Directions: In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as :
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If the assertion is true but the reason is false.
(d) If the assertion is false but the reason is true.
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Assertion: Neurohypophysis is under the direct regulation of the hypothalamus.
Reason: Neurohypophysis stores and releases two hormones called oxytocin and vasopressin which are actually synthesised by the hypothalamus.
(a) Neurohypophysis is also known as posterior pituitary, stores and releases two hormones called oxytocin and vasopressin which are actually synthesised by the hypothalamus and are transported axonally to neurohypophysis. Therefore, the posterior pituitary is under the direct neural regulation of the hypothalamus.
Assertion: Oxytocin is called the ‘milk-ejection hormone’.
Reason: Oxytocin acts on the smooth muscles of the uterus and stimulates its contraction.
(b) Oxytocin acts on the smooth muscles of our body and stimulates their contraction. In females, it stimulates a vigorous contraction of uterus at the time of child birth, and milk ejection from the mammary gland during suckling.
Assertion: Melatonin influences the menstrual cycle, pigmentation and defence capability.
Reason: Melatonin plays an important role in the regulation of the diurnal rhythm of our body.
Assertion: Thyroid hormones promote physical growth and development of mental faculties.
Reason: Hypothyroidism in adults causes retarded sexual development.
Assertion: PTH is a hypercalcemic hormone.
Reason: PTH stimulates the process of bone resorption.
(a) Parathyroid hormone (PTH) increases the \(\mathrm{Ca}^{2+}\) levels in the blood. PTH acts on bones and stimulates the process of bone resorption (dissolution/demineralisation). PTH also stimulates reabsorption of \(\mathrm{Ca}^{2+}\) by the renal tubules and increases \(\mathrm{Ca}^{2+}\) absorption from the digested food. It is, thus, clear that PTH is a hypercalcemic hormone, i.e., it increases the blood \(\mathrm{Ca}^{2+}\) level.
Assertion: Immune response of old persons become weak.
Reason: Thymus degenerates in old individuals.
(a) Thymus plays a major role in the development of the immune system. This gland secretes the peptide hormones called thymosins. Thymosins play a major role in the differentiation of T-lymphocytes, which provide cell-mediated immunity. In addition, thymosins also promote the production of antibodies to provide humoral immunity. Thymus is degenerated in old individuals resulting in a decreased production of thymosins. As a result, the immune responses of old persons become weak.
Assertion: Adrenal cortex is not vital for survival and may be removed without subsequently leading to death.
Reason: Adrenal cortex secretes corticoids.
(d) The outer layer of adrenal is called adrenal cortex. This part of adrenal is vitally important for life and its destruction or removal kills the animal. It secretes a number of steroid hormones which are broadly classified into three groups, viz. glucocorticoids, mineralocorticoids and sex corticoids. Glucocorticoids regulate the metabolisms of carbohydrates, fats and proteins. Mineralocorticoids regulate the balance of water and electrolytes is our body. Sex corticoids stimulate the development of external sex characters.
Assertion: Adrenal medullary hormones help in combating the stress condition.
Reason: Both adrenaline and noradrenaline act on same organs and produce similar effects.
Assertion: Cortisol produces anti-inflammatory reactions and suppresses the immune response.
Reason: Cortisol stimulates gluconeogenesis, lipogenesis and proteogenesis.
(c) The adrenal cortex produces glucocorticoids which stimulate gluconeogenesis, lipolysis and proteolysis, and inhibit cellular uptakes and utilisation of amino acids. In our body, cortisol is the main glucocorticoid; cortisol produces anti-inflammatory reactions and suppresses the immune response.
Assertion: Insulin stimulates glycogenolysis and gluconeogenesis resulting in hyperglycemia.
Reason: Prolonged hyperglycemia leads to complex disorder called diabetes mellitus.
(d) Insulin stimulates conversion of glucose to glycogen (glycogenesis) in the target cells. Prolonged hyperglycemia leads to a complex disorder called diabetes mellitus.
Assertion: Insulin is an anabolic hormone.
Reason: A fall in blood amino acids also increases insulin secretion.
Assertion: Androgens stimulate muscular growth.
Reason: Androgens produce anabolic effects on protein and carbohydrate metabolism.
(a) Androgens produce anabolic (synthetic) effects on protein and carbohydrate metabolism. This anabolic effect causes greatly increased deposition of protein everywhere in the body, but especially in the muscles. Androgens, therefore, stimulate muscular growth.
Assertion: The estrogen level falls after menopause.
Reason: The estrogen is synthesised and secreted mainly by uterine lining.
(c) The estrogen is synthesised and secreted mainly by the growing ovarian follicles. Menopause is the time in a woman’s life when the ovaries cease to produce an egg every month. Therefore, menstruation also ceases. This may happen because both the ovaries, by menopause, have run out of ovarian follicles. Without developing follicles, there is a reduced supply of estrogen and progesterone.
Assertion: Renal cells are involved in stimulating the formation of RBCs.
Reason: The juxtaglomerular cells of kidney produce erythropoietin.
Assertion: Insulin forms hormone receptor complex which regulates gene expression.
Reason: Insulin is a peptide hormone which can easily pass cell membrane to interact with hormone-receptor complex.
(c) Insulin is a protein hormone which is water soluble. Water soluble hormones require extracellular receptors that generate second messengers for carrying out their activity. Insulin binds to its specific receptor molecule located on the plasma membrane to form the hormone receptor complex, which in turn generates second messengers that regulate cellular mechanism. Water soluble hormones (e.g., amino acid derivatives, peptides and protein hormones) do not enter the target cell.
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