Control of Hind Limb Muscle Spindles from the Mesencephalon and Diencephalon in the Cat

Dickson, Michael (1990) Control of Hind Limb Muscle Spindles from the Mesencephalon and Diencephalon in the Cat. PhD thesis, University of Glasgow.

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Appelberg and Emonet-Denand (1965) observed an increase in dynamic sensitivity of muscle spindles in hind limb muscles during stimulation in the mesencephalon in the approximate location of the Red Nucleus. This was seen in a flexor (Peroneus Tertius) and an extensor (Flexor Digitorum Longus). Using this and later work as a basis, Appelberg (1981) described an area covering the dorsocaudal part of the Red Nucleus and dorsal and caudal to it, which on stimulation selectively recruited hindlimb gamma motoneurones. The aim of this project was to investigate the effect of stimulation in the region described by Appelberg (1981) on gamma motoneurones of the Tenuissimus muscle, and to assess its value as an experimental tool. Other possible areas for selective recruitment of dynamic and other types of gamma motoneurone were also to be investigated. Two types of experiment were carried out. In one, spindles of the Tenuissimus muscle were exposed (isolated) with their nerve and blood supplies intact. Then, by direct observation of intrafusal fibres, the effect of stimulation in the mesencephalon and telencephalon was assessed. In the other type of experiment, single group la afferent fibres from Tenuissimus, Peroneus Tertius, and Flexor Digitorum Longus muscles were prepared in dorsal root filaments. The nature of any changes in gamma firing was inferred from changes in the afferents' response to muscle length change. Static effects were seen in many experiments, and mixed dynamic and static in some. The static bag2 and chain fibres showed a large degree of independence in their excitation and inhibition, and were seen to be affected in opposite ways on some occasions. However, no clear area emerged as a particular site for recruitment of any type of intrafusal fibre in tenuissimus spindles. It was also seen that the act of inserting microelectrodes into the habenulae silenced spontaneous activity in a tenuissimus spindle. This was not the case for the red nucleus or the substantia nigra. It was concluded that tenuissimus is not affected from the area described by Appelberg (1981) and that the assertion that this area selectively recruits dynamic gammas in hind limb muscles has to be qualified until tested in individual muscles. The results from single experiments on Peroneus Tertius and Flexor Digitorum Longus support this view.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Physiology, Neurosciences
Date of Award: 1990
Depositing User: Enlighten Team
Unique ID: glathesis:1990-78128
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:39
Last Modified: 30 Jan 2020 15:39

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