How does cold exposure cause hypothermia?
During exposure to cold temperatures, most heat loss – up to 90% – escapes through your skin; the rest, you exhale from your lungs. Heat loss through the skin happens primarily through radiation and speeds up when skin is exposed to wind or moisture. If cold exposure is due to being immersed in cold water, the movement of waves and water can increase heat loss up to 50%. The hypothalamus, the brain’s temperature control centre, works to raise body temperature by triggering processes that heat and cool the body. During cold temperature exposure, shivering is a protective response to produce heat through muscle activity. In another heat-preserving response – called vasoconstriction – blood vessels temporarily narrow. Normally, the activity of the heart and liver produce most of your body heat. However, as core body temperature cools, these organs produce less heat, in essence causing a protective “shut down” to preserve heat and protect the brain. Low body temperature can slow brain acti
