Kerala Syllabus 10th Standard Biology Guide Chapter 3 Chemical Messages for Homeostasis
What is the speciality of endocrine system?
The endocrine system is an organ system that works along with the nervous system to control and co-ordinate all activities in the body.
Endocrine glands are known as ductless glands. Write reasons.
Hormones are chemical messengers that regulate cellular activities. Endocrine glands do not have particular ducts to carry hormones to various tissues. Hence they are known as ductless glands. Hormones are transported through blood.
Explain target cells.
Hormones reach every cell in the body as they are transported by blood. But each hormone acts only upon those cells which have specific receptors. The cells which are acted upon by hormones are their target cells.
How do hormones affect cells?
Only those cells having specific receptors can receive a specific hormone. Each hormone molecule binds with the receptor to form a hormone-receptor complex. Following this, enzymes are activated within the cell and certain changes occur in cellular activities.
Where is insulin and glucagon produced?
The beta cells in the islets of Langerhans, a special group of cells in pancreas secrete insulin and the alpha cells secrete glucagon.
Explain the action of insulin to prevent the rise in the level of glucose in blood.
When the level of glucose in blood is high, the production of insulin increases. Insulin enhances cellular uptake of glucose molecules and converts glucose into glycogen in the liver and muscles. As a result, the glucose in blood becomes normal.
Explain the action of glucagon when the level of glucose in blood decreases.
When the level of glucose in blood is low, the production of glucagon increases. Glucagon converts the glycogen stored in the liver to glucose and synthesizes glucose from amino acids. As a result, the glucose in blood becomes normal.
What is the normal level of glucose in blood?
The normal level of glucose in blood is 70-110 mg / 100 mg.
How is the level of glucose in blood maintained while fasting?
During fasting, the glucose in blood becomes low. In such situations, the alpha cells of islets of Langerhans in pancreas secrete glucagon. The glucagon converts the glycogen stored in the liver to glucose and synthesizes glucose from amino acids. Such actions help to maintain the blood glucose level tononnal.
What is the reason for increase in the level of glucose in blood.?
Decreased production of insulin due to the destruction of beta cells or the inability of cells to utilize the insulin produced, raises the level of glucose in blood. Excess glucose in the blood is expelled through urine.
What is diabetes mellitus?
Diabetes is clinically referred to as a condition when the level of glucose before breakfast is above 126mg/ 100ml of blood.
Write about the symptoms and reasons for diabetes.
Increased appetite and thirst and frequent urination are the major symptoms of diabetes. Decreased production of insulin is the reason for diabetes.
Write the test to detect the presence of glucose in urine.
Take 2ml of the urine in a test tube. Add 2ml Benedict solution into it. Heat for 2 minutes. Observe the change in colour. Formulate your inference by comparing the glucose indicator on the reagent bottle.
What is metabolism?
The anabolic and catabolic processes taking place in the body are commonly referred as metabolism. Metabolic activities are also under the control of hormones.
Name the hormones secreted by thyroid gland.
The thyroid gland secrets two hormones- thyroxine and calcitonin.
What are the functions of thyroxine?
Thyroxine plays an important role in controlling life activities. Thyroxine increases energy production and raises the rate of metabolism. It also accelerates the growth and development of the brain in the foetal stage and infancy and regulates growth in children.
What are the problems due to thyroxine deficiency?
Hypothyroidism is a condition in which the production of thyroxine decreases. The decrease in production of thyroxine during the foetal stage or infancy, hinders proper physical and mental development. This condition is Cretinism. Prolonged deficiency of thyroxine in adults leads to a condition called Myxoedema. Low metabolic rate, sluggishness, increase in body weight, hypertension and inflammation in body tissues are the major symptoms of this disorder.
What are the problems caused by excessive production of thyroxine?
All the life activities controlled by thyroxine are accelerated due to the excessive production of thyroxine. This condition is known as hyper-thyroidism. The major symptoms are high metabolic rate, rise in body temperature, excessive sweating, increased heart beat, sleeplessness, weight loss, emotional imbalance, etc. Persistent hyperthyroidism may lead to Graves disease, characterised by bulging of the eyeballs.
How is iodine related to thyroid gland?
Iodine is essential for the production of thyroxine. The production of thyroxine is obstructed in the absence of iodine. In an attempt to produce more thyroxine, the thyroid gland enlarges. This condition is called goitre.
What is the normal level of calcium in blood?
The normal level of calcium in blood is 9-11 mg / 100 ml.
What is the role of calcitonin in regulating the level of calcium in blood?
When the level of calcium in blood increases, thyroid gland secretes a hormone named calcitonin. It lowers the level of calcium in blood. This hor-mone helps in maintaining the level of calcium in blood by depositing excess calcium in bones and by preventing the mixing of calcium with blood from the bones.
What is the role of parathormone in regulating the level of calcium in blood?
Parathyroid gland secretes a hormone called parathormone. The function of this hormone is to raise the level of calcium in blood. When the level of calcium in the blood decreases, parathormone helps in the reabsorption of calcium to the blood from the kidneys and also prevents the deposition of calcium in bones.
Complete the illustration showing the maintenance of the level of calcium in blood by the action of hormones.
D. Depositing excess calcium in bones and by preventing the mixing of calcium with blood from the bones.
E. Helps the reabsorption of calcium to the blood from kidneys and also prevents the deposition of calcium in bones.
Write the importance of thymus gland.
Thymus gland is very active during infancy but constricts as we reach puberty. The major function of this gland is to control the activities and maturation of lymphocytes which help to impart immunity. This gland secretes a hormone called thymosin.
Name the hormones secreted by the adrenal cortex.
The outer part of the adrenal gland is known as the cortex which produces hormones namely cortisol, aldosterone and sex hormones.
Write the function of cortisol.
The synthesis of glucose from protein and fat, controls inflammation and allergy, slows down the action of defence cells, are the functions of cortisol.
How does the maintenance of salt-water balance take place in the body?
Aldosterone is produced from the cortex of adrenal gland. Aldosterone maintains the salt-water level by acting in kidneys.
Explain the functions of epinephrine and norepinephrine during emergencies.
Epinephrine and norepinephrine are produced from the medulla, the inner part of Adrenal gland. Epinephrine acts along with the sympathetic nervous system during emergencies. We can resist or withdraw ourselves from such situations. In these situations, norepinephrine acts along with epinephrine. The action of epinephrine and norepinephrine prolongs the body activities for more time, when the sympathetic system gets stimulated.
How does melatonin help in maintaining the rhythm of our daily activities?
Pineal gland secretes the hormone, melatonin which helps in maintaining the rhythm of our daily activities. The production of melatonin is high at night and low during the day. When the level of melatonin increases, we feel sleepy and when it decreases we wake up. Thus, this hormone regulates the rhythm of life. This hormone also controls reproductive activities of organisms with definite reproductive periods.
Describe the structure of pituitary gland.
Pituitary gland is a two lobed gland seen below the hypothalamus.
Prepare a table containing the hormones secreted by the anterior lobe of the pituitary gland and its function.
|Hormones secreted by the anterior lobe of the pituitary gland||Function|
|Thyroid Stimulating Hormone (TSH)||Stimulates the activity of the thyroid gland|
|Adreno Cortico Tropic Hormone (ACTH)||Stimulates the activity of adrenal cortex|
|Gonado Tropic Hormone (GTH)||Stimulates the activity of testes in males and ovary’ in females|
|Growth Hormone (GH) Somato Tropic Hormone (STH)||Promotes the growth of the body|
|Prolactin||Production of milk|
Write the function of somatotropin.
Somatotropin is secreted by the anterior lobe of pituitary gland. It promotes growth of the body during its growth phase.
Explain dwarfism, gigantism and acromegaly.
- If the production of somatotropin decreases during the growth phase, it causes dwarfism.
- If the production of somatotropin increases during the growth phase, it leads to the excessive growth of the body. This condition is called gigantism.
- Acromegaly is the condition caused by the excessive production of somatotropin after the growth phase. It is characterised by the growth of the bones on face, jaws and fingers.
The posterior lobe of pituitary gland is a storage centre. Write your opinion about this statement.
This is a correct statement. The hormones oxytocin and vasopressin which are secreted from the posterior lobe of the pituitary are actually produced in the neuro-secretory cells of the hypothalamus. The posterior lobe of pituitary stores these two hormones and releases them into blood.
What is the function of oxytocin?
Oxytocin facilitates child birth by stimulating the contraction of smooth muscles in the uterine wall. Oxytocin also facilitates lactation.
Explain the function of vasopressin in kidneys.
Vasopressin helps in the reabsorption of water in kidneys. Thus vasopressin regulates the loss of water through urine.
Write the reason for excessive production of urine during the rainy season.
The production of vasopressin is less during winter and rainy seasons. This decreases the reabsorption of water in the kidneys and thus the quantity of urine increases.
What is the role of vasopressin in preventing loss of water from the body?
When the normal water level in blood decreases, the production of vasopressin increases. This increases the reabsorption of water in kidneys and thus the quantity of urine lowers.
What is diabetes insipidus?
When the production of vasopressin decreases, the reabsorption of water in the kidney is decreased and excess amount of urine is eliminated. This condition is known as diabetes insipidus. Frequent urination, increased thirst, etc. are the symptoms
Explain the action of male sex hormones.
The male sex hormone testosterone controls sperm production and secondary sexual characters in males such as change in voice, growth of hair, etc.
Write the action of female sex hormones.
Ovary produces the female sex hormones namely estrogen and progesterone. Estrogen controls secondary sexual characters, ovulation, menstrual cycle, etc. Progesterone controls ovulation, menstrual cycle and implantation of embryo in the uterus.
Explain the influence of gonadotropic hormones in sex organs.
Testes and ovary, the male and female sex organs respectively, secrete different types of hormones. Gonadotropic hormones from the pituitary regulate the development and functions of the sex organs.
Hypothalamus plays an important role in maintaining homeostasis. How?
Vasopressin, oxytocin, releasing hormones and inhibitory hormones are secreted by hypothalamus. Vasopressin regulates the water level. Oxytocin facilitates child birth by stimulating the contraction of smooth muscles in the uterine wall and facilitates lactation. Releasing hormone stimulates the anterior lobe of the pituitary and secretes tropic hormones.
The tropic hormones are TSH which stimulates the activity of the thyroid gland, ACTH which stimulates the activity of adrenal cortex and GTH which stimulates the sex organs. The inhibitory hormone inhibits the production of tropic hormones in the anterior lobe of the pituitary gland, thus controls the activity of endocrine glands.
Write about pheromones and their function.
Chemical substances that are secreted by certain animals to the surroundings to facilitate communication are called pheromones.
Pheromones help in attracting mates, informing the availability of food, determining the path of travel, signalling dangers, etc. The chemical messages of pheromones also help honey bees and termites to live in colonies. The muscone in the musk deer, the civeton in the civet cat, bombykol in the female silk worm moth, etc., are examples for pheromones.
What are plant growth regulators?
There are certain chemical substances in plant cells to control and co-ordinate life activities as in animals. These are the plant hormones. These are also called plant growth regulators.
Prepare a table containing plant hormones and their functions.
|Gibberellin||Stimulates break down of stored food to facilitate germination, sprouting of leaves|
|Auxin||Cell growth, cell elongation, promoting the growth of terminal buds, fruit formation.|
|Cytokinin||Cell growth, cell division, cell differentiation.|
|Abscisic acid||Dormancy of embryo, dropping of ripened leaves and fruits.|
|Ethylene||Ripening of leaves and fruits, excess amount of ethylene causes dropping of leaves and fruits.|
Prepare a short note on artificial plant hormones.
Plant hormones are synthesized artificially by identifying the chemical structure of hormones. Use of such hormones has contributed a lot to the progress of the agricultural sector.
- Auxins –
It is used in the agricultural field to prevent the dropping of premature fruits, for the sprouting of roots and as a weedicide.
- Gibberellins –
It is used for increasing fruit size in grapes and apple and also for preventing ripening of fruits to assist marketing.
- Ethylene –
Ethylene is used for the flowering of pineapple plants at a time and for the ripening of tomato, lemon, orange, etc. Ethyphon, a chemical which is available in liquid form, gets transformed into ethylene, when used in rubber trees and it increases the production of latex.
- Abscisic acid –
It is used for harvesting fruits at the same time.
Let Us Assess
Identify the word-pair relationship to fill in the blank.
Thyroxine : Thyroid gland
Epinephrine : …………………
Analyse the information given in the box and answer the questions.
X -The production of this hormone is more in night and less in day time.
Y -Hormones from the adrenal gland work along with the sympathetic system.
a. Identify and name the hormone ’X’ and its gland.
b. Identify the hormones indicated as ‘Y’.
a. Melatonin, Pineal gland
b. Epinephrine (Adrenaline), Norepinephrine (Noradrenaline)
Analyse the illustration and complete the table appropriately.
|Hypothalamus||Below the thalamus||Oxytocin, Vasopressin, Releasing hormone, Inhibitory hormone|
|Pituitary||Below the hypothalamus||Tropic hormones (TSH, ACTH, GTH), Growth hormone, Prolactin|
|Thyroid||In the throat just below the larynx.||Calcitonin, Thyroxine|
|Parathyroid||Behind the thyroid gland||Parathormone|
|Thymus||Just below the sternum||Thymosin|
|Pancreas||Below the stomach, near the duodenum||Insulin, Glucagon|
|Ovary (female)||On either side of uterus||Estrogen, Progesterone|
|Testis (male)||In the scrotum, outside the abdominal cavity||Testosterone|
|Adrenal||Above the kidneys||Cortisol, Aldosterone, Sex hormones, Epinephrine, Norepinephrine|
|Pineal||Centre of brain||Melatonin|
The hormone that helps in the reabsorption of water in the kidneys.