Bovine biology series
Part - 31 Nervous system (2/4)
The nervous system
The word "pain" is derived from the Latin word poena, which in turn was derived from the Greek word poine. The very old words meant penalty, or the action verb, to pay.
Appropriately then, I use this word in continuing our discussion of the nervous system. Why? Because in all of us, the interpretation of pain is one of penalty, in that somewhere something is wrong. We must take corrective action or the penalty is paid. The penalty is, of course, discomfort, or in severe cases, the partial or total inability of an organ or tissue or body part to perform its function.
I know this all well, for as an athlete, I have and continue to deal with a right ankle that is chronically injured. Most of the time the injury is subclinical even though chronic, but the pain is minimal and I can run and race. However, at times the chronic injury is painful to the point that I must pay the penalty.....that is, I limp or slow my gait and thus while I may run, I cannot race. For the penalty of discomfort is severe enough that I must take correction action, otherwise the penalty is too great. Of course, thank goodness for Ibuprofen!
What if we did not experience pain, so that a payment for discomfort was not required? I can imagine that we might destroy ourselves. That is, in the manner of pushing forward, soon our bodies would experience a total breakdown of function, for without the experience of pain, the body does push forward because the brain interprets normal function on all fronts. At some point, however, a bone may break, an organ may fail, a tissue may be atrophied, thus severely or completely stopping normal function.
As a runner, pain is my friend, for as stated, it is telling me that a payment must be made when I push forward when the body is not ready for it, and therefore the payment for pain is the discomfort, and I make the adjustment. Such as rest or slower running. The objective is to heal, so that once more we can race instead of just run!
How does the nervous system function in this interpretation and sensation of pain, the penalty of discomfort and the inability of the body to perform? First we must examine the parts involved.
The central nervous system, CNS, is comprised of the brain, spinal cord and the neurons reaching too and from all parts of the body. As wiring in a home, all parts of the body, from the fingertips and toes to the muscles in our eyes, from the sciatic nerve running into our legs to the neurons of the abdominal muscles, all are linked in such a manner that through the spinal cord, they end up at the brain in the cerebrum. The brain, of course, is analogous to the junction box in our garage, in that all wires end up there and begin there.
One further differentiation of the nervous system is this: the central nervous system, comprising the spinal cord and brain, is but one part. The other may be called the peripheral nervous system, which functions in carrying information too and from the central nervous system.
The spinal cord of the CNS system is a hollow tube running the length of the back. It can flex minimally, although its function to protect the nerve cells running in this tube is paramount, so the backbone is fairly rigid.
The contents of the spinal cord are the gray and white areas. The gray area resembles a butterfly shaped region; here, the bodies of neurons and interneurons exist, interpreting reflexive information from motor and sensory neurons in various body parts. Outside of the gray matter, the white matter carries other neurons that are covered with the myelin sheaths for protection, hence the white color.
The spinal cord is a rope like cord that contains these nerve cells, and we may liken them to hundreds of very small diameter wires running through a tube.
The spinal cord is encapsulated in the spinal column, a series of bones configured for protection and some movement for flexibility. They are the vertebrae. Their purpose is twofold: one, a hollow region for the spinal cord and two provide the support for the skeleton. More important in the human so that we may walk upright, the 33 vertebrae support the body so that we may breath deeply, turn our head, move our arms and legs, and yet in times of rest, we may stay elongated so that our body cavity can remain stretched so that we can breath and digest food.
A cow requires a slightly different spinal column function, in that it must integrate the skeletal movement of the front portion of the cow with the back portion. The spinal column must support the tremendous weight of several hundred pounds of body cavity and food consumed, as well as the udder tissue and fetus if the cow is pregnant.
The spinal cord is directly linked to the brain in the form of a brain stem, adjoining the base of the brain.
We know that while the nerves of the spinal cord receive and deliver messages to all the body, the incoming messages from the body, once moved through the spinal cord via the neurons and interneurons, are more completely interpreted in the cerebrum portion of the brain.
One interesting note about the integration of the brain itself with the spinal cord is the sharing of the cerebrospinal fluid. This cloudy appearing liquid is originated in the brain, for this organ filters blood and the filtrate fills the spaces around the brain and spinal cord.
The cerebrospinal fluid cushions the brain and spinal cord against shock and trauma. The fluid, surrounding the brain and filling the hollow spaces near the spinal cord, bring nutrients, hormones and white blood cells to these parts of the CNS. After supplying the cells with nourishments, the wasteproducts are carried into the veins for disposition.
Next month, we examine the peripheral nervous system.....the sensory and motor divisions
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