Concepts in Homeostasis | Control at organism level |

Concepts in Homeostasis.

"The protection of the internal environment from the harm of fluctuation in the external environment is called homeostasis. " The homeostasis reduces the internal fluctuations in the body as compared to many external fluctuations. It reduces these fluctuations with the help of different control systems.

Each organism inherits a specific set up of the internal environment at different levels of organizations. This internal environment is most suitable for the external environment. The external environment and component fluctuate continuously. But the organisms resist these changes. The organisms have internal adjustment. So that its internal fluctuation remains within a narrow range. Thus homeostasis protects its internal environment form the term of the fluctuations in the external environment.  

(a) Control at the organism level:

The fluctuation in the external environment affects the three components of the internal environment. These are water, solute, and temperature. There are following processes which control the fluctuation of these three internal environmental components:

1. Osmoregulation:

"To maintain the water and salt balance in the body or control of osmosis is called osmoregulation. It is a mechanism of regulation of solute between the internal and external environment.

2. Excretion:

"The mechanism of elimination (W (S) )of nitrogenous wastes is called

excretion. The adaptation of this mechanism also depends on the

availability of water.

3. Thermoregulation:

"The maintenance of internal temperature within a tolerable range is called thermoregulation. "

(b) Control at the cell level:

There is also a control system at cell level. This control system keeps the fluctuations in intracellular and extracellular environments in a narrow range. The intracellular environment is present within the cell membrane. While the extracellular environment is interstitial fluid. This system keeps the water, solute, metabolites, hormone etc in a required range in the cells.

Objects of homeostasis:

The homeostasis does not mean to keep the internal environment fixed. But to maintain the changes within a specific range This range is necessary for the normal functioning of the body. For example, the availability of water may fluctuate for the organisms greatly in the external environment. It may be from abundant supply to almost dry conditions. However, the quality of water in the body (internal environment) may vary in response to the abundant or dry condition. But this variation is within a narrow range. The control system does not allow excessive water to enter into the body when there is an abundant supply of water. It also does not allow it to dehydrate in dry conditions. Furthermore, the adaptation to the lower level range in dry condition and higher-level range in the abundant supply of water is good for the organism. Thus the organism feels normal even in drastic external fluctuations.

Nature of controlling system:

The control system is used for different homeostatic regulations. This living control system works exactly on the mechanism of the physical control system. This control system has three components:

➤ Receptor

➤ Control centre

➤ Affecter

There is a sensor in physical control system like temperature control system in refrigerators. This sensor is in the form of the thermometer. It monitors the change of temperature from the set point. It sends signals to control centre. The control center takes necessary action. If there is a drop or rise in temperature as compared to the setpoint, the control center switches on the heater or cooler units.

Similarly, the endothermic (warm-blooded) animals have a set point. The receptors detect the temperature change like sensor. These receptors send signals to the control centre. The cooling or warming system of the control centre takes action as the case may be. The detection of change, sending signals to the control center and the response of effectors is a feedback mechanism. In this process, the effectors show inverse to the change in the external environment. Thus if warm temperature is sensed in the external temperature, the effectors show response in the form of cooling the body. It is called a negative feedback mechanism.