The Communication Process of Neurons in the Brain

The average human brain contains as many as 100 billion neurons. These neurons vary in size and shape and each is specialized to receive and transmit information. Each neuron is made up of a nucleus, cytoplasm, and cell membrane. What makes each neuron special in its own way are the tiny fibers that extend from the cell body. The short fibers branching out around the cell are called dendrites. These dendrites pick up incoming messages and transmit the message to the cell’s body. The long fiber extending from the cell body is an axon. The axon carries outgoing messages to neighboring neurons, glands or muscles. The end of the axon splits into many terminal branches. The axon is covered by a myelin sheath, which provides insulation to a signal and helps increase transmission speed of the signal.
Neurons communicate with each other by on-off electrochemical impulses. When at rest, fluids that are inside and outside of the neuron are temporarily barred from each other. At rest, the negative ions inside the neuron have no contact with the positive ions outside the neuron. Once stimulated, the ions become charged.
An incoming message stimulates the cell membrane. The membrane opens at a point and the positive ions flow in and cause an electrical charge, called a neural impulse, to be created. Thie neural impulse travels down the axon. This “fired” impulse can travel as fast as 400 feet per second, depending on myelination of the axon. This action travels to the end of the axon, through the terminal branches, into a tiny swelling called the terminal button. It is in the terminal button that there is a release of chemicals called neurotransmitters.
There are hundreds of neurotransmitters but the brain has some of its own. Some neurotransmitters of the brain are: Acetylcholine (ACh), which plays a major role in arousal, memory, attention, and motivation; Dopamine which affects voluntary movement, learning, memory, and emotions; Glutamate which involves long-term memory and perception of pain; and Serotonin which is involved in the regulation of sleep, mood, pain, and aggressive behavior. These are but a few common neurotransmitters.
Once the neurotransmitters are released they must cover a distance between the terminal button of the processing message to the dendrite of the receiving of the message. This distance is called the synaptic cleft. A neurotransmitter can not just cross this synaptic cleft. They must be received by the presynaptic neuron located in the receiving dendrite.
Within the terminal button of the presynaptic neuron are sacs called synaptic vesicles. These vesicles release a specific chemical that sends messages to the incoming neurotransmitters. The neurotransmitters cross the cleft, briefly binding with the receptor sites. The receptor receives only neurotransmitters of a certain shape, like a key and lock. If the shape is not specific, the message will not be transmitted. Imbalances of neurotransmitters can contribute to types of mental illnesses.