From "The Brain: Understanding neurobiology," NIH. The brain of an adult human weighs about 3 pounds and contains billions of cells. The two distinct classes of cells in the nervous system are neurons (nerve cells) and glia (glial cells). The basic signaling unit of the nervous system is the neuron. The brain contains billions of neurons; the best estimates are that the adult human brain contains 10 to the 11th neurons. The interactions between neurons enable people to think, move, maintain homeostasis, and feel emotions. A neuron is a specialized cell that can produce different actions because of its precise connections with other neurons, sensory receptors, and muscle cells. A typical neuron has four morphologically defined regions: the cell body, dendrites, axons, and presynaptic terminals.
But how to explain our emotions; falling in love, joy in the birth of a child, the pain of loss? Glia, neurons, synapses? Or something more? An intangible humanity, unknowable, ethereal, and eternal.