Nervous system would not exist without the human brain. Most neurons send signals via their axons, although some types are capable of dendrite-to-dendrite communication. (In fact, the types of neurons called amacrine cells have no axons, and communicate only via their dendrites.) Neural signals propagate along an axon in the form of electrochemical waves called action potentials, which produce cell-to-cell signals at points where axon terminals make synaptic contact with other cells. Synapses may be electrical or chemical. Electrical synapses make direct electrical connections between neurons, but chemical synapses are much more common, and much more diverse in function. At a chemical
Drug delivery to the brain Drug delivery to the brain Drug delivery to the brain is the process of passing therapeutically active molecules across the blood–brain barrier for the purpose of treating brain maladies. This is a complex process that must take into account the complex anatomy of the brain as well as the restrictions imposed by the special junctions of the blood–brain barrier. The blood–brain barrier is formed by special tight junctions between the epithelial cells that surround the brain tissue. All tissue is separated by this layer of epithelial cells, however only the brain epithelial cells have these tight junctions that do not