The nervous system controls movement, sensation, thinking and behavioral activities. It consists of various elements which comprise the whole complex working process. It is not segmented as individual working parts but rather a very complicated system that overlaps in layers of functions.
Two anatomic components of the nervous system are the central and peripheral nervous systems. It is important to distinguish where your injury is to understand the recovery process. The central nervous system consists of the brain and spinal cord. Both are housed in structures made of bone. The brain is encased in the skull for which there is only room for the brain and the fluid that surrounds it for protection and cushioning. The skull does not expand so an injury or stoke which can cause swelling creates pressure throughout the brain. The spinal cord is contained in the boney vertebrae of the back. These are small segments of bone that work together allowing movement of the spine. Sometimes people ‘break their back’ or have a broken vertebrae bone. This will heal like any other bone without consequences. When the break in the bone damages the spinal cord or if the spinal cord is stretched, paralysis occurs. Very rarely is the spinal cord actually cut all the way through. Therefore, everyone has optimism for recovery. The key to recovery in the central nervous system is being understood in significant strides.
The peripheral nervous system consists of all of the nerves in the body that are outside of the brain and spinal cord. These nerves are not encased in bone but are protected by muscle and other body tissues. The peripheral nerves track from the spinal cord through the boney vertebrae of the back. The peripheral nerves have specific jobs. Some go to the arms, some to the legs and some make our internal organs work such as the heart beating, lungs to breath, etc. Some peripheral nerves conduct signals for movement and others conduct signals for feeling or sensation. Peripheral nerves occasionally become damaged by compression (as in carpal tunnel injuries of the wrist) or by stretching (such as a pulled nerve). Damaged peripheral nerves may regenerate and heal themselves at a rate of one inch per month. Therefore, if you have an injury to your foot affecting your nerve, the peripheral nerve may regenerate one inch per month from the root of the nerve where it exits the spinal cord. If you measure from the base of your spinal cord to your foot, the number of inches is the number of months for recovery to possibly occur. That is a long time to recover but it happens.
Nerves work through autonomic or somatic processes. Somatic is voluntary control of movement. Information in this process of the nervous system transmits signals to and from a body part for voluntary controlled movement. This could be for walking, controlling toileting, taking a deep breath, scratching, etc. This is movement that we choose to do. The autonomic nervous system is body processes that are done without our thinking about it such as our heart beating, breathing, working of our internal organs and glands and other functions that take place to keep our bodies working. Autonomic nerves signal to the brain that the bladder is filling. This happens automatically in our bodies without our control Somatic nerves perform the function of voluntarily deciding it is time to toilet and then walking and releasing urine into the toilet. This process is under our direction or control.
The autonomic nervous system controls the automatic functions of our bodies. There are two processes that work within the autonomic nervous system; one is sympathetic which arouses the body, like screaming or running away when something scares us. The other is the parasympathetic with calms us after excitement. The sympathetic and parasympathetic nerves keep our autonomic nervous system in balance. After spinal cord injury above the T6 level, the autonomic nervous system can be disrupted which affects those automatic responses that we do not have any control over such as blood pressure, stuffy nose, headache, flushing.
When there is a problem with in the body, the nerves try to transmit the issue to the brain. If the bladder is full, the autonomic sensation is transmitted to the brain to the somatic system which tells you to physically go to the appropriate location to voluntarily empty the bladder. This is what should happen. If that message cannot be send directly to the brain for interpretation, it becomes scrambled and may be exhibited by alternate routes under control of the autonomic nervous system such as the sympathetic system ‘screaming’ resulting high blood pressure, headache, stuffy nose, flushing, sweating above the level of injury, slowing heartbeat, goose bumps below the level of injury. The parasympathetic system is unable to calm these signals. All of these symptoms are under control of the autonomic nervous system. When one nerve of the autonomic nervous system cannot convey a message, other parts will try to convey this important message.
You may have all of the symptoms of an out of control autonomic nervous system or just some. Not everyone has the same responses of what is called: autonomic dysreflexia. If you do not have high blood pressure but you have other symptoms, you still have autonomic dysreflexia. Most people will have a few of the autonomic responses but not all of them. It is important to know how your body functions so you can relay information to your healthcare professional as well as being better prepared to care for yourself.
Because the nervous system is so complex, nerve signals don’t just follow one simple route. This explanation of the nervous system is greatly over simplified but it provides a picture of what happens when the nervous system is not processing well.
Messages can be mixed even without nerve injury. We are all familiar with left arm pain being a signal of a heart attack. Or you probably know of people who complain that their nose runs while they eat. In this case, the nerves in the nose are mixed with the signal to increase saliva production for eating. These are all mixed messages in the autonomic nervous system. Adding paralysis makes the mixing of nerve messages more complicated and easier to become confused. Sometimes, people with paralysis will have shoulder pain indicating a gall bladder attack. Paying attention to unusual sensations, especially with paralysis can be lifesaving.
Nurse Linda is online in the spinalcordinjury-paralysis.org forums every Wednesday from 8-9 PM ET to answer your SCI and paralysis related questions.
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