INTRODUCTION TO HOMEOSTASIS

Most animals can survive fluctuations in the external environment that are more extreme than any of their individual cells could tolerate. During the course of a day, a human may be exposed to substantial changes in outside temperatures but will die if the internal body temperature goes more than a few degrees above or below an average of about 37°C. The spring peeper, a North American tree frog often spends an entire winter with much of its body frozen. Most of its blood and interstitial fluid turns to ice, but its cells and a film of water surrounding them are kept from freezing by specialized proteins and a high level of glucose throughout the frog's body. Without these protections, ice crystals would rupture the cell membranes, and the animal would die.

Homeostasis may be defined as “the maintenance of the internal conditions of body at equilibrium, despite changes in the external environment.” For example, the core temperature of human body remains at about 37°C despite fluctuations in the surrounding air temperature. Similarly, the blood glucose level remains about 1 gram per liter despite eating a meal rich in carbohydrates. Body cells need the internal environment in which conditions do not change much. Stable internal conditions are important for the efficient functioning of enzymes.

Concepts in Homeostasis:

The protection of internal environment from the harmful fluctuations in external environment is termed as homeostasis.

Each organism of a species has assumed, a specific set up (internal environment) at various levels of organization suitable to its surroundings i.e., external environment. External environment and its components fluctuate continuously, however, the organism resists and manages these changes by making adjustments to keep its own internal fluctuations within a narrow range thus protects internal environment from the harmful fluctuations of external environment. The homeostasis keeps 'the internal fluctuations in a narrow range with various control systems compared to wider external fluctuations.

Components Affected by Fluctuations:

Most susceptible components of internal environment that may be affected by fluctuations in external environments are water, solutes and temperature.

Mechanisms to Maintain Homeostasis:

The mechanism, an organism has adapted to eliminate harmful nitrogenous wastes depends upon the availability of water.

Osmoregulation:

It is maintenance of the amounts of water and salts in body fluids (i.e. blood and tissue fluids). We know that the relative amounts of water and salts in body fluids and inside cells control the processes of diffusion and osmosis, which are essential for the functioning of cells. The mechanism of regulation, generally between organism and its environment, of solute and the gain and loss of water is osmoregulation.

Excretion:

Excretion is also a process of homeostasis. In this process, the metabolic wastes like nitrogenous wastes are eliminated from body to maintain the internal conditions at equilibrium. The mechanism which eliminates nitrogenous waste is referred to as excretion. Metabolic waste means any material that is produces during body metabolism and that may harm the body.

Thermoregulation:

The maintenance of internal body temperature is called thermoregulation. The enzymes of body work best at particular temperatures (optimum temperature). Any change in body temperature may affect the functioning of enzymes. The maintenance of internal temperature within a tolerable range is designated as thermoregulation.

Homeostasis is the central requirement in the maintenance of an organism which compels the adaptations in the constant changing conditions and contributes in evolutionary process.