a compend of human physiology

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Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: lions which are exhibited by different portions of the body are comprised under the term reflex action, for the reason that they are the immediate results of stimulations of afferent nerves at their peripheral terminations and, in a general way, may be said to take place independently of the brain. The conversion of an afferent impulse into an efferent impulse takes place in a nerve center, termed a reflex center. The parts involved in any reflex act are as follows:— 1. A sentient surface : skin, mucous membrane, sense organ, etc. 2. An afferent nerve fiber. 3. A receptive center in connection with the afferent nerve. 4. A commissural tract. 5. An emissive center in connection with the efferent nerve. 6. An efferent nerve. 7. A responsive organ, muscle, gland, blood-vessel, etc. A stimulus of sufficient intensity applied to a sentient surface develops in the afferent nerve a series of nerve impulses which, traveling inward to the centers, are converted into efferent impulses and reflected outward to either muscle, gland, or blood-vessel, or all three simultaneously with the production of muscular contraction, glandular secretion, vascular contraction or dilatation. The reflex actions take place for the most part through the spinal cord and medulla oblongata, which, in virtue of their contained centers, coordinate the various organs and tissues concerned in the performance of the organic functions. The movements of mastication, the secretion of saliva, the muscular,glandular, and vascular phenomena of gastric and intestinal digestion, the respiratory movements, the mechanism of micturition, etc., are illustrations of reflex activity. (See function of spinal cord.) FOODS AND DIETETICS. During the functional activity of every organ and tissue of the b...
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