Abstract
Excitatory postsynaptic potentials (e.p.s. p.s.) elicited by impulses in single muscle spindle afferent fibers from the medial gastrocnemius (m.g.) muscle were recorded intracellularly from homonymous and heteronymous motoneurons in order to study factors that influence the amplitudes of such responses. Impulses in large afferent fibers elicited larger single-fiber e.p.s.p.s. than those in smaller afferents. Mean e.p.s.p. amplitudes were related exponentially to afferent conduction velocities of both Ia and spindle group II fibers. The closer a motoneuron was to the spinal entry point of an afferent fiber, the larger was the mean e.p.s.p. amplitude evoked in it. Impulses in the same afferent fiber elicited larger e.p.s.p.s in small than large motoneurons when the two cells were located at the same craniocaudal levels. Other factors being equal, the single-fiber e.p.s.p.s evoked in homonymous and heteronymous motoneurons were approximately equal in amplitude. Relatively simple morphological and topographical explanations for the findings were advanced and their functional significance for orderly recruitment in partitioned and unpartitioned reflexes was described.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.