I am not even sure what we think of these today:. Are they electrical impulses? Chemicals?
The brain and nervous system work with both electrical and chemical signals. Nerve impulses are electrical. But the signals are carried between synapses in the brain are (primarily) by chemical compounds (neurotransmitters).
The synapse (article) | Human biology | Khan Academy
How neurons communicate with each other at synapses. Chemical vs. electrical synapses.
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