What is Homeostasis?

Bodytomy Staff Sep 30, 2018
Ever wondered why we sweat or shiver and what makes us feel hungry or thirsty? Well, it is due to a mechanism called 'homeostasis' that helps our body maintain its internal milieu. Know more about this interesting phenomenon and its importance.
Homeostasis, in simple terms, means the maintenance of internal equilibrium. Variations in the external environment can affect the body processes and induce an imbalance in various physiological aspects. Body responds to these external variations, neutralizes their effects and restores stability through homeostasis.
The basic underlying principle behind such a response is a feedback mechanism that operates through our organs and hormones. Through feedback, various aspects like body temperature, energy and water levels and the nutrients' levels in blood and body organs are maintained. Let's understand this mechanism and the different types of homeostasis in our body.

Feedback Mechanism

A feedback mechanism is the way our body communicates changes to the concerned organs. There are two types of feedback mechanisms: positive and negative. Positive feedback enhances an activity or process, whereas a negative feedback reduces or inhibits an activity or process in the body. Homeostasis is mainly achieved via negative feedback mechanisms.
The main components of a negative feedback mechanism are:
  • Variable: The entity that gets affected due to a change in the external environment
  • Sensor/Receptor: Identifies the change in the variable and communicates the change to a control center
  • Control Center: Activates the necessary effector organs
  • Effector: Reverses the change in the variable
This cycle continues till the variable attains its normal state. The sensor detects the restored normal state and stops communication to the control center. As a result, the control center withdraws the activation signal passed to the effector. The action of the effector no longer continues and the cycle is complete.

Thermoregulation

Organs Involved: Skin, hypothalamus, skeletal muscles, arterioles of skin, sweat glands, adrenal glands and thyroid gland.

Process: A stable internal temperature is maintained through the process of thermoregulation. The temperature changes in the environment are communicated through skin and blood to the hypothalamus.
The hypothalamus then directs the effector organs to initiate reactions like sweating in a hot environment or shivering in a cold environment. These reactions decrease or increase the body temperature respectively, till the normal temperature is attained.
Importance: Constant body temperature is essential to retain the structure and the activity of proteins. Most hormones and enzymes in our body are proteins whose activities are temperature-dependent. Temperature imbalance can lead to hypothermia (if internal temperature falls below 35°C or 95°F) or cause a heat stroke if temperature increases uncontrollably.

Water Balance

Organs Involved: Hypothalamus, salivary glands, pituitary gland, adrenal glands, kidneys and lungs.

Process: Water content in the body is regulated by controlling the processes through which water is retained in the body or excreted from the body. The water content of the body reduces due to sweating, evaporation from skin, urination and through exhaled air.
When water content reduces, activities like salivation and urination are reduced, and the sensation for thirst is triggered in order to prevent dehydration. On the contrary, excessive water intake leads to an increase in the excretion of water through urination and through exhaled air. Kidneys play a major role in maintaining the fluid balance of our body.
Importance: Water makes up 60% of our body. Transport of oxygen, nutrients, and waste metabolic products depends on the water content of blood. Each cell of our body needs an optimum amount of water to function effectively. Excess of water causes cells to burst, while extremely low water content causes shriveling of cells. In either case, cell death occurs.

Food and Energy Balance

Organs Involved: Stomach, intestines, pancreas, liver, adipose tissue, hypothalamus and pituitary gland.

Process: The sensations of hunger and satiety regulate our food intake. The activation of the hunger and satiety centers of the hypothalamus drives these sensations.
The center to be activated depends on hormonal signals from stomach and pancreas. Also, pancreas and pituitary gland control the levels of glucose in blood and ensure a constant energy supply to all the organs.
Importance: These signals influence our eating habits and body weight. When food consumption is delayed (for example, while fasting), supplementary processes are required to fulfill the energy requirements. Also, these processes need to be stopped once food is consumed.
Such a regulation of the supplementary processes is achieved through this homeostatic process. The most common results of an imbalance in this process are eating disorders, hypoglycemia, hyperglycemia, diabetes and obesity. Such imbalances have also been associated with heart problems and cancer.

Other Homeostatic Processes

Homeostatic processes exist at the cellular level, organ level as also at the level of a functional system. Such processes regulate the following:
  • Concentrations of cellular components
  • Cell proliferation and differentiation
  • Sleep and circadian rhythms
  • Blood pressure
  • Salt and ion content of blood
  • pH balance of blood
  • Calcium levels in blood and bones
  • Lipid metabolism and cholesterol levels in blood
  • Amounts of iron, phosphate, zinc, copper and other minerals in blood as well as their distribution throughout the body
  • Amount of toxic molecules in the body, namely urea and carbon dioxide
Organs Involved: Practically every organ is involved in some or the other form of homeostasis. The brain helps in controlling the autonomic nervous system and endocrine system. Different endocrine glands are involved in cell proliferation and differentiation.
Kidneys are responsible for controlling salt and ion content in the blood. They play an important role in regulating iron content in our blood, and are also involved in urea or uric acid homeostasis. Liver is involved in metabolism of toxic substances. Lungs are involved in maintaining the carbon dioxide levels.
Importance: Homeostatic imbalance leads to minor health problems as well as major disorders that require serious attention. Lipid metabolism and cholesterol influence heart functions and are associated with atherosclerosis and cardiac disorders.
High levels of urea lead to kidney stones and gout. Malfunctioning of calcium homeostasis also contributes to kidney stones and affects bone health. Improper distribution of minerals affects various cellular functions as well as bone strength.
All our body processes require a set of optimum conditions to operate effectively. Homeostasis ensures the maintenance of these optimum conditions. The efficiency of these processes determines our regular activities, overall health and longevity.