Telangana TSBIE TS Inter 2nd Year Zoology Study Material Lesson 4(a) Endocrine System and Chemical Coordination Textbook Questions and Answers.
TS Inter 2nd Year Zoology Study Material Lesson 4(a) Endocrine System and Chemical Coordination
Very Short Answer Type Questions
Question 1.
What is acromegaly? Name the hormone responsible for this disorder. [March 2015 (A.P.)]
Answer:
Hyper secretion of growth stimulating hormone (somatotropin) in adults results in an abnormality called acromegaly. It is characterized by enlargement of bones of Jaw, hand and feet, thickened nose, lips and eyelids and gorilla like appearance of the person affected.
Question 2.
Which hormone is called anti-diuretic hormone ? Write the name of the gland that secretes it. [May/ June 2014]
Answer:
Vasopressin is called anti – diuretic hormone (ADH). It is secreted by posterior lobe of pituitary gland.
Question 3.
Name the gland that increases in size during childhood and decreases in size during adulthood. What important role does it play in case of infection? [March 2019]
Answer:
Thymus gland increases in size during childhood and decreases in size during adulthood. The secretion is thymosin plays a major role in the differentiation of T – lymphocytes, which provide cell mediated immunity. It also promote production of antibodies.
Question 4.
Distinguish between diabetes insipidus and diabetes mellitus. [March 2020, 2018 (A.P.); March 2014]
Answer:
a) Diabetes insipidus: Deficiency of vasopressin causes diabetes insipidus in which the patient excretes large volumes of urine, resulting in dehydration and thirst.
b) Diabetes mellitus: A condition resulting from lack of insulin as a result of which, the body cannot store or oxidise sugar efficiently (and sugar is lost through urine).
Question 5.
What are Islets of Langerhans?
Answer:
The endocrine portion of pancreas is just 1 to 2% and consists of 1 to 2 millions of Islets of Langerhans which are having α – cells and β – cells, α – cells produce hormone glucagon. β cells produce insulin.
Question 6.
What is ‘insulin shock’? [March 2018, ’15 (A.P.)]
Answer:
Hyper secretion of insulin leads to decreased level of glucose in the blood (hypoglycemia) resulting in insulin shock.
Question 7.
Which hormone is commonly known as fight and flight hormone? [March 2015 (T.S.)]
Answer:
Fight or flight hormone is the common name adrenaline or epinephrine. This hormone enhances alertness, dilation of pupils, piloerection, sweating. Increase heart beat to face emergency situation.
Question 8.
What are androgens? Which cells secrete them?
Answer:
Androgens are secreted by leiding cells or interstitial cells of testes in males. Androgens stimulate the secondary sexual characters in males and also enhance the process of spermatogenesis.
Question 9.
What is erythropoietin? What is its function? [Mar. 2019, ’14; May/June ’14]
Answer:
Kidneys produce a hormone called erythropoietin. It stimulates erythropoiesis (formation of RBC). The role of this hormone is to control the formation of red blood cells by regulating the differentiation and proliferation of erythroid progenitor cells in bone marrow.
Short Answer Questions
Question 1.
List out the names of endocrine glands present in human beings and mention the hormones they secrete.
Answer:
Endocrine glands of Man – Their Secretion
- Hypothalamus – Growth hormone releasing hormone (GHRH)
- Pituitary. – a) Anterior pituitary : Growth hormone, Prolactin, Thyroid stimulating hormone. (TSH)
Andreno corticotropic hormone (ACTH), Follicle stimulating hormone (FSH), Lutenizing hormone (LH).
b) Pars intermedia: Melanocyte stimulating Hormone (MSH)
c) Posterior pituitary: Vasopressin, oxytocin. - Pineal gland – Melatonin
- Thyroid gland – Thyroxine, calcitonin.
- Parathyroid glands – Parathormone
- Thymus gland – Thymosins
- Adrenal gland – Cortex – Gluco corticoids, mineral corticoids.
Medulla – Adrenaline, Noradrenaline. - Pancreas – Islets of langerhans – Insulin, Glucagon.
- Testes – Androgens
- Ovaries – Estrogen, Progesterone.
Question 2.
Describe the role of hypothalamus as a neuroendocrine organ.
Answer:
The hypothalamus is located below the thalamus, constituting the floor of the diencephalon, a part of the fore brain. It connects the neural and endocrine systems as it is closely tied to the pituitary gland. It responds to the sensory impulses received from different receptors by sending out appropriate neural or endocrine signals.
It regulates a wide range of body functions. It contains several groups of neurosecretory cells called ‘nuclei’ which produce hormones called neurohormones. They are transported to the neurohypophysis through the axons of the hypothalamo – hypophysial tract. The two types of hormones produced by the hypothalamus are 1) the releasing hormones (which stimulate secretion of pituitary hormones), and 2) the inhibiting hormones (which inhibit secretions of pituitary hormones.
Question 3.
Give an account of the secretions of pituitary gland.
Answer:
Previously, pituitary gland was called the “master” endocrine gland, because it controls several endocrine glands. Release of hormones by adenohypophysis is stimulated by releasing hormones and suppressed by inhibiting hormones of the hypothalamus.
Growth Hormone or Somatotropin: In response to human growth hormone, cells in the liver, skeletal muscle, cartilage, bone, and other tissues secrete insulin – like growth factors that cause cells to grow and multiply. These factors accelerate protein synthesis and decrease catabolism of proteins.
Thyroid – Stimulating Hormone :
It stimulates the synthesis and secretion of thyroid hormones by the thyroid gland.
Adrenocorticotropic Hormone (AGTH) :
It controls the secretion of glucocorticoids by the adrenal cortex.
Follicle – Stimulating Hormone :
In females FSH initiates the development of ovarian follicles. In males FSH stimulates spermatogenesis.
Luteinizing Hormone :
In females, LH stimulates ovulation, formation of the corpus luteum and the secretion of progesterone by the corpus luteum. In males, this hormone is called interstitial cell stimulating hormone. It stimulates leydig cells in the testis to secrete testosterone. FSH and LH are termed gonadotropins because their target organs are gonads.
Prolactin :
Prolactin, together with other hormones, initiates and maintains milk secretion by the mammary glands. The function of prolactin is not known in males.
Melanocyte – Stimulating Hormone (MSH) :
MSH increases skin pigmentation in lower vertebrates by stimulating the dispersion of melanin granules in melanocytes.
Neurohypophysis :
It does not synthesize hormones. It stores and releases oxytocin and vasopressin.
Oxytocin :
During delivery, oxytein enhances contraction of smooth muscle cells in the wall of uterus. After delivery, it stimulates milk ejection.
Vasopressin or Antidiuritic Hormone :
ADH causes the kidneys to absorb more water into the blood. In the absence of ADH, urine output increases from the normal 1 to 2 litres about 20 litres a day. ADH causes constriction of arterioles, which increases blood pressure. The amount of ADH secreted is regulated.
Question 4.
Compare a ‘pituitary dwarf’ and a ‘thyroid dwarf’ in respect of similarities and dissimilarities they possess.
Answer:
1. Pituitary dwarf :
Hypo secretion of growth harmone (STH) during childhood retards growth, resulting in a pituitary dwarf / midget. The pituitary dwarf is sexually and intellectually a normal individual.
2. Thyroid dwarf :
During pregnancy, due to hypothyroidism, defective development of the growing baby leads to a disorder called cretinism. Physical and mental growth get severely stunted and is called thyroid dwarf. This is due to untreated congenital hypothyroidism. Stunted growth, mental retardation, low intelligent quotient, abnormal skin, deafness and mutism are some of the characters of this disease.
Question 5.
Explain how hypothyroidism and hyperthyroidism can affect the body. [March 2017, May ’17 (A.P.)]
Answer:
Over activity of the thyroid, cancer of the gland or development of nodules of thyroid lead to hyperthyroidism. In adults, abnormal growth causes a disease called exophthalamic goiter, with characteristically protruded eyeballs. Hyperthyroidism also affects the physiology of the body (increased metabolic rate). Inadequate supply of iodine in the diet results in hypothyroidism and enlargement of the thyroid gland. This condition is called simple goiter.
During pregnancy, due to hypothyroidism, defective development of the growing baby leads to a disorder called cretinism. Physical and mental growth gets severely stunted (Thyroid dwarf) due to untreated ‘congenital hypothyroidism’ (deficiency of thyroid hormones by birth). Stunted growth, mental retardation, low intelligence quotient, abnormal skin, deafness and mutism are some of the characteristic features of the this disease. In adult women, hypothyroidism may cause irregular menstrual cycles. In adults the hypothyroidism results in a condition called myxedema, Lethargy, mental impairment, intolerance to cold, puffiness of face and dry skin and some of the symptoms of myxedema.
Question 6.
Write a note on Addison’s disease and Cushing’s syndrome.
Answer:
Addison’s disease is caused due to hyposecretion of glucocorticoids by the adrenal cortex. This disease is characterised by loss of weight, muscle weakness, fatigue and reduced blood pressure. Sometimes darkening of the skin in both exposed and nonexposed parts of the body occurs in this disorder. This disorder does not allow an individual to respond to stress.
Cushing’s syndrome :
It results due to over production of glucocorticoids. This condition is characterized by breakdown of muscle proteins and redistribution of body fat resulting in spindly arms and legs accompanied by a round moon face, buffalo hump on the back and pendulous abdomen. Wound healing is poor. The elevated level of cortisols causes hyperglycemia, over deposition of glycogen in liver and rapid gain of weight.
Question 7.
Why does sugar appear in the urine of a diabetic?
Answer:
Insulin secreted by a – cells of Islets of langerhans promotes conversion of glucose into glycogen in the target cells. Both glucagon and insulin maintain the homeostasis of glucose in the blood. Persistent hyperglycemia leads to a complex disorder called diabetes mellitus prolonged hyperglycemia leads to diabetes mellitus associated with loss of glucose through urine. It is called glycosuria and formation of harmful compounds called ‘Ketone bodies’. Insulin therapy is used to treat diabetic patients.
Question 8.
Describe the male and female sex hormones and their actions.
Answer:
Male sex hormones or Androgens are required for the development, maturation and functioning of the male accessory sex organs such as epididymis, vas deferens, seminal vesicles, prostate gland, urethra etc. These hormones control muscular growth, growth of facial and axillary hair, aggressiveness, low pitch voice (masculine voice) etc. Androgens stimulate the process of spermatogenesis. Androgens affect tbe central neural system, controlling the male sexual behavior (libido / sex drive / sexual urge) and also have an effect on protein and carbohydrate anabolism.
Ovaries act as endocrine glands too producing the female hormones chiefly: estrogen and progesterone. Ovarian follicles and stromal tissues are present in the ovary. The hormone estrogen is produced by the growing follicles of the ovary. After ovulation, the ruptured follicle becomes a ‘yellow body’ called corpus Juteum (which acts as a temporary endocrine gland) and secretes progesterone. After a few days, in the absence of pregnancy, the corpus luteum stops functioning and becomes the’corpus albicans’.
Estrogen is responsible for the development and the activity of the female secondary sex organs, development of the growing ovarian follicles, high pitch of voice etc., and the development of the mammary glands. Estrogen also controls the female sexual behaviour.
Progesterone has an important role in preparing the uterus for the implantation of the blastocyst in the wall of the uterus. It inhibits contraction of the uterus. Thus it supports pregnancy. In case of deficiency of this hormone, pregnancy fails to maintain. It stimulates the formation of alveoli (sac like structures which store milk) in the mammary glands and secretion of milk.
Question 9.
Write a note on the mechanism of action of hormones.
Answer:
Hormones stimulate or inhibit the target cells’ activities. Hence they are called regulators. Hormones play a vital role in regulating the functions of the body.
Hormones produce their effects on target tissue by binding to specific proteins called hormone receptors located in the target tissues only. Hormone receptors present on the cells membranes of the target cells are called membrane bound – receptors and the hormone receptors present inside the target cells are called intracellular receptors. Intracellular receptors are mostly nuclear receptors (present in the nucleus). Hormone receptors are specific, as each receptor is specific to a certain hormone only. A hormone and its receptor protein together form a hormone – receptor complex.
This hormone – receptor complex generates biochemical changes in the target cells. Hormones interacting with membrane bond receptors do not enter the target cell, but they generate ‘second messengers’ (e.g. Cyclic AMP produced from ATP by the action of the enzyme adenylate cyclase / Adenyl cyclase, IP3, Ca++ etc). These second messengers regulate cellular metabolism in the target cells in a cascading action amplifying the final effect. In this way even a very small quantity of the hormone can cause a series of enzymatic actions, each step having a multiplication effect, bringing a powerful cascading effect.
We can take an example to understand the action of hydrophilic hormone, such as Epinephrine, which cannot enter a cell. In the liver cells 1) Epinephrine attaches to cell membrane receptor 2) G protein of cell membrane binds to GTP and activates adenylate cyclase, a membrane enzyme 3) activated Adenylate cyclase forms cAMP from ATP 4) cAMP activates Protein Kinase – A, which activates the enzyme ‘phosphorylase’ 5) Phosphorylase ‘ phosphorylates” Glycogen to Glucose – 6 – phosphate and it, in turn produces glucose. Thus the liver cell is able to produce several molecules of glucose needed to the cell under the action of epinephrine (one of the fight and flight responses of the body).
(a) Membrane bound – receptor mechanism (b) Intracellular receptor mechanism
Hormones which interact with intracellular receptors (e.g. steroid hormones, iodothyronines, etc.) are lipid soluble and they diffuse through the plasma membrane into the cytoplasm. They bind to certain internal receptors, enter the nucleus and regulate gene expression. The hormonal mechanism of steroid hormones is called mobile -receptor mechanism (as the receptors are not fixed in the cell membrane). Cumulative biochemical actions result in physiological and developmental effects.
Mechanism of action of lipid soluble hormone : Aldosterone is a lipid soluble hormone which can easily diffuse through the cell membrane. It binds to a specific receptor in the cytoplasm forming an aldosterone – receptor complex molecule. This complex molecule enters the nucleus and binds to the DNA and stimulates the production of a specific mRNA molecule. The mRNA passes into the cytoplasm and attaches to ribosomes making them produce the specific protein. These proteins are produced by the cell as a response to aldosterone.
Thus hormones play a major role in maintaining homeostasis by their integrated actions and feedback mechanisms.