How many quanta of ACh are required to depolarize the motor end plate from -80 to -70 mV if a miniature end plate potential is 0.4 mV
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The current generated at an axo-dendritic synapse causes a maximum voltage change (EPSP) of 40 mV. The time constant of the postsynaptic membrane τ = 30 msec. What is the amplitude of the EPSP 40 msec after its peak? Show your work. The axon hillock is 250 μm away from this synapse. The membrane space constant λ = 400 μm. The threshold for firing action potentials is 20 mV depolarized relative to the resting membrane potential. Will the 40 mV EPSP trigger an action potential at the axon hillock? Show work supporting your answer.
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Normally, an end-plate potential (EPP) is always suprathreshold. However, in this experiment, curare was used at a concentration that blocked some but not all of the nicotinic acetylcholine receptors (nAChRs) in the muscle so that the EPP was subthreshold. This allowed researchers to record only the current associated with the EPP (no voltage-gated channels opened). Explain how and why curare could decrease the amplitude of the EPP. (Hint: consider whether there would be any effect on IEPP.)
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A microelectrode delivers a current pulse that depolarizes the presynaptic terminal above threshold. Describe the events that occur (in molecular detail) immediately after depolarization. Your answer should finish with the response of the postsynaptic neuron. The presynaptic neuron releases ACh and the postsynaptic neuron has ionotropic AChR. what channels are activated in terminal? what currents flows through the membrane? What direction? Why? what are all the proteins involved in the release of ACh vesicles? mechanism?
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