Why is it cold for people, why is it cold for a person and when it’s not cold?
Women are more likely to say that they are colder than men in the same environment.
When HMS Beagle landed on the south shore of Tierre del Fuego, Charles Darwin noted the ability of locals to cope with the cold: A woman, with a recently born baby on her chest, came to the boat the other day and remained standing there out of sheer curiosity while a drizzle fell and covered her bare skin, and the bare skin of a baby on her chest.
Japanese divers can endure long periods of cold water without the comfort of a diving suit, while many of us shiver in the waters of the relatively warm Pacific and Indian Oceans.
Why is there such a difference in reactions to cold?
The perception of cold starts when the nerve endings of the skin send impulses to the brain about skin temperature. These impulses not only show the skin temperature, but also the amount of change in skin temperature.
Therefore, we are much colder when we dip into cold water, when our skin temperature drops drastically, than when we slowly enter water, when our skin temperature is low but constant.
The onset of nerve impulses of falling skin temperature gives us an early warning of events that could cause the internal organs to fall in temperature. Unless we look at the warning, the temperature of the internal organs could fall dramatically and cause deadly hypothermia or cold.
In healthy people, psychological systems prevent hypothermia. Skin impulses reach the hypothalamus, the area of the brain that is responsible for controlling the interior of the body, which in turn generates instructions in the nervous system to prevent a fall in body temperature.
The nerve impulses sent to the muscles produce additional metabolic heat through shivering. Blood vessels that would normally transfer warm blood from the internal organs to the skin, where the blood would lose heat, shrink and retain most of the blood, and heat in the internal organs.
The impulses arrive at the cerebral cortex, where most of the thinking takes place, so it generates information about how cold we are. This information is combined with the impulse of the limbic system, which is responsible for our emotional state, to determine exactly how cold we feel and how we feel. These feelings motivate us to change behavior, such as fetal posture or wearing more clothes or regret.
The feeling of cold is not the same as the cold itself. Jumping into a cold lake may be cold, but it can increase the body temperature due to the abrupt narrowing of blood vessels, which causes warm blood to remain inside, and no heat is consumed over the skin. In this way, body temperature can remain elevated for up to one hour after the jump.
Many of us are cold at the onset of the flu, when body temperature begins to rise. During the flu, the nerve circuits that control body heat move to a higher level, so the body responds as if it is cold until the temperature stabilizes around that area of elevated temperature.
But while the flu indicates a problem, is everything okay when we are cold and not really cold?
Some of us are in bad luck and suffer from the Raynaud phenomenon, a condition in which the blood flow is too slow to keep your fingers and toes warm. Feeling cold in pregnancy, when the fetus acts like a small furnace, could indicate a lack of thyroid hormone activity, which requires hormone therapy.
But some perfectly healthy people may feel colder than others in the same environment. Women are often colder than men, probably due to a decrease in skin temperature, a consequence of more subcutaneous fat and estrogen.
Some of us inherit a greater sensitivity to cold. Research conducted on twins shows that cold hands and feet are hereditary, implying a genetic basis for excessive temperature perception. For some of us it is simply cold because of the way people look to us, the phenomenon of catching cold. In one study, healthy volunteers felt colder when they were shown a video of their actors acting cold, than of acting warm. The temperature of volunteers’ hands dropped due to narrowing of blood vessels, even when they were not in a cold environment.
Most of us who are healthy but constantly cold, however, can blame ourselves. Unlike the Darwin Fuegians, we are accustomed to being pleasantly warm. In the developed world, we are rarely exposed to the cold, with the help of warm clothing and shoes and even heating.
Allowing this conformism and not accustoming our metabolism to the cold could contribute to obesity. We would probably all be better off if we got more cold.