Skip to main content Accessibility help
×
Hostname: page-component-77f85d65b8-9nbrm Total loading time: 0 Render date: 2026-04-23T02:36:00.000Z Has data issue: false hasContentIssue false

2 - Monosynaptic Ia excitation and post-activation depression

Published online by Cambridge University Press:  08 August 2009

Emmanuel Pierrot-Deseilligny
Affiliation:
Groupe Hospitalier Pitié-Salpétrière, Paris
David Burke
Affiliation:
University of Sydney
Get access

Summary

The extent to which the spinal stretch reflex is involved in normal motor control and the contribution of monosynaptic Ia connections in its generation are not yet completely clarified. Regardless of these uncertainties, there is continuing interest in the reflex connections of the primary endings of muscle spindles, as detailed below.

Muscle synergies laid down in the spinal cord

The execution of even the simplest movement involves a large number of muscles, but the pattern of muscle activity is consistent for any given type of movement (see Illert, 1996). Beevor (1904, cited by Illert, 1996) claimed that the neuronal arrangements for stereotyped movements are laid down in the spinal cord. The various muscle synergies could thus be represented by different sets of spinal connections, which have been termed ‘spinal functional units’ (Baldissera, Hultborn & Illert, 1981), and are thought to be mobilised during voluntary movements, as was postulated long ago by Forster (1879, cited by Hultborn, 2001). One objective in the study of reflexes is to identify the pattern of connections underlying a particular form of behaviour. This entails tracing the effects of a given input to see how widely it is distributed to excite or inhibit different neurones. The classical example of such a study was provided by Sherrington (1910), who detailed the muscles that contract or relax in the flexor reflex (see Chapter 9).

Information

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Book purchase

Temporarily unavailable

Save book to Kindle

To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats
×

Save book to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

Available formats
×