Chapter Summary
39.1 Animals Are Composed of Organs Built from Four Types of Tissues
Advantages of multicellularity include the ability to grow bigger and the opportunity for cells specialize.
The cells of the body are organized into assemblages called tissues.
Although there are many cell types, there are only four tissue types: epithelial, muscle, connective, and nervous tissues. Review Focus: Key Figure 39.2
Organs are made up of tissues, and most organs contain all four tissue types. Organs are grouped into organ systems. Review Figure 39.3, Activity 39.1
39.2 Physiological Systems Maintain Homeostasis of the Internal Environment
Multicellular animals provide for the needs of all their cells by maintaining a stable internal environment. That environment consists of two extracellular fluid compartments: the interstitial fluid and the blood plasma. Review Figure 39.4
Regulation of physiological systems is mostly through negative feedback. Feedforward information functions to change set points. Review Figure 39.5, Activity 39.2
39.3 Biological Processes Are Temperature-
Life is possible only within a narrow range of environmental temperatures. Q10 is a measure of the sensitivity of a life process to temperature. A Q10 of 2 means that the reaction rate of that process doubles as temperature increases by 10°C. Review Figure 39.7
Animals can acclimatize to seasonal changes in temperature through biochemical and physiological adaptations.
Even small changes in body temperature can have major physiological effects. Review Investigating Life: Can the Work Capacity of Muscle Be Increased by Extracting Heat from the Palms of the Hands?
39.4 Body Temperature Depends on the Balance between Heat In and Heat Out of the Body
The body temperature of ectotherms is determined primarily by external sources of heat. Endotherms can regulate their body temperature by varying their rates of metabolic heat production. Review Figure 39.8
Behavior is an important thermoregulatory adaptation.
The four avenues of heat exchange with the environment are radiation, convection, conduction, and evaporation. The balance between heat production and heat exchange can be expressed as an energy budget. Review Figure 39.9
Control of blood flow to the skin is an important means of temperature regulation. Review Figure 39.10
Circulatory system adaptations such as countercurrent heat exchange can conserve metabolic heat. Review Figure 39.11
39.5 Body Temperature Is Regulated through Adaptations for Heat Production and Heat Loss
Within the thermoneutral zone, resting endotherms have a basal metabolic rate (BMR) that correlates with body size. Review Figures 39.12, 39.13, Activity 39.3
In mammals, control of body temperature relies on commands from a regulatory center in the hypothalamus. This thermostat uses its own temperature as negative feedback information and skin temperature as feedforward information. Review Figure 39.15, Animation 39.1
Daily torpor and hibernation are regulated lowerings of body temperature. Review Figure 39.17
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