One of the first things that most designers forget about CSS descendant selectors is that they are flexible. When CSS defines a descendant, it doesn't care whether the tag in question is the direct child, the grandchild, or some great-great-great-descendant of the initial element.
From the retina, visual information passes onto the bipolar cells and then to the optic nerve's ganglion cells. The optic nerve, which begins at the retina, is the sole visual pathway to the brain. Light information is conveyed as an electrical action potential through the neurons.
Neurons communicate at structures called synapses in a process called synaptic transmission. The synapse consists of the two neurons, one of which is sending information to the other. The sending neuron is known as the pre-synaptic neuron (i.e. before the synapse) while the receiving neuron is known as the post-synaptic neuron (i.e. after the synapse). Although the flow of information around the brain is achieved by electrical activity, communication between neurons is a chemical process.