Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
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Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
CHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2ct sensory information from all over the body T ese senses are in contradistinction to the special senses, which mean specifically vision, hearing, smell, taste, and equilibriumCLASSIFICATION OF SOMATIC SENSEST e somatic senses can be classified into three physiological types: < 1) the mechanorecept Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2ive somatic senses, which include both tactile and position sensations that are stimulated by mechanical displacement of some tissue of the body. (2)Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
the thermoreceptive senses, which detect heat and cold, and (3) the pain sense, which is activated by factors that damage the tissuesT is chapter dealCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2ouch, pressure, vibration, and tickle senses, and the position senses include static position and rate of movement senses.Other Classifications of Somatic Sensations. Somatic sensations are also often grouped together in other classes, as follows:Exteroreceptive sensations are those from the surface Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2 of the body. Proprioceptive sensations are those relating to the physical stare of the body, including position sensations. tendon and muscle sensatiEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
ons, pressure sensations from the bottom of the feet, and even the sensation of equilibrium (which IS often considered a •’special" sensation rather tCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2 from the internal organs.Deep sensations are those that come from deep tissues, such as from fasciae, muscles, and bone. T ese sensations include mainly "deep" pressure, pain, and vibration.DETECTION AND TRANSMISSION OF TACTILE SENSATIONSInterrelations Among the Tactile Sensations of Touch, Pressur Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2e, and Vibration. Although touch.pressure, and vibration are frequently classified as separate sensations, they are all detected by the same types ofEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
receptors. T ere are three principal differences among them: (I) touch sensation generally results from stimulation of tactile receptors in the skin oCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2sults from rapidly repetitive sensory-signals. but some of the same types of receptors as those for touch and pressure are used.Tactile Receptors. T ere are at least SIX entirely different types of tactile receptors, but many more similar to these also exist. Some were shown in Figure 47-1 of the pr Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2evious chapter, their special characteristics are the following.First, some free nerve endings, which are found everywhere in the skin and in many othEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
er tissues, can detect touch and pressure For instance, even light contact with the cornea of the eye. which contains no other type of nerve ending beCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2uscle (illustrated in Figure 47-1). an elongated encapsulated nerve ending of a large (type Afi) myelinated sensory nerve fiber Inside the capsulation are many branching terminal nerve filaments. T ese corpuscles are present in the nonhail y pans of the skin and are particularly abundant in the fing Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2ertips, lips, and other areas of the skin where ones ability to discern spatial locations of touch sensations is highly developed Meissner corpusclesEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
adapt in a fraction of a second after they are stimulated, which means that they are particularly sensitive to movement of objects over the surface ofCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2 contain large numbers of expanded tip tactile receptors, one type of which is Meikels discs, shown in Figure 48-1. T e hairy parts of the skin also contain moderate numbers of expanded tip receptors, even though they have almost no Meissner s corpuscles. T ese receptors differ from Meissners corpus Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2cles in that they transmit an initially strong but partially adapting signal and then a continuing607Unit IX The Nervous System: A. General PrinciplesEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
and Sensory PhysiologyFigure 48-1. An Iggo deme receptor Mote the multiple numbers of Merkel discs connecting to a single large myelinated fiber (A) CHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2dermis of the touch corpuscle, FF. fine bundles of collagen fibers (From iggo A Muir AR The structure and function of a slowly adapting touch corpuscle tn hairy skin, i Physiol 200 763. I960.)weaker signal that adapts only slowly. T erefore. they are responsible for giving steady-state signals that Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2allow one to determine continuous touch of objects against the skin.Merkel discs are often grouped together in a receptor organ called the Iggo dome rEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
eceptor, which projects upward against the underside of the epithelium of the skin, as IS also shown in Figure 48 1. T is upward projection causes theCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2of Merkels discs is innervated by a single large myelinated nerve fiber (type Ap>. T ese receptors, along with the Meissners corpuscles discussed earlier, play extremely important roles in localizing touch sensations to specific surface areas of the body and in determining the texture of what is fel Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2tFourth, slight movement of any hair on the body stimulates a nene fiber entwining Its base. T us. each hair and its basal nerve fiber, called the haiEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
r end-organ, are also touch receptors. A receptor adapts readily and. like Meissners corpuscles, detects mainly (al movement of objects on the surfaceCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2ffinis endings, which are multibranched, encapsulated endings, as shown in Figure 47-1. T ese endings adapt very slowly and. therefore, are important for signaling continuous states of deformation of the tissues, such as heavy prolonged touch and pressure signals. T ey are also found in joint capsul Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2es and help to signal the degree of joint rotation.Sixth. Pacinian corpuscles, which weie discussed in detail in Chapter 47. lie both immediately beneEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
ath the skin and deep in the fascial tissues of the body. T ey are stimulated only by rapid local compression of the tissues because they adapt in a fCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2the tissuesTransmission of Tactile Signals in Peripheral Nerve Fibers. Almost all specialized sensory receptors, such as Meissner s corpuscles. Iggo dome receptors, hair receptors. Pacinian coipuscles. and Ruffinis endings, transmit their signals in type A|i nerve fibers that have transmission veloc Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2ities ranging from 30 to 70 m sec. Conversely, free nerve ending tactile receptors transmit signals mainly by way of the small type AÔ myelinated fibeEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
rs that conduct at velocities of only 5 to 30 m. sec.Some tactile free nene endings transmit by way of type c unmyelinated fibers at velocities from aCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2on of tickleT us. the more critical types of sensory signals—those that help to determine precise localization on the skin, minute gradations of intensity, or rapid changes in sensory signal intensity—are all transmitted in more rapidly conducting types of sensory nerve fibers. Conversely, the crude Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2r types of signals, such as pressure, poorly localized touch, and especially tickle, are transmitted by way of much slower, very small nene fibers thaEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
t require much less space in the nerve bundle than the fast fibers.Detection of Vibration. All tactile receptors are involved in detection of vibratioCHAPTER 48 MSomatic Sensations: I. General Organization, the Tactile and Position SensesUNITXT e somatic senses are the nervous mechanisms that collec Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2because they respond extremely rapidly to minute and rapid deformations of the tissues. T ey also transmit their signals over type A0 nerve fibers, which can transmit as many as 1000 impulses per second. Low-frequency vibrations from 2 up to 80 cycles per second, in contrast, stimulate other tactile Ebook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2 receptors, especially Meissner s corpuscles, which adapt less rapidly than do Pacinian corpuscles.Detection of Tickle and Itch by Mechanoreceptive FrEbook Guyton and hall: Textbook of medical physiology (13th edition) - Part 2
ee Nerve Endings. Neurophysiological studies have demonstrated the existence of very sensitive, rapidly adapting mechanoieceptive free nerve endings tGọi ngay
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