All About The Spinal Cord and Its Importance
“No one can ever use his heart to listen or touch or feel or see or smell. It's just a lump of muscle pumping mechanically inside your ribs. It has no will and no ability to do anything but go on pumping until it gives up and withers away or is choked by some disease. Your spinal cord, on the other hand, feels. The central nervous system pours out from the spinal cord, and with it one feels pain. Pain is the most trustworthy sensation a human being can know because it teaches us what hurts. With the spinal cord, one can hear what will hurt, smell the sting of suffering, taste it, feel it, and see the world with new eyes. I learned a long time ago not to follow my heart, the hunk of meat flexing in the chest. I trust the tube locked up in a column of bone, the tube that shows me what pain is.” - Joshua S.Porter, The Spinal Cord Perception
Almost all the sensory and motor nerves that activate the muscles extend from the spinal cord. The cord is a long cable-like structure made up of hundreds of nerve fibers, which is approximately 17 inches (42 cm) long. It is suspended in the bony canal formed by the long string of vertebral, bashed by a clear fluid called the spinal fluid and enclosed within the vertebral column. The cord runs up the spine and through the opening of the bottom of the cranium where it expands and becomes the brain. It extends from the foramen magnum of the skull to the first and second lumber vertebra. It provides a two-way conduction pathway to and from the brain. It is also a major reflex center where the spinal reflexes are completed.
The spinal cord is covered by three meninges: the dura mater which is the outermost, the arachnoid membrane and the innermost is the pia mater. These meninges are continuous with that in the brainstem and cerebral hemispheres, with cerebrospinal fluid found in the subarachnoid space.
The cells that make up the nervous system are called neurons. All cells react to stimulation, but none in the unusual way that neurons do. Neurons are capable of transmitting an impulse to its neighboring cell. The billions of neurons packed together into the nerve paths deliver a message to the brain in the following way. The impulse travels rapidly in one direction; each neuron disturbing the next one along the route of a sensory nerve until the section of the concerned organ or body part is informed. The response is flashed back in identical manner through a motor nerve to the muscles it activates. The first neuron in a sensory nerve that is stimulated starts a chain reaction that ends with the contraction of a muscle through a motor nerve.
Functions of the spinal cord
The functions of the spinal cord can be divided into three categories:
- Reflex activities/Reflex Action (reflex arc)
Some messages that the sensory nerves send to the brains are marked urgent. They are the messages of pain. All over the surface of our body are sensory nerves on the look out for anything that might hurt us. When the point of a pin pricks our finger, the nerve that carries the messages of pain to the brain does not wait to see if the brain is busy doing anything else. It demands that the message be answered immediately. The call for help is answered by way of the motor nerves, and the muscles of the hand snap the finger away from the pin. These actions are not planned; they are called reflex arc/reflex action. Most reflex actions are the result of an excited sensory nerve calling a motor nerve to its aid. In many cases the message goes no further than the spinal cord, where the connection between sensory and motor nerves takes place. Some reflex actions occur through the brain. Through one of the five senses we blink, jump or bring some other motor response into action. The reflex mechanism of the brain and the spinal cord is alert even when we are asleep. It is always protecting and warning us.
2. Conduction of sensory impulses is upward through ascending tracts to the brain.
3. Conduction of motor impulses is from the brain down through descending tracts to the efferent neurons that supply muscles or glands.
Spinal Nerve Roots
In humans, 31 pairs of spinal nerves arise from the cord and exit from the vertebral column to serve the body area close by. It is about the size of a thumb for more of its length.
8 cervical segments
12 thoracic segments
5 lumbar segments
5 sacral segments
1 coccygeal segment
The collection of spinal nerves at the inferior end of the vertebral canal is called caudal equina. Each spinal nerve continues only a very short distance away from the spinal cord and then branches into small posterior divisions and rather large anterior divisions. The larger anterior branches interlace to form networks called plexuses, which then distribute branches to the body parts.
The three main plexuses are:
- Cervical plexuses supplies motor impulses to the muscles of the neck.
- Brachial plexus sends numerous branches to the shoulder, arm, forearm, wrist, and hand.
- Lumbo sacral plexus supplies nerves to the lower extremities.
Disorders of the Spinal Cord
Poliomyelitis is caused by polio virus, which enters the body through the nose and throat and multiplies in the gastrointestinal tract then travels to the CNS, possibly by way of blood. It occurs most commonly in children.
Multiple sclerosis is an extremely disabling disease, which involves the entire spinal cord and the brain. Its symptoms include weakness, tingling, numbness, muscle stiffness, thinking problems, and urinary problems.
Amyotrophic Lateral Sclerosis (ALS) – is a disorder of the nervous system in which motor neurons are destroyed. It is also known as "Lou Gehrig's Disease,". ALS is a progressive neurodegenerative disease that affects nerve cells in the brain and the spinal cord.
Ice Bucket Challenge
The Ice Bucket Challenge, or the ALS Ice Bucket Challenge, is an activity which involved dumping a bucket of ice water on someone's head. This is done to promote awareness of the disease amyotrophic lateral sclerosis or ALS and to encourage donations to research. The said challenge started last July and August 2014.
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