The Histological Structure and Physiological Response of the Sensory Units in the Knee-Joint of the Cat

Boyd, Ian Alexander (1954) The Histological Structure and Physiological Response of the Sensory Units in the Knee-Joint of the Cat. PhD thesis, University of Glasgow.

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1. Using a 'single-fibre' technique, afferent discharges from single sensory units in the capsule of the knee-joint of the decerebrate cat have been recorded from the posterior articular nerve to this joint. 2. The responses are of two types - 'rapidly-adapting' and 'slowly-adapting'. 3. The rapidly-adapting responses consist of impulses during movement of the joint but not while the joint is stationary. Such responses were found on only a few occasions and are similar to those from the C organs of Matthews (1933), and also to those attributed by Gray & Matthews (1951) to Pacinian corpuscles. 4. The slowly-adapting responses were more frequently encountered. They are characterized by maintained steady discharges while the joint is stationary, with 'exaggerated' changes in frequency during movement. The degree of exaggeration depends on the rate of movement, and the exaggerated response is followed by adaptation to a new, steady impulse-frequency. 5. The steady, adapted impulse-frequency in any one position is independent of the rate, but not always of the direction, of the movement used to reach that position. If the movement is one which produces a decrease in the frequency of the impulses, the final steady value may he less than that in the same position following a movement in the direction producing an increase in impulse-frequency. The degree of this 'directional' effect varies from unit to unit. 6. The sensory units giving rise to both types of response can he made to discharge by direct pressure on the part of the capsule in which they lie. By locating them in this way, the slowly-adapting units have been found to he most numerous in the centre of the hack of the joint-capsule, whereas the rapidly-adapting units tend to lie towards the sides of the joint. 7. Using the Gairns (1930) gold chloride technique, two types of sensory unit have been demonstrated histologically in the posterior part of the knee-joint capsule, a 'spray' type and a 'lamellated' type. 8. By obtaining a single-fibre discharge from the articular nerve and, while still recording the discharge, excising the particular area of capsule containing the sensory unit responsible for the discharge, it has been possible to correlate the structure of the sensory units with their physiological response. 9. The sensory units of spray type consist of a number of sprays supplied by a single axon, and are situated in the fibrous layer of the joint-capsule; they are undoubtedly the 'typical Ruffini endings' described by Gardner (1944). They are definitely responsible for the slowly-adapting discharges in the posterior articular nerve. It is suggested that these spray sensory units are capable of providing accurate information about the relative position of the bones forming the joint. 10. The lamellated sensory units, which also lie in the fibrous capsule, are much scarcer than the spray type. They consist of several receptors supplied by a single axon. These receptors are double the length of the spray receptors, but are very much smaller, and relatively more elongated, than Pacinian corpuscles. The lamellated type of sensory unit is almost certainly responsible for the rapidly-adapting discharges in the posterior articular nerve. 11. It is doubtful if other types of organised nerve-ending exist in the capsule, but some free nerve-endings are present. On one occasion tendon-organs were found in a cruciate ligament. 12. It is suggested that the larger fibres in the articular nerve innervate tendon-organs in the ligaments of the joint, and that the response of these is similar to the response of the spray sensory units in the capsule. The possibility is discussed that the capsular spray units, the sensory units of spray type (tendon-organs) in ligaments and tendons, and the flower-spray units in muscle-spindles form a series of sensory units, graded in size, which are all basically similar in structure and in function.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Physiology, Histology
Date of Award: 1954
Depositing User: Enlighten Team
Unique ID: glathesis:1954-79069
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 11:45
Last Modified: 05 Mar 2020 11:45

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