Human body is a highly complex biological system that exists in the world, in large part due to its capability to ensure the maintenance of a stable internal environment despite the constantly changing external conditions. The body is subjected to differences in temperature, food consumption, stress, physical exercise, hydration levels and innumerable other internal and external factors every day. In spite of such fluctuations, it still operates effectively due to the presence of well-structured regulatory mechanisms that maintain internal balance. This is what is called homeostasis and the existence of feedback mechanisms is one of the most significant scientific principles of this balance. The mechanisms enable the body to sense the changes, process the changes and act in a manner that can restore normal conditions. The dynamic character of homeostasis is greatly reflected in this ongoing process and it is a fact that balance in the body is not fixed but it is a continuous process that is kept constant through continuous physiological adaptations.
Homeostasis is dynamic and so the body is never really resting internally. Although a person may look still and serene, there are numerous processes that are under monitoring and control. Blood pressure is monitored on a minute-to-minute basis, body temperature is monitored regularly, blood sugar levels are monitored post-meal and during fasting and fluid levels are maintained to aid organ functioning. The presence of feedback loops (especially, negative feedback and positive feedback) make these activities possible. Whereas negative feedback acts to undo the changes and restore the body to its natural state, positive feedback intensifies a certain process until a particular biological objective is reached. A combination of these mechanisms constitutes a scientific foundation of the way the body remains stable and survives in the ever-changing environment.
Realizing the Dynamic Character of Homeostasis
Homeostasis is the capacity of the body to have a relatively stable internal environment despite external upheavals. This entails the maintenance of body temperature, blood glucose, blood pH, fluid balance, oxygen blood levels and hormone concentrations. The rationale behind the importance of the phrase dynamic nature of homeostasis is that internal balance is not a product of holding everything constant at a single value. Rather, the body does permit slight variations within a safe zone and then constantly corrects any variance that becomes excessively large.
As an example, during exercise, it is common to experience a slight increase in body temperature and a slight decrease in body temperature during sleep. After eating, the level of blood glucose increases and falls when fasting. However these changes are not hazardous as the body notices them at their onset and triggers the body functions to reestablish the balance. It is this continual correction that renders homeostasis dynamic. It is not a passivity but a process.
All feedback systems typically comprise three primary parts: a receptor, a control center and an effector. A change is recognized by the receptor, the information is interpreted by the control center and the decision on what to do is made and the response is executed by the effector. This coordinated communication system is a good illustration of the dynamic aspect of homeostasis.
Negative Feedback: The Primary Process of Stability
The most regular type of feedback within the body is negative feedback which keeps most of the homeostatic functions in check. It operates by reversing a change such that the variable in question goes back to its normal range. To put it in simple terms, when something increases too much, negative feedback will make it fall and when it decreases too much, it will be raised by the same feedback.
The temperature regulation is one of the finest examples of negative feedback. Normal body temperature of human beings ranges at 37oc (98.6F). Thermoreceptors on the skin and in the internal organs detect the rise in body temperature, and send signals to the hypothalamus which is the thermostat of the body. This triggers cooling mechanisms like vasodilation and sweating by the hypothalamus. The evaporation of heat through Sweating and dilating blood vessels in the vicinity of the skin makes more heat available to the environment.
When the body is too cold the reverse happens. Shivering and vasoconstriction are triggered by the hypothalamus. Shivering generates heat by contracting the muscles rapidly and vasoconstriction causes blood vessels to become narrower around body parts near the skin to decrease heat loss. Response is slowed down when the temperature goes back to normal. This process of detection and correction is an ongoing cycle, which is an excellent example of the dynamic character of homeostasis.
One more obvious instance is blood glucose regulation. Blood sugar level increases after eating. The pancreas senses this rise and secretions of insulin, which assists cells to take in glucose and reduces blood sugar. When the glucose level drops below the normal range, glucagon is released by the pancreas, leading to the release of the stored glucose into the blood by the liver. This negative feedback mechanism maintains blood sugar at a safe level and stops the lack of energy and the excess of sugar.
Positive Feedback: Enhancing a Biological Process
Positive feedback does not strive to undo change as does negative feedback. Rather, it reinforces and enhances the response until a desired effect is attained. It is not as common but nevertheless, it is an essential component of the dynamic nature of homeostasis.
An archetypal illustration is childbirth. As the baby is being pushed out, the head of the baby pushes against the cervix, creating a stimulant pressure receptor. These receptors relay signals to the brain which in turn respond by releasing hormone oxytocin in the pituitary gland. Oxytocin augments the intensity and frequency of uterine contractions. When the contractions intensify, the baby presses harder on the cervix and this causes further release of oxytocin. This process goes on and becomes more intense until the baby is born. After childbirth is over, the feedback loop ceases.
Blood clotting is another crucial example. When a blood vessel is torn or ruptured the platelets accumulate at the injured area and release chemicals attracting other platelets. This causes clotting to occur quickly. The larger the number of platelets arriving, the greater the number of chemical signals released and this further speeds up the formation of clots till the bleeding is stopped. This positive feedback process is necessary to avoid undue haemorrhage.
These instances demonstrate that the process of homeostasis is dynamic and that it is not always necessary to correct it.
The Way the Body Identifies Change
To make feedback mechanisms effective, the body needs to first perceive that there has been a change. Such is the work of receptors.
The receptors are special sensory organs that keep a check on parameters like temperature, pressure, blood glucose, pH and oxygen concentration. To illustrate, thermoreceptors sense heat and cold, and baroreceptors check the blood pressure.
When a receptor detects a deviation it forwards the signal to a control center, which is often the brain or an endocrine gland. The control center makes comparisons of the current state against the normal range and decides what action is required.
This process of continuous monitoring is a powerful expression of the dynamism of homeostasis since the body is never not gathering data on itself.
The Reason Feedback Mechanisms are Critical to Surviving
In the absence of feedback mechanisms, the body would cease to survive.
During exercise or hot weather temperature may increase to dangerous levels. The blood glucose might not be returning to normal after meals and posing a risk of tissue damage. It might cause blood pressure to become unstable and essential organs would not get enough blood.
The feedback systems make sure that all organs are within safe physiological limits.
This is the importance of the dynamic nature of homeostasis. Stability does not occur by chance but is a process that is actively cherished in each second.
Examples of the Dynamic Character of Homeostasis in Everyday Life
Homeostasis is dynamic and can be seen in day-to-day life. Fluid regulation is feeling thirsty after sweating. During exercise, breathing is increased to ensure that there is a balance of oxygen and carbon dioxide. Direct feedback responses are the sweating in hot weather and shivering in cold weather.
All these examples make it possible to simplify the idea and demonstrate that feedback mechanisms are at work all the time.
Conclusion
Homeostasis and internal stability are scientifically based on feedback mechanisms. Negative feedback restores the balance by reversing the deviations whereas positive feedback intensifies the biological reactions until a certain event is fulfilled. Combined, these systems make it very clear that homeostasis is dynamic and thus, the environment within the body is maintained by continuous monitoring, signalling, and adjustment.
