this video is going to wrap up our series on the nervous system and this video will cover the topic of neuronal pools and circuits a neuronal pool is a group of neurons dedicated to a particular function neuronal pools are made of a series of neuronal circuits the circuit describes the structural orientation of the neurons in that neuronal pool and in this picture we can see five different circuits but we are going to discuss only four of those our first circuit is a diverging circuit in a diverging circuit one nerve fiber is going to branch into axon collaterals and synapse with several postsynaptic cells these postsynaptic cells are going to branch and then connect to many and more cells so at each Junction we're making the number of cells that we communicate with larger this is how one motor neuron can stimulate thousands of muscle cells so as we diverged we are going to be communicating with more and more cells in a converging circuit we are going to do the opposite we are going to take signals from many axons and bring them into one postsynaptic cell this is how much of our sensory nervous system works so we get sensory inputs from many different areas involved in making a decision regarding all of that output and that sensory info could be something like respiration we've got stretch information quemo receptive information and Baro receptive information coming into our medulla oblongata and we have one cell making a decision this one cell can then make a decision about what should occur regarding respiration our third type of circuit is called a reverberating circuit a reverberating circuit is going to be self reinforcing because an axon collateral is going to double back and re stimulate and neuron early in the circuit to keep that signal going to our target organs so this circuit is self-perpetuating as our input comes down that input also doubles back to re-stimulate the entire process a good example is medulla oblongata control over breathing so our module ascends one signal that says breathe and then that signal doubles back on itself and continues to rista mule eight the circuit until the pathway is interrupted that interruption may come from a stretch receptor chemoreceptor or baroreceptor as we mentioned in our previous example of a converging circuit lastly we have a parallel after discharge circuit this is going to combine a diverging circuit with a converging circuit the key here is that our signal is going to arrive at our target cell at differing because we have a different number of neurons involved in each of those pathways a great example of a parallel after discharge circuit are the circuits in your eye so if you blink you may not even notice that you blink because you have these separate pathways bringing in that visual information and those pathways all arrive at different times so that you do not necessarily have a break in the information coming into your brain regarding your visual stimuli or if you look at a lamp or the Sun you get that after image because that information is still being delivered to your brain even after you have stopped looking at that lamp or the Sun this concludes our video series on the nervous system if you have any questions please do not hesitate to contact your instructor