The human body is a marvellous machine when you put into consideration that billions, even trillions of cells are in constant activity and you rarely notice that something goes wrong with the activity of the cells. The ability of the body to orchestrate such a harmony is a wonder in its own right.
The word homeostasis is a term coined by Walter Cannon in order to describe the wisdom of the body. By coining the term homeostasis, Walter Cannon is trying to explain the ability of the body to maintain relatively stable internal conditions with respect to the dynamic changes that are happening outside the confines of the body.
Homeostasis is not merely referring to the unchanging state but rather point towards a dynamic, constant change in order to attain something of balance or equilibrium. Even if the body is in homeostasis, changes in internal conditions do happen but within a very narrow limit.
Homeostatic Control Mechanisms
One vital and fundamental fact in order for the body to attain homeostasis is the ability of the individual cells and organ-systems to communicate with one another. This is the burden relied on the nervous and the endocrine systems. Electric impulses, coupled with hormones, act as messengers that constantly give the internal occupants of the body an open communication.
Three interdependent components are present in all control mechanisms for homeostasis to occur. First on the list is the receptor which monitors the condition and receives stimuli. This stimulus is then sent to the control centre for further interpretation. The control centre is the second component in the control mechanism and is tasked in interpreting the stimuli sent by the receptors. The control centre is the one that analyzes and then it makes the necessary action or response. The last component is the effector. The effector is the working arm of the control centre since it is the means by which changes will be made. The changes made will have an effect on the stimulus, whether to enhance it or depress it. It all depends on the analysis of the control centre.
Negative Feedback Mechanisms
From the word negative, this feedback mechanism aims to depress or to some extent shut off the original stimulus. This is the most common feedback mechanism, aiming to reduce the intensity of a stimulus.
An example of this mechanism may be likened to a home heating system. In the body, the ideal temperature is set to 37 degrees Celsius. When internal temperatures go down, the hypothalamus which serves as the body’s own thermostat kicks into action to correct the change. It then sends stimuli that cause actions to produce heat, thereby bringing the internal temperature back to within normal range.
The ability of the body to regulate body temperature is just one of the many known ways that the nervous system acts in order ideal body temperature. Other example of negative feedback mechanism is the split-second withdrawal of the hand when touching a hot surface.
The endocrine system works differently because it employs hormones to do the controlling task. An example of this mechanism is best seen when studying the ADH as it controls blood volume. When the blood volume decreases, ADH compels the kidneys to retain more water and return it to the bloodstream. This action then increases the blood volume and when the desired volume is attained, ADH secretion is shut off.
Positive Feedback Mechanisms
This type of feedback mechanism is not common and it aims in increasing or enhancing the original stimulus. This in turn will accelerate the activity tied with that stimulus. An example of this mechanism is best seen with the hormone oxytocin during labour. Oxytocin continues to be released in order for labour contractions to intensify during delivery. When the baby is delivered, the release of oxytocin is stopped.