F4: The body’s physiological response to high temperatures Jess HOMEOSTASIS AND THERMOREGULATION: Metabolic processes and optimal functioning of body cells require an internal body temperature of 37°C. At this temperature, enzymes are able to function at its maximum capacity and hence homeostasis (maintaining steady temperature despite external temperature changes) is incredibly important within the human body. The hypothalamus (located above the brainstem) governs body temperature through the synthesis of hormones with neural feedback mechanisms. Temperatures that are above 37°C will cause the enzyme to denature; ruining it’s active site and hence the enzyme will lose its function as it can no longer bind to the substrate. Due to this matter, sweating of the skin occurs almost instantly when the skin’s temperature reaches 37°C. If the temperature drops below 37°C, the enzymes will decrease the rate of metabolic processes and a range of responses will occur to ensure an increase in heat production.

HEAT TRANSMISSION: Temperature regulation in the human body is extremely important as it must be maintained at 37°C, as mentioned before. There are four methods of heat transfer both in and out of the human body to maintain this temperature:

• Conduction – heat directly being transmitted through an object due to difference in temperature or electrical potential • Convection (sensible heat) –movement in circular motion of heat in one region to another

• Radiation – emission of heat energy waves or particles

BMS1031 -­‐ Lisa Hai My Do

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Latent heat (evaporation/conduction)-­‐ the conversion of solid state into liquid state or liquid state to vapour state

Figure1 “The four forms of heat transfer” http://www.fao.org/docrep/008/y7223e/y7223e09.htm

RESPONSES TO HIGH TEMPERATURE: When your body is exposed to extremely high temperatures, it must regulate itself to maintain a stable internal temperature and hence must transfer the excessive heat to the environment utilising the four heat transfer mechanisms. The human body can either increase the conduction rate or the transfer rate to elevate the rate of heat transmission; where the rate of conduction is the movement of heat from core to surface and the rate of transfer is the movement of heat from surface to environment. The rate of conduction is dependent on the dilation and contraction of vessels, while perspiration, clothing option, external temperature and level of activity affects the transfer rate.

Sdsdssssss – Latent Heat of the body: When the external temperature is greater than 37°C, sweat glands are simulated by sympathetic cholinergic fibers and epinephrine in the blood. The sweat then evaporates