Flashcards in 10.1 Temperature Regulation Deck (42):
Psychologist Walter B. Cannon (1929) introduced the term ____ to refer to temperature regulation and other biological processes they keep the body variables within a fixed range.
Similarly, homeostatic processes in animals trigger psychological and behavioural activities that keep certain variables with in a set range. In many cases, the range is so narrow that we refer to it as a ___ ____, a single value that the body works to maintain.
Mechanisms maintain ____ blood levels of water, oxygen, glucose, sodium chloride, protein, fat, and acidity.
Processes that reduce discrepancies from the set point are known as ____ ____.
Much of ____ ____ can be described as negative feedback: something causes a disturbance, and behaviour proceeds until it relieves the disturbance.
The body's setpoints change from time to time. To describe these dynamic changes, researchers use the term ____, which means the adaptive way in which the body changes its set points depending on the situation. Much of that control depends on cell in the hypothalamus.
If you were to list your strongest motivations of life, you might not think to include ____ ____, but it has a high priority biologically.
An average young adult expends about 2600 _____ (kcal) per day. Where do you suppose all that energy goes?
Most of our energy goes to ____ ____, the energy used to maintain a constant body temperature while at rest. Maintaining your body temperature requires about twice as much energy as do all other activities combined.
Amphibians, reptiles, and most fish are ____. That is, their body temperature matches the temperature of their environment.
Poikilothermic animals lack physiological mechanisms of temperature regulation, such as shivering and sweating. The informal term is ____, but that term is misleading because poikilothermic animals remain warm most of the day by choosing an appropriate location.
Mammals and birds are ____, except that certain species become poikilothermic during hibernation. Homeothermic animals use physiological mechanisms to maintain a nearly constant body temperature despite changes in the temperature of the environment.
Homeothermy is costly, especially for small animals. An animal generates heat in proportion to its total ____, but it radiates heat in proportion to its ____ ____.
Mass : surface area
To cool ourselves when the air is warmer than body temperature, we have only one physiological mechanism – _____. Humans sweat to expose water for evaporation.
As water evaporates, it ____ the body. However, if the air is humid as well as hot, the moisture does not evaporate.
Furthermore, you endanger your health if you cannot drink enough to replace the water you lose by sweating. If you sweat without drinking, you start becoming ____. You then protect your body water by decreasing your sweat, despite the risk of overheating.
Several physiological mechanisms increase your body heat in a cold environment. One is ____. Any muscle contractions, such as those of shivering, generate heat.
A second mechanism is ____ ____ to the skin prevents the blood from cooling too much.
A third mechanism works well for most mammals, though not humans: when cold, they fluff out their fur to increase ____.
We also use ____ mechanisms, just as poikilothermic animals do. In fact, we prefer to rely behaviour when we can. The more we regulate our temperature behaviourally, the less energy we need to spend physiologically.
We ___ a great deal to support our high metabolism so that even when the weather is cold, we can still run as fast and as far as we need to.
If warmer is better, why not heat ourselves to an even ____ ____? First, maintaining a high temperature requires more fuel and energy. Second, and more importantly, beyond about 40° or 41°C, proteins begin to break their bonds and lose their useful properties.
Our body temperature of 37°C is a trade-off between the advantages of high temperature for ____ ____ and the disadvantages of high temperature for ____ ____.
rapid movement : protein stability
Birds lay eggs and sit on them, instead of developing them internally, because the birds ____ ____ is too hot for an embryo.
The physiological changes that defend body temperature – such as shivering, sweating, and changes in bloodflow to the skin – depend on areas in and near the hypothalamus, mainly the ____ ____ and the preoptic area, which is just anterior to the anterior hypothalamus.
Because of the close relationship between the preoptic area and anterior hypothalamus, researchers often treat them as a single area, the ____ ____/____ ____, or POA/AH.
preoptic area/anterior hypothalamus
The POA/AH and a couple of other hypothalamic areas send output to the hindbrain's ____ ____, which controls the physiological mechanisms.
The POA/AH monitors body temperature partly by monitoring its own ____.
That is, the animal acts as if it feels hot when it's ____ is hot, and acts as if it feels cold when it's ____ is cold.
Cells of the POA/AH also receive input from temperature receptors in the ____ and the ____. The animal shivers most vigourously when both the POA/AH and the other receptors are cold. It sweats or pants vigorously when both are hot.
skin and spinal-cord
Seperate populations of cells within the POA/AH and a couple other hypothalamic areas regulate different aspects of temperature regulation, such as _________.
shivering and changes in blood flow
After damage to all of the POA/AH, mammals can still regulate body temperature but only by the same ____ ____ that a lizard might use, such as seeking a warmer or cooler location.
Bacterial and viral infections generally cause ____, an increase in body temperature.
The fever is not part of the illness; it is part of the body's ____ against the illness.
When bacteria, viruses, fungi, or other intruders invade the body, they metabolise ____ (white blood cells) to attack them.
The leucocytes release small proteins called ____ that attack the intruders.
Cytokines also stimulate the ____ ____, which sends signals to the hypothalamus, increasing the release of chemicals called ____.
vagus nerve : prostaglandin
____ of a particular kind of prostaglandin receptor in one nucleus of the hypothalamus is necessary for fever.
A fever represents ____ ___ ____ for body temperature. Just as you shiver or sweet when your body temperature goes below or above its normal 37°C, when you have a fever of say 39°C, you shiver and sweet whenever your body temperature deviates from that level.
increased set point
Certain types of ____ grow less vigorously at high temperatures than at normal mammalian body temperature.
Fever enhances activity of the ____ ____. Developing a moderate fever probably increases an individual's chance of surviving a bacterial infection.