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Human Physiological Function And Homeostasis

Info: 1703 words (7 pages) Essay
Published: 27th Apr 2017 in Biology

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The human organism consists of trillions of cells all working together for the maintenance of the entire organism. While cells may perform very different functions, all the cells are quite similar in their metabolic requirements. Maintaining a constant internal environment with all that the cells need to survive (oxygen, glucose, mineral ions, waste removal, and so forth) is necessary for the well-being of individual cells and the well-being of the entire body. The varied processes by which the body regulates its internal environment are collectively referred to as homeostasis.

What is Homeostasis?

Homeostasis in a general sense refers to stability, balance or equilibrium. It is the body’s attempt to maintain a constant internal environment. Maintaining a stable internal environment requires constant monitoring and adjustments as conditions change. This adjusting of physiological systems within the body is called homeostatic regulation.

Homeostatic regulation involves three parts or mechanisms: 1) the receptor, 2) the control center and 3) the effector.

The receptor receives information that something in the environment is changing. The control center or integration center receives and processes information from the receptor. And lastly, the effector responds to the commands of the control center by either opposing or enhancing the stimulus. This is an ongoing process that continually works to restore and maintain homeostasis. For example, in regulating body temperature there are temperature receptors in the skin, which communicate information to the brain, which is the control center, and the effector is our blood vessels and sweat glands in our skin.

Because the internal and external environments of the body are constantly changing and adjustments must be made continuously to stay at or near the set point, homeostasis can be thought of as a dynamic equilibrium.


All organisms need some control on their internal environmental conditions in order to ensure that they will be able to survive. Since many of the metabolic reactions that occur within an organism depend on the use of enzymes or even the use of other organisms such as prokaryotic bacteria, it is essential that the optimal conditions required for the functioning of that enzyme be provided. Homeostasis therefore, is ‘the tendency of organisms to regulate and maintain relative internal stability’, and involves, among other processes, the maintenance of a constant body temperature, glucose concentration, pH, osmotic pressure, oxygen level, and ion concentrations. The ability to maintain a constant internal environment, with which we are most familiar, is that of a constant body temperature in homeothermic organisms. For example, the average body temperature of a human

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The mechanisms that regulate homeostasis operate by feedback mechanisms. Negative and positive feedback mechanisms operate in living things. Negative feedback mechanisms reverse the direction of the change. This maintains the constant, steady state and so represents homeostasis. Positive feedback, on the other hand, acts to change the variable even more in the direction in which it is changing. Thus, positive feedback is not a homeostatic mechanism.

Temperature control is an example of a negative feedback homeostatic mechanism. The region of the brain called the hypothalamus monitors the human body’s temperature. Variation from the normal temperature of 98.6Â°F (37Â°C) triggers a response from the hypothalamus. The temperature can be lowered by activation of glands capable of sweating, or raised by signalling muscles to shiver to produce heat.

Homeostatic mechanisms are a fundamental characteristic of living things. Without these mechanisms, facets of a body that need to be kept operating in a steady state, such as temperature, salinity, acidity, hormone levels, concentration of gases such as carbon dioxide, and the concentrations of nutrients, would become so unbalanced as to threaten the life of the organism. In a healthy body, homeostatic mechanisms operate automatically at different levels; molecular, cellular, and at the level of the whole organism.

At the molecular level, the activity controlled by one gene can be under regulatory control by another gene. At the cellular level, a well-studied homeostatic mechanism is contact inhibition, in which cells stop dividing when they begin to crowd in on each other. Cancer, in which a hallmark is the rampant growth and division of cells, is a condition where the homeostatic mechanism of contact inhibition is inoperative or defective.

At the whole organism level, a homeostatic mechanism is a vital part of birth. During labor, the contraction of the uterus causes the release of a hormone called oxytocin from the hypothalamus. The hormone increases contraction frequency, which in turn stimulates the release of more oxytocin. This increasing contraction cycle propels the fetus down the birth canal and into the world. After birth, the oxytocin acts to contract the expanded uterus in order to minimize bleeding, thereby maintaining the mother’s blood volume

The importance of homeostatic mechanisms to the well being of an organism is underscored by the consequences of their failure. For example, at body temperatures of 107Â°F (42Â°C), the negative feedback systems cease to function. The high temperature then acts to speed up the body’s chemistry, raising temperature even more. This, in turn, further accelerates body chemistry, causing a further rise in temperature. This cycle of positive feedback is lethal if not halted.


Pancreas Receptors





The Liver







Fight or Flight





The homeostatic control of water is as follows

A change in water concentration leads to active via negative feedback control







This is illustrated by the flow chart below

Evolutionary Adaptations in Water Regulation




Both plant and animal adaptations are investigated


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