The teleology of this phenomenon appears to be to produce a condition so that even

teleology of this phenomenon appears to be to produce a condition so that even if the corticospmal tract fires repetitively, the frequency of the muscle contraction remains less {Renshaw cell inhibition lasts for quite a few milli seconds), and thus the muscle is protected against too high frequency stimuli Fig. 10A.3. 7. Renshaw cell inhibition Importance of synaptic inhibition should be understood. The importance of reciprocal innervation and Renshaw cell inhibition has already been discussed. Presynaptic inhibition is seen only in sensory neuron. A notable example is presynaptic inhibition at the level of SCR (substantia gelannosa Rolandii) in connection with endogenous pain inhibiting mechanism (fig 10B1, 23).. Facilitation of synaptic transmission also occurs. Serotonin (5HT) acting as a ST can achieve this. To understand the phenomenon, the same figure of 1QA.3. 5 may be reconsidered. Let us presume, this time, The neuron i is secreting serotonin and this serotonin. via the anoaxionic synapse (shown by red circle) causes a prolongation of AP (action potential) in the e. (This prolongation is produced as follows. Serotonin blocks or closes the ligand gated k+ channels of the cell membrane of e accumulation of K+within the neuron terminal e no decay of AP at e, ieb the AP is prolonged; recall, the decay or extinction of AP is primarily due to exrt of K+ ions, (fig. 1.2.4 ) Prolonged AP causes vigoros development of EPSP facilitation, that is, a weaker stimulus, which is not ordinanly effective, can become effective now). One thing by now should be clear that is inhibition and facilitation are (one of the) means to control neuronaf activities in the CNS PLASTICITY OF FUNCTIONS OF THE SYNAPSES This topic has been drawing much attention now a days An example will help to understand the phenomenon; (a) a normal unperturbed man is sleeping in his bed room Suddenly some queer sounds occur, the sleep is momentarily disturbed, but from experience, the man knows that the sound is due to movement of rats he instinctively ignores the stimulus (= the