17Su11Lec2b

17Su11Lec2b - Cogs17 Lecture 2 Neurobiology of Cognition...

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Cogs17 Neurobiology of Cognition SSI 2011 Lecture 2 Structure & Function of Cells in the Nervous System CONTINUED NT can have two basic types of effects on the polarity of the Postsynaptic cell: EPSP = Excitatory Post-Synaptic Potential = An increase that cell’s likelihood of releasing NT - i.e. Post-Syn cell becomes Hypo-Polarized (less polarized, less difference between inside and out) and thus closer to its threshold for firing. - Usually a function of Na+ entering cell IPSP = Inhibitory Post-Synaptic Potential = A decrease in the cell’s likelihood of releasing NT - i.e. Post-Syn cell becomes Hyper-Polarized (more polarized, greater difference between inside and out) and thus farther from its firing threshold - Usually a function of K+ exiting or Cl- entering the cell Summation The response of a given Neuron is nearly always the product of a Summation of EPSPs and/or IPSPs - A Neuron virtually never receives input from only one other cell, and can receive from 1000s of others! - Often both excitatory and inhibitory NTs simultaneously converge on a cell, summating their +/- effects - If effects reach or exceed cell’s Threshold of Firing , trigger an Action Potential (In cells that have AP’s) - When one (or more) cells repeatedly stimulate another in rapid succession, it is called Temporal Summation - When multiple cells converge on a single cell at the same time, the effect is called Spatial Summation Spontaneous Activity – Important to note: Some Neurons show Spontaneous Firing, in absence of incoming NT! - These are usually Graded Potentials that release variable amounts of NT - Converging NTs increase or decrease such cells’ activity, modifying how much NT they will then release Mechanisms - NT affects the Postsynaptic cells via one of two types of mechanisms:
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17Su11Lec2b - Cogs17 Lecture 2 Neurobiology of Cognition...

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