Temperature is an indicator of the amount of heat contained in a system. Heat is a form of energy and every reaction in a human body occurs at a certain energy or temperature level. It's essential for the normal functioning of the human body, that this internal temperature be maintained. That's why, the core body temperature of a human body is an important factor, which is always considered while evaluating the health condition in a checkup.
What is the Normal Core Body Temperature Range in Humans?
An important difference between mammals, including humans and other organisms like reptiles is that we are warm blooded creatures. The body temperature of mammals is maintained at a constant level, despite the changes in environmental temperature.
Core temperature is the exact temperature at which all the functions of the human body can go ahead with optimal efficiency. The temperature of human body is not uniform throughout and it is higher in the internal organs, than on the outside. It is considered to be the temperature of internal organs and it is very slightly higher than the temperature in the external skin layers. Normally the rectal temperature or vaginal temperature is considered as the core temperature. The ideal core temperature is considered to be around 98.6° Degree Fahrenheit or 37° degree Celsius. This temperature is however, the average body temperature and the overall normal temperature varies from a minimum of 97.7° Fahrenheit (36.5° Celsius) to a maximum of almost 99.5° Fahrenheit (37.5° Celsius). Any temperature above or below this range is abnormal. At the ideal temperature, all human body systems function with maximum efficiency.
The average temperature varies throughout the time of the day and physiological condition of a person. One important factor that decides this temperature is the base metabolic rate of a body, which is the rate at which we burn calories and use up our energy stores. Other factors like administration of medications can also affect it.
It has been discovered that core body temperature is the lowest around 4 a.m. and attains the highest temperature around 4 p.m. in the afternoon. The variation is controlled by the circadian rhythm to which our bodies are naturally adapted. This range or margin of temperature variation is about 0.5 to 0.6° Celsius.
What sustains the human body is a series of chemical reactions, regulated by enzymes. These reactions can occur only at an optimum energy level and temperature. If the body temperature is not maintained, then these chemical reactions cannot occur and it can lead to several problems. That's why we cannot survive for long in too cold or too hot conditions for an extended period of time.
How is the Temperature Regulated?
How is temperature regulation or thermoregulation of the human body achieved? The control center for body temperature lies in the brain and it's known as hypothalamus. When we are in colder and lower temperature surroundings, the temperature of the body starts going down, due to the higher rate at which heat is radiated from the body. In such conditions, the hypothalamus gets alerted and it reduces blood flow towards the external layers of skin and directs it more, towards the internal organs, whose functioning needs to be sustained. This is achieved by the constriction of blood vessels that carry blood to external layers of skin. Also, the hypothalamus triggers shivering which is actually our body's way of generating heat to counter the cold.
The hypothalamus initiates an exactly opposite action when the environmental temperature goes high above the maximum temperature. It directs the blood flow more towards the skin than the internal organs, so that more heat is radiated out. That's why, many fair people turn red, when they've been in the sun for too long. Sweating is another mechanism through which our body loses heat in such conditions. The human body is a beautiful and well oiled machine which is designed to adapt to external conditions through internal regulatory mechanisms.