Neurons are the basic building blocks of the nervous system. They transmit information, chemically or electrically, throughout the body. There are several types of neurons: sensory neuron-they convert external stimuli into internal electrical impulses and transmit this information to the brain and motor neurons-located in the central nervous system, they directly or indirectly control muscles
Neurons have extensions called dentrites that look like spikes extending from the body of the cell. It is primarily the surface of the dentrite that receives chemical messages from other neurons. Another important extension is the axon that transmits electro-chemical signals to other neurons.
There are 100 billion (more or less) neurons in the adult brain!! Each of these neurons have 7,000-10,000 synaptic connections to other neurons (Bonnie Badenoch, 2008).
Neurotransmitters facilitate communication between neurons by carrying messages that increase (excite) or decrease (inhibit) electrical activity in the neuron. Thought, mood, behavior and the manner in which we relate to others is greatly influenced by these neurotransmitters.