A Comparative Study on Structure and Function Between the Extrafusal Receptor and the Spindle Receptor in the Frog

Ito, Fumio; Toyama, Keisuke; Ito, Ryo

doi:10.2170/jjphysiol.14.12

Cited by 35 publications

(11 citation statements)

References 27 publications

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“…Although the diameter of its sensory fibres is similar to that of the motor nerve fibres, all of the terminals are of the flower-spray type characteristic of the mammalian secondary (group II) spindle ending. In addition to sensory fibres from spindle and unmyelinated receptors, Kobayashi, Oshima & Tasaki (1952) and Ito, Toyama & Ito (1964) distinguished at least two prominent extrafusal receptor types. The sensory fibres of these two types of receptors are somewhat smaller and have a slower conduction velocity than those from spindle receptors.…”

Section: Resultsmentioning

confidence: 99%

“…A major difficulty in determining whether there is any specificity of interactions has been our inability to produce antidromic responses of identified types of sensory fibres. Both the muscle (Ito et al 1964;Kobayashi et al 1952) and cutaneous (Maruhashi, Mizuguchi & Tasaki, 1952) nerves contain a variety of types of sensory fibres which are probably not all affected in a similar fashion. It seems likely that we have studied primarily the largest sensory fibres, which would be the tactile receptors from skin and the spindle receptors from muscle.…”

Section: Resultsmentioning

confidence: 99%

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The organization of primary afferent depolarization in the isolated spinal cord of the frog

Carpenter¹,

Rudomín²

1973

The Journal of Physiology

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SUMMIARY1. The organization of primary afferent depolarization (PAD) produced by excitation of peripheral sensory and motor nerves was studied in the frog cord isolated with hind limb nerves.2. Dorsal root potentials from sensory fibres (DR-DRPs) were evoked on stimulation of most sensory nerves, but were largest from cutaneous, joint and flexor muscle afferents. With single shock stimulation the largest cutaneous and joint afferent fibres gave DR-DRPs, but potentials from muscle nerves resulted from activation of sensory fibres with thresholds to electrical stimulation higher than 1-21-5 times the threshold of the most excitable fibres in the nerve. This suggests that PAD from muscle afferents is probably due to excitation of extrafusal receptors.3. Dorsal root potentials produced by antidromic activation of motor fibres (VR-DRPs) were larger from extensor muscles and smaller or absent from flexor muscles. The VR-DRPs were produced by activation of the lowest threshold motor fibres.4. Three types of interactions were found between test and conditioning DRPs from the same or different nerves. With maximal responses occlusion was usually pronounced. At submaximal levels linear summation occurred.Near threshold the conditioning stimulus frequently resulted in a large facilitation of the test DRP. All three types of interactions were found with two DR-DRPs, two VR-DRPs or one DR-DRP and one VR-DRP.5. The excitability of sensory nerve terminals from most peripheral nerves was increased during the DR-DRP. The magnitude of the excitability increase varied roughly with the magnitude of the DR-DRP evoked by the conditioning stimulus. D. 0. CARPENTER AND P. RUDOMIN 6. There was a marked excitability increase of cutaneous and extensor muscle afferent terminals during the VR-DRP. Flexor muscle afferent terminals often showed no excitability changes to ventral root stimulation. In those experiments where afferent terminals from flexor muscles did show an excitability increase, the effects were smaller than those of cutaneous and extensor terminals.7. The VR-DRPs appear to reflect activity of a negative feed-back loop from extensor motoneurones on to sensory fibres from cutaneous and extensor muscles. This system may have a role in modulating the ballistic movement of the frog. DR-DRPs, on the contrary, are widespread in origin and distribution. PAD from sensory fibres may function to sharpen contrast between incoming afferent information.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

The organization of primary afferent depolarization in the isolated spinal cord of the frog

Carpenter¹,

Rudomín²

1973

The Journal of Physiology

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“…2) are thus given as By the equations (2) and (3), these values Pd, Pi, Pb are converted to the spike frequency Fd, Fi, Fb as described in the equations (4), (5), (6). The three quantities G1/G2, n/G2, kG1 relating to the parameters of the model, were derived from the equations (10)- (12) in the following way.…”

Section: Appendixmentioning

confidence: 99%

An Analysis of Impulse Discharges From the Spindle Receptor

Toyama

1966

Jpn.J.Physiol

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“…Ito, Toyama & Ito, 1964). Most of the spindles consisted of only one intrafusal muscle fibre, approximately 15 ,um in diameter; a few spindles had two intrafusal fibres in which one was about 15 gm in diameter but the other less than 10 tm.…”

Section: Microscopic Observationsmentioning

confidence: 94%

Frog muscle spindles with unbranched myelinated afferent axons: the response to stretch and the length of the first myelinated segment.

Ito¹,

Komatsu²

1977

The Journal of Physiology

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SUMMARY1. Twenty-five muscle spindles innervated by unbranched myelinated axons in the capsule were isolated from sartorius muscles in young frogs (2.2-9.5 g in weight, 28-47 mm in rostro-caudal length).2. The lengths and the diameters of the first myelinated segments varied from 30 to 170 ,m and from 9 to 20 ,m respectively. There was no relationship between the lengths and the diameters.3. Dynamic and static components were analysed from discharge rates of the muscle spindles during ramp-and-hold stretches of 0-8 mm from different initial lengths. The values of the dynamic components to a certain stretch stimulation increased with shortening in the length of the first myelinated segment. The values of the static components were independent in length.4. The amplitudes of action potentials recorded from the spindle terminal decreased during the dynamic phase of the stretch. The ratio of amplitude decrease at the end of the dynamic phase versus the initial length depended upon the length of the first myelinated segment.5. These results suggest that the discharges during stretch may arise at the first node, though the spontaneous discharges may be generated at the terminal.

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A Comparative Study on Structure and Function Between the Extrafusal Receptor and the Spindle Receptor in the Frog

Cited by 35 publications

References 27 publications

The organization of primary afferent depolarization in the isolated spinal cord of the frog

The organization of primary afferent depolarization in the isolated spinal cord of the frog

An Analysis of Impulse Discharges From the Spindle Receptor

Frog muscle spindles with unbranched myelinated afferent axons: the response to stretch and the length of the first myelinated segment.

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