Consider the neuron below, which has a membrane resting potential of -70mV, membrane space constant of Imm, membrane time constant of 100ms, and spike firing threshold of -65mV. The neuron receives input from three synapses. Synapse A generates an EPSP of 12m amplitude and 2ms duration, synapse B generates an EPSP of 8mV amplitude and 1ms duration, and synapse C generates an IPSP with an amplitude of -2mV and duration of 3ms. A axon hillock 0.5mm B Justify your answers to the following questions mathematically (round distances to nearest 0.5mm). You can neglect propagation time (ie. assume EPSPS/IPSPS arrive at axon hillock at same time irrespective of distance). (a) Would the cell fire an action potential if A is active? (b) Would the cell fire an action potential if A and B are active simultaneously? (c) Would the cell fire an action potential if B is activated twice with a delay of 2ms? (d) Would the cell fire an action potential if all three are simultaneously active? (e) If an excitatory synapse were also located at C, how large must the EPSP be to fire an action potential?

Consider the neuron below, which has a membrane resting potential of -70mV, membrane space constant of Imm, membrane time constant of 100ms, and spike firing threshold of -65mV. The neuron receives input from three synapses. Synapse A generates an EPSP of 12m amplitude and 2ms duration, synapse B generates an EPSP of 8mV amplitude and 1ms duration, and synapse C generates an IPSP with an amplitude of -2mV and duration of 3ms. A axon hillock 0.5mm B Justify your answers to the following questions mathematically (round distances to nearest 0.5mm). You can neglect propagation time (ie. assume EPSPS/IPSPS arrive at axon hillock at same time irrespective of distance). (a) Would the cell fire an action potential if A is active? (b) Would the cell fire an action potential if A and B are active simultaneously? (c) Would the cell fire an action potential if B is activated twice with a delay of 2ms? (d) Would the cell fire an action potential if all three are simultaneously active? (e) If an excitatory synapse were also located at C, how large must the EPSP be to fire an action potential?

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter4: Principles Of Neural And Hormonal Communication

Section: Chapter Questions

Problem 4TAHL: Assume presynaptic excitatory neuron A terminates on a postsynaptic cell near the axon hillock and...

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Assume presynaptic excitatory neuron A terminates on a postsynaptic cell near the axon hillock and presynaptic excitatory neuron B terminates on the same postsynaptic cell on a dendrite located on the side of the cell body opposite the axon hillock. Explain why rapid firing of presynaptic neuron A could bring the postsynaptic neuron to threshold through temporal summation, thus initiating an action potential, whereas firing of presynaptic neuron B at the same frequency and the same magnitude of EPSPs may not bring the postsynaptic neuron to threshold.
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