NEET AIPMT Biology Chapter Wise Solutions – Chemical Coordination and Integration
1. Which one of the following hormones is not involved in sugar metabolism? (AIPMT 2015)
2. Which one of the following hormones though synthesised elsewhere, is stored and released by the master gland? (AIPMT 2015)
(b) Melanocyte stimulating hormone
(c) Antidiuretic hormone
(d) Luteinising hormone
3. A chemical signal that has both endocrine and neural roles is (AIPMT 2015, Cancelled)
4. Identify the hormone with its correct matching of source and function. (AIPMT 2014)
(a) Oxytocin – posterior pituitary, growth and maintenance of mammary glands.
(b) Melatonin – pineal gland, regulates the normal rhythm of sleepwake cycle.
(c) Progesterone – corpus luteum, stimulation of growth and activities of female secondary sex organs.
(d) Atrial natriuretic factor – ventricular wall, increases the blood pressure.
5. Fight-or-flight reactions cause activation of (AIPMT 2014)
(a) the parathyroid glands, leading to increased metabolic rate.
(b) the kidney, leading to suppression of renin-an-giotensin-aldosterone pathway.
(c) the adrenal medulla, leading to increased se¬cretion of epinephrine and norepinephrine.
(d) the pancreas leading to a reduction in the blood sugar levels.
6. Figure shows human urinary system with structures labelled A to D. Select option which correctly identifies them and gives their characteristic and/ or functions. (NEET 2013)
(a) C – Medulla – inner zone of kidney and contains complete nephrons.
(b) D – Cortex – outer part of kidney and do not contain any part of nephrons.
(c) A – Adrenal gland – located at the anterior part of kidney. Secrete catecholamines which stimulate glycogen breakdown.
(d) B – Pelvis – broad funnel shaped space inner to hilum, directly connected to loops of Henle.
7. A pregnant female delivers a baby who1-suffers from stunted growth, mental retardation, low intelligence quotient and abnormal skin. This is the result of (NEET 2013)
(a) cancer of the thyroid gland
(b) oversecretion of pars distalis
(c) deficiency of iodine in diet
(d) low secretion of growth hormone.
8. Which of the following statements is correct in relation to the endocrine system? (NEET 2013)
(a) Non-nutrient chemicals produced by the body in trace amounts that act as intercellular messenger are known as hormones.
(b) Releasing and inhibitory hormones are produced by the pituitary gland.
(c) Adenohypophysis is under direct neural regulation of the hypothalamus.
(d) Organs in the body like gastrointestinal tract, heart, kidney and liver do not produce any hormones.
9. Select the answer which correctly matches the endocrine gland with the hormone it secretes and its function/deficiency symptom.
10. Select the option which correctly matches the endocrine gland with its hormone and its function. (Karnataka NEET 2013)
11. Norepinephrine (Karnataka NEET 2013)
(i) is released by sympathetic fibers
(ii) is released by parasympathetic fibers
(iii) increases the heart rate
(iv) decreases blood pressure.
Which of the above statements are correct?
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (ii) and (iv)
(d) (i) and (iv)
12. Which of the following represents the action of insulin? (Karnataka NEET 2013)
(a) Increases blood glucose level by stimulating glucagon production.
(b) Decreases blood glucose levels by forming glycogen.
(c) Increases blood glucose levels by promoting cellular uptake of glucose.
(d) Increases blood glucose levels by hydrolysis of glycogen.
13. A person entering an empty room suddenly finds a snake right in front on opening the door. Which one of the following is likely to happen in his neuro-hormonal control system? (Prelims 2012)
(a) Sympathetic nervous system is activated releasing epinephrine and norepinephrine from adrenal medulla.
(b) Neurotransmitters diffuse rapidly across the cleft and transmit a nerve impulse.
(c) Hypothalamus activates the parasympathetic division of brain.
(d) Sympathetic nervous system is activated releasing epinephrine and norepinephrine from adrenal cortex.
14. Which one of the following pairs of hormones are the examples of those that can easily pass through the cell membrane of the target cell and bind to a receptor inside it (mostly in the nucleus)? (Prelims 2012)
(a) Insulin, glucagon
(b) Thyroxine, insulin
(c) Somatostatin, oxytocin
(d) Cortisol, testosterone.
15. What is correct to say about the hormone action in humans? (Prelims 2012)
(a) Glucagon is secreted by (3-cells of islets of Langerhans and stimulates glycogenolysis.
(b) Secretion of thymosins is stimulated with aging.
(c) In females, FSH first binds with specific receptors on ovarian cell membrane.
(d) FSH stimulates the secretion of estrogen and progesterone.
16. Match the source gland with its respective hormone and function and select the correct option.
17. Given below is an incomplete table on hormones, their source glands and one major effect of each human body. Identify the option representing correct grouping of hormone its gland and effect. (Prelims 2011)
18. The 24 hour (diurnal) rhythm of our body such as the sleep-wake cycle is regulated by the hormone (Mains 2011)
19. Injury to adrenal cortex is not likely to affect the secretion of which one of the following? (Prelims 2010)
(b) both androstenedione and dehydroepiandrosterone
20. Low CA++ in the body fluid may be the cause of (Prelims 2010)
(c) angina pectoris
21. Which one of the following pairs is incorrectly matched? (Prelims 2010)
(a) glucagon – beta cells (source)
(b) somatostatin – delta cells (source)
(c) corpus luteum – relaxin (secretion)
(d) insulin – diabetes mellitus (disease).
22. Toxic agents present in food which interfere with thyroxine synthesis lead to the development of (Prelims 2010)
(a) toxic goitre
(c) simple goitre
23. Select the correct matching of a hormone, its source and function. (Prelims 2010)
24. A health disorder that results from the deficiency of thyroxine in adults and characterised by (i) a low metabolic rate, (ii) increase in body weight and (iii) tendency to retain water in tissues is (Prelims 2009)
(a) simple goitre
25. Which one of the following pair of organs includes only the endocrine glands? (Prelims 2008)
(a) thymus and testes
(b) adrenal and ovary
(c) parathyroid and adrenal
(d) pancreas and parathyroid.
26. The blood calcium level is lowered by the deficiency of (Prelims 2008)
(a) both calcitonin and parathormone
27. Feeling the tremors of an earthquake a scared resident of seventh floor of a multistoryed building starts climbing down the stairs rapidly. Which hormone initiated this action? (2007)
28. A person is having problems with calcium and phosphorus metabolism in his body. Which one of the following glands may not be functioning properly? (2007)
29. Which hormone causes dilation of blood vessels, increased oxygen consumption and glucogenesis? (2006)
30. Which of the following is an accumulation and release centre of neurohormones? (2006)
(a) anterior pituitary lobe
(b) posterior pituitary lobe
(c) intermediate lobe of the pituitary
31. A steroid hormone which regulates glucose metabolism is (2006)
(d) 11 -deoxycorticosterone
32. Which one of the following is not a secondary messenger in hormone action? (2006)
33. Which one of the following statements is correct? (2006)
(a) endocrine glands regulate neural activity, but not vice versa
(b) neurons regulate endocrine activity, but not vice versa
(c) endocrine glands regulate neural activity, and nervous system regulates endocrine glands
(d) neither hormones control neural activity nor the neurons control endocrine activity
34. Which one of the following hormones is modified amino acid? (2004)
35. Which one of the following pairs correctly matches a hormone with a disease resulting from its deficiency? (2004)
(a) Luteinizing hormone – Failure of ovulation
(b) Insulin – Diabetes insipidus
(c) Thyroxine – Tetany
(d) Parathyroid hormone – Diabetes mellitus.
36. Chemically hormones are (2004)
(a) biogenic amines only
(b) proteins, steroids and biogenic amines
(c) proteins only
(d) steroids only.
37. Which one of the following pairs correctly matches a hormone with a disease resulting from its deficiency? (2003)
(a) Relaxin – Gigantism
(b) Prolactin – Cretinism
(c) Parathyroid hormone – Tetany
(d) Insulin – Diabetes insipidus
38. Acromegaly is caused by (2002)
(a) excess of S.T.H.
(b) excess of thyroxine
(c) deficiency of- thyroxine
(d) excess of adrenaline.
39. Adrenaline directly affects on (2002)
(a) S.A. node
(b) P-cells of Langerhans
(c) dorsal root of spinal nerve
(d) epithelial cells of stomach.
40. When both ovaries are removed from rat then which hormone is decreased in blood? (2002)
(d) gonadotropin releasing factor.
41. Mainly which type of hormones control the menstrual cycle in human beings? (2002)
(c) FSH, LH, estrogen
42. Which set is similar (2001)
(a) corpus luteum – graafian follicles
(b) sebum – sweat
(c) bundle of His – pace maker
(d) vitamin B7– – Niacin.
43. Melatonin is secreted by (2000)
(a) pineal body
(c) pituitary gland
44. Which gland secretes odorous secretion in mammals? (2000)
(c) anal gland
45. MSH is secreted by (2000)
(a) anterior lobe of pituitary
(b) middle lobe of pituitary
(c) posterior lobe of pituitary
46. Cholecystokinin and duocrinin are secreted by (1999)
(a) adrenal cortex
(b) thyroid gland
47. The function of oxytocin is to help in (1999)
48. Secretion of progesterone by corpus luteum is initiated by (1999)
49. The gonadotrophic hormones are secreted by (1999)
(a) anterior lobe of pituitary
(b) interstitial cells of testes
(c) adrenal cortex
(d) posterior part of thyroid.
50. Diabetes is due to (1999)
(a) enzyme deficiency
(b) iodine deficiency
(c) NA+ deficiency
(d) hormonal deficiency
51. Calcitonin is a thyroid hormone which (1998)
(a) elevates calcium level in blood
(b) has no effect on calcium
(c) elevates potassium level in blood
(d) lowers calcium level in blood.
52. The hormone that stimulates the stomach to secrete gastric juice is (1998)
53. The contaction of gall bladder is due to (1998)
54. The hormone which regulates the basal metabolism in our body is secreted from (1998)
(a) adrenal cortex
55. Hormones thyroxine, adrenaline and the pigment melanin are formed from (1997)
56. Which hormone stimulates the secretion of milk from female? (1996)
57. Which one of the following endocrine glands stores its secretion in the extracellular space before discharging it into the blood? (1995)
58. According to the accepted concept of hormone action, if receptor molecules are removed from target organs, then the target organ will (1995)
(a) continue to respond to the hormone without any difference
(b) not respond to the hormone
(c) continue to respond to the hormone but will require higher concentration
(d) continue to respond to the hormone but in the opposite way.
59. The immediate cause of induction of ovulation in human female is the large plasma surge of (1994)
60. Testosterone is produced by (1993)
(a) sertoli cells
(b) Leydig’s cells
(c) oxyntic cells
(d) pituitary gland.
61. Gastric secretion is stopped by hormone (1993)
62. ADH or vasopressin is (1991)
(a) enzyme that hydrolyses peptides
(b) hormone secreted by pituitary that promotes reabsorption of water from glomerular filtrate
(c) hormone that promotes glycogenolysis
(d) energy rich compound connected with muscle contraction.
63. Occurrence of Leydig’s cells and their secretion is (1991)
(a) ovary and estrogen
(b) liver and cholesterol
(c) pancreas and glucagon
(d) testis and testosterone.
64. Insulin is a (1990)
65. Addition of a trace of thyroxine or iodine in water containing tadpoles will (1990)
(a) keep them in larval stage
(b) hasten their metamorphosis
(c) slow down their metamorphosis
(d) kill the tadpoles.
66. Which hormone possesses anti-insulin effect? (1988)
67. MSH of pars intermedia of middle pituitary is responsible for (1988)
(a) darkening of skin in lower vertebrates
(b) light colouration of skin in lower vertebrates
(c) both A and B
(d) darkening of skin in human beings.
Aldosterone (salt-retaining hormone) is the principal mineralocorticoid in humans, secreted by adrenal cortex. Its main function is to regulate sodium content of the body. Insulin and glucagon are respectively secreted by beta cells and alpha cells ofislets ofLangerhans ofpancreas. Cortisone is a glucocorticoid secreted by adrenal cortex. All these three hormones are involved in sugar metabolism.
Two hormones viz oxytocin (OT) and antidiuretic hormone (ADH) are synthesised in the hypothalamus, but stored and released by the posterior lobe of pituitary gland.
Hormones epinephrine and norepinephrine are secreted from adrenal medulla. They are emergency hormones released in condition of stress, emergency etc. Epinephrine and norepinephrine are also released by adrenergic nerve fibres of sympathetic nervous system where they act as neurotransmitters.
Oxytocin is produced by hypothalamus and generally secreted by posterior pituitary. It stimulates secretion of milk from mammary glands; causes contraction of uterus at the time of child birth. Progesterone is secreted by corpus luteum. It stimulates uterus for pregnancy, implantation, formation of placenta and development of mammary glands. Atrial natriuretic factor is secreted by atrial wall in response to an increased return of the venous blood. This hormone regulates the blood volume through increased excretion of ions and water.
The adrenal medulla secretes two hormones called adrenaline or epinephrine and noradrenaline or norepinephrine. These are commonly called as catecholamines. Adrenaline and noradrenaline are rapidly secreted in response to stress of any kind and during emergency situations and are called emergency hormones or hormones of Fight or Flight. These hormones increase alertness, pupillary dilation, piloerection (raising of hairs), sweating etc. Both the hormones increase the rate of heart beat, the strength of heart contraction and the rate of respiration. In addition, they also stimulate the breakdown of lipids and proteins.
In the given figure, A is adrenal gland which secretes two catecholamines; adrenaline (epinephrine) and noradrenaline (norepinephrine). Adrenaline increases the conversion of glycogen to glucose providing quick energy for “fight or flight” response. B is renal pelvis which is a sac like cavity of the kidney leading to ureters, is not directly connected to loop of Henle. C is medulla, the inner region of kidney containing loop of Henle, collecting ducts and ducts of Bellini. D is cortex which has proximal and distal convoluted tubules and contains Malpighian corpuscles.
The functions of thyroxine (T4) and triiodo-thyronine (T3), include regulation of the metabolic rate of the body and thereby maintenance of basal metabolic rate (BMR); protein synthesis and growth of the body tissues; regulation of the development of mental faculties, maintainence of body temperature and speeding the action of neuro-transmitters like adrenaline and noradrenaline. Iodine is needed for the synthesis of T3 and T4. Iodine binds to the tyrosine residues in thyroglobulin, which is then hydrolysed into iodotyrosines that combine to form triiodothyronine (T3) or thyroxine (tetra-iodothyronine or T4). Therefore, deficiency of iodine in the diet of a pregnant female will lead to improper synthesis of thyroid hormones in newly borne infant. The deficiency of thyroid hormones in infants causes ‘cretinism’ whose symptoms are slow heart beat, lower blood pressure, decrease in temperature, stunted growth, low intelligence quotient and abnormal skin.
Releasing and inhibiting factors are released by hypothalamus. The hypothalamus is connected to adenohypophysis by hypophysial portal vein and is connected to the neurohypophysis by axons of neurosecretory cells. Hence, neurohypophysis is directly under the neural control. The cardiocytes of atria of the heart secrete peptide hormone, called atrial natriuretic factor (ANF) in response to an increased return of the deoxygenated (venous) blood. The liver produces angiotensinogen which is changed to angiotensin II by an enzyme renin secreted by juxtaglomerular apparatus (JGA).
Iodine is required for production of thyroxine, thus lack of iodine results in hyposecretion of thyroxine. To compensate, thyroid gland enlarges and the condition is known as goitre. Corpus luteum secretes progesterone which maintains uterine endothelium and mucus secretion in uterus, Fallopian tubes and vagina. Oxytocin stimulates uterine contractions but is secreted by posterior pituitary. Anterior pituitary secretes GH, whose oversecretion causes abnormal growth.
Interstitial cells (or Leydig ‘s cells) are the cells interspersed between the seminiferous tubules of the testis. They secrete androgens including testosterone in response to stimulation by luteinizing hormone from the anterior pitutary gland. Androgens produce and maintain male characteristics and stimulate germinal epithelium to undergo spermatogenesis.
Norepinephrine is secreted by some neurons of the sympathetic nervous system and also by adrenal medulla. It accelerates heart rate.
Insulin decreases the level of glucose in the blood. It acts by increasing the rate at which glucose is transported out of the blood and into cells and by stimulating liver cells and muscle cells to take up sugar from the blood and convert it into glycogen. Insulin is antagonistic to glucagon. When the blood sugar level drops, the secretion of insulin is suppressed. When the blood sugar level increases, the secretion of insulin is stimulated.
Epinephrine and norepinephrine are secreted by adrenal medulla in response to stress of any kind and during emergency situations and are called emergency hormones or hormones of flight, or fight.
Steroid hormones such as cortisol, testosterone, estradiol and progesterone, mostly regulate gene expression or chromosome fiinction by the interaction of hormone-receptor complex with the genome. So, these easily pass through the cell membrane of the target cell and bind to a receptor inside it.
Hormone action involves their reception by target cells. Specific proteins called hormone receptors that are located in target tissues only bind with these hormones. Hormone receptor may be of two types membrane bound receptor and intracellular receptors. Steroid hormones etc., bind with intracellular receptors
Posterior lobe of pituitary stores and releases two hormones, called oxytocin and vasopressin. These hormones are actually produced by the nuerosecretary cells in the hypothalamus and stand in the terminals of their axons that pass into the posterior lobe through a stalk. They are released via posterior lobe when required. Vasopressin is also called antidiuretic hormone (ADH). It decreases the loss of water in the urine by increasing reabsorption of water in the distal convoluted tubules, collecting tubules and collecting ducts in the kidneys, i
The correct option for the three blanks A, B and C are ovary, glucagon and growth hormone respectively. Estrogens are secreted by the Graafian follicle, which surrounds the mature ovum in the ovary and stimulate the female reproductive tract to grow to lull size and become functional. They also stimulate the differentiation of ova (oogenesis) in the ovary and stimulate the development of accessory sex characters such as enlargement of breasts, broadening of pelvis, growth of pubic and auxiliary hair, deposition of fat in the thigh; and onset of menstrual cycle. Glucagon is secreted by the alpha cells of the islets of Langerhans in response to a fall in the blood glucose level. Somatotrophic or growth hormone (STH or GH) or somatotrophin hormone is secreted by the anterior lobe of pituitary. Growth hormone stimulates growth and development of all tissues by accelerating protein-synthesis and cell-division and by retaining calcium in the body. Over secretion of growth hormone leads to gigantism.
Melatonin is a hormone secreted by the pineal gland and retinas of vertebrates. Melatonin secretion by the pineal is linked to the dark-light cycle of the organism’s environment, being greatest at night and lowest by day. The hormone is involved in regulating certain diurnal and seasonal changes in the body, such as the reproductive- cycle in seasonally breeding animals. It is used as a drug to treat sleep disorders and symptoms of jet lag.
Adrenal glands or (suprarenal glands) are two triangular endocrine glands, each of which covers the superior surface of a kidney. Each gland has two parts, the medulla and cortex. The medulla forms the grey core of the gland; it consists mainly of chromaffin tissue and is stimulated by the sympathetic nervous system to produce adrenaline and noradrenaline. The cortex is a yellowish tissue surrounding the medulla. It is stimulated by pituitary hormones (principally ACTH) to produce three kinds of corticosteroid hormones, which affect carbohydrate metabolism (e.g. cortisol), electrolyte metabolism (e.g. aldosterone), and the sex j glands (oestrogens and androgens). Thus injury to adrenal cortex is not likely to affect the secretion of adrenaline.
Tetany is a spasm and twitching of the muscles, particularly those of the face, hands, and feet. Tetany is usually caused by a reduction in the blood calcium level, which may be due to underactive j parathyroid glands, rickets, or alkalosis.
Glucagon is a hormone, secreted by the a (or A) cells of the islets of Langerhans in the pancreas, that increases the concentration of glucose in the blood by stimulating the metabolic breakdown of glycogen. It thus antagonizes the effects of insulin.
Simple goitre is caused by deficiency of iodine in diet because iodine is needed for the synthesis of thyroid hormone. Toxic agents present in the food may also interfere with thyroxine (thyroid hormones) synthesis. It causes thyroid enlargement. It may lead to cretinism or myxoedema. This disease is common in hilly areas.
Vasopressin reduces water loss through urine by stimulating resorption of water by the distal tubules of the kidney. Glucagon is released from a-cells. Prolactin is produced from anterior pituitary.
Myxoedema is caused by deficiency of thyroid hormone or thyroxine in adults. It is characterized by low metabolic rate, body gain, puffy appearance, low body temperature etc. This disease can be treated by administration of thyroid hormones.
Parathyroid and adrenal glands are the the endocrine glands because these manufacture hormones and secretes them directly into the blood stream to act at distant sites in the body. Thyroid and pituitary are its other examples.
Parathormone is secreted by chief cells of the parathyroid that regulates the metabolism of calcium and phosphate. It increases calcium absorption from the intestine and also increases calcium resorption from the nephrons of the kidneys. So its deficiency leads to low blood calcium level.
Adrenaline (epinephrine), also called emergency hormone, is a hormone, produced by the medulla of the adrenal glands, that increases heart activity, improves the power and prolongs the action of muscles, and increases the rate and depth of breathing to prepare the body for ‘fright, flight, or fight’. At the same time it inhibits digestion and excretion. Similar effects are produced by stimulation of the sympathetic nervous system.
The parathyroid glands are small endocrine glands in the neck, usually located behind the thyroid gland, which produce parathyroid hormone. Parathyroid hormone (PTH, also known as parathormone) is a small protein that takes part in the control of calcium and phosphorus homeostasis, as well as bone physiology. When blood calcium level drops below a certain point, calcium-sensing receptors in the parathyroid gland are activated to release hormone into the blood. It then stimulates osteoclasts to break down bone and release calcium into the blood, and increase gastro-intestinal calcium absorption.
The parotid gland, found wrapped around the mandibular ramus, secretes saliva through Stensen’s duct into the oral cavity to facilitate mastication and swallowing. Inflammation of one or both parotid glands is known as parotitis. The most common cause of parotitis was mumps. Pancreas is a large, elongated gland located behind the lower portion of the stomach that secretes the hormones insulin and glucagon into the blood. These hormones are essential in regulating blood sugar levels. The pancreas also secretes enzymes into the small intestine that help with digestion and neutralize acid from the stomach. Thyroid gland is bilobed endocrine gland situated in the base of the neck and secretes, two iodine- containing thyroid hormones, thyroxine (T4) and triiodothyronine (T3). They control the rate of all metabolic processes in the body and influence physical development and activity ofthe nervous system. Disorders associated with thyroid gland are – cretinism, myxoedema, goitre, Hashimoto’s disease due to its hyposecretion and Grave’s disease due to its hypersecretion.
Adrenaline is the hormone secreted by adrenal medulla. It prepares the animal to face special conditions created by physical stress. All these conditions require more energy which is provided by increasing heart beat, blood pressure, respiratory rate, sugar level of blood, blood supply of heart and skeletal muscles and brain through dilation of their small arteries, and oxidative metabolism. It also stimulates the breakdown of liver and muscle glycogen (glucogenesis) to provide glucose for respiration.
The neurosecretory cells of the hypothalamus, when stimulated, release hormones, called neurohormones via axons into the capillaries. The neurohormones are carried by the portal blood to the anterior lobe of the pituitary gland and stimulate the latter to release its hormones. On this account, such hypothalamic hormones are also called releaser hormones. Certain hypothalamic hormones inhibit the secretion of some pituitary hormones. These are termed inhibitory hormones or factors (IH or IF).
Glucocorticoids (eg. cortisol) are secreted by the middle region of the adrenal cortex. They regulate the metabolism of carbohydrates, proteins and fats. They increase the blood-glucose level by converting proteins and fats into carbohydrates which are, in turn, converted to glucose.
Secondary messengers are low-weight diffusible molecules that are used to relay signals within a cell. They are synthesized or released by specific enzymatic reactions, usually as a result of an external signal that is received by a transmembrane receptor. cAMP, cGMP and CA2+ act as secondary messengers and are located within the cytoplasm. Sodium is an essential nutrient which helps to maintain blood volume and keeps nerves functioning.
The endocrine system links the brain to the organs that control body metabolism, growth and development, and reproduction. The endocrine system is regulated by feedback. For example, the hormones that are regulated by the pituitary gland, a signal is sent from the hypothalamus to the pituitary gland in the form of a “releasing hormone,” which stimulates the pituitary to secrete a “stimulating hormone” into the circulation. The stimulating hormone then signals the target gland to secrete its hormone. As the level of this hormone rises in the circulation, the hypothalamus and the pituitary gland shut down secretion of the releasing hormone and the stimulating hormone, which in turn slows the secretion by the target gland. This system results in stable blood concentrations of the hormones that are regulated by the pituitary gland.
Epinephrine is synthesized from tyrosine which is a non-essential amino acid possessing cyclic structure with a straight side chain bearing carboxylic and amino group. The conversion of tyrosine to epinephrine involves 4 steps – (a) ring hydroxylation (b) decarboxylation, (c) side-chain hydroxylation (d) N-methylation.
Tyrosine —> Dopa —> Dopamine —> Norepinephrine —> Epinephrine.
Ovulation occurs under the influence of luteinizing hormone and FSH (follicle stimulating hormone) of anterior pituitary gland. Thus, deficiency of lutenaizing hormone results in failure of ovulation. Diabetes mellitus, tetany and diabetes insipidus occur due to deficiency of insulin (secreted from pancreas), parathormone (secreted by parathyroid gland) and vasopressin (ADH) of posterior pituitary respectively.
Hormones are chemical messengers produced by the ductless glands (sometimes by neurons) and transported in the circulation to target cells. They regulate metabolic processes. Chemically hormones are of different nature like biogenic amines (like thyroxine, adrenaline etc), proteinaceous or polypeptide (like hypothalamic hormones etc.) and steroids (like sex hormones and adrenocorticoids).
Parathormone is a hormone secreted by parathyroid glands. Hyposecretion of parathormone lowers concentration of calcium ions in the blood and tissues due to excretion of calcium in urine. This increases the excitability of nerves and muscles, causing cramps and convulsions. Sustained contractions (tetany) of the muscles of larynx, face, hands and feet are pr9duced. This disorder is known as parathyroid tetany. Hypersecretion of parathormone draws more calcium from the bones, resulting in their softening, bending and fracture. This condition is called osteoporosis.
Acromegaly is caused by excess of STH (somatotrophic hormone), released by anterior lobe of pituitary after adolescence. The bones of the lower jaw and limbs become abnormally enlarge but the body does not attain a giant stature. Excess of thyroxine causes cretinism and myxoedema. Excess of adrenaline causes increased BMR, heart beat, excitement etc.
Adrenalin directly atfects the SA node to increase rate of heartbeat. Adrenalin prepares the body for emergency reactions like fight & flight. Thus there is increase in heart rate, breathing rate, blood pressure, glucose level in blood, peripheral circulation, etc. b- cells of islet of Langerhans secrete insulin that lower blood glucose level. Secretion of digestive juice by epithelial cells of stomach is inhibited during this time.
Ovary secretes two hormones. Oestrogen before ovulation and progesterone after ovulation. Oxytocin, prolaction are pituitary hormones and gonadotropin releasing factor is secreted by hypothlalamus of brain to stimulate pituitary for the secretion of gonadotropic hormones.
Menstrual cycle is controlled by several endocrinal parameters. In beginning of the cycle FSH (follicle stimulating hormone) of pituitary initiates development of an ovarian follicle. A growing ovarian follicle gradually secretes increasing amount of oestrogen. This in turn leads to sudden surge of LH secretion by the pituitary. As the LEI (leutinising hormone) level in blood suddenly increases there is ovulation.
Thus only FSH or LH cannot control all the events of menstrual cycle. Progesteron is released by a corpus luteum after ovulation which actually prepares the uterus for a possible pregnancy. If there is no fertilisation progesteron level falls and there is beginning of a new cycle.
After ovulation many of the follicular cells remain in the collapsed Graafian follicle on the surface of the ovary. The antrum (cavity) of the collapsed follicle fills with a partially clotted fluid. The follicular cells enlarge and fill with a yellow pigment, lutein. Such a follicle is called a corpus luteum – literally, yellow body. Sebum is secreted by sebaceous glands. SA node is known as pacemaker. Niacin is a vitamin that forms a part of coenzymes (NAD, NADP). Vitamin B7 (Biotin) acts as coenzyme in fatty acid synthesis and in change of pyruvate to oxaloacetate.
Pineal gland is a stalked, small rounded organ. It is located on the midline, attached to the posterior end of the roof of the third ventricle in the brain. It secretes two biogenic hormones – melatonin and serotonin. Melatonin causes concentration of pigment granules in the melanocytes. It also regulates the working of gonads. Pituitary gland secretes a number of hormones, e.g., follicle-stimulating hormone, luteinising hormone, oxytocin etc. Thyroid secretes thyroxine and triiodothyronine. Skin synthesize vitamin D in the presence of sunlight. It exists in two forms calciferol or D2 and cholecalciferol or D3. D3. circulates in the blood. Calcitriol is active form of Dr It increases absorption of calcium and phosphorus from chyme in the small intestine and accelerate bone formation.
The anal glands are small paired sacs located on either side of the anus between the external and internal sphincter muscles. These sebaceous glands within the lining secrete a foul smelling liquid that is used for identification of members within a species. These glands are found in all carnivora except bears. A pair of Bartholin’s glands occur one on each side of the vaginal opening. They secrete viscid fluid and their ducts pour the fluid into the vestibule to lubricate the vulva during copulation. The prostate gland is present in males surrounding the urethra. It secretes a milky fluid that aids in sperm motility. Liver is the largest gland of the body and performs various functions like deamination, production of bile, glycogenesis, storage etc.
Middle lobe of pituitary secretes a hormone named melanocyte-stimulating hormone. It stimulates the synthesis of black pigment melanin in the skin, and also causes dispersal of melanin granules in the pigment cells, thereby darkening the colour in certain animals (fishes; amphibians). In man it has no such role. Anterior lobe of pituitary secretes FSH, LH, TSH, ACTH and STH. Posterior lobe of pituitary secretes oxytocin and vasopressin.
Cholecystokinin and duocrinin, are secreted by intestine. It stimulates pancreas to release enzymes in pancreatic juice and stimulates gall bladder to release bile. Duocrinin causes release of viscous mucus from Brunner’s glands into intestinal juice.
Oxytocin is secreted by posterior lobe of pituitary gland. It induces contractions of smooth muscles of myoepithelial cells of the mammary glands to cause release of milk during sucking by the infant. Because of its role, oxytocin is called “birth hormone” and “milk ejecting hormone”.
Luteinsing Hormone (LH) in the male, induces the interstitial cells of the testes to produce male sex hormones named androgens such as testosterone. In the female, the luteinising hormone causes ovulation, secretion of female sex hormone, estrogen from the maturing ovarian follicle, and progesterone by the corpus luteum. Testosterone makes the male genital system to become fullgrown and functional. Thyroxine promotes growth of body tissues. MSH stimulates synthesis of melanin in the skin.
Gonadotrophic hormones are secreted by anterior lobe of pituitary gland. They are as follows
(a) Follicle-stimulating hormone (FSH). It stimulates growth of ovarian follicles and their secretion of oestrogens in the female, and spermatogenesis (formation of sperms) in the male.
(b) Interstitial-cell stimulating hormone (ICSH). It activates the Leydig’s (interstitial) cells of the testis to secrete androgens. In female, it stimulates the corpus luteum of the ovary to secrete progesterone. In female it is termed luteinizing hormone (LH).
Diabetes mellitus is caused by the deficiency ofhormone insulin which is secreted by pancreas. Insulin lowers the blood-glucose level. Deficiency of antidiuretic hormone (ADH) leads to diabetes insipidus.
Calcitonin is secreted by the C cells. It regulates the concentration of calcium and phosphorus in the blood. It is under the feedback control of plasma calcium concentration, and is secreted when concentration of calcium rises in the blood. It then lowers the concentration of calcium and phosphorus in the plasma by decreasing their release from the bones.
Gastrin hormone is secreted by mucosa of stomach and it stimulates secretion of gastric juice. Enterogastrone is secreted by duodenal epithelium. Enterokinase is an enzyme that converts trypsinogen into trypsin. Renin converts caesin of milk into paracaesin and whey protein.
Cholecystokinin is secreted by duodenal epithelium and it stimulates gall bladder to release bile that causes emulsification of fats to increase lipase action on them. Enterogastrone and secretin are also secreted by duodenal epithelium. Enterogastrone slows gastric contractions to delay its emptying and also stops secretion of gastric juice. Secretin causes release of sodium bicarbonate in pancreatic juice, steps up secretion of bile and inhibits secretion of gastrin. Gastrin stimulates secretion of gastric juice and is secreted by mucosa of pyloric stomach.
The basal metabolism is the minimum amount of energy the body uses in order to maintain vital processes of the body. Generally, this expenditure of energy is expressed in terms of heat production per unit of body surface per day on the basal metabolic rate (BMR). Thyroid is the largest endocrine gland secreting three hormones thyroxine, triiodothyronine and calcitonin. Thyroxine and triiodothyronine control BMR of the body by regulating the rate of oxidation and production of energy. Calcitonin regulates the concentration of calcium and phosphorus in the blood. Adrenal cortex secretes mineralocorticoids, glucocorticoids and sexcorticoids. Pituitary gland consists of three lobes and all of them secrete separate hormones. Pancreas secrete four hormones – insulin, glucagon, somatostatin and pancreatic polypeptide.
Hormones thyroxine, adrenaline and the pigment melanin are formed from tyrosine. Tyrosine is transformed into dopa through the enzyme tyrosinase. Then through different metabolic pathways it produces thyroxine, adrenaline, melanin etc.
Prolactin hormone stimulates the growth of milk glands during pregnancy and the secretion of milk after delivery. Oxytocin causes release of milk during sucking by the infant. LH causes ovulation and secretion of estrogen and progesterone from ovarian follicle and corpus luteum respectively. Oxytocin, LH and prolactin are released by anterior lobe of pituitary gland. Progesterone is secreted by corpus luteum.
The thyroid gland secretes three’hormones thyroxine or tetraiodothyronine (T4), triiodothyronine (T3) and calcitonin. Thyroxine and Triiodothyronine are iodinated forms of the amino acid tyrosine. They are stored in the colloid that fills the follicles, and are released to the blood when needed. The storage occurs in an unusual place, the extracellular colloid.
The molecules of hormones that are amino acid derivatives, peptides or proteins are large and insoluble in lipids, and cannot enter the target cell. Therefore, they act at the cell surface. They bind to specific receptor molecules located on the surface of the cell membrane. Therefore, if receptor molecules are removed from target organs, then the target organ will not respond to the hormone.
LH (luteinising hormone) is released by anterior lobe of pituitary gland. It causes ovulation, secretion of estrogen from mature ovarian follicle and progesterone from corpus luteum. FSH stimulates sperm formation in the male and growth of ovarian follicles in the female. Progesterone suspends ovulation during pregnancy, fixes the foetus to the uterine wall, forms placenta and controls the development of the foetus in the uterus. Estradiol is the major estrogen in humans.
Refer answer 10.
Enterogastrone is secreted by duodenal epithelium and it slows gastric contractions to delay its emptying and also stops secretion of gastric juice. Gastrin stimulates secretion of gastric juice. Cholecystokinin stimulates release of enzymes in pancreatic juice and release of bile from gall bladder. Cholecystokinin is also known as pancreozymin.
Antidiuretic hormone (ADH) or vasopressin is secreted by the posterior lobe of the pituitary gland. It increases the reabsorption of water in the distal convoluted tubule, collecting tubules and collecting ducts of the nephrons of the kidneys. As a result, the reabsorption of water from the glomerular filtrate is increased. Enzyme that hydrolysis peptides is known as peptidase. Hormones that promotes glycogenolysis is glucagon and adrenaline. Energy rich compound connected with muscle contraction is ATP.
A pair of testes is situated in the scrotum of male. The connective tissue present between the seminiferous tubules in a testis contains small clusters of endocrine cells called interstitial cells or Leydig’s cells. These cells secrete various male sex hormones called androgens. The principal androgen is testosterone.
Insulin is a hormone secreted by the (3-cells of pancreas on stimulation by a rise in blood-glucose level.
In 1912, Gudernatsch discovered that metamorphosis in frog’s tadpole is increased by the thyroxine hormone which has the iodine as the main constituent. If thyroxine or iodine in added in water having tadpoles in it, then it increases the rate of metamorphosis in tadpole.
Insulin decreases the level of glucose in the blood while cortisol (secreted by middle region of adrenal cortex) increases the blood-glucose level by converting proteins and fats into carbohydrates which are, in turn, converted to glucose.
Pars intermedia is the boundary between the anterior and posterior lobes of the pituitary. It contains three types of cells – basophils, chromophobes and colloid-filled cysts. This area produces melanocyte stimulating hormone or MSH. It stimulates the synthesis of black pigment melanin in the skin and also causes dispersion of melanin granules in the pigment cells, thereby darkening the colour in certain animals (fishes , amphibians). In man it has no such role.