Fusimotor effects on position and velocity sensitivity of spindle endings in the external intercostal muscles of the cat.

Position and velocity responses of spindle endings in the external intercostal muscle of the cat have been determined in the absence and in the presence of fusimotor fibre stimulation at a constant rate. The length input signal had triangular wave form. A close functional resemblance was found between intercostal and leg muscle spindles: primary and secondary endings could be separated among intercostal afferents with the same methods that have been used in leg muscles; dynamic and static fibres were discerned and the fusimotor effects on position and velocity sensitivity were the same as in the hind limb; the ratio between dynamic and static fibres was about 1: 3, i.e. the same as in the hind leg. Some dissimilarities existed: the number of ‘intermediate’ endings was larger in the intercostal than in the leg muscles; position and velocity sensitivities were generally larger in intercostal endings. These discrepancies are discussed. As a general conclusion it is stated that a spindle model elaborated from studies on leg spindles can easily be modified to account also for intercostal spindle behaviour.

[1]  G Lennerstrand,et al.  Position and velocity sensitivity of muscle spindles in the cat. I. Primary and secondary endings deprived of fusimotor activation. , 1968, Acta physiologica Scandinavica.

[2]  G Lennerstrand,et al.  Position and velocity sensitivity of muscle spindles in the cat. IV. Interaction between two fusimotor fibres converging on the same spindle ending. , 1968, Acta physiologica Scandinavica.

[3]  Y. Laporte,et al.  Action of static and dynamic fusimotor fibres on secondary endings of cat's spindles , 1966, The Journal of physiology.

[4]  P. Rack,et al.  The effects of suxamethonium and acetylcholine on the behaviour of cat muscle spindles during dynamic stretching, and during fusimotor stimulation , 1966, The Journal of physiology.

[5]  P. Matthews,et al.  The central control of the dynamic response of muscle spindle receptors , 1962, The Journal of physiology.

[6]  P. Matthews,et al.  The effects of stimulation of static and dynamic fusimotor fibres on the response to stretching of the primary endings of muscle spindles , 1964, The Journal of physiology.

[7]  T. Sears,et al.  The fibre calibre spectra of sensory and motor fibres in the intercostal nerves of the cat , 1964, The Journal of physiology.

[8]  G. Eklund,et al.  Spontaneous and reflex activity of intercostal gamma motoneurones , 1964, The Journal of physiology.

[9]  P. Matthews,et al.  The response of de‐efferented muscle spindle receptors to stretching at different velocities , 1963, The Journal of physiology.

[10]  P. Matthews,et al.  Observations on the fusimotor fibres of the tibialis posterior muscle of the cat , 1965, The Journal of physiology.

[11]  G. Lennerstrand,et al.  Position and velocity sensitivity of muscle spindles in the cat. 3. Static fusimotor single-fibre activation of primary and secondary endings. , 1968, Acta physiologica Scandinavica.

[12]  A. Lundberg,et al.  Gower's Tract and “Spinal Border Cells” , 1968 .

[13]  V. Critchlow,et al.  Intercostal muscle spindle activity and its γ‐motor control , 1963 .

[14]  P. Matthews,et al.  Fusimotor stimulation and the dynamic sensitivity of the secondary ending of the muscle spindle , 1967, The Journal of physiology.

[15]  G Lennerstrand,et al.  Position and velocity sensitivity of muscle spindles in the cat. II. Dynamic fusimotor single-fibre activation of primary endings. , 1968, Acta physiologica Scandinavica.

[16]  C. von Euler,et al.  Dynamic and static contributions to the rhythmic γ activation of primary and secondary spindle endings in external intercostal muscle , 1966, The Journal of physiology.

[17]  G. Lennerstrand,et al.  Reflex and cerebellar influences on α and on ‘rhythmic’ and ‘tonic’ γ activity in the intercostal muscle , 1966 .

[18]  G. Eklund,et al.  EXTERNAL INTERCOSTAL AND PHRENIC ALPHA-MOTOR RESPONSES TO CHANGES IN RESPIRATORY LOAD. , 1965, Acta physiologica Scandinavica.

[19]  P. Matthews.  The differentiation of two types of fusimotor fibre by their effects on the dynamic response of muscle spindle primary endings. , 1962, Quarterly journal of experimental physiology and cognate medical sciences.

[20]  P. Matthews,et al.  Further studies of static and dynamic fusimotor fibres , 1964, The Journal of physiology.

[21]  I. A. Boyd.  The structure and innervation of the nuclear bag muscle fibre system and the nuclear chain muscle fibre system in mammalian muscle spindles , 1962, Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences.

[22]  P. Matthews,et al.  The response of de‐efferented muscle spindle endings in the cat's soleus to slow extension of the muscle , 1961, The Journal of physiology.

[23]  Schwieler Gh.  Respiratory regulation during postnatal development in cats and rabbits and some of its morphological substrate. , 1968 .

[24]  G Lennerstrand,et al.  Dynamic analysis of muscle spindle endings in the cat using length changes of different length-time relations. , 1968, Acta physiologica Scandinavica.

[25]  T. Sears.  Efferent discharges in alpha and fusimotor fibres of intercostal nerves of the cat , 1964, The Journal of physiology.

[26]  P. H. Hammond,et al.  Nervous gradation of muscular contraction. , 1956, British medical bulletin.