Class 11-science NCERT Solutions Biology Chapter 19 - Chemical Coordination And Integration

1. Exocrine glands: Glands which release their secretions into ducts which carry them either on the body surface or to specific body organs are called exocrine glands.
2.  Endocrine glands: Glands which are ductless and release their secretions into the blood and transported to a distantly located target organ are called endocrine glands.
3.  Hormone: A non-nutrient chemical which acts as an intercellular messenger and produced in trace amounts is called a hormone.

(a) Pituitary gland  

(b) Thyroid gland

(c) Adrenal cortex

(d) Testis and ovaries

(e) Pigment cells of the dermis of the skin

Parathyroid hormone (PTH):

• The parathyroid hormone maintains the calcium levels in the body.
• It increases the calcium levels of the blood.
• It stimulates bone resorption which demineralises bones increasing blood calcium levels.
• It also stimulates calcium absorption by renal tubules and from the digested food.

Thyroid hormones:

• Thyroxine/tetraiodothyronine (T₄):

• It regulates the basal metabolic rate (BMR).
• It regulates body growth such as ossification of bones and mental development.
• It controls body weight.
• It also controls tissue differentiation and metamorphosis of the tadpole larva into an adult frog.
• It suppresses RBC formation.

• Tri-iodothyronine (T₃):

• It increases the body's oxygen and energy consumption.
• It increases the heart rate and force of contraction which increases the cardiac output.

• Calcitonin:

• o It regulates calcium and phosphate levels in the blood. 

Thymosin:

• Thymosin stimulates the differentiation of T-lymphocytes and provides cell-mediated immunity.
• It promotes the production of antibodies to provide humoral immunity.
• It also stimulates the rate of cell division in kids and hence promotes growth.

Androgens:

• Testosterone:

• Testosterone helps in the maturation of sperms.
• It stimulates the growth and development of the male reproductive system.
• It stimulates the development of secondary sexual characters such as beard and moustache.
• It produces anabolic effects on protein and carbohydrate metabolism.

• Androsterone:

• It affects the masculinisation of the foetus and child, and maintains or creates masculine traits in adults. 

Oestrogen:

• It stimulates the development of ovarian follicles.
• It stimulates the growth and development of female reproductive organs such as the fallopian tube, uterus and vagina.
• It increases the sensitivity of the uterus to oxytocin.
• It decreases the secretion of FSH and increases the secretion of LH.
• It promotes the development of mammary glands.
• It also regulates female sexual behaviour. 

Insulin:

• It plays a major role in the regulation of glucose homeostasis.
• It acts on hepatocytes and adipocytes.
• It stimulates the transport of glucose from blood to muscle.
• It promotes the oxidation of glucose and the conversion of glucose to glycogen, i.e. glycogenesis, resulting in hypoglycaemia.

Glucagon:

• It plays a major role in the maintenance of normal blood glucose levels.
• It acts on hepatocytes and stimulates the conversion of glycogen into glucose.
• It also stimulates the process of gluconeogenesis, i.e. the conversion of non-carbohydrate substances such as fats and proteins to glucose.

1. Hyperglycemic hormone: Glucagon
   Hypoglycemic hormone: Insulin
2. Hypercalcemic hormone: Parathormone hormone (PTH)
3. Gonadotropic hormones: Luteinising hormone (LH) and follicle-stimulating hormone (FSH)
4. Progestational hormone: Progesterone
5. Blood pressure-lowering hormone: Atrial natriuretic factor (ANF)
6. Androgens: Testosterone and androsterone
   Oestrogens: β-oestradiol

(a)   Diabetes mellitus: Insufficient secretion of insulin

(b)   Goitre: Insufficient secretion of thyroxine

(c)    Cretinism: Insufficient secretion of thyroxine

• Follicle-stimulating hormone (FSH) is a glycoprotein polypeptide hormone.
• It is insoluble in lipid and hence cannot enter the target cell.
• This hormone binds to the cell surface and activates cellular systems to perform functions.
• Steps in action of FSH:
  • A molecule of FSH binds on the receptor protein present on the cell surface and forms the hormone–receptor complex.
  • Formation of hormone–receptor complex activates the enzyme adenyl cyclase.
  • Adenyl cyclase converts ATP into cyclic AMP (cAMP) as a second messenger.
  • cAMP activates the follicular cells of membrane granulose to secrete oestrogens.