Fifteen different presynaptic neurons synapse on a single postsynaptic neuron. T

Question

Fifteen different presynaptic neurons synapse on a single postsynaptic neuron. The postsynaptic neuron has a RMP of -70 mV. At the trigger zone, 14 of the presynaptic neurons produce excitatory postsynaptic potentials of 2 mV each, and the other one produces an inhibitory postsynaptic potential of 9 mV. The threshold for the postsynaptic neuron is -50 mV. Will action potentials be produced in the postsynaptic neuron? Is this an example of temporal summation or spatial summation? Explain your answers.

Explanation / Answer

The excitatory postsynaptic potential produced by 14 neurons is = 14* 2 = 28 mV

The inhibitory postsynaptic potential produced by one neurone is = -9 mV

The resting membrane potential is = -70 mV

Threshold potential is = -50 mV

The potential difference contributed by the synapses is = 28-9 = 19 mV

The resting membrane potential changes to -70+19 = -51 mV (does not reach threshold potential difference). Thus, no action potential will be produced. This is an example of spatial summation because different neurones are involved in this.

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