Receptors or neurons - in nerve tracts , centers or even entire areas of the cerebral cortex that serve such sensory services as hearing , seeing , smelling , etc., are referred to as sensory. This general psychophysiological definition has traditionally been followed by a majority of authors.
Sensory in the sense of a psychophysiological definition and as an adjective form of the nominal designation “ sensorium ” (= consciousness) presupposes that the corresponding services of sensory cells are at least to a small extent capable of consciousness or perceptible. Sensory neurons are part of the cerebrospinal nervous system .
The term “sensitive” is often used to denote emotional qualities , as sensitivity is given a special position within the sensory system. According to individual authors, however, sensitivity is no longer included in this sensory system. This creates a transition to the imperceptible or barely perceptible (non-perceptual) afferents.
More detailed definition
Sensitive and sensory
The adjective "sensory" is a neuropsychological Latin technical term that does not appear in ancient writers , but rather represents a later formation. It is derived from the Latin sentire 'feel', 'feel', 'perceive', 'grasp spiritually;' sensorius 'serving the sensation '. However, the same derivation also applies to the adjectival term "sensitive". There is therefore no difference between the root of "sensitive" and "sensory".
Contrary to this common word meaning, Robert Herrlinger also represents the delimiting conceptual point of view of the special "tactile or sensory organs" for the skin senses ( surface sensitivity ) and deep sensitivity . The group of receptors meant by this is summarized in this way and also differentiated from the other sensory organs in terms of their performance. In addition, there are already different conduction pathways in the spinal cord for both groups of sensitivity.
Hermann Voss and Robert Herrlinger designate all parts of the sense organs that serve the sensory perception as “tactile or sensory organs” (i.e. apart from the sensory function of the sense of touch “a whole range of other sensations”). A distinction is made between the sensory and skin systems in the title of the popular anatomy book. Nevertheless, the “skin system” is included in the general “sensory system”. The title of other textbooks also differentiates between skin and sensory organs.
The term “sensory” is used especially in German-language literature. Especially in the “objective” sense physiology , the term “receptor” is broader in scope and narrower in content. In contrast to the sensory functions of stimulus-receiving organs, receptors can also be non-perceptive d. :H. process information that is not related to conscious experiences, e.g. B. the signals of the pressoreceptors of the carotid sinus . Following a general theory of the senses, “sensory” should be understood as a generic term for all brain centers serving conscious sensory perception, or for the afferent or centripetal nerve pathways leading to them and also for any special receptors that may be present. The skin, feeling and touch senses specially marked with the adjective “sensitive” indicate the peculiarities of these special sensory qualities.
The distinction between sensible and sensory would therefore not mean a fundamental physiological distinction and in particular no contradiction to the general theory of the senses, according to which the reception, transmission and processing of information about the environment and the inner world are important for all sensory modalities. In principle, the skin, including deep sensitivity, should be viewed as a sense organ like all other sense organs. However, the skin senses or the "organs of touch or sensibility" have a certain special status in anatomical and partly also psychological terms, see Chap. Special position of the emotional qualities .
Therefore, when defining sensitivity in the narrower sense of the term "tactile or sensory organs" and in the broader sense of "sensory systems". Reference is made to the distinction between “sensitive” and “sensory” in topical brain research .
In the neurosciences common name of sensitivity , however, does not refer to a number of authors to the concept of sensation in general, as it is needed for the "totality of all the senses." It is often associated specifically and even exclusively with feeling ( sentire ' to feel').
In the Pschyrembel clinical dictionary , the use of the term “sensitivity” is expressly reserved for feelings and excluded from the other sensory modalities. There it says about sensitivity: “A sum of different sensations that do not come from the eye, from the ear or from the apparatus of taste and smell.” The dictionary of medicine by Zetkin and Schaldach closes the meaning of sensory nerves as “conveying sensations” on, cf. on the other hand the next chapter. Special position of the emotional qualities .
Special position of the emotional qualities
The question of whether the receptors of the skin (surface sensitivity) and the internal organs (depth sensitivity) can be described as a unified sensory organ as a whole have a special status for the emotional qualities . The corresponding receptors are at least not structured as a delimited organ similar to the nose , ear and eye in macroscopic-anatomical terms. On the contrary, at least the skin appears to be accessible to all external stimuli as a delimiting organ of the body from the outside world. There are no auxiliary devices upstream of the receptors, such as the organization of the nose, eyes, ears and the sense of taste. They at least partially change the stimuli of the outside world and are to be understood as protection against inadequate stimuli.
According to Peter R. Hofstätter, the skin senses can be differentiated as "near senses" from the "far senses" as the sense organs of optical, olfactory and acoustic modality. This does not mean, however, that these “higher sense tools” ( Benninghoff ) are not also effective in the close range. In particular, the smell , which plays a role both at a distance and also in taste through the tongue. Even a distinction between surface and depth sensitivity is not free from internal contradictions, if only because both merge into one another. The same receptors are found in the skin as in the deeper tissues or in the internal organs. The places of transition between the skin and the mucous membrane are more abundantly endowed with receptors. It is well known that small children tend to touch objects and, if necessary, put them in their mouths. The skin or the lips and the mucous membrane of the mouth play an important ontogenetic role as “near sense” in the early development of humans ( oral phase ). Oral contact with their caregivers also unconsciously creates a psychological closeness (see anaklise , internalization and introjection ).
René A. Spitz has therefore carried out a further classification of the sense organs. He called the labyrinth of the inner ear and the skin, especially the hand, organs of "primitive perception". The diverse and complexly structured receptors of the skin as well as the receptor-free free nerve endings cannot be assigned to a specific sensory quality of the skin, such as pain, touch, warmth and cold sensation. The distinction between surface and depth sensitivity is also not exclusively and necessarily linked to the presence of certain receptors in the skin or in internal organs or in the mucous membrane. Specific and mutually independent receptors and pathways to the central nervous system are not available. On the contrary, the pathways of different receptors are often branched and connected to one another (anastomoses). There are therefore, in terms of quality feelings of doubt about the Johannes Müller established law of specific nerve energies .
Another distinction between the emotional qualities and the other sensory modalities is determined by the special way in which these stimuli are transmitted and processed within the spinal cord and the brain stem. There is a network-like system of afferent and efferent neurons at the same and different levels of stimulus response, the formatio reticularis .
In contrast, the concept of the reflex i. e. See neurology typical for a nervous reaction at the same level of stimulus response. Hofstätter speaks of a level scheme for response to stimuli that not only applies to emotional qualities, but is characteristic of them in a special way. This means that a skin stimulus can be answered at different levels of the spinal cord and the brain stem . If nervous control takes place via reflexes without reaching the psychophysical level , one speaks of an involuntary or stereotypical performance, especially if the neuronal interconnection is not carried out by the autonomic nerve cells of the autonomic nervous system . In these two cases, there is usually no conscious awareness .
However, the term sensitive applies precisely to those nerve tracts that do not belong to the autonomic nervous system. Sensory performance should not be used in these cases because of the lack of consciousness components. - It can be assumed that most of the receptors in the intestines do not have the task of generating sensations. Rather, they trigger reflexes, such as the chemo- and pressoreceptors of the carotid sinus and aortic regions and the stretch receptors of the lungs and bronchi. The excitation of the muscle spindles is also not directed via sensory brain centers.
Some examples of the use of the term
Since "sensory" is already a generic term for a wide variety of sensory modalities such as olfactory, visual, tactile, auditory, vestibular, gustatory, etc., it is also suitable as a term for the totality of the corresponding peripheral receptors, nerve tracts, including their mutual linkages, interconnections and processing levels, see. for example the combination of different sensory components in olfactory perception .
This summarizes the entire sensory system of organisms, see Chap. Sensorium .
Due to the numerous information processing processes, the increasing coordination of different sensory data leads to a sensory integration and thus to special central nervous excitation patterns that ultimately become conscious as primary cognitive acts or as sensations . The ability to achieve higher conceptual knowledge is also referred to neuropsychologically as gnosis .
In sensory physiology , the term sensory systems is often used in a generalizing and simplifying way . This is particularly advantageous when the classic sensory physiological division of the sensory modalities and the sensory qualities in certain delimitations and differentiations appears too complex and sometimes insufficient. Epistemological questions are traditionally questions of philosophy.
The sensory systems include the following parts of the brain, centers and nerve tracts :
- Somatosensory cortex is that part of the cerebral cortex which is used for the central processing of the “skin senses”.
- Sensory projection centers is the generic term for all brain centers that are used to process conscious sensory data.
- Sensory cerebellar pathway is the pathway to the center of processing static signals of the VIII nerve in the cerebellum.
- The sensory language center is the Brodmann area A22 in the superior temporal gyrus , cf. Cerebral cortex map . Correspondingly, sensory aphasia is also caused by failure of this center.
- Radiatio acustica is a section of the central auditory pathway.
- The visual pathway is the sensory affective connection between the eyes and the visual center.
Sensory neurons are nerve cells that belong to one of the sensory systems. They must not be confused with receptors (see above) or equated with them. Receptors do not necessarily represent nerve cells. Histologically and ontogenetically, they are to a large extent to be regarded as separate receiving devices or as specially differentiated sensory cells, especially since they each have a different development. Only the olfactory and visual cells are also nerve cells in humans. Regardless of the different origins of these sensory cells, the sensory epithelium is also known as the neuroepithelium .
In terms of developmental history (ontogenesis), olfactory and visual cells emerge from a protuberance of the neural tube . With regard to the later form of the olfactory cells, this is initially referred to as the olfactory placode and then as the olfactory dimple. In the end, it represents the olfactory bulb together with the olfactory fila. In the case of the visual cells, this protuberance first forms the ocular vesicles , then the eye cups and ultimately the retina , which contains the light-sensitive sensory cells. In contrast to the centrifugal protuberance of the ocular vesicles and ocular cups, the development of neurons progresses from peripheral to central, cf. the concept of centralization and the path of development illustrated there using the example of the eye. In contrast, the auditory and equilibrium organs develop from plate-shaped thickenings (placodes) of the ectoderm . It is similar with the taste buds. The group of developing sensory cells mentioned last pass their excitations on to the branches of the peripheral neurite of a ganglion cell.
The sensory system, on the other hand, includes sensory neurons not only as receiving devices of the olfactory and visual apparatus, but also the receptors of the rest of the sensory system that cannot be regarded as nerve cells as receiving devices for sensory stimuli. This also includes the sensory neurons ( ganglion cells , interneurons ) as a guide apparatus and the various sensory centers of the brain base, the limbic system and the cerebral cortex as end stations of specific stimulus reception.
A few more terms
In addition, the term sensory is used in the following combinations:
- Sensory-tonic field is the possibly hereditary, relatively close relationship between perception and motor skills (or muscle tone) in the sensory fields of the cerebral cortex in analogy to this same relationship in the spinal cord. Example: The field of vision of the eyes corresponds to the field of movement of the arms. The sensory language center corresponds to a motor one.
- Sensory integration is the coordination of different sensory data.
- Sensory memory is the mostly only short-term memory for sensory impressions without subjectively recognizable meaning.
- Sensory adaptation reduces the responsiveness of a sensory system to long-term input from stimuli.
The subjectively different sensory stimulus processing, as it is carried out in the peripheral sensory apparatus and the sensibility of the different brain regions, are summarized in the concept of consciousness .
This term includes the meaning of a conscience as a unifying word formation “different perceptions and experiences”, namely in particular through the prefix formation Ge ... - cf. Bushes, teeth, mountains - as a merging “knowledge” or as an oriented synopsis of conscious “experiences”.
In a similar manner, the Greek philosophy this view with terms how ancient Greek συνείδησις syneidesis , German , Miterscheinung, Mitbild, complicity ' in the Stoics and ancient Greek συναίσθησις Synaisthesis , German , Mitwahrnehmung, Mitempfindung' in Plotinus represented.
- Philip G. Zimbardo , Richard J. Gerrig: Psychology . Pearson, Hallbergmoos near Munich 2008, ISBN 978-3-8273-7275-8 ; (a) p. 76 - on tax "Sensory Neurons"; (b) p. 236 - re. “Sensory memory”; (c) p. 116 - on head. "Sensory adaptation".
- Herbert Volkmann (Ed.): Guttmanns Medical Terminology . Derivation and explanation of the most common technical terms of all branches of medicine and their auxiliary sciences. Urban & Schwarzenberg, Berlin 1939; (a) Col. 880 - on lexicon lemma: "sensory"; (b) Col. 880 - on lexicon lemma: "Sensorium".
- sensory . In: Norbert Boss (Ed.): Roche Lexicon Medicine. 2nd Edition. Hoffmann-La Roche AG and Urban & Schwarzenberg, Munich 1987, ISBN 3-541-13191-8 , p. 1565, Gesundheit.de/roche
- Zetkin-Schaldach: Dictionary of Medicine. dtv, Munich / Georg Thieme, Stuttgart 1980, ISBN 3-423-03029-1 (dtv) and ISBN 3-13-382206-3 (Thieme); (a) p. 1288 - on Wb.-Lemma “Sensibility”; (b) p. 1288 - on Wb.-Lemma “sensibel”, 1. sensible nerves.
- Hermann Voss , Robert Herrlinger : Taschenbuch der Anatomie. Volume 3: nervous system, sensory system, skin system, increment system. 12th edition. VEB-Gustav-Fischer, Jena 1964; (a) p. 2 f. - to chap. I. "Structure, construction plan, division"; (b) p. 208 - to chap. II. “The Sensory System”, (c + d) p. 208 f. - to Stw. "Scheme of stimulus conduction in a sense organ".
- Willibald Pschyrembel : Pschyrembel. Clinical Dictionary. 154-184. Edition. Walter de Gruyter & Co., Berlin 1964; (a + b) p. 802 - on Wb.-Lemma "Sensibility"; (c) p. 742 - on Wb.-Lemma "Reflex".
- Non-perceptual afferents (e.g. pressoreceptors of the carotid sinus) . In: Herbert Hensel : General sensory physiology: skin senses, taste, smell . Springer, Berlin / Heidelberg / New York 1966, p. 65 ff.
- Hermann Triepel : The anatomical names. Your derivation and pronunciation. 26th edition. Published by JF Bergmann, Munich 1962, edited by Robert Herrlinger ; P. 66 - on the lemmas "sensibilis" and "sensorius".
- Alfred Benninghoff , Kurt Goerttler : Textbook of Human Anatomy. 7th edition. Shown with preference given to functional relationships. Volume 3: Nervous System, Skin and Sensory Organs. Urban & Schwarzenberg, Munich, 1964; (a) see book title; (b) p. 410 - on head. "Auxiliary Apparatus"; (c) p. 411 - re. “Surface sensitivity”; (d) p. 411 - to district “field of vision”.
- Wilhelm Karl Arnold et al. (Ed.): Lexicon of Psychology. Bechtermünz, Augsburg 1996, ISBN 3-86047-508-8 ; (a) Col. 1911 f. - to Lex.-Lemma: “Receptor”; (b) Col. 2041 - on Lex.-Lemma: "Sensory"; (c) Col. 494 f. - to Lex.-Lemmas: "Recognize", "Epistemology".
- Peter R. Hofstätter (Ed.): Psychology. The Fischer Lexicon. Fischer-Taschenbuch, Frankfurt am Main 1972, ISBN 3-436-01159-2 ; (a) P. 174 ff. - to chap. "Skin senses"; (b) p. 284 f. to chap. "Stimulus and reaction"; (c) p. 349 - to chap. "Perception Theory"; (d) p. 85 - to chap. "Awareness".
- Hermann Rein , Max Schneider : Introduction to Human Physiology. 15th edition. Springer, Berlin, 1964; P. 673 ff. - to the district “depth sensitivity”.
- René A. Spitz : From infant to toddler . Natural history of mother-child relationships in the first year of life. 11th edition. Klett-Cotta, Stuttgart 1996.
- Sven Olaf Hoffmann , G. Hochapfel: Neuroses, psychotherapeutic and psychosomatic medicine. Compact textbook. 6th edition. Schattauer, Stuttgart 2003, ISBN 3-7945-1960-4 ; P. 33 - to Stw. "Organs of Primitive Perception".
- Robert F. Schmidt (Ed.): Outline of Neurophysiology. 3. Edition. Springer, Berlin 1979, ISBN 3-540-07827-4 ; Pp. 108, 118 - on the term “reflex term”.
- Sensory aphasia . In: Rudolf Degkwitz et al. (Ed.): Mentally ill . Introduction to Psychiatry for Clinical Study. Urban & Schwarzenberg, Munich 1982, ISBN 3-541-09911-9 , p. 81.
- Otto Grosser arr. by Rolf Ortmann: Outline of the human development history . 6th edition. Springer, Berlin 1966; (a) p. 92 - to head. "Smell placode, olfactory dimples" Fig. 95 + 96 and p. 96 to chap. "Nasal cavity with facial and gauami formation"; (b) P. 88 ff. - to chap. "Organ of vision"; (c) p. 93 f. - to chap. "Hearing and balance organs"; (d) p. 93 f. - to chap. "Hearing and balance organs".
- sensory-tonic field . In: Jean Delay , Pierre Pichot: Medical Psychology. Translated and edited by Wolfgang Böcher. 4th edition. Georg Thieme-Verlag, Stuttgart 1973, p. 54.
- Sensory integration . In: Peter Duus: Neurological-topical diagnostics. Anatomy, physiology, clinic . 5th edition. Georg Thieme, Stuttgart 1990, ISBN 3-13-535805-4 , p. 389.
- Conscience . In: Günther Drosdowski: Etymology. Dictionary of origin of the German language; The history of German words and foreign words from their origins to the present . Volume 7. 2nd edition. Dudenverlag, Mannheim 1997, ISBN 3-411-20907-0 , p. 241 f.