Nervous System
How the Nervous System Works:
The nervous system’s main function is to regulate and coordinate the other systems of the body. It works with the endocrine (hormonal) system to perform this function. Without the nervous system to make the body function, death occurs quickly. In fact, one of the ways we determine death is by measuring the function of the brain (the most complex part of the nervous system).
The nervous system can be thought of a system–a web of interconnected neurons, or nerve cells. These neurons are bundled together to form nerves. Neurons transmit electrical signals along the entire length of the cell and then passes that signal on to the next neuron in line. Most neurons do not actually touch
One set of neurons send signals to your spinal cord or brain telling your body what is going on in the outside world and in other parts of the body. These are sensory neurons; they allow your to feel the clothes against your skin, feel the food in your stomach, feel the pain of a needle, and read the words on this page.
The central nervous system (brain and spinal cord) is responsible for interpreting the information that sensory neurons bring and then figuring out an appropriate response.
Another set of neurons (called motor neurons) act as the messengers for the central nervous system. They allow the central nervous system to perform an action. They pass signals toward a target tissue. When the last neuron reaches its target (such as a muscle), that electrical signal triggers an action in the target (such as a muscle contraction). Other actions that motor neurons can stimulate are hair raising (which is actually muscle contractions as well), eyes dilating, secretion of sweat, dilating or constriction of arteries, contraction of the bladder wall, release of saliva, and many other actions. Some of these you have conscious control over and some you do not. You have conscious control over the neurons that go to our large skeletal muscles (the ones you move all the time). You do not have control of the neurons that control your smooth muscles and glands (pupils dilating, sweating, salivating, hair standing up, etc.)
A very simple example of how this works is your eye detects light bouncing off of an object that is getting bigger and bigger. Sensory neurons from your eye transmit signals along your optic nerve to the brain. The brain interprets the information as a ball coming toward you through the air. The brain the sends signals to all of the muscle involved and you catch the ball. A more complex example would be to the decision-making process involved in deciding what to do next: you would perform different actions if you were a player in a baseball game versus if someone had malicious thrown the ball to try to hurt you. We do not really understand the mechanisms that occur to allow you to make those decisions, especially as quickly as we do.
Another subject that needs to be discussed is the myelin sheath. You may have already gathered that the neuron are like little wires and they are then bundled together to make a nerve which is similar to a cord. Well around every cord and wire, there is a plastic or rubber insulating material. The nerves are built the same way. Around every neuron and nerve, there is material that is collectively known as the myelin sheath. Myelin’s job is to allow faster transmission of nerve signals down each neuron. They are also involved in providing nourishment, protections, and even repair of neurons.
Earlier, I mentioned that a neuron (nerve cell) transmits an electrical signal along the entire length of the cell and then passes that signal on to the next cell in line like in a relay race. Many of the neurons in the body do not touch directly so the electrical signal cannot pass directly from cell to cell. There is a chemical messenger that is sent out from the first neuron and stimulates a new electrical signal on the second cell. This chemical messenger is called a neurotransmitter. You hear about these all the time; common examples are serotonin, melatonin, adrenaline, and dopamine. Each of these neurotransmitters acts a little differently. From here, this discussion gets very complex and is beyond the scope of this page.
This is a very basic overview of how the nervous system works. I would recommend searching on Youtube for video representations of what I wrote about above. Medical school web sites and physiology textbooks will offer more detailed explanations.
