The Importance of the Human Nervous System - Essay Example

Human Nervous System The human nervous system is separated into the central nervous system, consisting upon the peripheral nervous system, brain and the spinal cord which contains the whole nervous construction outer part of the central nervous system, mainly the nerve courses, sensory receptors and in special part called ganglia there are a little quantities of nerve cells. All over the body Ganglia are found at diverse positions (Alberts, 2008). They are the only locations of neurons outside the central nervous system. Information from incoming cells can be transmitted to the ganglion cells, which in turn can transmit that information to other locations. The advantage of having a nervous system is that it supplies as the chief managing structure to the human body. One of the main tasks contains the harmonization of the many body parts, the incorporation of physical actions, the investigation of inward spurs, and all brain motions, counting reminiscence and theoretical analysis. The nervous system regulates these activities by communication between various nerve cells by controlling the actions of skeletal, smooth, and cardiac muscle, it also stimulates the secretion of products from various glands of the body (Lovinger, 2008). The disadvantages of the nervous system include the effects that can be caused in the event of a disease or injury in the cells of the nervous system, especially within the brain. This will create problems that are unique to that organ. In addition, the cells of the brain are constrained to a limited area (Bloom et al, 2007). Any neural injury or disease that destroys cells effectively results in a decreased number of neurons this is because neurons are not very good at repairing themselves. Furthermore, the space in the skull is tightly packed with cells and cerebrospinal fluid. There is no room for the blood that might appear as the result of an injury or the fluid accumulation that might be caused by tissue infection or tumors (Evans-Martin, 2010). Any of these conditions will increase the pressure within the skull and will also increase the extent of the injury to the nervous tissue. Although the brain and the spinal cord contain several different types of cells that are morphologically unique, there is only one functional cell present, which by convention is always referred to as the neuron. The neuron is one of the few cells in the body that cannot reproduce. A fixed number of these cells develop in infancy, and the number never increases. The number of neurons can, however, decrease in the event of an injury or a disease (Evans-Martin, 2010).The neuron consists of a cell body that is similar to that of the typical animal cell familiar to most people. In addition, the neuron has extensions called processes. In the typical neuron, there are two types of processes: dendrites and axons (Marieb, 2008).Usually a neuron has many dendrites. Dendrites are very short, receive information from nearby cells, and relay that information to the cell body. A nerve is made up of a bundle of these axons together with connective tissue and blood vessels. Each cell has only a single axon, which may be very long, extending up and down the spinal cord or from the spinal cord to the ends of the fingers or toes. The axons conduct information from the cell bodies to the effectors such as, the muscles and glands or to other neurons (Alberts, 2008). Functionally, the nervous system is split into two areas: the somatic nervous system and the autonomic nervous system. The somatic system controls posture and locomotion by stimulating the skeletal muscles. It is responsible for knowing where the body is in space and for ensuring that there is sufficient muscle contraction (tone) to maintain posture. Responses of the somatic system occur through the motor neurons (Marieb, 2008). The Autonomic nervous system controls the internal processes of the body such as digestion and the heartbeat. It has two divisions that work opposite each other to maintain homeostasis. The sympathetic nervous system automatically stimulates the body when action is required, for example, if a person where to put their hand on a hot plate accidentally they would involuntary pull their hand away without even thinking about doing it .It is solely responsible for what is referred to as the fight or flight response, this is when a surge of adrenaline is stimulated giving the body a surge of energy so that has the ability to escape from a dangerous situation quickly. The parasympathetic system is responsible for slowing down the heart rate after a fight or flight response is no longer needed. It is also responsible for the digestive functions of the body, controls stimulation of salivary gland secretions, increased blood flow to digestive organs, and movement of materials through the digestive system. The sympathetic and parasympathetic systems usually function in balance the parasympathetic system predominates after meals, and the sympathetic system predominates during periods of stress or physical activity (Bear et al, 2007). Neurons with further neurons converse through neurotransmitters which can be known as chemical couriers. When the axon ends, there is the synaptic knob which is a broad part. Leaving a space of approx 20nm called the synaptic cleft from where the synaptic knob links with the dendrite cell structure of the subsequent axon (Bear et al, 2007).The synaptic knob keeps numerous mitochondria for the production of energy for developing transmitter chemicals, these chemicals releases and accumulates neurotransmitter stuff. Neurotransmitter affects for the shorter period, they are small molecules which have the ability to diffuse with ease across the synaptic cleft. There are many types of neurotransmitters, some of which are well known, such as acetylcholine and norepinephrine (Collins Advanced Science). When ever a change occurs in membrane potential, Neurons generate signals. Action potential is one of those changes in the neuron's membrane potential and it is a main particle that helps in producing an action potential which is called a voltage-gated sodium channel. When the inner wall of membrane turns out to be less negative then this modification in membrane potential is called a depolarisation. During depolarisation nerve impulse gives no or all signals. If the requirement of threshold is not fulfilled then the process of depolarisation will not be able to take place and signals will not spread. An action potential can be increased by depolarisation because a depolarisation develops the chances of opening voltage-gated sodium channels (Jakab, 2006). Actual electrical conduction in a neuron involves membrane depolarisation and the influx of sodium ions and the efflux of potassium ions. Electrical conduction along a neuronal segment involves the depolarisation of the membrane with the movement of sodium actions into the neuron (Jakab, 2006). The initial depolarisation is triggered by neurotransmitters contacting the dendritic membrane. Sodium and potassium ion pumps continue the successive steps of depolarisation and repolarisation with the cell structure, dendrites and neuron axons awaiting neurotransmitters are produced diagonally a synaptic break from a terminal axon to depolarize the upcoming neuron membrane. If only reactive increase is occurred by neurons, the indication (the alteration in membrane prospective) would decrease as it increases submissively down through the axon (Seeley, 2007). In every area of membrane where the axon neurons take new prospective action to avoid this problem. Instead of submissively spreading action potential from one end to the other, a new accomplishment likely generates at both points down the axon. This system is appropriately called renewal or propagation. The action potential upholds its amplitude and reliability by occurring in the axon of the sensory neuron close to the toe, beyond up the leg, and that each full appears in the axon entering to the spinal cord are propagated action potentials. There are different types of nerve cell impulses. When electrical impulse gives signals then Neurotransmitters are produced beside the axon. After releasing, neurotransmitter links to the cells with proper receptors lying on their dendrites. Neurotransmitters may either stimulate or inhibit the activity of the second cell. If there is significant stimulation of the second cell, it will conduct the information along its axon and release a neurotransmitter from the axon terminal, which will in turn stimulate or inhibit the next neuron or effector (Benarroch, 2007).. There must be a mechanism for the immediate removal of neurotransmitters from the synaptic cleft if the stimulation of the second neuron is to cease and if other impulses are to be conducted. Neurotransmitters can influence only those cells that have the appropriate receptors on their surfaces. It is through the neurotransmitter-receptor complex that neurotransmitters are able to influence cells and any alteration of the number of receptors or type of receptors on a cell membrane will lead to an alteration of cellular functioning (Benarroch, 2007). There are more than fifty types of neurotransmitters identified and these are mainly placed into four main groups. Acetylcholine (neurons that release acetylcholine and are described as cholinergic), these act throughout the brain modifying the activity of other neuron transmitters. The chemicals used in some nerve gases work by inhibiting acetyl cholinesterase. Amino Acids an example of one would be gamma amino butyric acid (GABA). Monoamines that would include things like dopamine and serotonin and finally Neoropeprides which are chains of amino acids such as endorphins. The axons of some neurons are covered with multiple layers of a cell membrane known as myelin. The myelin is produced by specialized cells in the brain known as oligodendrocytes and by cells in the peripheral axons known as Schwann cells (Marieb, 2008). Myelin serves as an insulator for axons and is effective in speeding up the conduction of nerve impulses. It is essential for the normal functioning of the nervous system. Myelinated neurons have the ability to conduct impulses at twice the speed of those that are unmyelinated. Demyelinating diseases are those that result in changes in the myelin sheaths of neurons. The most common example is multiple sclerosis, a disorder of the brain and spinal cord; it affects myelin in the central nervous system but not in the peripheral nervous system (Bloom et al, 2007). Although there are varying degrees of severity, the condition causes limb weakness, impaired perception, and optic neuritis, among other things. Some cases present only mild symptoms, while others are degenerative and can lead to death in some patients. Many patients, however, survive for more than twenty years. The cause of the disease is not yet clear, although viral infections have been associated with some demyelinating diseases. Although there is no mechanism for replacing cells that have died, the prognosis is not totally bleak. There are cells in the brain that can, in the event of disease or injury, assume the responsibilities of the dead cells. For example, a person who has lost the capacity to speak following a stroke may relearn using cells that previously did not perform that particular function. Among the problems with which the nervous system must cope, there are many things that can go wrong at the synapse of a neuron. The cell may produce too little or too much neurotransmitter. It is possible that the neurotransmitter may not be released on cue or that, if it is released, the postsynaptic cells will not have the appropriate receptors. There also may be no mechanism for removal of the neurotransmitter from the synaptic cleft. These are only a few of the problems that can interfere with communication between neurons and between neurons and other effectors. As science learns more about the communication system of neurons, efforts to correct these problems will intensify. Already there are many drugs available that can alter activity at the synapse. Correcting these errors can also lead to methods for the treatment of mental diseases. Clearly the nervous system of the human body is of the highest importance, without it the body simply cannot function effectively. References Alberts, Bruce, et al. (2008). Molecular Biology of the Cell. 4th Ed. New York: Garland. Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. (2007). Neuroscience: Exploring the Brain. 3d ed. Philadelphia: Lippincott Williams & amp; Wilkins. Benarroch, Eduardo E. (2007) “Neuron-Astrocyte Interactions: Partnership for Normal Function and Disease in the Central Nervous System." Mayo Clinic Proceedings 10. Bloom, Floyd E., M. Flint Beal, and David J. Kupfer, eds. (2007). The Dana Guide to Brain Health. New York: Simon & amp; Schuster. Evans-Martin Fay F. (2010). The nervous system. Chelsea House in New York. Retrieved from http://openlibrary.org/works/OL15517627W/The_nervous_system on 19 Jan. 2011. Jakab Cheryl. (2006). The nervous system. Smart Apple, Retrieved from http://openlibrary.org/works/OL5852855W/The_nervous_system on 19 Jan. 2011. Lovinger, David M PHD. (2008). "Communication Networks in the Brain: Neurons, Receptors, Neurotransmitters, and Alcohol." Alcohol Health & Research World. 01 Jul. Marieb, Elaine N. (2008). Essentials of Human Anatomy and Physiology. 8th ed. San Francisco: Cummings. Seeley, Rod R., Trent D. Stephens, and Philip Tate. Anatomy and Physiology. 7th Ed. New York: McGraw-Hill, 2007Pearson/Benjamin Read More