Behaviour of single motor units in human skeletal muscle

In the first part it was shown that the firing frequencies of motor units at particular grades of isometric contraction depend on the total number of units available for recruitment and so are regulated by length and tension receptors in the muscle. Procainisation showed the importance of the gamma- regulated length receptors in voluntary contraction. In hypertonie Parkinsonism, however, increments of voluntary contraction are presumably largely dependent on recruitment of extra units. Certainly the units recorded in the present study showed a very marked tendency to fire at unusually slow rates. They did so with a regular rhythm suggesting strong tonic inhibition. This is in contrast to the evidence reported in Chapter 8 (Paired response) pointing to the presence of motoneurone facilitation. This paradox would be solved if two antagonistic mechanisms were in action - for instance a supraspinal facilitation and a peripheral as well as supraspinal inhibitory one. Hufschmidt's (1959) work has already been discussed. He has shown that inhibitory reflexes from muscle and tendon receptors are overactive in Parkinsonism. It is now submitted that the mechanism described by him is only one of at least two important factors regulating spinal motoneurones in Parkinsonism, and it may well be that the peripheral inhibitory overaction is reactive, a regulatory reflex called into premature activity owing to the absence of the gamma regulation of the length servo (see Chapter 9).

Grantor dc:publisher

The University of Edinburgh

Year dc:date.issued

1962

Author dc:creator

• Dasgupta, Anupam

Advisor dc:contributor.advisor

• Simpson, J. A.

• muscle contraction
• central nervous system

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/1842/35449

OAI identifier oai:identifier

oai:era.ed.ac.uk:1842/35449