Chapter 22 Chemical Coordination and Integration
Define the following:
(a) Exocrine glands
(b) Endocrine glands Hormones
(a) Glands with duct is known as an exocrine gland. They secrete their secretions through ducts. Eg: Pancreas.
(b) Gland without duct is known as an endocrine gland. They directly secrete their secretions. Eg: Pituitary gland.
(c) Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts. Eg: thyroxine.
Diagrammatically indicate the location of the various endocrine glands in our body.
List the hormones secreted by the following.
(a) Hypothalamus: Gonadotrophic releasing hormone (GnRH), somatostatin.
(b) Pituitary: Growth hormone, prolactin, thyroid-stimulating hormone, luteinizing hormone and follicle stimulating hormone, oxytocin, vasopressin.
(c) Thyroid: triiodothyronine (T3) and tetraiodothyronine (T4).
(d) Parathyroid: Parathyroid hormone.
(e) Adrenal: Adrenaline or epinephrine and noradrenaline or norepinephrine.
(f) Pancreas: Insulin and glucagon.
(g) Testis: A group of androgens mainly testosterone.
(h) Ovary: Estrogens and progesterone.
(i) Thymus: Thymosins.
(j) Atrium: Atrial Natriuretic factor (ANF)
(k) Kidney: Erythropoietin.
(l) G-I tract: Gastrin, secretin, cholecystokinin (CCK).
Fill in the blanks:
Hormones Target gland
(a) Hypothalamic hormones ……………….
(b) Thyrotrophin (TSH) ………………
(c) Corticotrophin (ACTH) ………………
(d) GonadobTjpfains(LH,FSH) ……………….
(e) MeIanotrophin(MSH) ………………..
(a) Anterior pituitary and posterior pituitaiy.
(b) Thyroid glands
(c) Adrenal cortex
(d) Gonads (testis and ovary)
Write short notes on the functions of the following hormones:
(a) Parathyroid hormone (PTH)
(b) Thyroid hormones
(f) Insulin and Glucagon
(a) The secretion of PTH is regulated by the circulating levels of calcium ions. Parathyroid hormone (PTH) increases the Ca2+ levels in the blood. PTH acts on bones and stimulates the process of bone resorption. PTH also stimulates reabsorption of Ca2+ by the renal tubules and increases Ca2+ absorption from the digested food. PTH is a hypercalcemic hormone, i.e., it increases the blood Ca2+ levels. Along with TCT, it plays a significant role in calcium balance in the body.
(b) Thyroid hormones play an important role in the regulation of the basal metabolic rate. These hormones also support the process of red blood cell formation. Thyroid hormones control the metabolism of carbohydrates, proteins, and fats. Maintenance of water and electrolyte balance is also influenced by thyroid hormones. The thyroid gland also secretes the protein hormone thyrocalcitonin (TCH) which regulates blood calcium levels.
(c) 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.
(d) Androgens regulate the development, maturation and functions of the male accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate gland, urethra etc. These hormones stimulate muscular growth, growth of facial and axillary hair, aggressiveness, low pitch of voice etc. Androgens play a major stimulatory role in the process of spermatogenesis and act on the central neural system and influence male sexual behaviour. These hormones produce anabolic effects on protein and carbohydrate metabolism.
(e) Estrogens produce wide-ranging actions such as stimulation of growth and activities of female secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters, mammary gland development. Estrogen also regulate female sexual behaviour.
(f) Glucagon is a peptide hormone, and plays an important role in maintaining normal blood glucose levels. Glucagon acts mainly on the liver cells and stimulates glycogenolysis resulting in increased blood sugar. In addition, this hormone stimulates the process of gluconeogenesis which also contributes to hyperglycemia. Glucagon reduces cellular glucose uptake and utilisation. Thus, glucagon is a hyperglycemic hormone.
Insulin is a peptide hormone, which plays a major role in the regulation of glucose homeostasis. Insulin acts mainly on hepatocytes and adipocytes and enhances cellular glucose uptake and utilisation. As a result, there is a rapid movement of glucose from blood to hepatocytes and adipocytes resulting in decreased blood glucose levels (hypoglycemia). Insulin also stimulates conversion of glucose to glycogen in the target cells. The glucose homeostasis in the blood is thus maintained jointly by the two insulin and glucagons.
Give example(s) of:
(a Hyperglycemic hormone and hypoglycemic hormone
(b Hypercalcemic hormone
(c) Gonadotrophic hormones
(d Progestational hormone
(e) Blood pressure lowering hormone
(f) Androgens and estrogens
(a) Glucagon and insulin
(b) Parathyroid hormone
(c) LH and FSH
(e) Atrial Natriuretic Factor (ANF)
(f) Testosterone and estradiol
Which hormonal deficiency is responsible for the following:
(a) Diabetes mellitus
Diabetes mellitus: Insulin deficiency.
Goiter: Deficiency of thyroid hormones due to deficiency of iodine.
Cretinism: Deficiency of thyroid hormones during childhood.
Briefly mention the mechanism of action of FSH.
Follicle-stimulating hormone (FSH) and LH Stimulate gonadal activity. In males, FSH and androgens regulate spermatogenesis. In females, FSH is responsible for the growth and development of the ovarian follicles, maturation of egg, and secretion of estrogens
Match the following:
Column I Column II
(a) T4 (i) Hypothalamus
(b) PTH (ii) Thyroid
(c) GnRH (iii) Pituitary
(d) IH (iv) Parathyroid
(a) – (ii)
(b) – (iv)
(c) – (i)
(d) – (iii)
VERY SHORT ANSWER QUESTIONS
Give two examples of endocrine glands.
Examples of endocrine glands are
(i) pituitary gland
(ii) pineal gland.
Which gland secretes glucagon?
Pancreas secretes glucagon.
What is the location of the pituitary gland?
The pituitary gland is located in a bony cavity called Sella tursica and is attached to the hypothalamus by a stalk.
Which hormone is secreted by pars intermedia?
Pars intermedia secretes melanocyte-stimulating hormone (MSH).
Which hormone is secreted by the pineal gland?
Pineal gland secretes melatonin hormone.
Name one disorder caused by hyperfunctioning of the pituitary.
Gigantism caused by hyperfunctioning of the pituitary.
How many lobes does the thyroid gland have?
The thyroid gland is composed of two lobes which are located on either side of the trachea.
Which gland produces the hormone called thyrocalcitonin (TCT) which regulates the blood calcium levels?
Thyroid gland secretes a protein hormone called thyrocalcitonin (TCT) which regulates the blood calcium levels.
Name the organ which secretes progesterone.
Ovary secretes progesterone.
Name two hormones of pancreas.
Glucagon and insulin are two hormones of pancreas.
Which gland secretes somatostatin?
Hypothalamus secretes somatostatin.
Which complex is formed during the binding of hormone to a receptor ?
Hormone-receptor complex is formed during the binding of a hormone to a receptor.
Name one hormone secreted by gastro-intestinal tract.
Gastrin is secreted by gastro-intestinal tract.
Which hormone is secreted by testes and write the function of hormone also.
Testosterone is secreted by testes. It controls growth and development of male secondary
What are membrane bound receptors?
Hormone receptors that are present on the cell membrane of the target cells are called membrane bound receptors.
How many types of cells are present in Islets of Langerhans?
There are two types of cells present in Islets of Langerhans which are a-cells and P-cells.
Why is oxytocin called as birth hormone ?
Oxytocin stimulates the contraction of smooth muscles of uterus and facilitates the child birth.
Why is vasopressin known as antidiuretic hormone?
Vasopressin stimulates the reabsorption of water and electrolytes and reduces the loss of water through urine, known as diuresis. Hence it is called as anti-diuretic hormone.
What is cretinism ?
Cretinism is reduction in body growth as well as underdevelopment of brain resulting in various structural and functional defects mainly due to deficiency of thyroxine (hypothyroidism) in infants and children.
Which hormone interacts with membrane bound receptor and does not normally enter the target cell?
Follicle stimulating hormone interacts with membrane bound receptor and does not normally enter the target cell.
Which hormone opposes parathormone?
Thyrocalcitonin opposes parathormone.
Which hormone is known as anti-aging hormone?
Melatonin, secreted by pineal gland is known as anti-ageing hormone.
SHORT ANSWER QUESTIONS
Discuss the location and function of parathyroid hormone.
There are four parathyroid glands present on the back side of thyroid glands, two on each of the lobes of the thyroid gland.
The parathyroid glands secrete parathyroid hormone (PTH), a peptide hormone. Parathyroid hormone (PTH) increases the Ca2+ levels in the blood. PTH acts on bones and stimulates the process of bone resorption (dissolution/ demineralization. PTH also stimulates reabsorption of Ca2+ by the renal tubules and increases Ca2+ absorption from the digested food.
What is progesterone? Name two important functions of progesterone.
Progesterone is a steroid hormone secreted by ovary.
Functions of progesterone are as follows:
• It supports pregnancy.
• It acts on mammary glands and stimulates the formation of alveoli (sac-like structures which store milk) and milk secretion.
Name the principal mineralocorticoid secreted by adrenal cortex. Give its any two functions
Aldosterone is main mineralocorticoid secreted by adrenal cortex.
Functions of aldosterone are :
• It stimulates reabsorption of Na+ and water.
• It stimulates excretion of K+ and phosphate ions.
What are hormone receptors? What are the modes of their action ?
Receptors are specific proteins present on the surface of target cell which bind with hormones and produce physiological changes in cell. Their are two types of hormone receptors which are discussed below:
Name the gland that functions as a biological clock in our body. Where is this gland located ? Name its one secretion.
Pineal gland functions as a biological clock in our body.
- It is located on the dorsal side of the forebrain.
- It secretes melatonin.
Where is thymus gland located in the human body ? Describe its role.
The thymus gland is a lobular structure located on the dorsal side of the heart and the aorta.
– It secretes hormone thymosin, which has a stimulating effect on the immune system.
– Thymosin promotes proliferation and maturation of T-lymphocytes.
How does insulin act on high glucose content in the blood in a normal human body ?
• Insulin is a peptide hormone, which plays a major role in the regulation of glucose homeostasis. Insulin acts mainly on hepatocytes and adipocytes (cells of adipose tissue), and enhances cellular glucose uptake and utilisation. As a result, there is a rapid movement of glucose from blood to hepatocytes and adipocytes resulting in decreased blood glucose levels (hypoglycemia)
• Insulin also stimulates conversion of glucose to glycogen (glycogenesis) in the target cells.
• The glucose homeostatasis in blood is thus maintained jointly by the two enzyme insulin and glucagon.
What is corpus luteum ? Name its one secretion.
Corpus luteum is the structure formed by the ruptured ovarian follicles after ovulation.
– It mainly secretes the hormone progesterone.
Long ANSWER QUESTIONS
Explain briefly the structure and functions of middle ear.
Calcitonin (from thyroid) : Essential for maintaining bone strength as it does not allow calcium mobilisation from bones. It also lowers plasma level of calcium ifthe same is high. Parathormone: Low level of parathormone secretion decreases blood plasma level of calcium, prevents reabsorption from bones and causes tetany. Higher levels of parathormone (PTH) increase plasma level of Ca2+ by withdrawal from bones resulting in (i) Inflammation and tenderness in bones due to dissolution of calcium from bones, formation of cavities which get plugged with fibrous nodes and cysts (osteitis fibrosa cystica) making bones soft deformed and prone to fracture, (ii) Excess plasma calcium gets deposited in various parts of body which often leads of obstruction and death.
Draw a well labelled diagram showing the location of parathyroid gland. Discuss the function/(s) of parathormone and hyperparathyroidism.
Function : Parathormone (Collip’s hormone) regulates the metabolism of calcium and phosphate between blood and other tissue.
(i) Hyperparathyroidism : It leads to demineralisation resulting in softing and bending of bones. An excess of parathormone cause osteoporosis and kidney stones.
What are the causes for following disorders?
Disorders and their causes.
(a) Acromegaly (Acro-extremity, megaly – large) – It is caused by excess secretion of growth hormone after adulthood is reached.
(b) Cretinism : It is caused by deficiency of thyroid hormone in infant.
(c) Gigantism : It is caused by excess of growth hormone from early age.
(d) Myxoedema: It is caused by deficiency of thyroid hormone in adults.