it is tonushormone for circulatory system)
Thymus GlandThymus is a pyramidal shaped lymphoid organ situated in front of the heartin the upper part of sternum. Thymus is active in young ones but graduallybecomes inconspicuous after sexual maturity. Hence the decline anddisappearance of this gland by the middle age is the primary cause ofageing.Hormone of thymus glandTHYOMSINE- Polypeptide hormone secreted by reticular epithelial cells.- Lymphocyte formation- Promotes immunocompetence in young T-lymphocytes- Accelerates cell division- Attainment of sexual maturity- Produces antibodies to keep the young ones immune to somediseases and allergies.- Hypersecretion may lead to Myasthenia gravis, characterizedby abnormal neuromuscular excitation.
Insulin As a regulator of carbohydrate metabolism it stimulatesglyco-genesis (conversion to glycogen) in muscles and liver andmaintains normal glucose level in the blood i.e. 80-120 mg per100 ml of blood. It increases the rate of protein and fat synthesis and actsas an anabolic hormone It reduces the breakdown of fats and proteins It increases the uptake of sugar n various tissues, there bylowering the blood sugar level.
GlucagonsGlucagon has opposite effect to that of insulin. It’ssecreted wherever there is decreased level of plasmaglucose.It promotes glycogenolysis or conversion of glycogen toglucose.It is also responsible for gluconeogenesis (formation ofglucose) and deamination of amino acids.Hypersecretion : Glycosuria
Diabetes mellitus - Occurs due to either deficient insulin production or due to failure of cells to take up insulin from blood. - It is characterized byHyperglycemia – High level of blood glucose (300-1200 mg/100 ml)Polyuria – Excessive urination due to increase in water content of urinePolydipsia – Excessive thirstGlycosuria – glucose in urinePolyphagia – excessive eating - Increased oxidation of fats produces increased amount of ketone bodies in body - Loss of weight and tiredness - Dehydration, reduced healing power due to which injuries may result in gangrenes, blurred vision etc.Hypoglycemia - hunger, sweating, irritability double vision
Diabitis MellitusIf you have diabetes, the amount of blood glucose istoo high - a condition called hyperglycemia. Thishappens for one of two main reasons:The body is producing no insulin - this is DiabetesType- 1The cells do not respond correctly to the insulin - thisis Diabetes Type- 2 Diabetes mellitus are of twotypes – type I diabetes and type II diabetes.
What is type 1 diabetes?In Type 1 Diabetes, the persons own body has destroyed the insulin-producing beta cells in the pancreas. When your own body destroys goodstuff in your body it has what is called anautoimmune disease. DiabetesType 1 is known as an autoimmune disease.Quite simply - a person with Diabetes Type 1 does not produce insulin. Inthe majority of cases this type of diabetes appears before the patient is40 years old. That is why this type of diabetes is also knownas Juvenile Diabetes or Childhood Diabetes. Diabetes Type 1 onset canappear after the age of 40, but it is extremely rare. About 15 per cent of alldiabetes patients have Type 1.People with Type 1 have to take insulin regularly in order to stay alive. Whether a person is fat, thin, fit or unfit, makes no difference to his orher risk of developing Type 1. In the case of Diabetes Type 2, much of itsonset is the result of bodyweight, fitness and lifestyle. The vast majority ofpeople who develop Type 1 are not overweight, and are otherwise healthyduring onset. You cannot reverse or prevent Type 1 by doing lots of exerciseor eating carefully. Quite simply, the Diabetes Type 1 patient has lost his/herbeta cells. The beta cells are in the pancreas; they produce insulin.
What is type 2 diabetes?• Person with Diabetes Type 2 has one of two problems, and sometimes both: 1. Not enough insulin is being produced. 2. The insulin is not working properly - this is known as insulin resistance.• The vast majority of patients who develop Type 2 did so because they were overweight and unfit, and had been overweight and unfit for some time. This type of diabetes tends to appear later on in life. However, there have been more and more cases of people in their 20s developing Type 2, but it is still relatively uncommon. Approximately 85% of all diabetes patients have Type 2. Insulin resistance The body produces insulin, but its insulin sensitivity is undermined and does not work as it should do - glucose in not entering the bodys cells properly. Consequently, blood sugar levels rise, and the cells are not getting their required nutrients for energy and growth.
Diabetes Mellitus Vs. Diabetes insipidusDiabetes Mellitus is mainly caused by deficiency of insulin dueto either destruction of Istet of Langerhans present in thepancreas or any autoimmune cause. Here there is increasedblood sugar level and sugar starts to appear to come with urine.It even becomes fatal when sugar level increases very much.Diabetes insipidus is caused by defect in secretion ofvasopressin (Antidiuretic Harmone) which is secreted frompituitary gland present in hypothalamus. Its function is toreabsorb water from distal tubules in the kidney and due to thisit control the concentration of urine. But its deficiency causesincreased water excretion through urine even in low intake ofwater.
What is diabetes insipidus?Diabetes insipidus (DI) is a rare disease that causes frequenturination. The large volume of urine is diluted, mostly water. Tomake up for lost water, a person with DI may feel the need todrink large amounts and is likely to urinate frequently, even atnight, which can disrupt sleep and, on occasion, causebedwetting. Because of the excretion of abnormally largevolumes of dilute urine, people with DI may quickly becomedehydrated if they do not drink enough water. Children with DImay be irritable or listless and may have fever, vomiting, ordiarrhea. Milder forms of DI can be managed by drinkingenough water, usually between 2 and 2.5 liters a day. DI severeenough to endanger a persons health is rare.
GONADS The main function of the gonad is to produce gametes which are mixed glands i.e. they are both exocrine and endocrine in function. Secretion of both gonadal hormones are stimulated by GTH of pituitary. MALE GONAD – TESTESTestes is situated in the scrotum of male. Endocrine partof testis is formed of group of cells called interstitial cells or leydig cells. These cells secrete male sex hormone androgen.
AndrogensFour types of androgen are testosterone, androsterone, epiandrosteroneand dehydroepiandrosterone.The principle androgen is testosterone and it is known to be asculanizationhormone.Testosterone, a steroid hormone, is responsible for the growth anddevelopment of male secondary sex organs (like epididymis, seminal vesicleetc.) and male secondary characteristic (like beard, moustaches etc.)It stimulates spermatogenesis and erythropoiesis.Eunochoidism is a hormone disorder due to non-secretion of testosterone in agenetically male individual.(1) This condition retards growth of genitalia, muscles and bones, as well asthe development of sexual characteristics. It leads to following changes in thebody.(2) Their genitals are of chills size and have under development of secondarymale sex organs like prostrate and seminal vesicles.(3) Failure of testis to produce sperms(4) Failure of the development of male sex characters like beard, moustaches,and deepening of voice.
FEMALE GONAD – OVARY Just like testes, the ovaries are cryptogenic as well endocrine infunction. Ovaries lies in the abdominal cavity. It secretes 3 types of femalehormones – estrogen, progesterone and relaxin.Estrogen Estrogen, group of steroid hormone is mainly secreted by follicularepithelial cells of membrane granulosa of graafian follicles (a mature follicle). Secretion of estrogen is stimulated by LH of anterior lobe of pituitarygland. It includes estradiol, estriol, and estrone. Principle estrogen is estradiol. It stimulates the growth and development of female secondary sexorgans and female secondary sexual characteristics. It decreases the secretion of FSH and increases the secretion of LHduring menstrual cycle. During pregnancy, estradiol is secreted by placenta.
Progesterone Progesterone is a steroid hormone secreted by corpus luteum. Small amount of progesterone is also secreted by adrenalcortex and placenta. Progesterone is responsible for the maintenance ofpregnancy, hence called as pregnancy hormone. Hyposecretion of progesterone results in abortion. It is alsocalled antiabortion hormone. During pregnancy progesterone helps in attaching embryo touterine wall, development of placenta and growth of secretaryalveoli in mammary glands. It has negative feedback effects on FSH and LH secretion. Maintains secretary activity of the uterus during the lutealphase. Progesterone is thermogenic and is probably responsible forthe rise in basal body temperature at the time of ovulation.
RelaxinIt is a proteinaceous hormone, secreted by corpusalbicans (which is formed from the corpus luteum at theend of gestation period).It softens the pubis symphysis to help in parturition (childbirth) in rats and guinea pig. In humans, this role isplayed by estrogens and progesterone.
VITAMIND D3 is produces in the skin under theinfluence of sunlight. Final hydroxylation and activationoccurs in the kidney, and activity which is stimulated byPTH. The primary function of 1, 25-dihydroxy vitamin D 3,also called calcitroil, is the stimulation of intestinalabsorption of calcium and phosphate. Osteomalacia andrickets occur as defective minerlization of bones,because of vitamin D deficiency. This contrasts witosteoporosis, where there is reduction in bone mass asa whole, rather than just the mineral content.
PheromonesPheromones constitutes an environmental factor. Organisms asancient as bacteria and slime moulds produce a chemical substancethat on its release into the environment influences the behaviorural andphysiological action of other member of the same species. Hencepheromones are chemicals used for communication amongst individualsof the same species. Also known as ectohormones/sex attratants etc.Pheromones invoke a specific response in other membranes likerecognition, warning and attraction.Types of pheromonesSex pheromone- Bombykol (silkworm), Queen substance (honey bee),Civertone (cat), Muskkone (muskdeer)Aggregation pheromones – Geradiol (honey bee)Alarm pheromone – Danger signalsMarking pheromones – Mark the territory in wild animals