Excitatory Synaptic Transmission Between Neurons

The synapse at the neuromuscularjunction is unusual in one important aspect: a single action potential in the presynaptic motor neuron produces a sufficiently large depolarization in the postsynaptic muscle cell to trigger a postsynaptic action potential. Such a synapse is called a one-for-one synapse because one action potential appears in the output cell for each action potential in the input cell. Most synapses between neurons are not so strong, however. Instead, a single presynaptic action potential typically produces only a small depolarization of the postsynaptic cell. The synapse between a single stretch receptor sensory neuron and a quadriceps motor neuron is typical of this situation, as illustrated schematically in Figure 9-1.

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