Each of the systems and organs in the body are structurally designed to perform a special function which have been alluded to in the opening discussion on receiving processing and exporting but in this section we are going to expand and advance the principles. Although each structure will have a specialised function it will also have structural components that enable it to have the other elements that are characteristic of biological units. For example the liver is a specialized metabolic organ that processes raw products of digestion, but it also has mechanism that control its function, protect its components, allow its cells to grow, and mechanisms to store its products and products for the body at large. Similarly we as adults have a specfic role in the society for which we get paid – our so called “specialised function”. We also however need to protect ourselves and our families, make sure that we grow, store our foods. Thus specialised function infers our valuable contribution to the society but we have to excercise and perform the other functions that allow us to live comfortably and in a state of order.
The nervous system is considered the master control system as its most outstanding property. This is best and most easily understood when we view its role in the autonomic system of the body where it controls the second to second, and minute to minute function of the body organs. It receives input from the afferent nerves of the sympathetic and parasymathetic systems and coordinates these signals in the hypothaalamus and midbrain and then automatically, without our concious input, senses our physiological needs. It reacts according to need and transmits its message via the efferent nerves to the organs, instructing them how fast or how slow to work. When we consider the higher functions of the nervous system that have a concious element we see the brain as a decision maker – the so called chief executive. It senses the external environment through the sensory organs, uses its talents of perception, analysis, and comprehension of the event, integrates that information with aspects of the mind such as memory, experience and emotional ambience, weighs the pro and cons, and then makes a decision. The output of the decision will be executed via contraction of muscle or secretion of a chemical substance. Thus for example, at a very simple level, you are in the woods and a bear attacks you. This is a survival situation and the conciousness in this case is not overtly involved. You sense the danger in a split second with detection perception and analysis occurring spontaneously and simeltaneously, the decision is made to run, and your leg muscles start moving taking you in the oppposite direction of the oncoming bear. If on the other hand you are presented with a situation in which your full conciousness needs to be involved – and it is not a matter of survival – say perhaps you are a judge in a court of law. The sensory input involves listening to the evidence which needs to be heard perceived analysed and comprehended. The information then needs to be integrated with other similar cases that you have come across in your experience and in your studies as a lawyer and a judge. You hope that any emotional and biased aspects you may have are excluded from the decision process, and then you use prudence to judge and make a decision. You excercise your judgement by contracting your muscles of phonation and by proclaiming the words “guilty!” or “not guilty!”
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As an artist or writer you are presented with the sensory input of a creative idea. As you think about the idea you try and perceive, analyse comprehend what it is, and you mostly get nowwhere at this point. You try and draw memory and experience and you still may not get anywhere and then an emotional charge gets to you and then quick decision to pull out a pen or brush and you contract the muscles of of your working arm and the first word or stroke is down on paper. Now you look, read or listen, perceive analyse and comprehend, remember, feel and think, decide, contract or secrete – and a second component gets executed…. and you may or may not be on your way.
The point of this discussion is to outline the higher functions of the brain as it works in the person as a chief executive officer as well as its function as a thermostat of minute to minute bodily funcions.
The endocrine system is the hormonal equivalent and assistant to the nervous system. It functions to control the metabolic functioning of the organs using different mechanisms to sense the ambient needs and to execute the needed adaptations. It works at a subconcious level. The master endocrine ogan is the pituitary that controls the workings of the thyroid, parathyroid, adrenal, pancreas, and gonadal glands and organs, while having effects on the breasts and the kidneys as well. Control of metabolism reproduction and growth become outstanding functions , but as we delve we will appreciate the full depth of the endocrine system.
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The outstanding function of the cardiovascular system is its role to transport products to and from their destinations. In performing its function it links all the organs and cells together and thus acts as the equivalent of a mail system or bodywide web as well. The blood is received from the systemic and portal venous circulations via the venae cava. The right atrium is specialised as a receiving chamber and a conduit to the right ventricle where its secondary role of a muscle helps top up the right ventricle. The specific function of the right ventricle is to relax and store the blood momentarily so that a critical volume can be accumulated, and then it pumps out the blood to pulmonary circulation for exchange of gases to take place. The pulmonary veins transport the blood to a second receiving chamber – the left atrium which like the right atrium has to function as a conduit for the blood to the rileft ventricle. Like the right atrium its small contraction acts to top up the left ventricle. The specific function of the left ventricle is to relax and store the blood momentarily so that a critical volume can be accumulated, and then it forcefully pumps out the blood to systemic circulation for delivery of oxygen, the products of metabolism created by the liver, water, members of the defense system and products of the endocrine system.
The respiratory system has as its most outstanding function the transport and exchange of gases with particular emphasis on oxygen and carbon dioxide. It has two functional and structural components including the tubular system of airways and a filtering system consisting of alveoli and alveolar membranes that allow the exchange. The airways receive the air from the environment through the nasopharynx and oropharynx and transport the air to the trachea, which subsequently transports the air through a tree like tracheobronchial tree to the alveoli. On the one side of the alveolar membrane is the newly inspired air rich in oxygen and on the other side is the pulmonary capillary network that is rich in carbon dioxide and poor in oxygen – both incorporated in solution. The properties of the gases allow them to convert from their gaseous form to a form that transpotable in the serum as they cross from the alveoli tthe blood. Similalrly they are converted from their “in solution” form to their gaseous form as they cross from the blood to the alveoli . The gradients across the membrane and the properties of the gases enable them to cross the mebrane from a higher to a lower concentration. Thus the gradient forces allow the cycle of receiving and exporting to occur.
The genitourinary system consists of two diverse systems – the genital system is involved with sexual function and reproduction and the urinary system that is involved with water and electrolyte metabolism and the excretion of nitrogenous waste. The cells of the reproductve system including the sperm and the ova are unique biological units. In the case of the sperm they develop from germ cells that divide and mature to form a continued source of mature sperm via a process called spermatogenesis from the onset odf sexual maturation to old age.. The ova are all present at birth, finite in number and waiting in line for their turn to mature as the monthly cycle demands. At menopause this process ceases as the hormonal cycles slow down and all the ova have been used.
The urinary system has both a tubular component and a filtering component. The tubular system of the urinary tract is similar to the gastrointestinal tract in that the tube acts as both a transport system but also contributes in a major way to the functioninal specialty of the system. The loops of Henle in the medulla of the kidney are organized in such a way so as to create gradient across which water and solutes will be exchanged.. In addition to the functioning tubular systems the Bowman’s capsule acts as a filter for the plasma and selectively removes nitrogenous waste. The absorbtion of water and needed electrolytes is part of the other major function of the urinary system.
The musculoskeletal system consists of the muscular (skeletal ) system and the skeletal system itself. The muscular system has as its most outstanding function, its ability to contract and relax and hence enable the organism to move in its environment. Sometimes this movement relates to survival, including the moving away from danger or moving toward a source for food and water. Sometimes the movement is for mere pleasure and fulfilment such as experienced by the jogger sportsman, walker, or dancer.
The reticuloendothelial system consisting of the spleen, lymph nodes, lymphatics, bone marrow and to some extent the blood has protection and policing as its main function. Through mechanical, chemical and immunological means it is designed to recognize the “enemy” or factors that may be harmful to the body with an ability to rid the body of these intruders.
Each biological unit has a specific value to the society and this extends to towns and cities and countries that we live in. Boston USA for example specializes in higher education and electronics, while Johannesburg South Africa had specialized and to some extent still does by mining of gold and other raw products.
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