Chapter 12: Temperature Regulation
Identify a primary adaptation of heat acclimation
Increased plasma volume
Identify a true statement about the process of conduction
It requires physical contact between the body and an object
Identify the response of the hypothalamus to an increase in core temperature
It stimulates the sweat glands
Identify the most important means of heat loss during exercise
evaporation
Heat production increases during exercise due to muscular contraction and is directly proportional to the _____
exercise intensity
The input to the temperature-regulating centers in the preoptic-anterior hypothalamus (POAH) comes from receptors in the _____ and the core
skin
The progressive decline in muscle blood flow during exercise in a hot or humid environment is due to competition for blood between the working muscles and the _____
skin
The term ____ _____ refers to the amount of heat energy required to raise 1 kg of body tissue by 1 C
specific heat
Heat/cold-sensitive neurons that sense changes in the core temperature of the body are located in both the _____
spinal cord and the preoptic-anterior hypothalamus
Complete loss of heat tolerance can occur following _____ of no heat exposure
28 days
Identify the results of the body's inability to lose heat during exercise in a hot/humid environment. (Check all that apply.)
-A high sweat rate (more fluid loss) -A high core temperature
Which of the following help cold-acclimatized people maintain heat production with less shivering? (Check all that apply.)
-An increase in the release of norepinephrine -An increase in nonshivering thermogenesis
During exercise in a hot environment, what are the major changes that occur in muscle metabolism that contribute to muscle fatigue? (Check all that apply.)
-Increased muscle lactate production -Increased skeletal muscle production of free radicals
Identify the end result of heat acclimation during submaximal exercise. (Check all that apply.)
-Lower heart rate -Lower core temperature
During exercise, specific heat for the human body is _____ per kilogram of body mass
0.83 kilocalorie
Heat tolerance can decline significantly within _____ of no heat exposure
7 days
Heat acclimation in athletes is achieved within _____ after the first exposure
7 to 14 days
Identify an impact of hyperthermia on the central nervous system
A reduction in the mental drive for motor unit recruitment
_____ is very effective in transporting heat because it has a high capacity to store heat
Blood
_____ is a form of conductive heat loss in which heat is transmitted to either air or water molecules in contact with the body.
Convection
Identify a true statement about exercising in a cold environment
It enhances an athlete's ability to lose heat
Which of the following is true of the response of the preoptic-anterior hypothalamus (POAH) to cold?
It initiates the release of norepinephrine
Which of the following is true of piloerection reflex?
It is a response to a significant drop in core temperature
Identify a common site of core temperature measurement in a laboratory setting
Rectum
True or false: People and many animals live their entire lives only a few degrees from their thermal death point
True
_____ temperature can be used as a good estimate of the actual brain temperature
Tympanic
Match the types of heat production in the body (in the left column) with their mechanisms (in the right column).
Voluntary heat production --> Heat produced during exercise Involuntary heat production --> Heat produced by shivering
Heat acclimation results in an earlier onset of sweat rate, which translates into _____
a lower core temperature
Evaporation occurs due to _____
a vapor pressure gradient between the skin and the air
The physiological adaptation that occurs when an individual undergoes repeated exposure to a stressful environment is referred to as
acclimation or acclimatization
The method of heat loss during continuous exercise is modified according to the _____
ambient conditions
The Heat Index is a measure of the _____
body's perception of how hot it feels
In the context of the four processes by which heat loss from the body may occur, radiation refers to heat loss _____
by infrared rays
Heat stress during exercise in a hot or humid environment can result in _____
cardiovascular strain
The transfer of heat from the body into the molecules of cooler objects in contact with its surface is referred to as _____
conduction
A key aspect of heat acclimation is a(n) _____
earlier onset of sweating
Once the hypothalamus responds to an increase in body temperature due to exercise, the internal temperature reaches a new _____
elevated steady-state level
True or false: High humidity decreases an individual's perception of how hot the environment feels
false
True or false: The temperature-maintenance strategy of homeotherms uses a "refrigerator" rather than a "furnace" to maintain body temperature at a constant level
false
True or false: People who are cold acclimated begin shivering at a higher skin temperature when compared to unacclimated individuals
false People who are cold acclimated begin shivering at a LOWER skin temperature when compared to unacclimated individuals.
When the body is attempting to lose heat, blood _____
flow is increased to the skin
The maintenance of a constant body temperature requires _____
heat loss to match the rate of heat production
When the relative humidity is high, the Heat Index of the body is also high due to an increase in _____
heat storage
Humans and other animals that maintain a rather constant body core temperature are called _____
homeotherms
The combined effect of fluid loss and high core temperature increases the risk of _____
hyperthermia
The combination of metabolic heat production and warm clothing prevents the development of _____ during short-term work on a cold day
hypothermia
Both hyperthermia and dehydration can directly diminish exercise performance by _____
impairing the function of the central nervous system
When human body temperature rises above 450C, it results in a(n) _____
inability to produce cellular energy
During prolonged exercise in the heat, there is a(n) _____ in the body
increase in the rate of muscle glycogen degradation
When the body temperature rises, the temperature control center in the brain responds by _____
increasing the rate of heat loss
Biochemical heat production caused by the secretion of hormones such as thyroxine and catecholamines is considered _____
involuntary heat production
In the body, the amount of heat loss due to convection is dependent on the _____
magnitude of the airflow over the skin
Women generally tolerate mild cold exposure better than men because they have _____
more body fat
According to the temperature-maintenance strategy of homeotherms, the body temperature is set _____
near the high end of the survival range
According to many exercise physiologists, _____ is the only serious threat to health from exercise
overheating
The temperature control center is an area in the brain called the _____, which works like a thermostat
preoptic-anterior hypothalamus
_____ involves the transfer of heat from the surface of one object to the surface of another, without any physical contact
radiation
In the context of continuous exercise, as the ambient temperature increases, there is a decrease in the _____
rate of convective and radiative heat loss
Additional insulation from more subcutaneous fat improves cold tolerance by _____
reducing the rate of heat loss
Identify the most important factor influencing the rate of evaporative heat loss at high environmental temperatures
relative humidity
The Heat Index is calculated by combining the air temperature and _____ to compute an apparent temperature
relative humidity
Long-term exercise in a hot or humid environment is a serious challenge to _____
temperature homeostasis
Cooling by way of evaporation is most effective _____
under conditions of low humidity
In response to an increase in core temperature, the vasomotor control center _____
withdraws the normal vasoconstrictor tone to the skin