Final answer:
Neurons cannot be connected in series to create a huge voltage like electrical circuits, and thus, cannot generate harmful voltages in the body. Neuronal summation involves postsynaptic potentials adding together but can occur at slightly different times if the effects overlap temporally.
Step-by-step explanation:
The concept of neurons creating a huge voltage by being connected in series, like voltage sources in an electrical circuit, is not applicable to the human body. Neurons generate electrical signals known as action potentials through ionic exchanges across their membranes, not by creating voltages that add up in series. Furthermore, these electrical signals are transduced into chemical signals using neurotransmitters to communicate with other neurons at synapses. The mechanism of summation in neuroscience refers to how these postsynaptic potentials at the dendrites and cell body of a neuron can add together to influence the generation of a new action potential, but this process does not result in the addition of voltages in the same manner as electrical circuits. As such, it is not possible for neurons to create a large voltage that could be harmful to the body in the way electrical shocks are.
To answer your question about summation, in the context of neuronal communication, spatial summation does not have to occur all at once; signals can arrive on the postsynaptic neuron at slightly different times and still contribute to reaching the threshold potential if their effects overlap temporally.