Thinking Process

Endocrine glands lack ducts, hence are called ductless glands. Their secretion are called hormones.

Answer

(d)Pineal gland secretes a hormone called melatonin. It is involved in regulating biological rhythm and sleep-wake cycle.

Thyroid gland secretes a hormone called tetraiodothyronine. It primarily regulates metabolism of body.

Ovary secretes estrogen which is involved in growth and stimulation of female secondary sex organs and also in the development of growing ovarian follicles.

Adrenal medulla secretes epinephrine and norepinephrine in response to stress or in any kind of emergency situations.

• Option (a) is incorrect because:

  • Pineal gland does not secrete tetraiodothyronine; it secretes melatonin.
  • Thyroid gland does not secrete melatonin; it secretes tetraiodothyronine.
  • Ovary does not secrete epinephrine; it secretes estrogen.
  • Adrenal medulla does not secrete estrogen; it secretes epinephrine.

• Option (b) is incorrect because:

  • Pineal gland does not secrete tetraiodothyronine; it secretes melatonin.
  • Thyroid gland does not secrete melatonin; it secretes tetraiodothyronine.
  • Ovary does not secrete epinephrine; it secretes estrogen.
  • Adrenal medulla does not secrete estrogen; it secretes epinephrine.

• Option (c) is incorrect because:

  • Pineal gland does not secrete estrogen; it secretes melatonin.
  • Thyroid gland does not secrete melatonin; it secretes tetraiodothyronine.
  • Ovary does not secrete epinephrine; it secretes estrogen.
  • Adrenal medulla does not secrete tetraiodothyronine; it secretes epinephrine.

Thinking Process

The pituitary gland is divided anatomically into two parts, i.e., adenohypophysis and a neurohypophysis which are involved in secretion of different hormones accordingly.

Answer

(c) Oxytocin is the hormone of anterior pituitary origin. It acts on the smooth muscles of uterus and stimulates their contraction also plays role in milk secretion.

Follicle stimulating hormone stimulates growth of ovarian follicles whereas, in the female and spermatogenesis in the male.

Growth Hormone Stimulates body growth by promoting the synthesis and deposition of proteins in tissues and also in the growth of bones and muscles.

Adrenocorticotrophic Hormone stimulates adrenal cortex of adrenal gland to produce glucocorticoid and mineralocorticoid.

• Follicle stimulating hormone (FSH) is secreted by the anterior pituitary and stimulates the growth of ovarian follicles in females and spermatogenesis in males.
• Growth hormone (GH) is secreted by the anterior pituitary and stimulates body growth by promoting the synthesis and deposition of proteins in tissues, as well as the growth of bones and muscles.
• Adrenocorticotrophic hormone (ACTH) is secreted by the anterior pituitary and stimulates the adrenal cortex of the adrenal gland to produce glucocorticoids and mineralocorticoids.

Thinking Process

Adrenaline hormone is responsible for “flight or fight” response in our body.

Answer

(c) Mary, during her first five minutes before interview experiences sweating, increased heart rate and respiration because she is having stress which leads to release of emergency hormones or hormones of flight and fight, i.e., adrenaline and noradrenaline. These hormones stimulate the breakdown of glycogen resulting in increase concentration of glucose in blood.

Estrogen and progesterone Estrogen regulates growth and development of female sex organs, female secondary structure, mammary gland development and progertrone supports pregnancy.

Oxytocin and vasopressin Oxytocin is involved in contraction of smooth muscles of uterus at the time of child birth in females and acts mainly on mammary gland for milk ejection. Vasopressin stimulates the absorption of water and electrolytes by distal tubules in kidney and also reduces loss of water.

Insulin and glucagon are the peptide hormones. Insulin decrease blood glucose level and glucagon is involved in increasing normal glucose levels in the blood.

• Estrogen and progesterone: Estrogen regulates growth and development of female sex organs, female secondary structure, mammary gland development, and progesterone supports pregnancy. These hormones are not involved in the body’s immediate stress response.

• Oxytocin and vasopressin: Oxytocin is involved in the contraction of smooth muscles of the uterus at the time of childbirth in females and acts mainly on the mammary gland for milk ejection. Vasopressin stimulates the absorption of water and electrolytes by distal tubules in the kidney and also reduces the loss of water. These hormones do not play a role in the acute stress response.

• Insulin and glucagon: Insulin decreases blood glucose levels, and glucagon is involved in increasing normal glucose levels in the blood. These hormones are primarily involved in the regulation of blood sugar levels and do not directly cause the symptoms of acute stress such as increased heart rate, sweating, and respiration.

Thinking Process

In humans steroid hormones are derived from cholesterol. Cholesterol is stored and produced in liver and is transported (in cells as High Density Lipoprotein or HDL) and Low Density Lipoprotein (LDL).

Answer

(d) Aldosterone acts at the renal tubules stimulating the reabsorption of $\mathrm{Na}^{+}$, water and excretion of $\mathrm{K}^{+}$and phosphate ion. Thus, it helps in maintenance of electrolytes, body fluid volume, osmotic pressure and blood pressure.

Insulin is a peptide hormone, that plays an important role in maintaining the normal blood glucose levels.

Testosterone is the male sex hormone, stimulating male features like muscular growth, growth of facial and axial hair, aggressiveness, low pitch of voice, etc, and spermatogenesis.

Melatonin hormone has a very important role in regulating 24 hours (diurnal) rhythm of our body.

• Insulin is a peptide hormone, that plays an important role in maintaining the normal blood glucose levels.

• Testosterone is the male sex hormone, stimulating male features like muscular growth, growth of facial and axial hair, aggressiveness, low pitch of voice, etc, and spermatogenesis.

• Melatonin hormone has a very important role in regulating 24 hours (diurnal) rhythm of our body.

Answer

(c) Thymosins play a major role in the differentiation of T-lymphocytes, which provide cell mediated immunity. It also promotes antibody production to provide humoral immunity. It hastens attainment of sexual maturity.

• (a) Thymosin is not responsible for raising the blood sugar level; this function is primarily regulated by hormones such as insulin and glucagon.
• (b) Thymosin does not raise the blood calcium level; this function is mainly controlled by parathyroid hormone (PTH) and calcitonin.
• (d) Thymosin does not decrease blood RBCs; the regulation of red blood cell production is primarily managed by erythropoietin.

Answer

(a) Cyclic AMP is one of the second messengers involved in the action of a protein hormone. The other three options are incorrect as

Insulin regulates glucose homeostasis.

$\mathrm{T}_{3}$ regulates the metabolic rate of the body and thus, helps in maintaining Basal Metabolic Rate (BMR).

Gastrin is a peptide hormone, that stimulates the secretion of hydrochloric acid and pepsinogen.

• Insulin regulates glucose homeostasis.
• $\mathrm{T}_{3}$ regulates the metabolic rate of the body and thus, helps in maintaining Basal Metabolic Rate (BMR).
• Gastrin is a peptide hormone, that stimulates the secretion of hydrochloric acid and pepsinogen.

Answer

(a) The Leydig cells or interstitial cells, which are present in the interstitial spaces of testis produce a group of hormones called androgens mainly testosterone.

Estrogen is secreted by growing follicles in ovaries and stimulates growth and development of female secondary sex orgAns.

Aldosterone is secreted by adrenal gland helps in maintaining electrolytes in the body fluid, volume, osmotic pressure and blood pressure.

Gonadotropins are secreted by anterior pitvitary Fend and stimulate the gonadal activity. These include LH and FSH.

• Estrogens are secreted by growing follicles in ovaries and stimulate the growth and development of female secondary sex organs.
• Aldosterone is secreted by the adrenal gland and helps in maintaining electrolytes in the body fluid, volume, osmotic pressure, and blood pressure.
• Gonadotropins are secreted by the anterior pituitary gland and stimulate gonadal activity. These include LH (Luteinizing Hormone) and FSH (Follicle-Stimulating Hormone).

Answer

(b) Corpus luteum secretes a hormone called as progesterone which supports pregnancy and stimulates development the mammary gland for the milk production in female.

Prolactin also known as luteotropic hormone, its a protein hormone that is involved in production of milk in females. The source for prolactin secretion is anterior pituitary gland.

Testosterone stimulates muscular growth, growth of facial and axillary hair, aggressiveness, low pitch of voice, etc. The source for the secretion of testosterone is Leydig cells or interstitial cells.

Aldosterone is secreted by adrenal cortex and plays a role in reabsorption of sodium ions, etc.

• Prolactin: Prolactin is a protein hormone involved in the production of milk in females. It is secreted by the anterior pituitary gland, not the corpus luteum.

• Aldosterone: Aldosterone is secreted by the adrenal cortex and plays a role in the reabsorption of sodium ions. It is not secreted by the corpus luteum.

• Testosterone: Testosterone stimulates muscular growth, growth of facial and axillary hair, aggressiveness, and a low pitch of voice. It is secreted by Leydig cells or interstitial cells, not the corpus luteum.

Answer

(c) Cortisol is secreted from the adrenal gland. The zona fasciculata region of adrenal cortex secretes cortisol, corticosterone and cortisone. These hormones are involved in maintaining glucose homeostasis.

Pancreas is a composite gland which secretes insulin glucagon and somatostatin

Thyroid gland secretes they roxin or tetraiodothyronine $\left(T_{4}\right)$ and triodothyronine $\left(T_{3}\right)$. which regulate the metabolic rate of the body and maintain basal metabolic rate. It also secretes calcitrnia

Thymus secretes thymosin, involved in providing cell mediated immunity to the body.

• Pancreas is a composite gland which secretes insulin, glucagon, and somatostatin.
• Thyroid gland secretes thyroxine or tetraiodothyronine (T4) and triiodothyronine (T3), which regulate the metabolic rate of the body and maintain basal metabolic rate. It also secretes calcitonin.
• Thymus secretes thymosin, involved in providing cell-mediated immunity to the body.

Answer

(c) Melatonin hormone plays a very important role in maintaining the normal rhythms of sleep-wake cycle.

Gastrin is secreted by the endocrine cells present in the gastrointestinal tract and stimulates the secretion of hydrochloric acid and pepsinogen.

Epinephrine is secreted from the adrenal gland and acts as a stress relieving hormone at the time of stress condition in the body.

Insulin secreted from pancreas is involved in maintaining glucose homeostasis.

• Gastrin is secreted by the endocrine cells present in the gastrointestinal tract and stimulates the secretion of hydrochloric acid and pepsinogen.
• Epinephrine is secreted from the adrenal gland and acts as a stress relieving hormone at the time of stress condition in the body.
• Insulin secreted from pancreas is involved in maintaining glucose homeostasis.

Thinking Process

Hormones produce their effects on target tissue by binding to specific proteins called hormone receptor.

Answer

(c) Hormone recepter are located in the target tissue only and are present on the plasma membrane/cell membrane of the target cell.

• (a) Extra cellular matrix: The extracellular matrix is a network of non-living tissue that provides support to cells. It does not contain receptors for protein hormones, which need to bind to specific receptors on the surface of target cells to initiate a response.

• (b) Blood: Blood is the medium through which hormones are transported throughout the body. However, it does not contain receptors for protein hormones. The receptors need to be on the target cells to trigger a specific response.

• (d) Nucleus: The nucleus contains the cell’s genetic material and is involved in processes like transcription and replication. Protein hormones typically bind to receptors on the plasma membrane, not directly to receptors in the nucleus. Receptors in the nucleus are more commonly associated with steroid hormones, which can pass through the cell membrane.

Answer

(b) Epinephrine increases heart beat and also called as stress hormone.

Testosterone stimulates muscle growth, as a secondary sexcharacter in males.

Glucagon leads to breakdown of the glycogen content in liver. It is secreted from pancreas.

Atrial Natriuritic Factor decrease blood pressure by vasodilation

• Option (a):

  • Epinephrine does not decrease blood pressure; it increases heart beat.
  • Atrial natriuretic factor does not increase heart beat; it decreases blood pressure.

• Option (c):

  • Epinephrine does not stimulate muscle growth; it increases heart beat.
  • Testosterone does not decrease blood pressure; it stimulates muscle growth.
  • Atrial natriuretic factor does not increase heart beat; it decreases blood pressure.

• Option (d):

  • Epinephrine does not stimulate muscle growth; it increases heart beat.
  • Testosterone does not increase heart beat; it stimulates muscle growth.
  • Glucagon does not decrease blood pressure; it leads to the breakdown of liver glycogen.
  • Atrial natriuretic factor does not increase heart beat; it decreases blood pressure.

Answer

(d) Thymosin hormone has no role in regulation of blood calcium homeostasis. It plays a major role in the differentiation of T-lymphocytes, which provides cell mediated immunity, While, vitamin-D, thyrocalcitonin and parathyroid hormone plays a vital role in maintaining calcium homeostasis by regulating blood calcium levels.

• Vitamin-D: Vitamin-D is crucial for calcium absorption in the intestines and helps maintain adequate serum calcium and phosphate concentrations, which are necessary for normal mineralization of bone.
• Parathyroid hormone: Parathyroid hormone regulates calcium levels in the blood, largely by increasing the levels when they are too low. It acts on the bones, kidneys, and intestines to increase blood calcium levels.
• Thyrocalcitonin: Thyrocalcitonin, also known as calcitonin, is produced by the thyroid gland and helps to lower blood calcium levels by inhibiting bone resorption and increasing calcium excretion by the kidneys.

Answer

(c) Liver, the largest gland of body surrounded by the abdominal cavity, is the only organs from the above mentioned options that does not consist of a central ‘medullary’ region, surrounded by a cortical region.

Rest three options, i.e., ovary, adrenal and kidney bear a prominent ‘medullary and cortical region’.

• (a) Ovary: The ovary has a distinct medullary region in the center, which contains blood vessels, nerves, and connective tissue, surrounded by a cortical region that contains follicles in various stages of development.

• (b) Adrenal: The adrenal gland has a central medullary region that produces adrenaline and noradrenaline, surrounded by a cortical region that produces steroid hormones such as cortisol, aldosterone, and androgens.

• (d) Kidney: The kidney has a central medullary region composed of renal pyramids, which are surrounded by a cortical region that contains the renal corpuscles and convoluted tubules.

Answer

(d) Exophthalmia, is a condition, that is not linked to deficiency of thyroid hormone. but to over secretion of thyroid hormone, but to oversecretion of thyroid hormone. In this condition there is a bulging of the eye anteriorly out of the orbit.

This is due to an increase in the amount of white blood cells (lymphocytes) in the eye and swelling due to excess accumulation of thyroid hormone, result the eyeballs being forced forward out of the eye sockets (orbits) wheneas, cretinism, goitre and myxoedema are the diseases linked to thyroid deficiency.

• Cretinism: This condition is linked to a deficiency of thyroid hormone, particularly during infancy and childhood. It results in stunted physical and mental growth.

• Goitre: This condition is associated with an enlargement of the thyroid gland, which can occur due to iodine deficiency or thyroid hormone deficiency.

• Myxoedema: This condition is related to severe hypothyroidism in adults, characterized by symptoms such as thickened skin, weight gain, and lethargy due to a deficiency of thyroid hormone.

Answer

In males a pair of testis is present in the scrotal sac. Testes perform dual functions as a primary sex organ as well as an endocrine gland. This gland is absent in females

In females a pair of ovaries is present which are located in the abdomen. Ovary is the primary female sex organ which produces ovum during menstrual cycle and act as an endocrine gland in producing hormone like estrogen and progesterone. This gland is absent in males.

Answer

Zona glomerulosa (outer layer) envelops zona reticularis (inner layer) from the outside.

Answer

Erythropoiesis is the process of formation of RBC. Peptide hormone erythropoietin secreted from the juxtaglomerular cells of kidney stimulates erythropoiesis.

Answer

Pars intermedia of pituitary gland secretes only one hormone called Melanocyte Stimulating Hormone (MSH). This hormone causes dispersal of pigment granules in the pigment cells, thereby darkening the colour in certain animals like fishes and amphibiAns.

Answer

Calcitonin/thyrocalcitonin is a 32 amino acid, linear polypeptide hormone that is produced in humans primarily by the parafollicular cells of the thyroid gland. It checks excess $\mathrm{Ca}^{2+}$ and phosphate in plasma by decreasing mobilisation from bones.

Deficiency of calcitonin results in osteoporesis or loss of bone density (due to dissolution of parathormone).

Answer

Thymosins play a major role in the development and differentiation of T-lymphocytes, which provide cell-mediated immunity. Thymosins also hastens attainment of sexual maturity.

Answer

The hormones that are derivatives of amino acids, polypeptides or proteins are called peptide hormones. These being insoluble in lipids can not enter the target cell.

These act at the surface of target cell as primary messengers and bind to the cell-surface receptor forming the hormone-receptor complex.

It involves following steps

(i) Hormone called first messenger attaches to the cell surface receptor protein on the outer surface of plasma membrane of the target cell, forming a hormone-receptor complex.

(ii) This complex activates the enzyme adenyl cyclase.

(iii) Adenyl cyclase catalyses the conversion of ATP to cyclic AMP on the inner surface of plasma membrane.

(iv) CAMP serves as the second messenger or intracelluar hormonal mediator delivering information inside the target cells. This activates appropriate cellular enzyme system by cascade effect. Which induces the cell machinery to perform its specialised function.

(v) CAMP has a very short existence. It is rapidly degraded by the cAMP phosphodiesterase. Water soluble hormones, such as amines, peptides, proteins and glycoproteins exert their control through the cyclic AMP. These are quick acting hormones and produce immediate effect.

Answer

(a) Gastrointestinal tract, kidney and heart also produce hormones other than endocrine glands hence, the statement is True. Gl tract secretes hormones such as gastrin, secretin, cholecysto kienin etc., Kidney secretes renin and erythropectin. Heart secretes anti-natriuretic factor

(b) Pars distalis produces six trophic hormones, i.e., Growth Hormone (GH) Prolactin (PRL), Thyroid Stimulating Hormone (TSH), Adrinocortico Trophic Hormone (ACTH), Luteinising Hormone (LH) and Follicle Stimulating Hormone (FSH) hence, the statement is True.

(c) T-lymphocytes are involved in providing cell-mediated immunity not B-lymphocytes hence, the statement is False.

(d) The Insulin Dependent Diabetes Mellitus (IDDM) is caused by the failure of beta cells to produce adequate amount of insulin hence, results in a disease called diabetes mellitus. So, the statement is True.

Thinking Process

Pancreas is a composite gland which acts both as exocrine and endocrine gland. The endocrine pancreas consist of Islets of Langerhans. The two main types of cells in the ‘Islet of Langerhans are called $\boldsymbol{\alpha}$-cells and $\beta$-cells.’

Answer

It is also known as hyperglycaemia hormone, and its action is opposite to that of insulin Excess of glucose in blood suppress the secretion of glucose, whereas fall in glucose level starts glucose production (since, doctor fend the slight line level of blood glucose)

Answer

(a) Insulin is a peptide hormone

(b) TSH is secreted from the pars distalis region of pituitary.

(c) Adrenaline is an emergency hormone.

(d) The adrenal gland is located on the anterior part of the kidney.

Answer

The correct matching is as follows

Thinking Process

LH and FSH stimulate gonadal activity and hence are called gonadotropins.

Answer

In males, luteinising hormone (LH) stimulates the synthesis and secretion of hormones called androgens from testis. Androgens along with FSH (Follicle Stimulating Hormone) regulate spermatogenesis.

In females, LH induces ovulation of fully mature follicles (Graafian follicles) and maintains the corpus luteum, formed from the remnants of the Graafian follicles after ovulation. Which secretes progesterone.

Answer

The hormones that are derivatives of amino acids, polypeptides or proteins are called peptide hormones. These being insoluble in lipids can not enter the target cell.

These act at the surface of target cell as primary messengers and bind to the cell-surface receptor forming the hormone-receptor complex.

It involves following steps

(i) Hormone called first messenger attaches to the cell surface receptor protein on the outer surface of plasma membrane of the target cell, forming a hormone-receptor complex.

(ii) This complex activates the enzyme adenyl cyclase.

(iii) Adenyl cyclase catalyses the conversion of ATP to cyclic AMP on the inner surface of plasma membrane.

(iv) CAMP serves as the second messenger or intracelluar hormonal mediator delivering information inside the target cells. This activates appropriate cellular enzyme system by cascade effect. Which induces the cell machinery to perform its specialised function.

(v) CAMP has a very short existence. It is rapidly degraded by the cAMP phosphodiesterase. Water soluble hormones, such as amines, peptides, proteins and glycoproteins exert their control through the cyclic AMP. These are quick acting hormones and produce immediate effect.

Answer

(a) People with swollen necks are suffering from goitre due to deficiency of iodine in the their bodies.

(b) lodine is essential for the synthesis of thyroid hormones- $T_{3}$ and $T_{4}$ which are iodinated forms of tyroxine. Deficiency of iodine in our diet results in hypothyroidism and enlargement of the thyroid gland occurs place.

(c) Hypothyroidism during pregnancy causes defective development and abnormalities in growing baby like stunted growth (cretinism) mental retardation, low intelligence quotient (IQ) abnormal skin, deafmutism, etc.

Thinking Process

The melatonin hormone secreted by the pineal gland is also called as ‘sleep hormone’ as it promotes sleep-wake cycle.

Answer

Jet lag is caused by the disruption of the body clock as it is out of synchronisation because of the unfamiliar time zone of the destination. The body experiences different patterns of light and dark conditions than it is normally used to, which disrupts the natural sleep-wake cycle.

Melatonin is a hormone that plays a key role in body rhythms and causes jet lag. After the sun sets, eyes perceive darkness and alert the hypothalamus to begin releasing melatonin, which promotes sleep. Conversely, when the eyes perceive sunlight, they tell the hypothalamus to withhold melatonin production.

However, the hypothalamus can not readjust its schedule instantly and it may take several days, to overcome this problem.

Answer

Glucocorticoids, particularly cortisol, produce anti-inflammatory reactions and suppress the immune response. The source for glucocorticoids is the middle zone, which is the widest of three zones, in adrenal cortex called zona fasciculata.

The functions of glucocorticoids as the name suggests they is that they affect carbohydrate metabolism and metabolism of proteins and fats. They stimulate gluconeogenesis, lipolysis and proteolysis.

They also inhibit cellular uptake and utilisation of amino acids. Cortisol is also called stress hormone as it copes with stress.

Thinking Process

Thymus plays a major role in the development of the immune system.

Answer

The thymus gland is a lobular structure located on the dorsal side of the heart and the aorta. It is derived from the endoderm of the embryo. Thymus secretes a hormone named thymosin which stimulates the development of White Blood Cells (WBCs), involved in producing immunity.

Thymus is degenerated in old individuals, resulting in decreased production of thymosin. As result the immune system becomes weak, in old people.

Answer

Hypothyroidism during pregnancy cause defective development and maturation of the growing baby leading to a stunted growth (cretinism), mental retardation, low intelligence Quotient (IQ), abnormal skin, deafmutism, etc.

Answer

Differences between hypothyroidism and hyperthyroidism are as follows

Answer

Suckling by the calf creates a neuroendocrine reflex which results in increase of oxytocin from the neurohypophysis. Oxytocin is synthesised in the hypothalamus in specific nuclei, the paraventricular nucleus and the supra optic nucleus (a cluster of nerve cells in the brain is often called a nucleus).

Neurons in this region (hypothalamic nuclei) synthesise the oxytocin precursor and package it into vesicles. The oxytocin concentration in the blood normally, gets increased within 1-2 min, after the udder stimulation.

It brings about contraction of smooth muscles of the udder resulting in the milk flow. A direct intra-udder function of oxytocin like hormone would do the same function.

It can be summarised as follows

Udder (suckling stimulus) $\rightarrow$ Brain (hypothalamus) $\rightarrow$ Neurohypophysis $\rightarrow$ Blood (oxytocin) $\rightarrow$ Udder (smooth muscles) $\rightarrow$ Milk flow.

Thinking Process

Pancreas is a composite gland which acts both as exocrine and endocrine gland. It plays a role in maintaining blood glucose levels.

Answer

(a) The pancreas is associated with this condition and the related hormone is insulin.

The pancreas consists of ‘islets of Langerhans. The two main type of cells in islets of Langerhans are $\alpha$-cells and $\beta$-cells. $\alpha$-cells secrete glucagon while $\beta$-cell secrete insulin.

Insulin is a peptide hormone, which plays a major role in the regulation of glucose homeostasis. It decreases the level of glucose in blood by increasing the rate at which glucose is transported out of blood and into the cell.

When insulin is dysfunctional or not produced adequately glucose uptake is hampered’ and hence glucose appear in urine along with ketone bodies.

(b) Insulin hormone mainly acts on hepatocytes (liver cells) and adipocytes (cells of adipose tissue) and enhances cellular glucose up take and utilisation.

(c) Prolonged hyperglycemic condition leads to a complex disorder called diabetes mellitus which is associated with loss of glucose through urine and formation of harmful compounds known as ketone bodies due to protein metabolism.

Diabetic patients are successfully treated with insulin therapy. It lowers the blood glucose levels and give relief to the patients.

Answer

The endocrine glands and hormones that are responsible for maintaining calcium homeostasis, are thyroid and parathyroid glands and their associated hormones are calcitonin and Parathyroid Hormone (PTH).

(i) Parathyroid glands are the glands developed from the endoderm of the embryo. The cells of parathyroid glands are of two types, i.e., chief cells and oxyphil cells. The chief cells of the parathyroid glands secrete parathyroid hormone (PTH).

This hormone (PTH) is involved in regulating calcium and phosphate balance between the blood and other tissue. It mobilises the release of calcium into the blood from bones. PTH increases calcium reabsorption by the body organs like intestine and kidneys.

(ii) Thyroid gland is the largest endocrine gland located anterior to the thyroid cartilage of the larynx in the neck. This gland plays a vital role in maintaining calcium homeostasis. It releases thyrocalcitonin hormone produced by the parafollicular cells, also called ’ $C$ ’ cells.

This hormone is secreted when the calcium level in blood gets high. It is a 32 amino acid peptide hormone that lowers the calcium level by suppressing release of calcium ions from the bones. Thus, calcitonin has an action opposite to that of the parathyroid hormone on calcium homeostasis.

Answer

Differences between the mechanism of action of a peptide and a steroid hormone are as follows

Peptide Hormone Action	Steroid Hormone Action
Peptide hormones interact with membrane bound receptors.	They interact with intracellular receptors to form hormone receptor complex
They generate second messengers (e.g. cyclic AMP, $\mathrm{IP}_{3}, \mathrm{Ca}^{2+}$, etc.)	They regulate gene expression or chromosomes function by the interaction of hormone receptor complex with the genome.
The second messengers regulate cellular metabolism. e.g. oxytocin insulin, glucagon, vasopressin. etc,	Cumulative biochemical actions results in physiological and development effects. e.g., cortisol, testosterone, estrogen and progesterone.

Answer

Hypothalamus is a very small but extremely important part of the diencephalon that is involved in the mediation of endocrine, autonomic and behavioural function.

It contains several groups of neurosecretory cells called nuclei which produce hormones. Hypothalamus provides anatomical connection between the nervous and endocrine system. It controls the release of major hormones by the hypophysis which are summarised below

(i) Adrenocorticotrophic Releasing Hormone (ARH) It stimulates the anterior lobe of pituitary gland to secrete Adrenocorticotropic Hormone (ACTH). ACTH stimulates the synthesis and secretion of steroid hormones called glucocorticoids by adrenal glands.

(ii) Thyrotropin Releasing Hormone (TRH) It stimulates the anterior lobe of pituitary gland to release Thyroid Stimulating Hormone (TSH).

(iii) Growth Hormone Releasing Hormone It stimulates the anterior lobe of the pituitary gland to release growth hormone or somatostatin.

(iv) Gonadotropin Releasing Hormone It stimulates the anterior lobe of the pituitary gland to release gonadotropic hormones ( $\mathrm{FSH}$ and $\mathrm{LH}$ ).

(v) Prolactin Releasing Hormone (PRH) It stimulates the anterior lobe of the pituitary gland to secrete prolactin.

(vi) MSH Releasing Hormone It stimulates the intermediate lobe of the pituitary gland to secrete Melanocyte Stimulating Hormone (MSH)

These hormones released from hypothalamus are involved in the process like temperature regulation, control of water balance in body, sexual behaviour and reproduction, control of daily cycles in physiological state, behaviour and mediation of emotional responses. Hence, hypothalamus is called as super master endocrine gland of body.