The term Homeostasis was stamped in 1930 by the physician Walter Cannon, who reported in his book,” The Wisdom of the Body”, about the homeostasis in human bodies. His description included how our bodies are able to balance the internal temperature and other components of the blood despites other external changes. This mechanism is applied to most of environmental events on earth. The word homeostasis is originally derived from the two Greek words “homo” which means “same” and “stasis” which refers to “steadiness”. The definition of homeostasis is then adapted as the tendency towards balance environment within physiological components.
The importance of hemostasis comes from the maintenance of human bodies balanced regardless the outer conditions. This process is directed by certain regulators, that communicate with each other in order to keep all body systems stable. The nervous system with its neurotransmitters and the endocrine system via hormones collaborate to organize this mechanism. The organization involve blood components, such as concentrations of sodium, potassium and calcium ions, and levels of blood sugar. It also involves the extracellular fluids and pH levels. All these remain within certain limits regardless the external conditions like hunger, heat, cold, etc...
Overall, the homeostasis process flows within the following steps. First, the receptor responds to the stimuli. The receptor is an organ(s) of sensory or afferent neurons, specialized to be sensitive to stimulating agents. When responding to these agents, it sends signals (inputs) to the control center through the afferent way. The control center runs the mechanism by detecting the action required to be done in order to preserve the static environment of the body. It sends its instructions to the effector through the efferent way, that in turn comes back with the suitable response.
After detecting the suitable response, the stimuli act either by decreasing (negative feedback) or increasing (positive feedback) the change. As a result, the change could be restricted or persisted until recovering to the homeostatic status.
We can simulate negative feedback with a thermostat to facilitate understanding. Imagine home heating system connected to a thermostat being set at 20°C (68°F). The heating system refers to the effector and the thermostat itself refers to the receptor and the control center. When room temperature exceeds 20°C, the thermostat will alert the system in order to restrict its activity. That is what we call negative feedback, and our bodies work in similar course, in which homeostatic status is controlled. The final effect of the stimulus triggers the system to reduce or stop the response. Some dynamics applies to negative feedback are: body temperature, heart rate, blood pressure, breathing rate, the release of hormones, and blood levels of glucose (blood sugar), oxygen, carbon dioxide, and minerals.
In contrast to negative feedback, positive feedback exacerbates the response. Some of the rare examples of this mechanism are baby delivery and coagulation as they happen in such exclusive situations. It is uncommon to encounter this mechanism because it tends to aggravate the original stimulus.
Our body systems work collaboratively to maintain the dynamics within normal ranges, although that each system acts with distinct functions. For example, the cardiovascular and lymphatic systems work on transporting body liquids with both solutes and water to control the pressure. In turn, the urinary system controls density of urine throughout increasing or decreasing the amount of water forming it. Thus, when water levels go too high, the kidney work on diluting urine and secreting the excess water out of the body, and vise versa. Another systems involved in controlling water levels are the integumentary and respiratory systems, but they work with different mechanisms. Digestive system also manages amounts of water by absorbing it from gastrointestinal lumens.
Another important hemostatic balance controlled by multiple systems is body temperature. The cardiovascular, integumentary, respiratory, and muscular systems all work on this mission. Dilation of skin blood vessels and sweat secretion for example are responses to high temperature levels. In contrast, when temperature levels fall, blood vessels in the skin contract, skin hair rise, muscles shiver to produce more heat, and blood that goes to extremities slows down, and that is why we have pale palms during cold temperatures. Oxygenation also is crucial to our bodies, and maintain delivering proper amounts is helped by the respiratory system, especially during exercises. When we play sport, we breath heavily just to get more oxygen to our muscles and get rid of the extra carbon dioxide produced by them.
Aging is the physiologic process on which our body does not response efficiently, and our status become less steady. This situation is called hemostatic imbalance. Hemostatic imbalance disturbs normal defenses and make the more susceptible to illnesses and diseases.
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