41 Questions with Answers and Explanations on “Endocrine System” for Biology Students.
1. MSH of pars intermedia of middle pituitary is responsible for
(a) darkening of skin in lower vertebrates
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(b) light colouration of skin in lower vertebrates
(c) both A and B
(d) darkening of skin in human beings.
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Answer and Explanation:
1. (a): 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.
2. Which hormone possesses anti-insulin effect?
(a) Cortisol
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(b) calcitonin
(c) oxytocin
(d) aldosterone.
Answer and Explanation:
2. (a): 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.
3. Addition of a trace of thyroxine or iodine in water containing tadpoles will
(a) keep them in larval stage
(b) hasten their metamorphosis
(c) slow down their metamorphosis
(d) kill the tadpoles.
Answer and Explanation:
3. (b): In 1912, Gudematsch 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.
4. Insulin is a
(a) vitamin
(b) lipid
(c) hormone
(d) enzyme.
Answer and Explanation:
4. (c): Insulin is a hormone secreted by the (3-cells of pancreas on stimulation by a rise in blood-glucose level.
5. Occurrence of Leydig’s cells and their secretion is
(a) ovary and estrogen
(b) liver and cholesterol
(c) pancreas and glucagon
(d) testis and testosterone.
Answer and Explanation:
5. (d): 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.
6. ADH or vasopressin is
(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.
Answer and Explanation:
6. (b): 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 peptide is known as peptidase. A hormone that promotes glycogenosis is glucagon and adrenaline. Energy rich compound connected with muscle contraction is ATP.
7. Gastric secretion is stopped by hormone
(a) enterogastrone
(b) gastrin
(c) pancreozymin
(d) cholecystokinin.
Answer and Explanation:
7. (a): 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.
8. Testosterone is produced by
(a) Sertoli cells
(b) Leydig’s cells
(c) oxyntic cells
(d) pituitary gland.
Answer and Explanation:
8. (b): Refer answer 5.
9. The immediate cause of induction of ovulation in human female is the large plasma surge of
(a) LH
(b) FSH
(c) progesterone
(d) estradiol.
Answer and Explanation:
9. (a): 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.
10. According to the accepted concept of hormone action, if receptor molecules are removed from target organs, then the target organ will
(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.
Answer and Explanation:
10. (b): The molecules of hormones that are amino acid derivatives, peptides Ci 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.
11. Which one of the following endocrine glands stores its secretion in the extracellular space before discharging it into the blood?
(a) testis
(b) thyroid
(c) pancreas
(d) adrenal.
Answer and Explanation:
11. (b): The thyroid gland secretes three hormones : thyroxine or tetraiodothyronine (T4)’, triiodothyronine (T,)2 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.
12. Which hormone stimulates the secretion of milk from female?
(a) oxytocin
(b) progesterone
(c) LH
(d) prolactin.
Answer and Explanation:
12. (d): 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.
13. Hormones thyroxine, adrenaline and the pigment melanin are formed from
(a) tyrosine
(b) proline
(c) tryptophan
(d) glycine.
Answer and Explanation:
13. (a): 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.
14. The hormone which regulates the basal metabolism in our body is secreted from
(a) adrenal cortex
(b) pancreas
(c) pituitary
(d) thyroid.
Answer and Explanation:
14. (d): 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 secretes four hormones – insulin, glucagon, somatostatin and pancreatic polypeptide.
15. The contraction of gall bladder is due to wine System
(a) Cholecystokinin
(b) enterogastrone
(c) gastrin
(d) secretin.
Answer and Explanation:
15. (a): Cholecystokinin is secreted by duodenal epithelium and it stimulates gall blader 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 pancreaticjuice, steps up secretion of bile and inhibits secretion of gastrin. Gastrin stimulates secretion of gastric juice and is secreted by mucosa of pyloric stomach.
16.
The hormone that stimulates the stomach to secrete gastric juice is
(a) enterokinase
(b) enterogastrone
(c) gastrin
(d) renin.
Answer and Explanation:
16. (c): 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.
17. Calcitonin is a thyroid hormone which
(a) elevates calcium level in blood
(b) has no effect on calcium
(c) elevates potassium level in blood
(d) lowers calcium level in blood.
Answer and Explanation:
17. (d): 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.
18. Diabetes is due to
(a) enzyme deficiency
(b) iodine deficiency
(c) Na+ deficiency
(d) hormonal deficiency
Answer and Explanation:
18. (d): Diabetes mellitus is caused by the deficiency of hormone insulin which is secreted by pancreas. Insulin lowers the blood-glucose level. Deficiency of antidiuretic hormone (ADH) leads to diabetes insipidus.
19. The gonadotrophic hormones are secreted by
(a) anterior lobe of pituitary
(b) interstitial cells of testes
(c) adrenal cortex
(d) posterior part of thyroid.
Answer and Explanation:
19. (a): Gonadotropic 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 test is to secrete androgens. In female, it stimulates the corpus luteum of the ovary to secrete progesterone. In female it is termed luteinizing hormone (LH).
20. Secretion of progesterone by corpus luteum is initiated by
(a) testosterone
(b) thyroxine
(c) MSH
(d) LH.
Answer and Explanation:
20. (d): 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 full grown and functional. Thyroxine promotes growth of body tissues. MSH stimulates synthesis of melanin in the skin.
21. The function of oxytocin is to help in
(a) child birth
(b) gametogeresis
(c) growth
(d) lactation.
Answer and Explanation:
21. (d): 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”.
22. Cholecystokinin and duocrinin are secreted by
(a) adrenal cortex
(b) thyroid gland
(c) intestine
(d) pancreas.
Answer and Explanation:
22. (c): 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.
23. MSH is secreted by
(a) anterior lobe of pituitary
(b) middle lobe of pituitary
(c) posterior lobe of pituitary
(d) endostyle.
Answer and Explanation:
23. (b): 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, and TSH. ACTH and STH. Posterior lobe of pituitary secretes oxytocin and vasopressin.
24. Which gland secretes odorous secretion in mammals?
(a) bartholins
(b) prostate
(c) anal gland
(d) liver.
Answer and Explanation:
24. (c): 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 camivora except bears.
A pair of Bartholin’s glands occurs 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.
25. Melatonin is secreted by
(a) pineal body
(b) skin
(c) pituitary gland
(d) thyroid.
Answer and Explanation:
25. (a): 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 Dv D3 circulates in the blood. Calcitriol is active form of D3. It increases absorption of calcium and phosphorus from chyme in the small intestine and accelerate bone formation.
26. Which set is similar
(a) corpus luteum – graafian follicles
(b) sebum – sweat
(c) bundle of His – pace maker
(d) vitamin B7 – Niacin.
Answer and Explanation:
26. (a): 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.
27. Mainly which type of hormones control the menstrual cycle in human beings?
(a) FSH
(b) LH
(c) FSH, LH, estrogen
(d) progesteron.
Answer and Explanation:
27. (c): 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 LH (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.
28. When both ovaries are removed from rat then which hormone is decreased in blood?
(a) oxytocin
(b) prolactin
(c) estrogen
(d) gonadotropin releasing factor.
Answer and Explanation:
28. (c): Ovary secretes two hormones. Oestrogen before ovulation and progesteron after ovulation. Oxytocin, prolaction are pituitary hormones and gonadotropin releasing factor is secreted by hypothalamus of brain to stimulate pituitary for the secretion of gonadotropic hormones.
29. Adrenaline directly affects on
(a) S.A. node
(b) B-cells of Langerhans
(c) dorsal root of spinal nerve
(d) epithelial cells of stomach.
Answer and Explanation:
29. (a): Adrenalin directly affects 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. (3-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.
30. Acromegaly is caused by
(a) excess of S.T.H.
(b) excess of thyroxine
(c) deficiency of thyroxine
(d) excess of adrenaline.
Answer and Explanation:
30. (a): Acromegaly is caused by excess of STH (somatotrophic hormone), relased 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, heartbeat, excitement etc.
31. Which one of the following pairs correctly matches a hormone with a disease resulting from its deficiency?
(a) Relaxin – Gigantism
(b) Prolactin – Cretinism
(c) Parathyroid hormone – Tetany
(d) Insulin – Diabetes insipidus
Answer and Explanation:
31. (c): 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 produced. 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.
32. Chemically hormones are
(a) biogenic amines only
(b) proteins, steroids and biogenic amines
(c) proteins only
(d) steroids only.
Answer and Explanation:
32. (b): 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.
33. Which one of the following pairs correctly matches a hormone with a disease resulting from its deficiency?
(a) Luteinizing hormone – Failure of ovulation
(b) Insulin – Diabetes insipidus
(c) Thyroxine – Tetany
(d) Parathyroid hormone – Diabetes mellitus.
Answer and Explanation:
33. (a): 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 (ADI I) of posterior pituitary respectively.
34. Which one of the following hormones is modified amino acid?
(a) epinephrine
(b) progesterone
(c) prostaglandin
(d) estrogen.
Answer and Explanation:
34. (a): 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.
35. Which one of the following statements is correct?
(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
Answer and Explanation:
35. (c): 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 I 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.
36. Which one of the following is not a secondary messenger in hormone action?
(a) cAMP
(b) cGMP
(c) calcium
(d) sodium
Answer and Explanation:
36. (d): 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, cGMPand 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.
37. A steroid hormone which regulates glucose metabolism is
(a) cortisone
(b) Cortisol
(c) corticosterone
(d) 11 -deoxycorticosterone
37. (b): Glucocorticoids (e.g. 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 carboy hydrates which are in turn, converted to glucose.
38. Which of the following is an accumulation and release centre of neurohormones?
(a) anterior pituitary lobe
(b) posterior pituitary lobe
(c) intermediate lobe of the pituitary
(d) hypothalamus
Answer and Explanation:
38. (d): 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).
39. Which hormone causes dilation of blood vessels, increased oxygen consumption and glucogenesis?
(a) glucagon
(b) ACTH
(c) insulin
(d) adrenaline
Answer and Explanation:
39. (d): 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.
40. A person is having problems with calcium and phosphorus metabolism in his body. Which one of the following glands may not be functioning properly?
(a) parotid
(b) pancreas
(c) thyroid
(d) parathyroid.
Answer and Explanation:
40. (d): 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 of the 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.
41. 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?
(a) adrenaline
(b) glucagon
(c) gastrin
(d) thyroxine
Answer and Explanation:
41. (a): 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.
