Thermoregulation is a term used to describe body temperature control mechanisms. So, protein structures and the brain are not damaged. Thermoregulatory control structures and processors are designed to keep the body core from becoming too hot or too cold. Normal core body temperature is 37 degrees centigrade or 98.6 degrees Fahrenheit. Core body temperature above 45 degrees centigrade destroys protein structures. Now, enzymes are made from proteins and are particularly susceptible to heat. And when too many enzymes are damaged, death can occur. When core body temperature falls below 34 degrees centigrade or 93.2 degrees Fahrenheit, metabolism slows way down. A slow metabolism disturbs heart activity and can also lead to death. In other words, the temperature homeostasis for effective body functioning falls within a very, very small range. Core body temperature is regulated through two parallel control processes. One is behavioral and the other is physiological. The physiological control apparatus involves peripheral and central structures. The skin and the sweat glands are the peripheral control apparatus and the brain, especially the hypothalamus is the central regulation structure. The hypothalamus is the main central structure responsible for balancing heat production with the heat loss of the body, so core temperature remains within a safe range for proteins and the brain's electrical signaling. The anterior hypothalamus responses to rising core body temperature whereas the posterior hypothalamus responds to a decrease in core body temperature. The hypothalamic temperature control mechanism resembles a thermostat in the way it works. For example, when the body temperature drops due to a cold external environment, receptors located in the skin send signals to the hypothalamic thermostat. The hypothalamus instructs the sympathetic nervous system to constrict blood vessels in the skin and the hormone thyroxin is released from the thyroid gland that increases cell heat production. Hypothalamus also initiates involuntary skeletal muscles contraction called shivering that generates heat and cold also stimulates voluntary behavior, such as huddling and hand rubbing and pacing and sheltering next to a heat source and adding layers of clothing. These processes all aid in warming the body. Now when skin heat receptors sent say, hi, environmental condition. That's very, very hot. They send alert signals to the hypothalamic thermostat in the same way. And in response, the sympathetic nervous system this time is inhibited and this causes vasodilation of the blood vessels in the skin and this helps dissipates the heat through the skin. And under extreme environmental heat, the sympathetic nervous system initiates sweating. There are also voluntary behavior responses, such as resting in the shade, wearing loose and light clothing, fanning, and drinking cold fluids that all help reduce body heat and it's also being hypothesized that high core temperatures slows the brain's activity. And this in turn, slows general body physiological functioning resulting in the sensation of fatigue. So clearly, the hypothalamus is a critical temperature control mechanism. When core body temperature drops below the safe range, the hypothalamus sets about increasing core body temperature. Blood vessels to the skin constrict, metabolic rate increases and the muscles generate heat due to involuntary shivering. And when the core body temperature becomes too hot, the hypothalamus activates the mechanisms that promote heat loss. Blood vessels in the skin dilate and there is a decreased metabolic rate, and sweating occurs.
