By Dr. Jigsaw Quietus (AKA; George Bilunka) <[email protected]>

The human brain contains a hundred billion brain cells called neurons. Neurons exchange signals throughout the brain and body. The processing of these signals is what enables planning, logic, memory, motor skills, and language. It affects the senses and our moods. A neuron resembles a tree. It has roots called dendrites, which connect to other neurons. It has a trunk called an axon. The axon carries signals from the dendrites (roots) to the axon terminals (branches). An axon terminal can be as short as a few millionths of an inch, in the brain, and as long as three feet, such as the sciatic nerve of a tall adult, which is near the hip. Some neurons can transmit signals at a rate of 120 miles per hour. A neuron’s axon terminals reach out to the dendrites of other neurons, so they can communicate with one another. The junction between the neurons, the axon terminal of one neuron and the dendrite of another, is called the synapse. Electrical signals travel down the axon but cannot cross the synapse. When a signal reaches the neuron’s axon terminal, chemicals called neurotransmitters are released. The neurotransmitters ferry across this gap known as the synaptic cleft, and they wash over the dendrite of the chosen neuron, which has special molecules on it called receptors. The neurotransmitters then stick, or bind, to these receptors, and the receiving neuron, better known as the post-synaptic neuron, responds to the signal and continues the process of transmitting information through the nervous system. Neurons are constantly sending signals to other neurons, and as we learn new things, these neurons grow and change; creating pathways and networks. These released chemicals (neurotransmitters) often work in combination with one another. I will be mentioning only a few of the over sixty (60) different neurotransmitters within the human brain, but one in particular; that is dopamine. The neurotransmitter serotonin and norepinephrine are also key players in a person’s state of mind. Many antidepressants and antianxiety medications target serotonin- and norepinephrine-producing-neurons, which is another discussion entirely. All substances of abuse trigger the neurotransmitter dopamine. It plays a big role in emotional arousal. It responds to pleasurable rewards and painful punishment. The dopamine pathway records actual experiences of pleasure and ensures that the behavior that led to its release is remembered and repeated. The brain is designed to believe that any experience that influences a spike, or surge, in dopamine is essential to its survival. The neurotransmitter norepinephrine controls wakefulness and arousal. Low levels of norepinephrine and dopamine are often associated with lethargy, trouble focusing, negativity, anxiety, and even mental fuzziness. The neurotransmitter serotonin regulates mood, memory, wakefulness, sleep, and temperature. It is also involved in appetite and aggressive behavior. This neurotransmitter is produced by the raphe ganglia and reaches all parts of the brain. Low levels of serotonin are often associated with depression, emotional rigidity, worry, and irritability. Neurotransmitters normally do not stay in the synaptic cleft for very long. They are taken back up inside the sending neuron by reuptake transporters to be recycled while others are broken down by special enzymes known as monoamine oxidase. This keeps the neuron from being over-activated. Synapses are the subject of much current brain research, for it is believed that most learning and development occurs in the brain through the process of strengthening or weakening these connections. Each one of our one hundred billion neurons may have anywhere from 1 to 10,000 synaptic connections to other neurons. This means that the theoretical number of different patterns of connections possible in a single brain is approximately forty-quadrillion (40,000,000,000,000,000). It is in this tiny gap that our psychoactive drugs, from Aspirin to Prozac, work their magic. The eight-month-old fetus has twice as many neurons as the adult brain, but as the child’s brain ages, neurons that are weak or unused, or simply don’t fit the job that needs to be done, are pruned away to leave more efficient connections for those that are performing brain work. The principle of “use it or lose it” begins with non-working “couch-potato” cells dying off while those that are exercised get stronger and develop more connections. The brain is a dynamic ecosystem. The various neurons and networks, within the brain, are engaged in a fierce competition for incoming stimuli. Networks that succeed in processing new experiences, or behaviors, end up as strong, permanent members of the neuronal neighborhood, while unused neurons, cut off from the ebb and flow of information, wither away and die. In effect, the brain’s structure becomes the information that it receives, and so how it perceives that information determines its future state. Nobel laureate, Gerald Edelman, has termed this neuronal-battle-process: “neural Darwinism”; it’s an 1864 theory that, inherent dynamic forces allow; only the fittest will prosper in a competitive environment or situation. Edelman argues that each network in the brain is striving against the others for feedback from the outside world. Please return for discussion continuation…


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