Abstract
ABSTRACT The intrasegmental feedback reflexes in the swimmeret system of the lobster Homarus americanas were activated while recording the responses from the swimmeret nerves and muscles. Two main sources of sensory feedback were identified; proprioceptors in the coxal region of the swimmeret, and sensory setae on the edges of the two rami of each swimmeret. The reflexes activated by these inputs are described. Reflexive feedback from the powerstroke movement to the powerstroke excitatory motor neurones is positive, further reinforcing the movement. Intrasegmental reflexes capable of independently initiating or terminating the powerstroke activity are absent, however. Therefore the powerstroke movement of each cycle can begin and end only in response to a purely central nervous motor command. It follows that the intrasegmental swimmeret reflexes are incapable of contributing to the periodicity seen in the motor output pattern which underlies swimmeret beating. In addition to strengthening the powerstroke, the intrasegmental reflexes strengthen the linkage between the powerstroke and the returnstroke within each movement cycle. The reflexes may also reinforce the reciprocity between excitor and inhibitor axon activity to the main powerstroke and returnstroke muscles. It is shown, however, that these three features of the motor output pattern are programmed into the CNS independently of the sensory feedback. The intrasegmental reflexes thus act as subservient amplifying devices for cyclic motor patterns which are produced independently by purely central nervous mechanisms.
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.