STPM Biology - chapter 9: Revision essay question 4

4. By using a specific organisms, explain how an endothermic organisms              
                         maintains its body temperature when the external temperature drops.

Answer


Endotherm such as humans use metabolic energy(internally generated energy) to mantain a
 constant body temperature.
     -Decrease in external temperature is detected by thermoreceptors(bulb of Krausse) in the skin.
     -Impulse is sent to hypothalamus, the temperature regulatory centre.
     -Hypothalamus then sends action impulse to the following effectors:
         ~Vasocontriction(diameter reduce) of subcutaneous capillaries occurs to reduce blood flow to
            the skin.
         ~Since blood transports heat, less heat is lost through the skin.
         ~Erector muscles on the skin contracts, hair on the skin becomes erect to trap a thick layer of
            air.
         ~The layer of air acts as an insulating layer to reduce heat loss through the skin.
         ~The medulla oblongata release impulse to skeletal muscles, which causes the skeletel
            muscles
            to contract and relax alternatively.
         ~Shivering occurs, contraction of the skeletel muscle muscle release heat to increase the body
            temperature.
         ~Thyroid gland secretes thyroxin, which increase the basal metabolic rate of the body to
            increase heat production.
         ~Adrenal gland secretes adrenaline to increase the conversation rate of glycogen to glucose in
            the liver.
         ~The glusoce produced is used for heat production in the body.
    -All of these physiological changes maintaince the body temperature at the normal range(37ºc).