6 10 14 15

6 10 14 15 - Neuro Essays#6 10 14 6 If you were designing a...

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Neuro Essays #6, 10, 14 6) If you were designing a neuronal circuit to produce a behavior quickly, what features would you build into the channels, the synapses, and the neurons in the circuit and why? Neurons: Length constant = measure of how potential decays with time. λ = sqrt(rm/ri). You can decrease the internal resistance by making the axon larger (wider). Doing so will increase the length constant and will provides more pathways for ion flow. If ions can flow faster through the axon, the action potentials will propagate more quickly. You can also insulate the axon with myelin and/or close leak channels to prevent current from leaking out across the membrane. This will mean that a smaller depolarization will be felt further down the axon. Express more calcium channels so that more calcium can rush into the cell more quickly once upon depolarization of the cell. Increased calcium influx will cause faster release of transmitter because more vesicles will be released in the same amount of time. However, the speed of vesicle release will be limited by the number of vesicles in the cell at the time. Synapses: You can also use electrical synapses instead of chemical synapses. Electrical synapses are slightly faster than chemical ones. They are more reliable than chemical synapses, and would be good for a quick behavior (like an escape reflex, etc.) You can also make synaptic contacts near the spike initiation zone. Any stimulation near this area of the neuron is more likely to produce a response because the spike initiation zone has the lowest threshold in the entire cell for firing a spike. Even with small stimulation, you could produce the desired behavior. Channels: Make it so that sodium channels open at a lower voltage. 10) The sense organs usually provide the brain with information about the what , where , when , and how much of a given environmental stimulus. Illustrate this statement by explaining how the nervous system represents or “encodes” of each of these four types of information for one of the following events:
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This note was uploaded on 02/25/2009 for the course BIO 2220 taught by Professor Hopkins,c.d. during the Spring '08 term at Cornell.

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6 10 14 15 - Neuro Essays#6 10 14 6 If you were designing a...

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