PHYSIOLOGY AND ANATOMY OF POSSIBLE OSCILLATORS IN THE CENTRAL-NERVOUS-SYSTEM

Pathologic tremors occur when the normal, continuous pattern of muscle activation is replaced by relatively synchronous bursting. This artic le discusses the possible roles of stretch reflex and central oscillat ors in producing tremor, The gain and conduction delay in some reflex arcs places the stretch reflex close to oscillation in some muscles du ring normal operation. Within the brain, cells in the thalamic relay n uclei and inferior olive contain a set of ionic conductancies in the c ell membrane that can interact to produce oscillations in membrane pot ential. This tendency is exaggerated by hyperpolarizing or depolarizin g the cell away from the normal resting potential. The activity of nei ghboring cells can be coupled (by electrotonic gap junctions in the ol ive and by recurrent axonal projections from the reticular nucleus in the thalamus), thus a large population of cells can oscillate together and exert a powerful rhythmic influence on motor output.