Temperature Control in Humans
The human body maintains a normal temperature range between 35.8°C and 37.7°C, with temperatures below 34°C or above 40°C considered dangerous if sustained. Despite varying temperatures in different body regions, the core temperature remains relatively stable, typically varying by only 1 or 2 degrees Celsius.
Heat loss from the body occurs through conduction, convection, radiation, and evaporation. The insulating properties of adipose tissue in the dermis reduce heat loss, with some mammals, like whales and seals, utilizing thick layers of blubber for enhanced insulation. The effectiveness of blubber insulation depends on its water-to-fat ratio.
Internally, heat is generated through respiration in tissues, while externally, heat can be gained from the surroundings or the Sun.
The body maintains heat balance through various mechanisms like overheating and overcooling.
Overheating
- Increased blood flow near the skin’s surface facilitates greater heat exchange with the surroundings.
- Sweating occurs as sweat glands secrete sweat onto the skin surface. Evaporation of sweat absorbs heat from the body, cooling it down.
Overcooling
- Reduced blood flow near the skin’s surface minimizes heat loss to the surroundings.
- Sweat production decreases, reducing heat loss through evaporation.
- Shivering, characterized by rapid muscular contractions in the limbs, generates heat as a byproduct of muscle respiration.
- These mechanisms help regulate body temperature around 37°C. Additionally, individuals can adjust their temperature by adding or removing clothing or engaging in physical activity.
Sensory nerve endings in the skin detect heat loss or gain, influencing our perception of feeling hot or cold. While changes in core temperature are not consciously detectable, the brain plays a critical role in temperature regulation. The hypothalamus contains a thermoregulatory center with temperature receptors that monitor blood temperature changes and coordinate appropriate responses. Temperature receptors in the skin also send information to the brain regarding temperature changes, contributing to overall temperature regulation.
