Neuroscience and Perceptual Threshold - Essay Example

Dissertation Intro Writing Neuroscience is the scientific study of the Nervous System, one of the most important systems in our body. It is one of the branches of Biology. It involves molecular studies of the individual nerve cells to imaging sensitivity and motor tasks in the brain. Nervous System: It is a big network of veins that operate just below the skin. It is used for decoding a lot of sensory and other perceptions. One of them is the pain. Pain is a technique wherein the body informs us that we have got hurt or that a body part has suffered stress or strain and it needs rest. It is a signal which asks for an immediate action. Whenever we fall or cut ourselves we experience pain, sometimes unbearable. Hence, our body tells us to take adequate care of that part so that the damage is looked after. We take the help of various pain killers that are available in the market to control and get rid of the pain. Apart from the medicines, anesthesia is also used to numb the pain. People are given local anesthesia before an operation. These are medicines which mix in our blood and we don’t feel the pain. Thus, the basic purpose of the pain killers is to numb the problem organ so that we do not feel any pain. Web site for Reference: www.sciencedaily.com TENS: It is one of the pain killers, which is the application of electric current through our skin for pain control. This research will showcase the reasons behind its working. We will also notice the intensity and the duration of the current passed into our skin. The unit used for this is called the TENS that is Transcutaneous Electrical Nerve Stimulation. TENS is unlike any other pain killers as it does not penetrate into the body. It is a safe nerve stimulation intended to reduce pain, both acute and chronic. There are results to show that TENS can be used as the best pain killer. The constant mode of TENS is found to give a better post analgesic effect for TENS users with chronic pain in clinical trials. However no one has investigated how the harmless feelings can be affected by constant mode TENS. Harmless or non-noxious stimulation is generally used by the animal to make it aware of the state of its body and of its immediate environment. This can be tested by using a non-painful stimulation method, 2 point discrimination test. Any changes after the TENS treatment can affect the awareness of movements and relative position of body parts. This can be a potential issue for some TENS users with balance problem. An experiment was done on this and was found that constant mode TENS gives a higher pain threshold than frequency modulated TENS during treatment, therefore an individual will have a more apparent effect on discriminative touch post TENS treatment. Book Reference: Pain Treatment by Transcutaneous Electrical Nerve Stimulation. Edited by Ottoson D, Lundeberg T. Berlin, Federal Republic of Germany, Springer-Verlag, 1988, 130 pp, paper.. This book has a good flow and follows a logical sequence. The illustrations are an excellent supplement to the text. At the end of each chapter are an adequate reference list and a suggested reading list. Perceptual Threshold: One fascinating characteristic of the central nervous system, which processes the sensory information, is the perceptual threshold. Perceptual threshold is the point of stimulus intensity needed for anyone to get familiarized to a particular sensation, like, a taste. Stimuli fire upon ones sensory receptors continuously, but the brain filters out and "rubs off" some stimuli. Everyone experiences a change in perceptual threshold when one "lowers the volume" of the television while answering a call or studying or when you “wander off” during a lecture. In these cases, the noise is sufficient to stimulate sensory neurons in the ear, but the traveling neurons cools down the grasped signal so that it does not reach the conscious brain. So this fall in intensity of the noise decreases perception of stimulus which is accomplished by inhibitor modulation, which in turn minimizes a suprathreshold stimulus until it is below the perceptual threshold. Restricted tone often occurs in the secondary and higher neurons of a sensory pathway. If the altered stimulus suddenly becomes important, that is when the lecturer asks you a question; you become conscious or come back to focus your attention and overcome the restricted tone. When you come back to the scene, your conscious brain searches and recall all the recent sound input which was getting stored in your subconscious to answer the question. The factors which affect this sensory perceptual threshold are varied. This variance is true for all the different parts of the nervous system. This can be experimented for all the various senses such as taste, noise, smell, touch and the like. We can’t sense extreme cold and extreme hot objects either by taste or touch. Similarly we can’t hear sounds which are very feeble or which are very loud. Our ears do not have the capacity to decipher them. These sounds have to be in such a range of frequency which our ears can hear. The two point discrimination 2PD test is done to observe the assessment of the sensory outcome of any nerve repair. Book Reference: Information, Sensation and Perception. Kenneth H. Norwich. San Diego, CA: Academic Press, 1993. 326 pp. Cloth. Web Site for reference: www.rehab.research.va.gov/jour/07/44/1/savic.html Dermatome: Nerves carry the signals to the brain which lets us see, taste, feel, hear and do other activities. One such nerve is the spinal nerve. Some facts on skins and spinal nerves are like, Dermatome is a Greek word which literally means "skin cutting". Dermatome is an area of skin that is mainly supplied by a single spinal nerve. The dermatomes are named according to the spinal nerve which supplies them. The dermatomes form into bands around the trunk but in the limbs their association is more complex as a result of the dermatomes being "pulled out" as the limb buds form and develop into the limbs during embryological development. There are eight cervical nerves, twelve thoracic nerves, five lumbar nerves and five sacral nerves. Each of these nerves relays sensation, including pain, from a particular region of the skin to the brain. Along the thorax and abdomen the dermatomes are like a stack of discs forming a human, each contributed by a different spinal nerve. Along the arms and the legs, the design is different: the dermatomes run longitudinally along the limbs. Although the general design is similar in all of us, the exact areas of innervations are as unique to an individual as fingerprints. Book Reference: Dermatology Venereology Pre-PG Test Review by G Omkarnath. Price: $4.50  Mechanoreceptors: A similar area activated by peripheral nerves is called a peripheral nerve field. There are Sensory receptors that give the organism the information about mechanical changes in the environment such as movement, tension, and pressure. They are Mechanoreceptors. They work when they are excited by mechanical disturbances of their surroundings. Their structure is deformed, through pressure or tension, or through a combination of these. We can conclude that little energy is sufficient for mechanical stimuli to cause a detectable excitation in mechanoreceptors. From a physical point of view, mechanoreceptors are energy transducers; they convert mechanical into electrical energy, which in turn triggers the nerve impulse. Deformation leads to a sequence of events. This can be explained as    Mechanical Stimulus→ Generator Current →Nerve Impulse (Action Potential) The generator current is the earliest detectable sign of excitation. The most salient characteristic of the generator current is its graded nature; its amplitude increases continuously, without visible steps, if the stimulus strength is progressively increased. When the generator current reaches certain critical amplitude, an all-or-nothing potential is discharged in the sense organ which may then propagate as an all-or-nothing nerve impulse along the afferent axon of the receptor. Lateral Inhibitions: We are into the fantasies of the nervous system. The nerves play the major part for a good living. It’s a link or network which make us see, feel, take decisions and the like. The nerves connecting the brain from all the parts of the body makes us think, feel and execute. What our eyes see is transmitted to the brain to decipher. It’s the trick of the brain that we see added information than actually the signals sent by the eyes. The complete network of the neurons from eyes to brain and back of all animals including humans can be said as Lateral inhibitions. This lateral inhibition helps us solve the optical illusions. This makes us understand how organized our brain is. Since our brain make sense to the signals transferred by the eyes. It just does not simply absorb and respond. This lateral inhibition makes us understand the signals which the two point discrimination sends. The two point discrimination tells the difference between two nearby objects touching the two points of our skin. To know how innervate is an area of our skin is, the skin is tested by two sharp points during any neurological examination. All these signals are reached to our brain by lateral inhibition. It is an action of one neuron onto the neighboring neuron. Book Reference: Sensory Neural Networks Lateral Inhibition by Nabet, Bahram; Pinter, Robert B Price: $2.00 Receptive field: When a simulation leads to response in an area by a particular sensory neuron, various activities of the cells are recorded in the process of eye - brain networking. The receptive field lies in the retina. The area of the sensory surface that obtains stimulation that modifies the cell under study is considered the receptive field. Major activity is done only when our eyes function. So eye brain networking continues day in and day out. There are billions of receptors in the retina. There are only about one million optic nerve fibers sending visual signals up to the high brain centers. As a result, individual receptors do not have private lines up to the visual cortex. Rather, multiple receptors come together on to subsequent neural units on their way to the higher visual centers. This union results in a physiological concept known as receptive fields. Spinal cord:  It is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain. The brain and spinal cord together make up the central nervous system. The spinal cord consists of millions of nerve fibers which transmit electrical information to and from the limbs, trunk and organs of the body, back to and from the brain. The nerves connecting the spinal cord to the body are referred to as the Peripheral Nervous System. The spinal cord is the main pathway for information connecting the brain and peripheral nervous system. This pathway which goes upwards from the spinal cord towards the brain carrying the sensory information from the body to the brain is the Ascending Pathway. Ascending & Descending Tracts: The nerves within the spinal cord are grouped together in different bundles called Ascending and Descending tracts. The ascending tracts pass the information from the body to the brain, whereas the descending tracts bring the information from the brain to the other parts of the body. The spinal nerves carry information to and from different levels in the spinal cord. Both the nerves and the segments in the spinal cord are numbered in a similar way to the vertebrae. The brain is the supreme to us humans. The brain is the organizing center for movement, sleep, hunger, thirst, and virtually all vital activity necessary for survival. The brain is a delicate organ that must be protected. It makes us think and act. The nerve cells are interlinked and together are in charge for the control of all intellectual functions. All the reflex actions are taken care of the brain. The highest center of the brain makes us use logics. Most of us listen to our intuition at any situation rather than just listen to somebody who commands. There is also something called as Logical thinking which is thinking rationally. Brain allows us to go by our intuition or think logically. Circumstances make us think differently. We may think foolishly also. The brain is divided into two. One helps thinking rationally while the other intuitionally. It’s all about the nervous system and the brain. We are here to test the nerve functions using the TENS unit. Web site for Reference: www.findingdulcinea.com Some experiments are done to see the various differences using intensity, and duration. TENS is commonly used electro analgesia. It’s used to relieve from various pain affecting our human body. Transcutaneous electrical nerve stimulation (TENS) unit: It consists of one or more electrical-signal generators, a battery, and a set of electrodes. The TENS unit is small and programmable, and the generators can deliver trains of stimuli with variable current strengths, pulse rates, and pulse widths. The preferred waveform is biphasic, to avoid the electrolytic and iontophoretic effects of a unidirectional current. The patients have a choice to choose the intensity at different frequency to get relieved from pain using the TENS analgesically. Patient comfort is a very important during treatment using the TENS unit. There are various modes of treatment using the TENS unit. Conventional mode is recommended by many. The tolerance level changes from person to person. Some patients can tolerate form 15 minutes to 30 minutes. Each patient responds to differently to different intensity. There may be difference in the skin thickness of the individuals. The advantage is that the patients are relieved from pain within 30minutes. There is nothing supernatural about Transcutaneous Electrical Nerve Stimulation (TENS). TENS is intended to be used to relieve pain. The TENS unit sends comfortable signals through the skin that kindle the nerve or nerves in the affected area. In many cases, this kindleling will greatly reduce or eliminate the sensation of pain the patient feels. The relief in pain varies by individual patient by the mode selected for therapy, and the type of pain. In many patients, the reduction or elimination of pain lasts longer than the actual period of stimulation. In others, pain is only modified while stimulation actually occurs. There are also restrictions in using the TENS such as during pregnancy or heart problems. The electrodes are to be placed in the same dermatome as the pain, so that the unit is working exactly where the pain is to send signals to the brain. Sometimes the skin is sensitive and may develop rashes. Use creams or consult a dermatologist. The chemical used to make the electrodes may be sensitive to certain skins. But they can be rectified by using good skin ointments. TENS is risk free from side effects or injury or addiction. The current which passes inside our body possess no danger to individuals. The aim of the experiment on the TENS unit is that, it can relieve pain instantly using constant mode. The research is done on the hypersensitive effect to the receptors after treatment. You will find the answer to this in this dissertation. This research is completely about our nervous system. We all experience pain and introduction of TENS unit is a gift to mankind. Any pain you name it, the TENS unit is there to help. The exertion on our nerves makes them weak and we experience pain. we exert too much nowadays to compete in this fast moving world. Lower back pain is the common pain associated with every body. Next is the pain related to the Spinal cord, abdominal pain, joints pain, etc. Care must be taken when using the TENS unit. It should be kept away form the eyes and never administer while sleeping. Web site for Reference: www.intelihealth.com  medicaljournal.tbzmed.ac.ir/PDF/bahar%2085/eng/2.pdf  diss.kib.ki.se/2006/91-7140-912-2/thesis.pdf Read More