Introduction to Human Physiology PDF

Introduction to Human Physiology Adaptation and Acclimatization: Processes Related to Homeostasis Adaptation denotes a characteristic that favors survival in specific environments. Homeostatic control systems are inherited biological adaptations. A body's response to a particular en...

Introduction to Human Physiology Adaptation and Acclimatization: Processes Related to Homeostasis Adaptation denotes a characteristic that favors survival in specific environments. Homeostatic control systems are inherited biological adaptations. A body's response to a particular environmental stress is not fixed; prolonged exposure, for example, can improve the function of an already existing homeostatic system. This altered response to prolonged exposure is termed acclimatization. Acclimatization, therefore, is an adjustment in the homeostatic system that better adapts the person to current conditions. Acclimatization is dynamic and reversible, such that processes will continually change as environmental conditions change. An example of acclimatization would be the ascent to altitude and the physiological changes associated with gas exchange resulting from the reduction in the partial pressure of oxygen in the atmosphere. Biological Rhythms and Homeostasis A striking characteristic of many body functions is that they are rhythmic. They exhibit cyclic changes. The most common type of cyclic change in the body is circadian rhythms, which have a periodicity of approximately 24 hours. Such variation is a means of anticipating and therefore limiting fluctuations in key homeostatic variables. For example, body temperature increases just prior to the wakeful period compared to the period of sleep. An increase in body temperature enhances the efficiency of metabolic activity necessary to support wakeful actions. These rhythms are not environmentally driven; rather, they are set internally, with environmental cues acting to establish the actual hours of the basic rhythm. This process is termed entrainment. The neural basis of these rhythms is located in a collection of neurons found in the hypothalamus. The suprachiasmatic nucleus serves as the pacemaker or time clock for circadian rhythms. What do biological rhythms have to do with homeostasis? They add an anticipatory component to homeostatic control systems and, in effect, are a feedforward system operating without detectors. The negative feedback