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Thermoregulation

Thermoregulation. Chapter 10. Mechanisms of Body Temperature Regulation . Transfer of Body Heat Conduction Convection Radiation Evaporation Humidity and Heat Loss. Mechanisms of Body Temperature Regulation. Effect of air temperature on effectiveness of avenues of heat loss.

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Thermoregulation

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  1. Thermoregulation Chapter 10

  2. Mechanisms of Body Temperature Regulation • Transfer of Body Heat • Conduction • Convection • Radiation • Evaporation • Humidity and Heat Loss

  3. Mechanisms of Body Temperature Regulation

  4. Effect of air temperature on effectiveness of avenues of heat loss

  5. Mechanisms of Body Temperature Regulation

  6. Mechanisms of Body Temperature Regulation • Efficiency of Energy Systems and Temperature • Hypothalamus • Body Temperature and Effectors • Sweat glands • Smooth muscle around arterioles • Skeletal muscle • Endocrine glands

  7. Physiological Responses to Exercise in the Heat • CV Responses • Energy Production • Glycogen dependence and lactate • Driven by epinephrine • Body Fluid Balance – Sweating • Heavy and light sweating – electrolytes • Blood volume changes – aldosterone and ADH secretion

  8. Exercise in the Heat • Heat Stress • Air temperature, humidity, air velocity, & amount of thermal radiation all influence heat stress • Wet bulb globe temperature (WBGT) – designed to account for all avenues of heat loss and gain. • Difference between WB and dry bulb is an indicator of environments ability to cool by evaporation • Black globe temperature is an indicator of environments capacity for transmitting radiated heat. • Overall challenge to body temperature is expressed as WBGT • WBGT = 0.1 TDB + 0.7 TWB + 0.2 TG

  9. Exercise in the Heat • Heat Related Disorders • Heat Cramps • Ss - severe cramping of primary muscles due to mineral losses and dehydration • Tx – move to cooler location and administer fluids or saline solution • Heat Exhaustion • Ss – extreme fatigue, dizziness, dyspnea, nausea, cold or clammy or hot and dry skin, weak, rapid pulse. • CV unable to meet body’s needs • Tx – move to cooler environment with elevated feet, salt water administered, IV saline if unconcious. If untreated can result in heat stroke

  10. Exercise in the Heat • Heat Stroke • Ss – core temperature >40⁰C (104 ⁰ F, cessation of sweating, hot and dry skin, rapid pulse and respiration, hypertension, confusion or unconciousness • Untreated can progress to coma and death • Tx – rapid cooling in a cold bath or wrapping in wet sheets and fanning the victim • Cause is failure of thermoregulatory mechanisms

  11. Exercise in the Heat • Preventing Hyperthermia • When possible decrease effort to decrease heat production • Recognize Ss of hyperthermia • When WBGT exceeds 28 ⁰C (82.4 ⁰ F) do not practice or compete outdoors • Frequent fluid breaks • Appropriate clothing – skin exposure

  12. Heat Acclimatization • Adjustments of the body to repeated, prolonged exercise bouts in the heat • Result is an increased ability to dissipate heat and reduce risk of heat illness • Sweat rate increases • Amount of sweat produced in exposed areas increases • Sweating starts earlier – creates heat gradient • Less mineral content in sweat

  13. Heat Acclimatization • Body temperature and heart rate increase to a lesser degree during exercise at any heat load • Decrease rate of glycogen utilization after acclimitization

  14. Heat Acclimatization • Achieving heat acclimatization depends on exposure to a hot environment plus • The environmental conditions during each session • Duration of heat exposure • Intensity of exercise • 5-10 days of training in the heat will result in acclimatization. • Training intensity should be reduced in first few days to prevent heat illness

  15. Exercise in the Cold

  16. Exercise in the Cold • Cold Stress – any environmental condition that causes a loss of body heat that threatens homeostasis • A decrease in skin or blood temperature stimulates mechanisms designed to produce heat and conserve heat

  17. Exercise in the Cold

  18. Exercise in the Cold • Mechanisms: • Shivering • Nonshiveringthermogenesis • Peripheral vasoconstriction • Factors to consider in heat loss • Temperature gradient • Surface area • Windchill

  19. Exercise in the Cold • Physiological Responses to Exercise in the Cold • Muscle function • Metabolic responses • Health Risks • Hypothermia • Cardiorespiratory effects

  20. Acclimatization to the Cold • Increased subcutaneous fat • Greater cold tolerance • Increased blood flow and warming of exposed areas

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