NCERT Exemplar Class 11 Biology Solutions Chemical Coordination and Integration
Multiple Choice Questions
1.Select the right match of endocrine gland and their hormones among the options given below
A.Pineal (i) Epinephrine
C.Ovary – (iii)Estrogen
D.Adrenal medulla (iv)Tetraiodothyronine Options:
(a) A-(iv), B-(ii), C-(iii), D-(i)
(b) A-(ii), B-(iv), C-(i), D-(iii)
(c) A-(iv), B-(ii), C-(i), D-(iii)
(d) A-(ii), B-(iv), C-(iii), D-(i)
2.Which of the following hormones is not secreted by anterior pituitary?
(a) Growth hormone
(b) Follicle stimulating hormone
(d) Adrenocorticotrophic hormone
Solution. (c) : The anterior lobe of the pituitary gland secretes the following hormones: thyroid stimulating hormone, adrenocortico -tropic hormone, growth hormone, prolactin or mammotrophic or luteotropic hormone and gonadotropic hormones [FSH and LH], Oxytocin is secreted by the posterior lobe of pituitary gland.
3.Mary is about to face an interview. But during the first five minutes before the interview she experiences sweating, increased rate of heart beat, respiration, etc. Which hormone is responsible for her restlessness?
(a) Estrogen and progesterone
(b) Oxytocin and vasopressin
(c) Adrenaline and noradrenaline
(d) Insulin and glucagon
Solution. (c) : Medulla of adrenal glands secrete two hormones, noradrenaline and adrenaline.
Norepinephrine (= Noradrenaline) regulates pressure under normal conditions. It causes . increased activity of the heart, inhibition of gastrointestinal tract, dilation of the pupils of the eyes and so forth. During emergency, adrenaline is released and causes dilation of blood vessels, so that the blood flow is increased. It also increases heart beat so that more oxygen is consumed and it also increases blood glucose levels. Therefore, it is also known as emergency hormone. Because of the role of their hormones, the adrenal glands are also called ‘gland of emergency’.
4.The steroid responsible for balance of water and electrolytes in our body is
(a) insulin (b) melatonin
(c) testosterone (d) aldosterone.
Solution.(d) : Aldosterone is a major mineralocorticoid, secreted by adrenal cortex. It controls excretion of sodium by the kidneys. It is secreted when the sodium level is low in the blood, thus acts on kidneys to cause more sodium to be returns to the blood. It also acts on kidneys to cause more potassium to be excreted. As the sodium concentration in the blood increases, water follow it by osmosis, so the blood volume also increases. Thus, the effect of aldosterone is to increase both sodium and water in the blood.
5.Thymosin is responsible for
(a) raising the blood sugar level
(b) raising the blood calcium level
(c) differentiation of T lymphocytes
(d) decrease in blood RBC.
Solution.(c) : Thymus secretes a hormone named thymosin which stimulates the development and differentiation of T-cells increasing resistance . to infections. It also hastens attainment of sexual maturity.
6.In the mechanism of action of a protein hormone, one of the second messengers is
(a) cyclic AMP (b) insulin
(c) T3(d) gastrin.
Solution. (a) : 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. The hormone-receptor complex activates G protein associated with the cytoplasmic C– terminal which initiate the release of an enzyme adenyl cyclase from the receptor site. Adenyl cyclase enzyme forms in the cell, cyclic adenosine monophosphate (cAMP) from ATP. The cAMP activates the existing enzyme system of the cell. This accelerates the metabolic reactions in the cell. The hormone is called the first messenger and the cAMP is termed the second messenger.
7.Leydig cells produce a group of hormones called
(a) androgens (b) estrogens
(c) aldosterone (d) gonadotropins.
Solution.(a) : The Leydig’s cells present in the connective tissue between seminiferous tubules produce a group of hormones called androgens mainly testosterone.
8.Corpus luteum secretes a hormone called
(a) prolactin (b) progesterone
(c) aldosterone (d) testosterone.
Solution. (b) : Corpus luteum of the ovary ‘ secretes progesterone, and relaxin. Prolactin is secreted by anterior lobe of pituitary gland. Aldosterone is a principal mineralocortioid secreted by the adrenal cortex and testosterone is secreted by the Leydig’s cells in the testes.
9.Cortisol is secreted from
(a) pancreas (b) thyroid
(c) adrenal (d) thymus.
Solution. (c): Adrenal or suprarenal glands are paired structures located on the top of the kidneys. The cells of zona fasciculata of adrenal cortex secretes mainly glucocorticoids. Glucocorticoids include three main hormones: cortisol (= hydrocortisone), corticosterone and cortisone. They effect carbohydrate metabolism, however, they also affect the metabolism of proteins and fats.
10.A hormone responsible for normal sleep-wake cycle is
(a) epinephrine (b) gastrin
(c) melatonin (d) insulin.
Solution. (c) : Melatonin is a hormone secreted by pineal gland. Immediately above the
optic chiasma (in the brain) in a nucleus, are present melatonin receptors that react to this hormone and synchronize the nucleus to the 24 hrs day/night rhythm, thus informing the brain when it is day and when it is night.
11.Hormones are called chemical signals that stimulate specific target tissues. Which is the correct location of these receptors in case of protein hormones?
(a) Extra cellular matrix
(c) Plasma membrane
Solution. (c): Hormones of protein nature binds to specific receptor molecules located on the plasma membrane to form the hormone receptor complex.
12.Choose the correct option among the following:
Column A Column B
A.Epinephrine (i)Stimulates in muscle growth
B. Testosterone (ii)Decrease in blood pressure
C. Glucagon (iii)Decrease in liver glycogen content
D.Atrial natriuretic factor (iv)Increases heart beat
(a)A-(ii), B-(i), C-(iii), D-(iv)
(b)A-(iv), B-(i), C-(iii), D-(ii)
(c)A-(i), B-(ii), C-(iii), D-(iv)
(d)A-(i), B-(iv), C-(ii), D-(iii)
13. Which of the following does not play any role in calcium balance in the body?
(a) Vitamin D
(b) Parathyroid hormone
Solution.(d) : Refer answer 5.
14. Which of the following organs in mammals does not consist of a central ‘medullary’ region surrounded by a cortical region?
(a) Ovary (b) Adrenal
(c) Liver (d) Kidney
15. Which of the following conditions is not linked to deficiency of thyroid hormones?
(a) Cretinism (b) Goitre
(c) Myxedema (d) Exophthalmosis
(d): Hypothyroidism is a disorder caused due to deficiency of thyroid hormone. It may lead to cretinism, myxoedema, simple goitre, Hashimoto’s disease. Exophthalamic goitre is thyroid enlargement in which thyroid secretes excessive amount of thyroid hormone.
Very Short Answer Type Questions
1.There are many endocrine glands in human body. Name the glands which is absent in male and the one absent in female.
Solution.Ovaries are absent in male and testes are absent in female. ‘
2.Which of the two adrenocortical layers, zona glomerulosa and zona reticularis lies outside enveloping the other?
Solution. Zona glomerulosa is the outer layer.
3.What is erythropoiesis? Which hormone stimulates it?
Solution. Erythropoiesis is formation of RBCs. Erythropoietin hormones secreted by juxtaglomerular cells of kidney stimulates erythropoiesis.
4.Name the only hormone secreted by pars intermedia of the pituitary gland.
Solution. Melanocyte stimulating hormone.
5.Name the endocrine gland that produces calcitonin and mention the role played by this hormone.
Solution.Calcitonin is secreted by thyroid gland. This hormone regulates the blood calcium levels.
6.Name the hormone that helps in cell – mediated immunity.
7.What is the role of second messenger in the mechanism of protein hormone action?
Solution.Second messenger (e.g. cAMP) acts as intracellular hormonal mediator delivering information inside the target cells. This activates appropriate cellular enzyme system by cascade effect which stimulates the cell machinery to perform its specialised function.
8.State whether true or false:
(a) Gastrointestinal tract, kidney and heart also produce hormones.
(b) Pars distalis produces six trophic hormones.
(c) B-lymphocytes provide cell-mediated immunity.
(d) Insulin resistance results in a disease called diabetes mellitus.
Solution.(a) True, (b) True, (c) False, (d) True.
9. A patient complain so fconstantthirst,excessive passing of urine and low blood pressure. When the doctor checked the patients’ blood glucose and blood insulin level, the level were normal or slightly low. The doctor diagnosed the condition as diabetes insipidus. But he decided to measure one more hormone in patients blood. Which hormone does the doctor intend to measure?
Solution.Doctor intends to measure vasopressin hormone. This hormone increases the reabsorption of water by the kidney. Deficiency of this hormone decreases the reabsorption of water and thus leads to formation of excessive dilute urine resulting in constant thirst and low blood pressure.
10.Correct the following statements by replacing the term underlined.
(a) Insulin is a steroid hormone.
(b) TSH is secreted from the corpus luteum
(c) Tetraiodothyronine is an emergency hormone.
(d) The pineal aland is located on the anterior part of the kidney.
Solution.(a) Insulin is a protein hormone.
(b) TSH is secreted from the anterior pituitary.
(c) Adrenaline is an emergency hormone.
(d) Adrenal gland is located on the anterior part of the kidney.
11. Rearrange the following hormones in Column I so as to match with their chemical nature in Column II.
Column I Column II
(a) Oxytocin i. Amino acid derivative
(b) Epinephrine ii. Steroid
(c) Progesterone in. iii.Protein
(d) Growth hormone iv. Peptide
Solution.(a) – iv, (b) – i, (c) – ii, (d) – (iii).
Short Answer Type Questions
1.What is the role-played by luteinizing hormones in males and females respectively?
Solution.In males, luteinizing hormone (LH) stimulates the synthesis and secretion of hormones called androgens from testes. In females, LH induces ovulation of fully mature follicles and maintains the corpus luteum, formed from the remnants of the follicles after ovulation.
2.What is the role of second messenger in hormone action?
Solution.Hormones which interact with mem ¬brane – bound receptors normally do not en ¬ter the target cell, but generate second mes ¬senger (e.g. cAMP) which acts as intracellular hormonal mediator, delivering information inside the target cells. This activates appropri ¬ate cellular enzyme system by cascade effect which stimulates the cell machinery to per-‘ form its specialised function.
3.On an educational trip to Uttaranchal, Ketki and her friends observed that many local people were having swollen necks. Please help Ketki and her friends to find out the solutions to the following questions.
(a) Which probable disease are these people suffering from?
(b) How is it caused?
(c) What effect does this condition have on pregnancy? ,
(b) Deficiency of iodine in the diet results in hypothyroidism and enlargement of the thyroid gland commonly called goitre.
(c) Hypothyroidism during pregnancy causes defective development and maturation of the growing baby leading to stunted growth (cretinism), mental retardation, low intelligence quotient, abnormal skin, deaf- mutism etc.
4.George comes on a vacation to India from US. The long journey disturbs his biological system and he suffers from jet lag. What is the cause of his diicomfort?
Solution. Jet lag is a temporary sleep disorder among air travellers who rapidly travel across time zones. Jet lag occurs as a result of the slow adjustment of the body clock to . the destination time. Consequently, the daily rhythms and the internal drive for sleep and wakefulness are out of synchronisation with the new environment.
The intrinsic body clock resides in the suprachiasmatic nuclei at the base of the hypothalamus, which contains melatonin receptors. Melatonin is manufactured in pineal gland and its synthesis and release are stimulated by darkness and suppressed by light, consequently, the secretion of melatonin is responsible for setting sleep-wake cycle. The body clock is adjusted to the solar day by rhythmic cues in the environment, mainly the light-dark cycle and the rhythmic secretion of melatonin.
5. Inflammatory responses can be controlled by a certain steroid. Name the steroid, its source and also its other important functions.
Solution.Cortisol is a steroid hormone that produces anti-inflammatory responses and suppresses the immune response. It is secreted by adrenal cortex. It also stimulates gluconeogenesis, lipolysis and proteolysis, and inhibit cellular uptake and utilisation of amino acids. It is also involved in maintaining the cardio-vascular system as well as the kidney function. It also stimulates the RBC production.
6.Old people have weak immune system. What could be the reason?
Solution.Thymus gland secretes a hormone, thymosin. This gland plays a major role in the development of immune system. But, thymus gland gets degenerate in old individuals resulting in decreased production of thymosin. As a result, the old people have weak immune system.
7.What are the effects of hypothyroidism (observed during pregnancy) on the development and maturation of a growing baby?
Solution. Refer answer 3(c).
8.Mention the difference between hypothyroid-ism and hyperthyroidism.
Solution. Hypothyroidism is the hyposecretion of thyroid hormone causing cretinism in children and myxoedema in adult. Hyperthyroidism is the hypersecretion of thyroid hormone. It is caused due to cancer of the thyroid gland or due to development of nodules of the thyroid glands. This results in increase in the rate of synthesis and secretion of the thyroid hormones to abnormal high levels leading to hyperthyroidism. Grave’s disease is a thyroid enlargement in which the thyroid secretes excessive amount of thyroid hormone.
9.You have learnt that a characteristic feature of endocrine system is the presence of feed back loops. By this what is meant if hormone A stimulates gland ‘X’ to secrete hormone B, the production of ‘A’ could be modified when the level of B changes in our blood. An example is the relation between hormones LH and estrogen ( E2). An old woman exhibits the following features. High levels of LH in blood but low levels of E2 in the blood. Another woman exhibits high level of LH in blood and also high level of E2 in the blood. Where is the defect in both these women? Provide suitable diagram to support this answer.
Solution.When the secretion of hormone is under the control of factors or other hormones it is called feedback control.
If there is high concentration of hormone B in our blood then it will have an inhibitory effect on the secretion of hormone A. Decreased secretion of A will eventually result in decrease in production of hormone. This is negative feedback control. If there is B low concentration of hormone B in our blood then it will have a stimulatory effect on the secretion of hormone A. Increased secretion of A will eventually result in increase in production of hormone B. This is positive feedback control.
Low level of E2 should have positive feedback control on secretion of LH resulting in increase in production of E2. But old woman shows low level of E2 and high level of hormone LH, this means LH is not stimulating gland X to secrete hormone E2.
High level of E2 should have negative feedback control on secretion of LH resulting in decrease in production of E2. But another woman shows high level of both E2 and LH, this means there is some defect in the negative feedback loop.
Long Answer Type Questions
1.A milkman is very upset one morning as his cow refuses to give any milk. The milkman’s wife gets the calf from the shed. On fondling by the calf, the cow gave sufficient milk. Describe the role of endocrine gland and pathway associated with this response?
Solution. Suckling by the calf creates a neuroendocrine reflex which results in increase in secretion of oxytocin from posterior lobe of pituitary gland. Oxytocin is synthesised in the hypothalamus in specific nuclei (cluster of nerve cells). Neurons of these nuclei synthesise oxytocin precursor and package it into vesicles, which are then send to the posterior pituitary. Oxytocin promotes contraction of the myoepithelial cells of the udder, thus resulting into milk flow.
It can be summarised as follows:
Udder (suckling stimulus) > Hypothalamus> Posterior lobe of pituitary > Oxytocin (in blood) > Udder (Smooth muscles) > Milk flow.
2. A sample of urine was diagnosed to contain high content of glucose and ketone bodies. Based on this observation, answer the following:
(a) Which endocrine gland and hormone is related to this condition?
(b) Name the cells on which this hormone acts.
(c) What is the condition called and how can it be rectified?
(a) Pancreas is the gland and hormone is Insulin decreases the level of glucose in blood by increasing the rate as which glucose is transported out of blood and into the cell. When insulin is not produced adequately glucose uptake is hampered and hence glucose starts appearing in urine along with ketone bodies.
(b) Hepatocytes and adipocytes.
(c) The condition is called diabetes mellitus. It can be rectified by insulin therapy.
3.Calcium plays a very important role in the formation of bones. Write on the role of endocrine glands and hormones responsible for maintaining calcium homeostasis.
Solution. Thyroid gland and parathyroid gland are responsible for maintaining calcium homeostasis. Both act antagonistic to each other. Thyroid gland secretes the hormone calcitonin when calcium level is high in the blood. It then lowers the calcium level by suppressing release of calcium ions from the bones. Parathyroid glands secrete the hormone parathormone. It increases the Ca2+ level in the blood. It acts on bones and stimulates the process of bone resorption. Parathormone also stimulates reabsorption of Ca2+ by the renal tubules and increases Ca2+ absorption from the digested food. Thus parathormone, along with calcitonin plays a very important role in calcium balance in the body.
4.Illustrate the differences between the mechanism of action of a protein and a steroid hormone.
Solution. Protein hormones being water soluble normally do not enter the target cell but interact with membrane bound receptors to generate second messengers like cAMP, 1P3, Ca2+ etc. which in turn regulate cellular metabolism. Steroid hormones being lipid soluble, enter the target cell and interact with intracellular receptors and regulate gene expression or chromosome function by the interaction of hormones – receptor complex with the genome. Cumulative biochemical actions result in physiological and developmental effects.
Diagrammatic representation of the mecha-nism of hormone action:
(a) Protein hormone
(b) Steroid hormone
5. Hypothalamus is a super master endocrine gland. Elaborate.
Solution. Hypothalamus is a super master endocrine gland as it secretes hormones that regulate the synthesis and secretion of pituitary gland which is a master gland. The hypothalamus is connected to the anterior lobe of pituitary gland by hypophysial portal veins, however, it is connected to the posterior lobe of pituitary gland mainly by axons of nuerosecretory cells. The hormones produced by hypothalamus are of two types, the releasing hormones (which stimulate the secretion of pituitary hormones) and the inhibiting hormones (which inhibit secretions of pituitary hormones). The hormones secreted by hypothalamus are summarised below:
(i) Adrenocorticotropic Releasing Hormone (ARH) or Corticotropin Releasing Hormone – It stimulates the anterior lobe of the pituitary gland to secrete its adrenocorticotropic hormone (ACTH).
(ii)Thyrotropin Releasing Hormone (TRH) – It stimulates the anterior lobe of the pitu ¬itary gland to secrete its thyroid stimulat ¬ing hormone (TSH).or thyrotropin.
(iii)Growth Hormone-Releasing Hormone (GHRH) – It stimulates the anterior lobe of the pituitary gland to release its growth hormone (GH) or somatotrophin.
(iv)Growth Hormone-Inhibitory Hormone (GHIH) – This hormone is also called somatostatin (SS). It inhibits the secretion of growth hormone from the anterior lobe of the pituitary gland.
(v) Gonadotropin Releasing Hormone (GnRH)- It stimulates the anterior lobe of the pituitary gland to secrete two gonadotropic hormones : Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH)).
(vi)Prolactin Releasing hormone (PRH) – It stimulates the anterior lobe of the pituitary gland to secrete its prolactin hormone.
(vii)Prolactin Inhibitory Hormone (PIH) – It inhibits the secretion of prolactin from the anterior lobe of pituitary gland.
(viii)MSH Releasing Hormone (MSHRH) – It stimulates the intermediate lobe of the pituitary gland to secrete its melanocyte stimulating hormone (MSH).
(ix) MSH Inhibitory Hormone (MSHIH) – It inhibits the secretion of melanocytes stimulating hormone from the intermediate lobe of the pituitary gland.
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