Figure 18 Extreme Heat Humans adapt to some degree to

Last updated: 8/28/2023

Figure 18 Extreme Heat Humans adapt to some degree to repeated exposure to high temperatures credit McKay Savage flickr The body can also respond effectively to short term exposure to cold One response to cold is shivering which is random muscle movement that generates heat Another response is increased breakdown of stored energy to generate heat When that energy reserve is depleted however and the core temperature begins to drop significantly red blood cells will lose their ability to give up oxygen denying the brain of this critical component of ATP production This lack of oxygen can cause confusion lethargy and eventually loss of consciousness and death The body responds to cold by reducing blood circulation to the extremities the hands and feet in order to prevent blood from cooling there and so that the body s core can stay warm Even when core body temperature remains stable however tissues exposed to severe cold especially the fingers and toes can develop frostbite when blood flow to the extremities has been much reduced This form of tissue damage can be permanent and lead to gangrene requiring amputation of the affected region Everyday CONNECTION Controlled Hypothermia As you have learned the body continuously engages in coordinated physiological processes to maintain a stable temperature In some cases however overriding this system can be useful or even life saving Hypothermia is the clinical term for an abnormally low body temperature hypo below or under Controlled hypothermia is clinically induced hypothermia performed in order to reduce the metabolic rate of an organ or of a person s entire body Controlled hypothermia often is used for example during open heart surgery because it decreases the metabolic needs of the brain heart and other organs reducing the risk of damage to them When controlled hypothermia is used clinically the patient is given medication to prevent shivering The body is then cooled to 25 32 C 79 89 F The heart is stopped and an external heart lung pump maintains circulation to the patient s body The heart is cooled further and is maintained at a temperature below 15 C 60 F for the duration of the surgery This very cold temperature helps the heart muscle to tolerate its lack of blood supply during the surgery Some emergency department physicians use controlled hypothermia to reduce damage to the heart in patients who have suffered a cardiac arrest In the emergency department the physician induces coma and lowers the patient s body temperature to approximately 91 degrees This condition which is maintained for 24 hours slows the patient s metabolic rate Because the patient s organs require less blood to function the heart s workload is reduced Narrow Range of Atmospheric Pressure Pressure is a force exerted by a substance that is in contact with another substance Atmospheric pressure is pressure This OpenStax book is available for free at tmptions org contentcl11496 1 Chapter 11 An Introduction to the Human Body 19 exerted by the mixture of gases primarily nitrogen and oxygen in the Earth s atmosphere Although you may not perceive it atmospheric pressure is constantly pressing down on your body This pressure keeps gases within your body such as the