Neural and muscular control of the human extensor digitorum muscle

Persistent Link:
http://hdl.handle.net/10150/280191
Title:
Neural and muscular control of the human extensor digitorum muscle
Author:
Keen, Douglas Andrew
Issue Date:
2002
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The human hand has incredible dexterity which depends, in large part, on the ability to move the fingers relatively independently. Interestingly, many of the primary finger flexor and extensor muscles possess a single belly that gives rise distally to multiple tendons that insert onto all the fingers and consequently might produce movement in all of the fingers. Therefore, the objective of this dissertation was to examine the neuromuscular organization of a multi-tendoned finger extensor muscle, the human extensor digitorum (ED). Initially, we found that ED spike-triggered average motor unit force was broadly distributed across the digits. Consequently, we hypothesized that linkages between the distal tendons of ED may cause force developed in a single compartment to be transmitted to neighboring tendons. However, force arising from intramuscular stimulation was fairly focused to a single digit suggesting that inter-tendonous connections account for little of the broad distribution of motor unit force. An alternative possibility was that our spike-triggered averages of motor unit force were contaminated by correlated activity among motor units residing in different compartments. Strong motor unit synchrony was found for motor unit pairs within compartments and a modest degree of synchrony for motor unit pairs in neighboring compartments which likely contributed to the appearance of spike-triggered average motor unit force on multiple fingers. These results suggest that last-order synaptic projections appear to supply predominantly sub-sets of motor neurons innervating specific finger compartments of ED but also branch to supply motor neurons innervating other compartments. Finally, single motor axons branch to innervate muscle fibers situated in multiple compartments of ED. Interestingly, force resulting from intraneural micro stimulation of single motor axons innervating ED was highly focused to a single digit. Therefore, it appears that the muscle fibers innervated by a motor axon are primarily confined to one of four distinct compartments of ED. Based on these experiments we believe that each finger is acted upon by ED through a discreet population of motor units. Consequently, extension of an individual finger would require the selective activation of motor neurons innervating a specific compartment of ED.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Neuroscience.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Physiological Sciences
Degree Grantor:
University of Arizona
Advisor:
Fuglevand, Andrew J.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleNeural and muscular control of the human extensor digitorum muscleen_US
dc.creatorKeen, Douglas Andrewen_US
dc.contributor.authorKeen, Douglas Andrewen_US
dc.date.issued2002en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe human hand has incredible dexterity which depends, in large part, on the ability to move the fingers relatively independently. Interestingly, many of the primary finger flexor and extensor muscles possess a single belly that gives rise distally to multiple tendons that insert onto all the fingers and consequently might produce movement in all of the fingers. Therefore, the objective of this dissertation was to examine the neuromuscular organization of a multi-tendoned finger extensor muscle, the human extensor digitorum (ED). Initially, we found that ED spike-triggered average motor unit force was broadly distributed across the digits. Consequently, we hypothesized that linkages between the distal tendons of ED may cause force developed in a single compartment to be transmitted to neighboring tendons. However, force arising from intramuscular stimulation was fairly focused to a single digit suggesting that inter-tendonous connections account for little of the broad distribution of motor unit force. An alternative possibility was that our spike-triggered averages of motor unit force were contaminated by correlated activity among motor units residing in different compartments. Strong motor unit synchrony was found for motor unit pairs within compartments and a modest degree of synchrony for motor unit pairs in neighboring compartments which likely contributed to the appearance of spike-triggered average motor unit force on multiple fingers. These results suggest that last-order synaptic projections appear to supply predominantly sub-sets of motor neurons innervating specific finger compartments of ED but also branch to supply motor neurons innervating other compartments. Finally, single motor axons branch to innervate muscle fibers situated in multiple compartments of ED. Interestingly, force resulting from intraneural micro stimulation of single motor axons innervating ED was highly focused to a single digit. Therefore, it appears that the muscle fibers innervated by a motor axon are primarily confined to one of four distinct compartments of ED. Based on these experiments we believe that each finger is acted upon by ED through a discreet population of motor units. Consequently, extension of an individual finger would require the selective activation of motor neurons innervating a specific compartment of ED.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Neuroscience.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePhysiological Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorFuglevand, Andrew J.en_US
dc.identifier.proquest3073238en_US
dc.identifier.bibrecord.b43472035en_US
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