Babinski reflex and corticospinal tract lesion

Functions of the Ia inhibitory interneuronsThe Ia interneuron allows higher centers tocoordinate opposing muscles at ajoint through a single command.1) Mediates reciprocal innervation instretch reflex circuits.2) Receives input from corticaldescending pathway. A singledescending signal that activates oneset of muscles automatically leads torelaxation of the antagonists.3) Other descending pathway providesexcitatory or inhibitory connectionsto Ia neurons (I.e. greater inhibitionallowing contraction of opposingmuscles to occur).15Functions of the Renshaw Cells• inhibitory interneuron• Inputs: Excited by collaterals of the axons ofmotor neurons (leads to presynaptic inhibition);descending pathways•Effects:•Inhibition of large transient movements•Dis-inhibition of the antagonist muscle•Central modulation regulates the sensitivity ofMN to afferent input16