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Class 10 SELINA Solutions Biology Chapter 12 - The Endocrine System

The Endocrine System Exercise Ex. 1

Solution A.1

(c) pancreas

Solution A.2

(b) thyroid

Solution A.3

(b) diabetes insipidus

Solution B.1

(a) Adrenaline

(b) Hypoglycemia

(c) Insulin

(d) Isthmus

(e) Anti-diuretic hormone (Vasopressin)

(f) Adrenaline

Solution B.2

If there was hyposecretion of the thyroid gland in a child; the child will suffer from cretinism. The symptoms of cretinism are dwarfism, mental retardation, etc.

Solution B.3

(a) Prostate

(b) Scurvy

(c) Cretinism

(d) Cortisone

Solution B.4

A (Condition)

B (Cause)

(a) Dwarfism and mental retardation

v. Hypothyroidism

(b) Diabetes mellitus

i. Excess of glucose in blood

(c) Shortage of glucose in blood

iii. Insulin shock

(d) Gigantism

ii. Over secretion of growth hormone


(e) Enlargement of breasts in adult males

vi. Over secretion of cortical hormones


(f) Exophthalmic goitre

iv. Over secretion of thyroxine

Solution B.5

(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.

Solution B.6

Column I

Column II

1. Beta cells of islets of Langerhans

(g) Insulin

2. Thyroid

(c) Exophthalmic goitre

3. Cretinism

(h) Under secretion of

thyroxine in a


4. Addison's disease

(b) Undersecretion of glucocorticoids

5. Hypothyroidism

(e) Thyroxine

6. Myxoedema

(a) condition due to under     secretion of thyroxine in adults

7. Adrenaline

(d) Increases heart beat

8. Cortisone

(f) Adrenal cortex

Solution B.7

(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). 

Solution C.1

a) Hyperglycemia

b) Simple goitre

c) Cretinism

d) Exophthalmic goitre

e) Acromegaly in adults and gigantism in children

Solution C.2

(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.

Solution C.3

(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 

Solution C.4



(a) Thyroxine

Regulates the basal metabolism

(b) Adrenaline

Increases heart beat and blood pressure

(c) Insulin

Reduces the blood sugar level

(d) Glucagon

Increases the blood sugar level

(e) Vasopressin

Constricts blood vessels and raises blood pressure


Solution C.5



(a) Contraction of uterine muscles during child birth


(b) Maintenance of corpus luteum

Luteinizing hormone (LH)

(c) Milk formation and secretion


(d) Development of external sex characters in males


(e) Stimulation of sympathetic nervous system



Solution C.6

Adrenaline is the hormone which prepares the body to meet any emergency situation. Adrenaline makes the heart beat faster. At the same time, it stimulates the constriction of the arterioles of the digestive system reducing the blood supply of the digestive system which makes the mouth dry.

Solution C.7



Gland cells

Hormone produced

Chief function

Effect of over secretion

Effect of under secretion




Regulates basal metabolism

Exophthalmic goiter

Simple goiter, cretinism in children and myxoedema in adults


Beta cells of Islets of Langerhans


Promotes glucose utilization by the body cells


Diabetes mellitus


Anterior pituitary

Growth hormone

Promotes growth of the whole body




Posterior pituitary


Increases reabsorption of water from kidney tubule

More concentrated and less amount of urine

Diabetes insipidus

Solution C.8


Hormone secreted

Effect on body



Regulates basal metabolism

Pancreas ("beta" cells)


Controls blood sugar level

Adrenal gland


Increases heart beat

Anterior pituitary

Thyroid stimulating hormone

Stimulates thyroxine secretion

Solution C.9



Effect on body



development of secondary sexual characteristics

Alpha cells of islets of Langerhans


Raises blood sugar level


Hypersecretion of thyroxine

Protruding eyes

Anterior pituitary

Hypersecretion of Growth hormone


Solution D.1

(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. 

Solution D.2

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

Exocrine glands

Endocrine glands

Secretions are carried through special ducts.

Secretions are poured directly into the blood.


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



Enzymes are protein in nature.

Hormones are peptides, amines or steroids.

Enzymes are substrate specific. These are present in all cells and show their activity there

Hormones are specific to the target cell, tissue, or system. They are produced at one site and show their activities at other sites.


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

Nervous control

Hormonal control

Transmitted electro-chemically through nerve fibres and chemically across synapses.

Transmitted chemically through blood.

Effect is only short-lived.

Effect is short term or long lasting.


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

Diabetes mellitus

Diabetes insipidus

Caused due to insufficient secretion of insulin.

Caused due to insufficient secretion of anti-diuretic hormone (ADH)

High concentration of sugar in blood.

No sugar in urine


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

Addison's disease

Cushing's syndrome

Caused due to hyposecretion of cortisone

Caused due to hypersecretion of cortisone

Low blood sugar level

High blood sugar level


Solution D.3

(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.

Solution D.4

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'.

Solution E.1

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.

Solution E.2

(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.

Solution E.3

(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.

Solution E.4

(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.

Solution F.1

Hormonal Response

Nervous Response

Hormonal response is slow.

Nervous response is immediate.

Hormones are chemical messengers transmitted through blood stream.

Nerve impulses are transmitted in the form of electro-chemical responses through nerve fibres.

This response brings about a specific chemical changes. Therefore it regulates the metabolism.

This response does not bring any chemical change during metabolism.

Solution F.2

Action of Hormones

Action of Nerves

The effect of hormones is wide spread in the body. They can show their effect on more than one target site at a time.

The nerve response affects only particular glands.

The effect of hormones can be short-lived or long lasting.

The effect of nervous response is always short-lived.

Cannot be modified by the previous learning experiences.

Can be modified by the previous learning experiences.

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