SELINA Solutions for Class 10 Biology Chapter 12 - The Endocrine System

(b) diabetes insipidus

(a) Adrenaline

(b) Hypoglycemia

(c) Insulin

(d) Isthmus

(e) Anti-diuretic hormone (Vasopressin)

(f) Adrenaline

(a) Larynx

Reason- Larynx is the sound box while the rest three i.e. glucagon; testosterone and prolactin are hormones.

(b) Penicillin

Reason - Penicillin is an antibiotic while adrenaline; insulin; thyroxine are hormones.

(c) Adrenaline

Reason - Adrenaline is a hormone while the stomach, ileum and liver are the organs of the digestive system.

(d) Insulin

Reason- Insulin is secreted by the pancreas while TSH, GH, ADH are the hormones secreted by the pituitary gland.

(e) Iodine

Reason- Iodine is required for the synthesis of thyroxine hormone. While cretinism, goitre, myxoedema are the deficiencies occur due to the deficiency of thyroxine.

(a) Beta cells : Insulin :: Alpha cells : Glucagon.

(b) Children : Cretinism :: Adults : Myxoedema.

(c) Undersecretion : Dwarfism :: Oversecretion : Gigantism.

(d) Diabetes mellitus : Insulin :: Diabetes insipidus : Antidiuretic hormone (ADH). 

a) Hyperglycemia

b) Simple goitre

c) Cretinism

d) Exophthalmic goitre

e) Acromegaly in adults and gigantism in children

(a) Thyroid: It is situated in the front part of the neck just below the larynx.

(b) Adrenal: It is present as a cap on the top of each kidney.

(c) Pancreas: It is located behind the stomach in the upper left abdomen.

(d) Pituitary: It hangs from the base of the mid-brain below the hypothalamus.

(a) Three hormones secreted from islets of Langerhans of pancreas:

1. Insulin
2. Glucagon
3. Somatostatin

(b) Two types of cortical hormones:

1. Glucocorticoids

2. Mineralocorticoids

(c) Six hormones secreted from anterior pituitary:

1. Growth hormone (somatostatin)

2. Prolactin

3. Adreno-corticotropic hormone (ACTH)

4. Thyroid stimulating hormone (TSH)

5. Follicle stimulating hormone (FSH)

6. Luteinizing hormone (LH)

(d) Two hormones secreted from posterior pituitary:

1. Vasopressin

2. Oxytocin

(e) The emergency hormone:

1. Adrenaline 

(a) Endocrine system: Endocrine system consists of several endocrine glands/glandular cells which activate each other and work as a system to bring about chemical coordination in the body.

(b) Hormones: Hormones are secretions from specific cells or glands in the body, which are carried to all body parts through the blood, but exert their effect only on one or more specific body parts (target organ or cells).

(c) Myxoedema: Myxoedema is a condition which occurs in adults due to hypothyroidism in which the person becomes sluggish with swelling of the face and hands. 

(a) Differences between exocrine and endocrine glands (manner of secretion):

(b) Differences between enzymes and hormones (chemical composition and mode of action):

(c) Differences between nervous control and hormonal control (transmission and effect):

(d) Differences between diabetes mellitus and diabetes insipidus (cause and symptoms):

(e) Differences between Addison's disease and Cushing's syndrome (cause and sugar level):

(a) Adrenaline is often described as the emergency hormone because it prepares the body to meet any emergency situation, for fight and face the danger or flight and run away from it. More adrenaline is secreted which makes the heart beat faster, increases the breathing, releases more glucose into the blood stream to fulfill the energy requirement.

(b) Pituitary is popularly called as the master gland because it controls the functioning of all the other endocrine glands.

(c) People living in the low Himalayan hilly regions often suffer from goitre because iodine is deficient in soil and hence, in the food grown there. Insufficient iodine produces less thyroxine which results in goitre.

(d) Iodised salt contains iodine which is an active ingredient in the production of thyroxine. Hence, it is recommended to use iodised salt in food to prevent simple goitre.

Chemically hormones are peptides, amines or steroids. They are involved in regulating the metabolism of the body. They can bring about specific chemical changes during metabolic process. Therefore hormones can be termed as 'chemical messengers'.

a. Glucagon: Alpha cells of the islets of Langerhans

Insulin: Beta cells of the islets of Langerhans

b. Insulin: It maintains the levels of glucose (sugar) in the blood.

Glucagon: It raises the blood glucose levels by stimulating the breakdown of glycogen to glucose in the liver.

c. An endocrine gland is one which does not pour its secretions into a duct, while an exocrine gland is a gland which pours its secretions into a duct. Because the pancreas produces hormones such as insulin, glucagon and somatostatin directly into the blood and not into a duct, it functions as an endocrine gland. Because it secretes the pancreatic juices for digestion via a duct, it functions as an exocrine gland. Hence, the pancreas is an exo-endocrine gland.

d. Insulin is not administered orally because the digestive juices degrade insulin, and thus the insulin is ineffective in the body.

e. Islets of Langerhans

f. The pancreas is located in the abdomen behind the stomach.

(a) This portion is located in the neck region above the sternum.

(b) 1- Larynx, 2 - Thyroid gland, 3 - Trachea

(c) Larynx is the voice box containing vocal cords. It helps in producing sound.

Thyroid gland produces thyroxine and calcitonin which are essential hormones.

Trachea is the wind pipe that helps in passing air to and from the respiratory system while breathing.

(d) Structure 2 is the thyroid gland. It is an endocrine gland, so it is ductless and pours its secretions directly into the blood. Hence, there is no duct.

(a) 1- Pituitary gland, 2 - thyroid gland, 3 - pancreas, 4 - adrenal glands

(b) All the glands shown in the above diagram are endocrine glands. They secrete essential hormones and pour their secretions directly into the blood.

(c) Iodine is essential for the normal working of thyroxine.

(a) A

(b) Hormone secreted by the endocrine gland is shown in the image A to be moving only in one direction i.e. towards the target organ. But actually the hormones poured into the blood stream may have one or more target sites at a time. The arrows shown are carried to all parts by the blood and their effect is produced only in one or more specific parts.