Class 10 Biology Control and Coordination Hormonal system in animals

Hormonal system in animals

Electrical impulses are excellent means for transmission of information but there are few limitations of using electrical impulses-

Impulses reach only those cells that are connected with nervous tissue.

Cells cannot continuously create and transmit impulse, the cells need some time to reset the mechanism before these can create and generate a new impulse.

Due the limitations, instead of generating electrical impulse, the stimulated cells release a chemical compound called hormones.

Hormones will diffuse to all the cells of the body and the cells have receptors to detect the hormones and to receive the information and transmit it.

Hormones are the chemical messengers which are secreted by the endocrine gland into the blood.

Different animal hormones are-

Thyroxin hormone-

  • Secreted by thyroid gland with the use of iodine.
  • Helps in the regulation of carbohydrates, proteins and fat metabolism in the body.
  • Deficiency of the hormone causes goitre.
  • Enlargedneck is the characteristic symptom of goitre.

Fig. goitre  


Growth hormone-

  • Secreted by pituitary gland.
  • Regulates growth and development of the body.
  • Deficiency of the hormone leads to dwarfism.

Sex hormones

  • Reproductive glands secrete testosterone in males and estrogen in females.
  • Development of sexual characters.


  • Secreted by pancreas.
  • Regulates blood sugar level.
  • Deficiency of the hormone causes diabetes mellitus, increase in blood sugar level.

Fig. endocrine system

Feedback mechanism

  • Hormones should be secreted in precise quantity.
  • Excess amount as well as deficiency of hormones causes disorder.
  • A mechanism is used by the body to regulate the secretion of hormone which is called as feedback mechanism.

For eg. If sugar level increases in blood, cells of the pancreas can detect this and produce more amount of insulin to control blood sugar and as the blood sugar level falls, secretion of insulin reduces.

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