• The term was coined by an American physiologist Walter Cannon in 1932 AD.
• It is defined as the tendency of biological systems to maintain a state of equilibrium.
• The body’s self-regulation of hormones and acid-base levels, the composition of body fluids and body temperatures are examples of it.
• Thus, the processes like excretion and osmoregulation are homeostatic processes.
Organs associated with homeostasis
• The chief homeostatic organs of man are skin, kidney and liver.
A) Homeostatic role of skin\
i) Skin has got various useful functions, among which temperature regulation is also one of them.
ii) The skin contains chromatophores, sweat glands and hairs, which help in controlling heat balance.
iii) The amount of fat present on the inner layer of skin makes it an efficient heat insulating layer.
iv) However, the cooling down the body through perspiration (sweating and evaporation) is one of the main functions of it.
v) Darkness (melanin pigment) absorbs solar heat and thus increases body heat.
B) Homeostatic role of kidneys
Kidneys are the chief excretory and osmo-regulatory organs that play a vital role in homeostasis. The important homeostatic functions of kidneys are as follows:
i) They remove nitrogenous waste of the body like urea, uric acid, etc.
ii) They help in loosing heat from the body during micturition.
iii) They expel more and hypotonic urine when water level is high in blood, and less and hypertonic urine when water level is low in blood.
iv) They regulate the amount of mineral salts in the body.
v) They remove unwanted substances from the body like drugs, poisons, excess of vitamins, etc.
vi). They produce erythropoietin hormone which stimulate bone marrow to produce more RBCs. Thus, they regulate the count in blood.
vii) They help in maintaining the pH of blood by expelling excess of acids or bases.
C) Homeostatic role of liver
It is the largest visceral organ of homeostasis. It controls many metabolic activities for the maintenance of body’s internal environment. However, the hypothalamus monitors sharply the body temperature; the main site of heat production is believed to be the liver. It has been found usually 1-20 C hotter than the rest of the body. The chief homeostasis roles of liver are as follows:
i) It is the main heat- producing center.
ii) It regulates the level of nutrients in the blood by glycogenesis, glycogenolysis and lipogenesis.
iii) It converts excess of amino-acids into ammonia and urea (deamination) which is later expelled out by the kidneys.
iv) It changes Hb of dead RBCs into bile pigments (bilirubin and biliverdin) which are expelled out along with faecal matters.
Homeostatic organs in man and their functions