Everything we do—from making a grocery list to climbing stairs, from creating a work of art to navigating a car—relies on the proper functioning of our brain. This amazing three-pound organ, which rests within our skull, orchestrates our body’s autonomic responses, such as breathing, digestion, and the dilation of our pupils, and continuously processes information we receive from our environment. It alerts us to danger, tells us we’re hungry, and governs our emotions. It is also the center of all our cognitive processes, allowing us to learn, remember, and to make decisions based on what we have learned.
The brain, along with your spinal cord, is your body’s central nervous system. Nerves that extend from the spinal cord to the far reaches of your body, such as toes and fingertips, make up the peri-pheral nervous system. This vast network of nerves has the enormous task of constantly receiving information from inside and outside the body, then relaying that information up to the brain so it can respond.
This information travels along an enormous network of nerve cells, called neurons. In the absence of disease or injury, these amazing cells are constandy repairing themselves and have the capability to live 100 years or more. What makes the human brain so amazing is the sheer volume of neurons it contains—approximately 100 billion!
Neurons continuously receive and process nerve impulses, which travel along the neuron and are then transmitted across gaps between neurons called synapses. Once in the synapse, the impulse triggers the release of chemical messengers called neurotransmitters, which then bind to receptors on the receiving cell, where the transmission of the impulse is repeated again. The message, or impulse, continues traveling from one neuron to the next throughout the body until it reaches its destination and relays its signal. For instance, if you fall and scrape your knee, the incident immediately sends a pain signal to your brain.
All of this activity happens in less than a split second and without conscious thought. At the end of this process, the brain has the task of interpreting the message and making the decision as to what to do about this new information. What should someone do about an injured knee? A child who receives pain signals to his knee for instance, may cry and run for his mother. A jogger may pause from his run to stretch. An elderly person may decide to take a pain reliever. How a person chooses to respond depends in large part on the memories stored in the brain that tell her how effective her previous responses were.