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How do endotherms control their body temperature

Biology assessment
by Aaron Nazareth on 20 November 2012

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Transcript of How do endotherms control their body temperature

How do endotherms
control their body temperature? Behavioural mechanisms(C grade) Respiration (D-grade) The Processes (B Grade) Thermoregulatory centre monitors (A* grade) Animals other than humans regulate and maintain their body temperature with physiological adjustments and behaviour. Desert lizards are ectotherms and so unable to metabolically control their temperature but can do this by altering their location. They may do this by in the morning only raising their head from its burrow and then exposing their entire body. By baking in the sun, the lizard absorbs solar heat. It may also absorb heat by conduction from heated rocks that have stored radiant solar energy. To lower their temperature, lizards exhibit varied behaviours. Sand seas, or ergs disambiguation needed, produce up to 57.7C and the sand lizard will hold its feet up in the air to cool down, seek cooler objects with which to contact, find shade or return to their burrow. They also go to their burrows to avoid cooling when the sun goes down or the temperature falls. Homeostasis is maintained by the respiratory system in two ways: gas exchange and regulation of blood pH. Gas exchange is performed by the lungs by eliminating carbon dioxide (CO2), a waste product given off by cellular respiration. As CO2 exits the body, oxygen needed for cellular respiration enters the body through the lungs. ATP, produced by cellular respiration, provides the energy for the body to perform many functions, including nerve conduction and muscle contraction. Lack of O2 affects brain function, sense of judgment, and a host of other problems. Sweating – The secretion of fluids by sweat glands from the skin of mammals. Sweating allows the body to regulate its temperature. Sweating is controlled from a center in the preoptic and anterior regions of the brain's hypothalamus, where thermo sensitive neurons are located.
Shivering - (also called shuddering) is a bodily function in response to early hypothermia in warm-blooded animals. When the core body temperature drops, the shivering reflex is triggered to maintain homeostasis. Muscle groups around the vital organs begin to shake in small movements in an attempt to create warmth by using energy. Shivering can also be a response to a fever, as a person may feel cold.
Vasodilation - the increase in the internal diameter of blood vessels that is caused by relaxation of smooth muscle within the wall of the vessels, thus causing an increase in blood flow.
Vasoconstriction - When blood vessels dilate, the blood flow is increased due to a decrease in vascular resistance.
Movement of hairs on the skin surface - When it is cold, our skin acts to prevent heat loss. The hair muscles contract and make the hair stand more upright. This traps warm still hair close to the surface of the skin. Less heat is lost by radiation. Sweat glands stop making sweat. Blood vessels near the surface of the skin get narrower, so more blood gets near to the surface. This reduces heat loss by radiation.When it is hot our skin acts to incease heat loss. The hair muscles relax and make the hairs lie flat. This traps warm still hair close to the surface of the skin. Less heat is lost by radiation. Sweat glands make sweat. Blood vessels near the surface of the skin get narrower, so less blood gets near to the surface. This increases heat loss by radiation. Negative feedback mechanisms consist of reducing the output or activity of any organ or system back to its normal range of functioning. A good example of this is regulating blood pressure. Blood vessels can sense resistance of blood flow against the walls when blood pressure increases. The blood vessels act as the receptors and they relay this message to the brain. The brain then sends a message to the heart and blood vessels, both of which are the effectors. The heart rate would decrease as the blood vessels increase in diameter (known as vasodilation). This change would cause the blood pressure to fall back to its normal range. The hypothalamus, which monitors the body temperature, is capable of determining even the slightest variation of normal body temperature (37 degrees Celsius). Response to such variation could be stimulation of glands that produce sweat to reduce the temperature or signaling various muscles to shiver to increase body temperature. Difference between endotherms and ectotherms relating to thermoregulation(A* grade) Endotherms are capable of internally regulating their body temperature - they generally have a layer of insulation (fur, fat etc) and use a high proportion of their energy intake to maintain a stable body temperature which does not vary with the temperature of their environment. Ectotherms do not internally regulate their body temperature and take on a temperature which is more closely linked to the temperature of their environment - so if it's cold, their body temperature will be low. Ectotherms may modify their body temperature through certain actions such as basking in the sun. Mammals are endotherms; amphibians are an example of an ectotherm. Body temperatures of different endotherms (A* grade) Birds: Around 40.6 degrees(C)
Mammals: Around 37.2 degrees (C)
Tuna fish: Between 23.3 and 35 degrees (C)
Skunk cabbages: Around -1.1 degrees (C)
Butterflies: Around 30 degrees (C)
Honey bees: Around 35 degrees (C) A grade Done in the B and C grade parts
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