Chapter-7. Control and Coordination Science class 10 in english Medium CBSE Notes

Control of the Time and Amount of Hormone Secretion

The time and amount of hormone secretion are controlled by a feedback mechanism. For example, if the blood sugar level increases, the cells of the pancreas detect it and, in response, secrete more insulin. When the blood sugar level decreases, the secretion of insulin also decreases.

Hormones

Hormones are chemical substances that perform the functions of control and coordination in animals and plants.

Formation of Hormones in Animals

In animals, hormones are produced by endocrine glands.

In humans and animals, glands are of two types:

1. Endocrine Glands
2. Exocrine Glands

(1) Endocrine Glands

The glands that do not have ducts are called endocrine glands. They release hormones directly into the blood.

Examples: Pineal gland, Pituitary gland, Thyroid gland, Parathyroid glands, Thymus gland, Adrenal glands, Pancreas, Ovaries and Testes.

(2) Exocrine Glands

The glands whose secretions are released through ducts are called exocrine glands.

Examples: Lacrimal glands, Salivary glands and Sweat glands.

Human Endocrine Glands, Hormones and Their Functions

1. Pituitary Gland

Hormones: Growth hormone, TSH, FSH, LH, ACTH, etc.

Functions:

• Growth hormone promotes the growth of bones and other body tissues.
• TSH stimulates the thyroid gland to produce thyroid hormones.
• FSH and LH help in the development and functioning of reproductive organs.
• The pituitary gland controls the activities of several other endocrine glands, so it is often called the master gland.

2. Thyroid Gland

Hormones: Thyroxine (T4) and Triiodothyronine (T3)

Functions:

• Regulates the metabolism of the body.
• Helps in the growth and development of the body.
• Supports the normal functioning of many organs.

3. Parathyroid Glands

Hormone: Parathyroid hormone (PTH)

Functions:

• Maintains the calcium level in the blood.
• Helps in the proper functioning of bones and muscles.

4. Adrenal Glands

Hormones: Adrenaline, Cortisol, Aldosterone, etc.

Functions:

• Adrenaline prepares the body to deal with emergency situations and is known as the “fight or flight” hormone.
• Cortisol helps the body respond to stress and regulates metabolism.
• Aldosterone helps maintain salt and water balance in the body.

5. Pancreas

Hormones: Insulin and Glucagon

Functions:

• Insulin lowers the blood glucose level.
• Glucagon increases the blood glucose level.
• Together, they help maintain the normal blood sugar level.

6. Pineal Gland

Hormone: Melatonin

Function:

• Regulates the sleep-wake cycle and biological rhythms of the body.

7. Thymus Gland

Hormone: Thymosin

Functions:

• Helps in the development and maturation of T-lymphocytes (T-cells).
• Supports the immune system.

8. Ovaries

Hormones: Estrogen and Progesterone

Functions:

• Estrogen helps in the development of female secondary sexual characteristics.
• It also helps in the development of female reproductive organs.
• Progesterone helps regulate the menstrual cycle and prepares the uterus for pregnancy.

9. Testes

Hormone: Testosterone

Functions:

• Helps in the development of male secondary sexual characteristics.
• Promotes the development of male reproductive organs.
• Helps in the production of sperms.

Phytohormones or Plant Hormones

The chemical substances that perform the functions of control and coordination in plants are called phytohormones or plant hormones.

There are five main types of plant hormones:

1. Auxins

• Auxins promote cell growth and cell differentiation in plants.
• Auxins promote the growth of fruits.
• They increase the length of cells.

2. Gibberellins

• Gibberellins promote cell growth and cell differentiation in plants.
• They promote the growth of fruits and stems.

3. Cytokinins

• Cytokinins promote cell division in plants.
• They help in the growth and development of plant tissues.

4. Abscisic Acid (ABA)

• It inhibits or regulates the growth of plants.
• It helps control water loss in plants.
• It can promote protein synthesis and is involved in plant stress responses.

5. Ethylene

• Ethylene promotes fruit ripening.
• It can increase the number of female flowers in some plants.
• It helps regulate stem growth and development.

Class 10, all subjects CBSE Notes in english medium, cbse class 10 Science notes, class 10 Science notes english medium, cbse 10 Science cbse notes, class 10 Science revision notes, cbse class 10 Science study material, ncert class 10 science notes pdf, class 10 science exam preparation, cbse class 10 physics chemistry biology notes