Thermal / Body Temperature Regulation Chapter 9 Presented by: Meghann Snyder, Kevin Lavoie, Professor Steven Dion Salem State college Sport, Fitness & Leisure Studies Department

Chapter 92 Without thermoregulation to facilitate exercise the body would overheat and the effect would result in death. Our core body temperature can drop 10 degrees and the body can still survive, but a core increase of just 5 degrees is all we can tolerate. Without thermoregulation to facilitate exercise the body would overheat and the effect would result in death. Our core body temperature can drop 10 degrees and the body can still survive, but a core increase of just 5 degrees is all we can tolerate. Many athletes have died of heat stress for this reason. It is important to know how to cool off in hot weather by understanding thermoregulation and the best ways to make it work to your advantage. Many athletes have died of heat stress for this reason. It is important to know how to cool off in hot weather by understanding thermoregulation and the best ways to make it work to your advantage.

Chapter 93 Thermal Balance A result of body mechanisms which: A result of body mechanisms which: –alter heat transfer to the shell –regulate evaporative cooling –adjust heat production

Chapter 94

5 Factors That Affect Heat Gain BMR, muscular activity, hormones, thermic effect of food, postural changes, and environment. (Total metabolic rate can increase 3 to 5 times from shivering and 20 to 25 times during sustained vigorous exercise in aerobically fit individuals. BMR, muscular activity, hormones, thermic effect of food, postural changes, and environment. (Total metabolic rate can increase 3 to 5 times from shivering and 20 to 25 times during sustained vigorous exercise in aerobically fit individuals. Heat is conserved when blood is shunted into the cranial, thoracic and abdominal cavities and portions of muscle mass for insulation from the shell. Heat is conserved when blood is shunted into the cranial, thoracic and abdominal cavities and portions of muscle mass for insulation from the shell.

Chapter 96 Factors That Affect Heat Loss Radiation, conduction, convection, and evaporation, which is most important. Radiation, conduction, convection, and evaporation, which is most important. The body is cooled when internal heat buildup causes the blood vessels to dilate and direct warm blood to the shell. The body is cooled when internal heat buildup causes the blood vessels to dilate and direct warm blood to the shell.

Chapter 97 Hypothalamic Regulation of Core Temperature The hypothalamus contains the central coordination center for temperature regulation. It initiates the responses that keep the body from overheating or overcooling The hypothalamus contains the central coordination center for temperature regulation. It initiates the responses that keep the body from overheating or overcooling Heat-regulating mechanisms are activated by either: Heat-regulating mechanisms are activated by either: –Thermal receptors in the skin or, –Temperature changes in the blood –Free nerve endings in the skin respond to heat and cold and relay the senses to the hypothalamus and cerebral cortex.

Chapter 98 Thermoregulation in Heat Stress: Heat Loss The body's thermoregulatory mechanisms primarily protect against overheating. The body's thermoregulatory mechanisms primarily protect against overheating. Body heat loss occurs in four ways: (page 271) Body heat loss occurs in four ways: (page 271) –radiation –conduction, –convection, –evaporation

Chapter 99 Heat Loss by Radiation Our bodies are usually warmer than the environment, so the air and the objects around us absorb our body heat. Our bodies are usually warmer than the environment, so the air and the objects around us absorb our body heat.

Chapter 910 Heat Loss by Conduction Heat loss by conduction involves the direct transfer of heat through a liquid, solid, or gas from one molecule to another. Heat loss by conduction involves the direct transfer of heat through a liquid, solid, or gas from one molecule to another. The rate of conductive heat loss depends on the temperature gradient between the skin and surrounding surfaces and their thermal qualities The rate of conductive heat loss depends on the temperature gradient between the skin and surrounding surfaces and their thermal qualities

Chapter 911 Heat Loss by Convection On a breezy day, cooler air continually replaces the warm air around the body, so heat loss increases because the air currents carry the heat away. On a breezy day, cooler air continually replaces the warm air around the body, so heat loss increases because the air currents carry the heat away.

Chapter 912 Heat Loss by Evaporation Water vaporization from the respiratory passages and skin surface continually transfers heat to the environment Water vaporization from the respiratory passages and skin surface continually transfers heat to the environment

Chapter 913

Chapter 914 Evaporative Heat Loss at High Ambient Temperatures Increased temperatures reduces the effectiveness of heat loss by conduction, convection, and radiation. Increased temperatures reduces the effectiveness of heat loss by conduction, convection, and radiation. When temperatures exceed the body's temperature, these mechanisms contribute to heat gain. When temperatures exceed the body's temperature, these mechanisms contribute to heat gain. When this occurs, the only avenue to dissipate heat is through evaporation. When this occurs, the only avenue to dissipate heat is through evaporation.

Chapter 915 Heat Loss in High Humidity Sweat evaporation depends on 3 things: Sweat evaporation depends on 3 things: –Surface exposed to the environment –Temperature and relative humidity of ambient air –Convective air currents around the body –Relative humidity exerts the greatest impact.

Chapter 916 Effects of Clothing on Thermoregulation in the Heat Dry clothing retards heat exchange, because if you switch to a dry shirt you do not let evaporative cooling take effect. (Sweating doesn’t cool you, evaporation does.) Dry clothing retards heat exchange, because if you switch to a dry shirt you do not let evaporative cooling take effect. (Sweating doesn’t cool you, evaporation does.) Heavy sweat shirts and rubber or plastic clothing cause high humidity near the skin and also retard evaporative cooling. Heavy sweat shirts and rubber or plastic clothing cause high humidity near the skin and also retard evaporative cooling. Loose clothing is recommended for evaporation since it permits the free convection of air between the skin and environment. Loose clothing is recommended for evaporation since it permits the free convection of air between the skin and environment. Light clothing to reflect light is recommended opposed to dark which absorbs it Light clothing to reflect light is recommended opposed to dark which absorbs it

Chapter 917 Football Uniforms Football gear causes a major barrier to heat dissipation and seals off 50% of the skin from evaporative cooling. Football gear causes a major barrier to heat dissipation and seals off 50% of the skin from evaporative cooling. The weight of the gear also makes the muscles produce more heat The weight of the gear also makes the muscles produce more heat Large players also have a small surface area to mass ratio and more body fat Large players also have a small surface area to mass ratio and more body fat Football has had many heat related deaths in the past 20 years Football has had many heat related deaths in the past 20 years

Chapter 918 The Modern Cycling Helmet does not Thwart Heat Dissipation Modern helmets are lightweight, aerodynamic, and ventilated. Modern helmets are lightweight, aerodynamic, and ventilated. They do not keep heat from escaping through the head. They do not keep heat from escaping through the head.