Biology - 5090


It is the maintenance of a constant internal environment irrespective of changes. It keeps the body parameters within the set limits.

The body temperature will remain 37 degrees Celsius no matter if the external temperature is -10 degrees Celcius or  50 degrees Celsius. The glucose levels in the blood will remain constant even if we eat high amounts of carbohydrates. The water level will remain constant through the excretion process. 

Negative Feedback

If there is a change in body conditions, for example, water, glucose or temperature change, the body system will keep it within set limits through the mechanism of negative feedback. In this process, the body does the opposite of the stimulus. 

Maintenance of the Blood Glucose Levels Through Negative Feedback 

Blood glucose is measured by the pancreas. There is two possible stimuli for this. One is an increased blood glucose level, while the other is decreased blood glucose level.

When the stimulus is increased blood glucose level, the sensory organ is the pancreas. They secrete insulin, which goes into the liver. The liver changes the glucose into glycogen, thus maintaining the blood glucose level.

When the stimulus is decreased blood glucose level, the sensory organ is again the pancreas. The pancreas secretes glucagon, which will then proceed to enter the liver. The liver will change the glycogen back into glucose, causing an increase in the blood glucose level until it goes back to the set limits.


Skin has many layers. Thee thick, outer layer of the skin is the epidermis. Beneath the epidermis is another thick layer, known as the dermis. The epidermis is a protective layer which tends to avoid the entry of pathogens into the skin. The dermis has hair follicles (place from where hair emerges out). In certain conditions, like extreme cold or nervousness, goosebumps occur on your skin. The hairs erect due to the hair erector muscle. When the muscle contracts, the hairs on the skin erect, trapping the air inside them. Therefore, skin becomes an insulating layer for trapping heat. This tends to increases the body temperature, resulting in temperature regulation through the process of homeostasis. This phenomenon usually occurs in animals (polar bears). 

Sebecious gland present in the skin produces sebum which is an oily substance. It keeps our scalp moist, and makes sure pathogens don't enter the skin. It also prevents the development of pathogens and fungus in the hair. In dermis, there is a gland called sweat gland which produces sweat. Sweat is released to the skin through the sweat duct, and it tends to take our body heat away. 

Cells or tissues of the dermis are associated with capillaries and nerves to have a connection with the nervous and circulatory system. There is an enormous emoting of sensory neurons present in the skin to detect touch and pressure. Below the dermis is a layer, known as adipose/fat layer, which is made up of adipose cells. When we eat fats, some of the fats are consumed while the rest are stored in the adipose layer. This layer also traps excess heat, and it prevents heat from getting released into the surroundings. The fat layer also provides insulation to the body, preventing us from shivering.

Homeostasis on Different Temperatures 

Hot summer day 

  • Sweating: The water molecules evaporate from the skin, evaporating body heat along with them. This removes the latent heat of vaporization and results in the cooling effect of the body. 

  • Vasodilation: The vessels widen, and the Skin arterioles dilate allowing more blood to flow. there is heat present in the blood. Therefore, when more blood flows, more heat is lost through evaporation. This is the loos of heat through conduction, convection and radiation.

  • Low metabolic rate: It generates less heat to keep the body cool. 

Cold Winter Day

  • Shivering: as a result of shivering, a lot of heat is generated because the muscles of The body shake. this keeps the body temperature within set limits.

  • Vasoconstriction: The Skin arterioles barrow allowing lesser blood to flow. thus, less heat will pass in the blood. as a result, not much heat is lost through evaporation.

  • High metabolic rate: Increase in metabolic activity will generate more heat, which in turn will keep the body warm.

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