BIO6: Hormonal Coordination in Animals

This unit explains Hormonal Coordination in Animals

Hormones are defined as chemical compounds secreted by specialized cells or glands which are helpful in transmitting information to different locations. It is also helpful in the wider distribution of information in animals. Hormones constitute an alternate way of coordination in animals besides electrical impulse transmission of information using nerve cells.

Growth regulation by hormones

Hormones secreted by various glands like endocrine glands in our body helps in regulating growth by performing certain specific functions e.g. adrenaline, thyroxin, growth hormone, insulin, Testosterone, and estrogen. Secretion of these hormones should be in an accurate quantity and very precise as minor changes in their level in the body may result in serious effects.

Endocrine glands in female and male


This hormone is secreted by the adrenal gland and is released in stress situations like fear, pain, anxiety etc. It generally acts on the heart. The response of this hormone includes faster heartbeat, increased breathing rate and contraction of muscles around the digestive system, skin, diaphragm and rib muscles.



This hormone is secreted by the thyroid gland and helps the body to get a balanced diet for proper growth. Thyroxin plays a major role in metabolizing protein, fats etc. Iodine plays a major role in the secretion of thyroxin. This is the reason why iodized salt is advised in the diet. Deficiency of iodine leads to goiter disease with symptoms of the swollen neck.

Growth hormone

This hormone helps in proper and balanced growth and development of the body. Deficiency of this hormone in childhood may lead to dwarfism.


This hormone is secreted by the pancreas and it regulates the glucose level in blood. As the level of insulin decreases in our body concentration of glucose starts increasing leading to diabetes and many other side effects.

Pituitary gland (master gland) (single):

  • Present in the Hypothalamus of the brain
  • It controls growth.
  • Controls secretion of other glands.

Pineal gland (single):

  • Present in the brain.
  • Responds to light exposure.

Thyroid gland (paired):

  • Present in the neck region.
  • Produces thyroxin (contains iodine).
  • Responsible for metabolic rate,healthy hair & skin.
  • Lack of iodine Deficiency of Thyroxine Goitre

Parathyroid gland (paired):

  • Present above the thyroid gland.
  • It is a Para hormone.
  • Controls and regulates the level of calcium and phosphorus in blood.
  • Lack of this hormone Brittle bones,

Pancreas (Islets of Langerhans):

  • It is present behind the stomach.
  • Produces insulin.
  • Regulates blood sugar level.
  • Deficiency of insulin causes diabetes.

Testes, ovaries (paired):

  • Males  Present outside the pelvic region and produces testosterone.
  • Females   Present inside the pelvic region and produces oestrogen.
  • Responsible for Secondary sexual characters, puberty, sperm production (males), Egg production (females)
  • Lack of secretion of these hormones would result in infertility & delay in onset of puberty.

Adrenal gland:

  • It is present above the kidney.
  • Produces adrenaline (fight or flight hormone).
  • Functions include  increases  heartbeat, supplies more oxygen to muscles, increases breathing rate, lowers blood supply to the digestive organs and increases supply to the skeletal system.

Testosterone and estrogen

Testosterone in case of males and estrogen in case of females are sex hormones that are produced at the time of puberty and helps in the development of secondary sex characters in our body.


ASSIGNMENT : Hormonal Coordination in Animals Assignment MARKS : 25  DURATION : 24 hours


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