The Basics of Mammalian Temperature Regulation

The Basics of Mammalian Temperature Regulation Do you find it surprising that reindeer, which spend much of their time standing in snow, dont get cold feet? Or that dolphins, whose thin flippers are gliding constantly through cool water, still manage to pursue very active lifestyles? A special circulatory adaptation known as countercurrent heat exchange enables both of these animals to maintain the appropriate body temperature in their extremities, and this is only one of the many clever adaptations mammals have evolved over the last hundred million years to help them to deal with variable temperatures. Mammals Are Endothermic All mammals are endothermic- that is, they maintain and regulate their own body temperature, no matter the external conditions. (Cold-blooded vertebrates, like snakes and turtles, are ectothermic.) Living in widespread environments around the world, mammals face daily and seasonal fluctuations in temperatures and some- for example, those indigenous to harsh arctic or tropical habitats- have to deal with extreme cold or heat. To maintain their correct internal body temperature, mammals must have a way to produce and conserve body heat in colder temperatures, as well as dissipate excess body heat in warmer temperatures. The mechanisms mammals have for producing heat include cellular metabolism, circulatory adaptations,  and plain, old-fashioned shivering. Cellular metabolism is the chemical process that constantly occurs within cells, by which organic molecules are broken down and harvested for their internal energy; this process releases heat and warms the body. Circulatory adaptations, such as the countercurrent heat exchange mentioned above, transfer heat from the core of the animals body (its heart and lungs) to its periphery via specially designed networks of blood vessels. Shivering, which youve probably done some of yourself, is easiest to explain: this crude process generates heat by the rapid contraction and shaking of muscles.   If An Animal Gets Too Warm What if an animal is too warm, rather than too cold? In temperate and tropical climates, excess body heat can accumulate quickly and cause life-threatening problems. One of natures solutions is to place blood circulation very near the surface of the skin, which helps to release heat into the environment. Another is the moisture produced by sweat glands or respiratory surfaces, which evaporates in comparatively dryer air and cools the animal down. Unfortunately, evaporative cooling is less effective in dry climates, where water is rare and water loss can be a real problem. In such situations, mammals, like reptiles, often seek protection from the sun during the hotter daylight hours and resume their activity at night. The evolution of warm-blooded metabolisms in mammals wasnt a straightforward affair, as witness the fact that many dinosaurs were apparently warm-blooded, some contemporary mammals (including a species of goat) actually have something akin to cold-blooded metabolisms, and even one type of fish generates its own internal body heat.

Learn More About Marie Curie and Radioactive Elements

Learn More About Marie Curie and Radioactive Elements Dr. Marie Curie is known to the world as the scientist who discovered radioactive metals such as radium and polonium. Curie was a Polish physicist and chemist who lived between 1867-1934. She was  born Maria Sklodowski in Warsaw, Poland, the youngest of five children. When she was born, Poland was controlled by Russia. Her parents were teachers, and she learned at an early age the importance of education. Her mother died when she was young, and when her father was caught teaching Polish - which had been made illegal under the Russian government. Manya, as she was called, and her sisters had to get jobs. After a couple of failed jobs, Manya became a tutor to a family in the countryside outside Warsaw. She enjoyed her time there, and was able to send her father money to help support him, and also send some money to her sister Bronya in Paris who was studying medicine. Bronya eventually married another medical student and they set up practice in Paris. The couple invited Manya to live with them and study at the Sorbonne - a famous Parisian University. In order to fit in better at the school, Manya changed her name to the French Marie. Marie studied physics and mathematics and quickly received her masters degrees in both subjects. She remained in Paris after graduation and started research on magnetism. For the research she wanted to do, she needed more space than her small lab. A friend introduced her to another young scientist, Pierre Curie, who had some extra room. Not only did Marie move her equipment into his lab, Marie and Pierre fell in love and married. Radioactive Elements Together with her husband, Curie discovered two new elements (radium and polonium, two radioactive elements that they extracted chemically from pitchblende ore) and studied the x-rays they emitted. She found that the harmful properties of x-rays were able to kill tumors. By the end of World War I, Marie Curie was probably the most famous woman in the world. She had made a conscious decision, however, not to patent methods of processing radium or its medical applications. Her co-discovery with her husband Pierre of the radioactive elements radium and polonium represents one of the best-known stories in modern science for which they were recognized in 1901 with the Nobel Prize in Physics. In 1911, Marie Curie was honored with a second Nobel prize, this time in chemistry, to honor her for successfully isolating pure radium and determining radiums atomic weight. As a child, Marie Curie amazed people with her great memory. She learned to read when she was only four years old. Her father was a professor of science and the instruments that he kept in a glass case fascinated Marie. She dreamed of becoming a scientist, but that would not be easy. Her family became very poor, and at the age of 18, Marie became a governess. She helped pay for her sister to study in Paris. Later, her sister helped Marie with her education. In 1891, Marie attended the Sorbonne University in Paris where she met and married Pierre Curie, a well-known physicist. After the sudden accidental death of Pierre Curie, Marie Curie managed to raise her two small daughters (Irà ¨ne, who was herself awarded a Nobel Prize in Chemistry in 1935, and Eve who became an accomplished author) and continue an active career in experimental radioactivity measurements. Marie Curie contributed greatly to our understanding of radioactivity and the effects of  x-rays. She received two Nobel prizes for her brilliant work, but died of leukemia, caused by her repeated exposure to radioactive material.