Final answer:
In spatial summation, several synapses happen simultaneously and integrate their signals to produce a greater effect on the neuron, potentially leading to the generation of an action potential.
Step-by-step explanation:
In spatial summation, several synapses happen at the same time. This means that multiple signals from different synapses on a neuron are combined to produce a greater effect. This summing up of multiple graded potentials at different locations of the neuron's membrane can lead to a larger depolarization and increases the likelihood that an action potential will be generated at the axon hillock, leading to the transmission of the nerve impulse.
Spatial summation contrasts with temporal summation, where multiple signals from a single synapse are integrated over time rather than space. To further clarify, spatial summation involves inputs from multiple locations arriving at the neuron simultaneously, which when combined, can have an additive or subtractive effect on the neuron's membrane potential - this can result in an action potential if the combined effect is excitatory and reaches a certain threshold.