In addition to reflexes, another group of biological responses is of great importance for homeostasis. We shall call them local homeostatic responses. They are initiated by a change in the external or internal environment (that is, a stimulus), and they induce an alteration of cell activity with the net effect of counteracting the stimulus. Like a reflex, therefore, a local response is the result of a sequence of events proceeding from a stimulus. Unlike a reflex, however, the entire sequence occurs only in the area of the stimulus. For example, damage to an area of skin causes cells in the damaged area to release certain chemicals that help the local defense against further injury. The significance of local responses is that they provide individual areas of the body with mechanisms for local self-regulation.
Temperature-sensitive nerve endings t Signaling rate i Body temperature
Specific nerve cells in brain
Altered rates of firing
Smooth muscle in skin blood vessels t Constriction
| Heat loss
EFFERENT PATHWAY (Nerve fibers)
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.