Crayfish muscle receptor organ: role in regulation of postural flexion.

Recordings were made from postural-control motor nerves with antagonistic functions in the crayfish abdomen through flexible suction electrodes. During unrestrained flexion of the abdomen, output from the tonic stretch receptor neuron of RM(1),(SR(1)) is sufficient to drive an extensor motor unit in the same segment. However, this intrasegmental "resistance" reflex is normally blocked by an intersegmental reflex in which output from SR(1)'s in caudal segments inhibits SR(1) discharge in more anterior segments.