11. Nutrition And Metabolism Flashcards
How is the body temperature regulation is being achieved? When do heat promoting and when heat loss mechanisms occur?
Most of the energy released as foods are oxidized escapes as heat. Less than 40% of available food energy is actually captured to form ATP.
The heat released warms the tissues and more important the blood, which circulates to all body tissues, keeping them at homeostatic temperatures which allows metabolism to occur efficiently.
Body temperature reflects the balance between heat production and heat loss. The body’s thermostat is in the hypothalamus of the brain. Through autonomic nervous system pathways the hypothalamus continuously regulates body temperature around a set point of 35.6 to 37.8C by initiating heat loss or heat promoting mechanisms.
Heat-promoting mechanisms occur when the environmental temperature is low, so the body must produce more heat to maintain normal body temperature. if the temperature of circulating blood falls, body heat must be reserved and more heat generated to restore normal body temperature. short-term means of accomplishing this are vasoconstriction of blood vessels of the skin and shivering.
When the skin vasculature constricts the skin is temporarily bypassed by the blood and blood is rerouted to the deeper more vital body organs. when this happens the temperature of the exposed skin drops to that of the external environment.
Heat-loss mechanisms occur when the body must be protected from excessively high temperatures. most heat loss occurs through the skin via radiation or evaporation. when body temperature increases above what is desirable the blood vessels serving the skin dilate and capillary beds in the skin become flushed with warm blood.
As a result heat radiates from the skin surface. If the external environment is as hot as or hotter than the body heat cannot be lost by radiation and the only means of getting rid of excess heat is by evaporation of respiration off the skin surface.
