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14 Cards in this Set

  • Front
  • Back
Objective

Give an example of how a homeostatic process works.
Homeostasis refers to temperature regulation and other biological processes that keep certain body variables within a fixed range. The process is analogous to the thermostat in a house with heating and cooling systems. Someone sets the minimum and maximum temperatures on the thermostat. When the temperature in the house drops below the minimum, the thermostat triggers the furnace to provide heat. When the temperature rises above the maximum, the thermostat turns on the air conditioner. Similarly, homeostatic processes in animals trigger physiological and behavioral activities that keep certain variables within a set range. In many cases, the range is so narrow that we refer to it as a set point, a single value that that body works to maintain. Some examples include regulation of blood levels of water, oxygen, calcium, sodium chloride, etc. Processes that reduce discrepancies from the set point are known as negative feedback.
Objective

Identify the factors that help determine an animal's body temperature.
1. Ambient temperature. Body temperature is partly determined by the range of temperatures to which an animal is exposed.

2. Physiological mechanisms. Some animals cool themselves y sweating. Species that do not sweat will instead pant or lick themselves. Sweating, panting, and licking release water, which cools the body as it evaporates. In contrast, there are some physiological mechanisms that increase body heat in a cold environment. One is shivering, which generates heat. By decreasing blood flow to the skin, animals can prevent the blood from cooling before it reaches the brain, heart, muscles, and so forth. Some animals will fluff out their fur to increase insulation.

3. Behavioral mechanisms. Finding a cool place on a hot day is much better than sweating. Finding a warm place on a cold day is much better than standing around shivering. Here are a few other behavioral mechanisms used in temperature regulation: (1) Put on more clothing or take it off (2) become more active to get warmer or less active to avoid overheating and (3) to get warm, cuddle or huddle with others.
Objective

Explain why mammals evolved a body temperature of 37ºC.
From the standpoint of muscle activity, we gain an advantage by being as warm as possible. A warmer animal has warmer muscles and therefore runs faster and with less fatigue than a cooler animal. However, we have tradeoffs. To get even hotter than 37 ˚C would require still more energy. Furthermore, beyond about 40˚C, proteins would begin to break their bonds and lose their useful properties.
Objective

Describe the role of the hypothalamus in regulating body temperature.
The most critical areas for temperature control are the anterior hypothalamus and the preoptic area, which is just anterior to the anterior hypothalamus. Because of the close relationship between the preoptic area and the anterior hypothalamus, they are often treated as a single area, the preoptic area/anterior hypothalamus (POA/AH). The POA/AH monitors body temperature by partly monitoring its own temperature. When the POA/AH is heated, an animal pants or sweats—even in a cool environment. If the same area is cooled, the animal shivers, even in a warm room. Besides monitoring their own temperature, cells of the POA/AH also receive input from temperature-sensitive receptors in the skin and the spinal cord. The animal shivers most vigorously when both the POA/AH and the other receptors are cold; it sweats or pants most vigorously when both are hot. Damage to the POA/AH impairs a mammal’s ability to regulate temperature.
Objective

Describe the benefits and risks of running a fever.
Bacterial and viral infections generally cause a fever, which is an increase in body temperature. The fever is not part of the illness; it is part of the body’s defense against the illness. When bacteria, viruses, fungi, or other intruders invade the body, the immune system mobilizes white blood cells to attack them. Certain types of bacteria grow less vigorously at high temperatures than at normal mammalian body temperatures. Other factors being equal, developing a moderate fever increases an individual’s chance of surviving a bacterial infection. However, a fever above about 39ºC (103ºF) in humans does more harm than good, and a fever above 41ºC (109ºF) can be life-threatening.
homeostasis
Temperature regulation and other biological processes that keep certain body variables within a fixed range
set point
A single value that the body works to maintain.
negative feedback
Processes that reduce discrepancies from the set point
allostasis
The adaptive way in which the body changes its set points in the response to changes in its life or changes in its environment.
basal metabolism
The energy you use to maintain a constant body temperature while at rest.
poikilothermic
Body temperatures match the temperature of the environment (ex. amphibians, reptiles, fish)
homeothermic
Species that use physiological mechanisms to maintain an almost constant body temperature over a wide range of environmental temperatures (ex. mammals and birds)
preoptic area/anterior hypothalamus
Area that monitors body temperature
cytokines
Small proteins released by white blood cells that attack intruders and also communicate with the brain