NCERT Class 11-Biology: Chapter – 22 Chemical Coordination and Integration Part 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 5:

Inflammatory responses can be controlled by a certain steroid. Name the steroid, its source and also its other important functions.


  • Cortisol is a steroid hormone which is secreted by adrenal cortex that produce anti- inflammatory responses and suppresses the immune response.
  • Functions of cortisol are:
    • Stimulates gluconeogenesis
    • Stimulates lipolysis and proteolysis
    • Inhibit cellular uptake
    • Helps in maintaining cardio-vascular system
    • Helps in maintaining kidney function
    • Stimulates RBCs production

Question 6:

Old people have weak immune system. What could be the reason?


Thymosin is a hormone secreted by thymus gland which play a major important role in development of immune system, but with the increasing age thymus gland degenerated or in the old people thymus gland starts to degenerate and thus thymosis hormone produce less, hence the old people have weak immune system. Thymosin is responsible for the differentiation maturation and development of T-lymphocytes and T-cells which provides cell- mediated immunity. So Thymosin is the important hormone that play an important role in immune system but with age thymus gland starts to degenerate and thus old people have weak immune system.

Question 7:

What are the effects of hypothyroidism (observed during pregnancy) on the development and maturation of a growing baby?


Hypothyroidism during pregnancy causes-

  • Defective development and stunted growth (cretinism) .
  • Mental retardation
  • Low intelligence quotient.
  • Abnormal skin
  • Low concentration of blood calcium level.
  • Neurons and muscle fibers depolarized

Question 8:

Mention the difference between hypothyroidism and hyperthyroidism.


Hypothyroidism and Hyperthyroidism
(i) Involves less than normal production of thyroid hormone(i) Involves more than normal production of thyroid hormone
(ii) Reduces metabolic rate.(ii) Increases metabolic rate.
(iii) May happen because of iodine deficiency.(ii) May happen because of development of tumor or nodules in thyroid gland
(iv) Symptoms include fatigue, dry hair, dry skin, muscle cramps, decreased menstrual flow, etc.(iv) Symptoms include feeling hot, forgetfulness, sweating, increased heart rate, disturbed bowel movement etc.

Question 9:

You have learnt that a characteristic feature of endocrine system is the presence of feed- back loops. By this what is meant if hormone A stimulates gland ‘X’ to secrete hormone B, the production of ‘A’ could be modified when the level of B changes in our blood. An example is the relation between hormones LH and estrogen () . An old woman exhibits the following features. High levels of in blood but low levels of in the blood. Another woman exhibits high level of LH in blood and also high level of in the blood. Where is the defect in both these women? Provide suitable diagram to support this answer.


Level of LH in blood is usually low before puberty and it increases during reproductive phase. LH levels in blood during the reproductive phase depend on the particular phase of the ovulation cycle. When ovulation is about to happen, the LH level peaks and so does the level of . This shows a perfectly normal condition.

But in older women, LH level is higher accompanied by low level of . Low level of shows cessation of reproductive phase. We know that menopause marks the end of the reproductive phase. After the menopause, no or negligible oocytes are left in the ovary. Hence, LH is not being utilized the way it was during reproductive phase. This explains the increased level of LH in blood in older women.

Long Answer Type Questions

Question 1:

A milkman is very upset one morning as his cow refuses to give any milk. The milkman՚s wife gets the calf from the shed. On fondling by the calf, the cow gave sufficient milk. Describe the role of endocrine gland and pathway associated with this response?


  • Oxytocin hormone from pituitary gland is responsible for this response.
  • Oxytocin hormone is protenious in nature.
  • Oxytocin hormone is the hormone which stimulates the release of milk from the mammary gland by causing surrounding cells to contract.
  • When the infant starts feeding breast stimulates the posterior pituitary to produce the oxytocin hormone and oxytocin hormone stimulates the milk secretion.
  • Oxytocin also cause contraction of smooth muscles of uterus to expel the fetus outside the body of the mother.
  • So on fondling by calf, the cow gave sufficient milk because calf touches activate the oxytocin hormone which it stimulates milk secretion.