Physical Structure of a Neuron - Report Example

PHYSICAL STRUCTURE OF A NEURON (Neuron-to-neuron Communication) ID Number: of of School (University) Estimated Word Count: 1,863 Date of Submission: January 14, 2012 PHYSICAL STRUCTURE OF A NEURON Introduction The human body is a very complex set of inter-connected living systems. There are at times when these body systems operate independently (involuntary) and sometimes voluntarily (it means this particular body system is dependent on some conscious command from the brain). Examples of the ten different body systems are the circulatory system, the digestive system, the integumentary (skin), the skeletal, the muscular, the digestive, respiratory, the reproductive, the endocrine and the nervous system. All these systems work together in harmony that makes the human body a complex whole. Vitamins, nutrients and minerals are necessary for all the systems to work perfectly to attain and maintain good health. Regular exercise, proper diet and a healthy lifestyle all contribute and work together to make these systems function properly. Perhaps one of the most complex body system is the nervous system. This is the set of body system that is composed of very highly-specialized cells involved with the receiving and its transmission of information from both internal and external stimuli. In other words, this system is responsible for the receipt and relay of various communications within the human body. It is a complex system composed of the brain, the spinal column and the nerves. The nervous system also includes the special sense organs of the eyes, the ears, nose, taste buds and skin. In effect, the nervous system is the control system of the human body. It is a sort of a command center made up of the central nervous system (brain and spinal column) and the peripheral nervous system (the spinal nerves and the twelve cranial nerves). This paper takes a look at the basic unit of the nervous system, which is the neuron, and how these communicate. Discussion A relatively new branch of science is gaining recognition for its importance in efforts to understand the human body better. This is called as psychobiology or the study of how various parts of the nervous system influence human behaviours, emotions and the thought processes. It is also known by other terms like biopsychology, behavioural neuroscience and physiological psychology but the ultimate aim is the same, which is to better understand how a human nervous system and its components explain our behaviours as well as various ailments. In this regard it is very important to study and understand how biological processes affect not only behaviours and emotions but the entire cognitive process as well. For this purpose, it is crucial to explore how a persons actions are greatly influenced by the brain, neurotransmitters and the nervous system. It is therefore necessary to study the complex inter-relationship between anatomy and physiology in the complex human process of biological growth and development. This very fascinating field of study has already yielded some useful insights into how the nervous system affects and influences the entire body and indeed the whole person through a discovery of the role of chemical transmission by neurotransmitters within this system in relay of information from various stimuli (Wickens, 2005, p. 11). It is in this connection that this paper is discussing the basic unit of the nervous system which is the neuron and how the neurons in turn transmit crucial information between them. An understanding of a neurons physical structure is a necessary adjunct to the process of understanding in the entire chemical transmission process. An example of a neurotransmitter is dopamine; too little of it causes Parkinsons and Alzheimers but too much of it is associated with psychological disorders like dyslexia and schizophrenia. Physical Structure of a Neuron – the neuron is a single cell which is the basic unit or building block of the entire nervous system. However, it is also composed of several parts itself. These are the nucleus (or cell body), the dendrites and the axon; each part will be discussed in a much greater detail below including their primary functions as part of the neuron. Before going any further, there are several types of nerve cells. These are the sensory neurons (responsible for carrying information from the sensory cells of the sense organs to the brain), the motor neurons which relay instructions from the brain to the muscles responsible for movement and locomotion and finally, interneurons which are specialized neurons responsible for communications between different neurons. Additionally, neurons share some similar characteristics with other cells in the body such as a nucleus that contains the basic genetic information, a cell membrane that allows it protection also, and lastly, its body likewise contains organelles (mitochondria and Golgi bodies) and the liquid cytoplasm. However, a key difference between a neuron and the other body cells is that the membrane of a neuron allows it to communicate by sharing information with the other surrounding cells through the transmission and receiving of chemical and electrical signals. This process is facilitated by connections with the gaps between nerve cells known as synapses. Another difference is that nerve cells in general do not reproduce themselves, unlike the other human body cells. In other words, neurons also die like other cells as time goes by but are not replaced by new cells. An important finding by neuroscientists is that neurons continue to build connections among and between all the other neurons throughout a persons life which has significant implication for learning and other cognitive processes. Aged person can stay mentally healthy and alert by engaging in intellectually stimulating activities such as a game of chess. Nucleus of a Neuron – the nucleus is contained within the cell body of a neuron which is called as the soma. This is the part where the neural signals from the dendrites are processed. The soma does not directly engage in communicating but performs other essential functions such as assemble various proteins, generate energy and maintain cell metabolism (Holtz, 2011, p. 38). Medical literature uses soma and cell body interchangeably; the word soma means body in Greek and this is where the ribonucleic acid (RNA) is produced, more specifically in a part of the soma called as the axon hillock; this part is where the axon originates outwards away from the cell. It is responsible for sorting out all the proteins produced and determine which proteins are sent out or will remain inside the soma. Moreover, this is the site for action potential initiation which will be discussed later in this paper regarding the actual transmission of electrical signals. Dendrites of a Neuron – these are the tiny tentacles-like extensions of a neuron that is primarily responsible for the acceptance of signals. Dendrites can be considered as protrusions of a neuron with the intention of covering as much surface area as possible in order to enhance their function which is to receive information from other surrounding or nearby neurons and transmit these electrical signals onwards and inwards to the soma. Dendrites are generally quite short but highly branched out with plenty of synapses (special structures to pass signals between cells) in them. The dendrites of a neuron are actually the receiving ends of a nerve cell (in this case, post-synaptic cells) being targeted by accepting the signals sent from another nerve cell (pre-synaptic) or put differently, dendrites are the mechanisms for inward transmission of signals sent out by an axon (outward transmission) of the sending nerve cell. Dendrites and axons work harmoniously to send and receive signals between nerve cells; these two tiny parts serve as their bridges. Axon of a Neuron – this is the part of the nerve cell that extends outward to send out a signal to a nearby cell. This is the counterpart of the dendrites, but unlike the dendrites which are mostly shorter but thicker, an axon is generally thinner but longer (Eroschenko, 2008, p. 144). In most nerve cells, an axon is the elongated nerve fiber extending from the cell body beginning at the clear, cone-shaped area of the soma and ends in numerous nerve terminals which are actually the ones responsible for transmission of signals to the next cell (as mentioned earlier). The rule of thumb is the bigger an axon, the faster the signals can be sent (similar to a wider bandwidth). Another indicator of speed transmission is the presence of insulation called myelin which is fatty substance that sheaths or protects the axon, although some axons do not have this protection. Not a few research neuroscientists have noted that the loss of this myelin covering is very notable in people with multiple sclerosis (MS) which affects some 2.5 million people worldwide. This is a disease in which there is axonal damage due to the process of demyelination where the cells axons lose their myelin covering insulation over time but the reverse process of remyelination is a failure (Hagemeier, Bruck & Kuhlmann, 2012, p. 278). Exact causes of this demyelination is not yet fully understood but some factors are suspected such as genetics, auto-immune reactions and the various infectious agents, including some chemicals in insecticides. The end result is a reduced or impaired function of the axon to carry and transmit these neural signals which results in reduced sensation, incoherent movements or impaired cognition seen in MS patients, depending on which particular nerve is affected. A damaged axon fails to send the signals properly, resulting in impaired communications between nerve cells because that axon is not able to conduct the electrical signals; MS causes permanent neurological damage. Neuron-to-Neuron Communication – the neurons communicate mainly through the so-called synapse. This is the gap between the dendrites and the axon between individual neurons. It is accomplished through the use of chemical messages known as the neurotransmitters of which there are about 100 different known kinds, although a lot more may be awaiting discovery. Gaps are bridged by jumping across the synapses by electrical impulses when the action potentials of a synapse exceeds the threshold limit of an axon hillock. This happens in the narrow gaps between an output zone (axon) of a neuron and input zone (dendrites) of another cell (Starr & McMillan, 2008, p. 244) when the calcium ions in a plasma membrane triggers the electrical signal. All the molecules in the neurotransmitter are received by receptor proteins of the receiving neuron cell. Learning disabilities can be traced to a faulty nervous system (Haworth & Plomin, 2007, p. 4). Conclusion The objective of psychobiology is to find some biological or physiological basis for a few psychological ailments which cannot be explained by psychology alone. In other words, it is a multi-pronged attempt at another alternative to understand and explain some mental disorders. The insights gained from psychobiology are very helpful in this regard, partly due to the major advances in scientific knowledge and medical technology, such as more powerful MRI and PET scan machines which can actually monitor the changes going on inside the human brain due to an interaction between drugs and disease, for example. There is no doubt that physical bases form a part of human behaviours and cognitive functioning which provides new perspectives such as the suspicion that autism is partly attributable to malfunctions in the wiring of the brain as suggested by some medical researchers due to an enlarged amygdala (Moldin & Rubenstein, 2006, p. 243). Reference List Eroschenko, V. P. (2008). Di Fiores atlas of histology with functional correlations. PA, USA: Lippincott Williams & Wilkins. Hagemeier, K., Bruck, W. & Kuhlmann, T. (2012, March). Multiple sclerosis: remyelination failure as a cause of disease progression (abstract). Histology and Histopathology, 27 (3), 277-87. Haworth, C. M. A. & Plomin, R. (2007). The genetic and environmental origins of learning abilities and disabilities in the early school years. Monographs of the Society for Research in Child Development, 72, 1-144. Holtz, J. L. (2011). Applied clinical neuropsychology: an introduction. New York, NY, USA: Springer Publishing Company. Moldin, S. O. & Rubenstein, J. L. R. (2006). Understanding autism: from basic neuroscience to treatment. Boca Raton, FL, USA: CRC Press. Starr, C. & McMillan, B. (2008). Human biology. KY, USA: Cengage Learning. Wickens, A. P. (2005). Foundations of biopsychology. Upper Saddle River, NJ, USA: Prentice-Hall. Read More