body temperature

[snow_storm]

If your body feels cold what does it do?

[Robb Phoenix]

Shivers, to generate heat.
Very low temperatures or sudden exposure to cold may also lead to hypothermia.

[Robb Phoenix]

Normal body temperature in humans is 36.6 �C (97.9 �F). Hypothermia can be divided in three stages of severity. In stage 1, body temperature drops by 1-2�C below normal temperature (1.8-3.6�F). Mild to strong shivering occurs. The victim is unable to perform complex tasks with the hands; the hands become numb. Blood vessels in the outer extremities constrict, lessening heat loss to the outside air. Breathing becomes quick and shallow. Goose bumps form, raising body hair on end in an attempt to create an insulating layer of air around the body (which is of limited use in humans due to lack of sufficient hair, but useful in other species). Often, a person will experience a warm sensation, as if they have recovered, but they are in fact heading into Stage 2. Another test to see if the person is entering stage 2 is if they are unable to touch their thumb with their little finger; this is the first stage of muscles not working.

In stage 2, body temperature drops by 2-4�C (3.6-7.2�F). Shivering becomes more violent. Muscle mis-coordination becomes apparent. Movements are slow and labored, accompanied by a stumbling pace and mild confusion, although the victim may appear alert. Surface blood vessels contract further as the body focuses its remaining resources on keeping the vital organs warm. The victim becomes pale. Lips, ears, fingers and toes may become blue.

[Robb Phoenix]

In stage 3, body temperature drops below approximately 32 �C (89.6 �F). Shivering usually stops. Difficulty speaking, sluggish thinking, and amnesia starts to appear; inability to use hands and stumbling is also usually present. Cellular metabolic processes shut down. Below 30 �C (86.0 �F), the exposed skin becomes blue and puffy, muscle coordination becomes very poor, walking becomes almost impossible, and the victim exhibits incoherent/irrational behavior including terminal burrowing or even a stupor. Pulse and respiration rates decrease significantly but fast heart rates (ventricular tachycardia, atrial fibrillation) can occur. Major organs fail. Clinical death occurs. Because of decreased cellular activity in stage 3 hypothermia, the body will actually take longer to undergo brain death.

[wildwood]

Good grief Robb, all I was going to say is that a reaction to the body feeling cold is that it lifts the body hairs away for the skin to create an insulating layer - this is a remnant involuntary bodily reaction from the days when we were more hairy.

I feel a bit insignificant now.

[Peter Pedant]

yeah shivering,
piloerection

no-one has yet mentioned non shivering thermogenesis, and the other thing frequently ignored is behavioural - you automatically seek out a warm envirnment or do warming things like jump around.

[laurenw5811]

Vasoconstriction
The blood vessels near the surface of your body, become narrower so that less heat (from the blood) reaches the surface & has a chance to radiate out