BPK 142 Chapter Notes - Chapter 12.1: Vasoconstriction, Hypoglycemia, Cardiac Output

• School: Simon Fraser University
• Department: Biomedical Physio & Kines
• Course: BPK 142
• Professor: All

Document Summary

Heat balance, mechanisms of heat loss, radiation - the exchange of electromagnetic energy waves emitted from one object and absorbed by another, conduction - occurs whenever two surfaces with differing temperatures are in direct contact. Still air is an excellent insulator, while water is an excellent conductor. Heat conduction in water is about 25 times greater than in air. For example, heat transfer from skin to moving air or water. Wind chill index - gives the equivalent still air temperature for a particular ambient temperature at different wind velocities. The temperature gradient between the skin and air and the air velocity are important factors in determining convective heat loss. Because the superficial blood vessels in the head do not constrict in the cold, the head is an important source of heat loss - accounts for 30 - 35% of total heat loss at rest. Behavioural responses to the cold are important - clothing, seeking shelter, starting a fire, etc.