Homeostasis: Physiology and Pharmacology for Nursing Practice - Essay Example

HOMEOSTASIS By Homeostasis The human body is made up billions of cells working hand-in-hand in the maintenance of the entire body (Lenford and Johnson, 2015). The cells may be entirely different in terms of their functions, but similarities can be pointed out in their metabolic requirements. A constant internal environment with elements such as oxygen, glucose, mineral ions, and waste removal is crucial for the cells’ survival and the overall well-being of individuals (Lenford and Johnson, 2015). The internal environment includes all the conditions present within an organism’s body and the composition of their tissue fluid. The assortment of processes by which the body controls the internal environment making it constant is jointly known as homeostasis. In a bid to ensure that the body’s internal environment is stable, the conditions of the body must be continually monitored and adjusted through homeostatic regulation (Lenford and Johnson, 2015). It engages the receptor, the control center, and the effector. The receptor detects information about changes that occur in the environment (Norris & Carr, 2013). They then send the information to the control centers, which interpret the information as either being below or above the homeostatic range (Clancy & McVicar, 2009). The control centers send commands to the effectors that correct the disturbance by either opposing or enhancing a stimulus thus reinstating homeostasis (Clancy & McVicar, 2009). This is a continuous process to ensure the continuity and maintenance of homeostasis. An example is where the temperature receptors in the skin detect a change in temperature; communicate this to the control centers which are in the brain, then to the effectors in the blood vessels and sweat glands facilitating the required adjustments (Lenford and Johnson, 2015). When disturbances in the physiological balance occur, the system reacts to two forms of feedback. These include the positive and negative feedback. The majority of the homeostatic control mechanisms operate on the principle of negative feedback (Lenford and Johnson, 2015). It involves the system responding so as to reverse the direction of the change. An example of this principle is blood sugar regulation in the body. An increase in blood glucose higher than the homeostatic range triggers the processes that reduce it. Still, when blood glucose levels are below homeostatic range, the processes that increase the glucose levels will be triggered. Both instances result in the blood sugar level being maintained at a constant level (Clancy & McVicar, 2009). Positive feedback magnifies the disturbance in the physiological balance facilitating a value higher than the appropriate homeostatic range instead of directing it back to the homeostatic range (Clancy & McVicar, 2009). It is relatively uncommon. An example of positive feedback is blood clotting. It has a self-catalytic effect where when the blood clotting process starts, it continues faster and faster until the bleeding stops (Lenford and Johnson, 2015). Homeostasis is important because it ensures that the body’s enzyme work correctly by keeping the temperature and pH of the body at an optimum level (Langhoff, 2001). It is essential for osmoregulation so as to achieve a balance of salts and water. It maintains the supply of hormones such as the thyroid hormone and nutrients such as glucose. Homeostasis also provides independence from external environment factors such as temperature making organisms survive in any climatic condition ranging from the arctic to the tropics (Langhoff, 2001). 2. The endocrine system The endocrine system is a control system comprised of glands secreting hormones within particular organs (Lenford and Johnson, 2015). The hormones have an effect on each of their target tissues. The endocrine system plays a significant role in the digestive, cardiovascular, and urinary systems such that homeostasis is maintained (Lenford and Johnson, 2015) through a negative feedback system, with the exemption of the birth process that uses positive feedback. The endocrine system, through the digestive hormones, helps in digestion regulation thus promoting the presence of nutrients in the blood (Longenbaker, 2011). It also regulates fuel metabolism through insulin and glucagon hormones that control the amount of glucose present in the blood. Blood pressure is maintained at the required level through hormones such as the Anti-diuretic hormone (Longenbaker, 2011). In the cardiovascular system, hormones trigger red blood cell production thus keeping blood pressure at bay. The endocrine system also regulates the calcium balance. Hormones in the nervous system also help in maintaining electrolyte balance (Sherwood, 2015). Regulation of blood glucose The levels of blood glucose in the blood vary following food intake. After a meal, the body is said to be in an absorptive state because it absorbs nutrients from the digestive tract (James and McFadden, 2004). In this state, the glucose levels in the blood rise and it are detected by the beta cells of the pancreatic islets of Langerhans (James and McFadden, 2004). They respond by increasing the release of insulin into the circulatory system. Insulin stimulates the adipose and the muscle cells to take up glucose from the blood. To get into cells, glucose use transmembrane transporters known as GLUT (GLUcose Transporter) (James and McFadden, 2004). When insulin attaches to insulin receptors on the cell membranes, the cells are stimulated to increase the number of GLUT (James and McFadden, 2004). Many hours after food consumption, the insulin levels go down together with the levels of blood glucose (James and McFadden, 2004). This leads to the hormone glucagon being released by the alpha cells of the pancreas. Glucagon increases the blood glucose levels and promotes the processes that hardly require glucose utilization. It also converts the glucagon stored in the liver to glucose and produces glucose from lipids and fatty acids (James and McFadden, 2004). The endocrine system works hand-in-hand with the nervous system to control the levels of glucose in the blood as well as other variables to keep them within homeostatic range (Sherwood, 2011). Neural and hormonal communication is critical for a balance in blood sugar levels to be maintained (Norris & Carr, 2013). The autonomic section of the nervous system controls the release of insulin and glucagon. The sympathetic stimulation that happens when the body is active stimulates the production of glucagon resulting in blood glucose levels being maintained. While resting, the parasympathetic activity stimulates digestion and also the release of insulin (James and Mcfadden) to counter the rise in blood glucose that is expected after digestion 2013). 3. The Nervous System The nervous system is made of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS) (Lenford and Johnson, 2015). The CNS contains regulators that are the brain and spinal cord (Lenford and Johnson, 2015). The hypothalamus that is contained in the brain is an agent of homeostasis. The PNS, which is made up of cranial and spinal nerves, contains motor neurons (Lenford and Johnson, 2015). The neurons are focused on receiving, processing, encoding and rapidly transmitting information from one system of the body to another (Sherwood, 2011). The relaying of information is done via highly structured neuronal pathways by broadcasting action potentials along the neuron’s length (Sherwood, 2011). It is also done through the chemical transmission of signals from a neuron to neuron at synapses and from neuron to muscles and glands through various neurotransmitter-receptor interactions at these connections (Sherwood, 2011). A majority of the activities controlled by the nervous system are aimed at maintaining homeostasis. Neuronal electrical signals relay information about changes in parameters such as blood pressure or temperature that have occurred in the body that could disrupt homeostasis (Sherwood, 2011). Through negative feedback, one internal parameter controlled by the sympathetic nervous system is blood pressure. It is crucial that blood pressure is maintained within reasonable limits to ensure the well-being of the human beings. The control centers of blood pressure regulation are located in the brain, particularly in the medulla (Watson, et. al., 2003). The baroreceptors detect the irregularities in blood pressure and are found throughout the cardiovascular system especially in the arteries and the carotid sinuses (Watson, et. al., 2003). The effector in the homeostatic control of blood pressure is the cardiovascular system that responds by changing the heart rate and also alter the diameter of the arterioles (Watson, et. al., 2003). An increase in blood pressure causes the blood vessels to stretch and signals are sent to the medulla. The baroreceptors are stimulated by the increased blood pressure resulting in a decreased heart rate and vasodilatation (Watson, et. al., 2003). The cardiac center reduces the heart rate while the vasomotor center is inhibited leading to vasodilatation (Watson, et. al., 2003). The slowed heart rate decreases the cardiac output while vasodilatation results in decreased peripheral resistance. This combination of activities reduces blood pressure and returns it back to a homeostatic state. Where the blood pressure and blood volume decreases, the nervous system responds by reducing the arterial baroreceptor activity (Blinn, Rohde and Templin, 2005). This results in vasoconstriction that in turn leads to an increase in heart rate. Vasoconstriction returns blood pressure to normal while increase in heart rate increases cardiac output (Blinn, Rohde and Templin, 2005). The drop in blood volume is detected by the hypothalamus in the brain which stimulates the pituitary gland to produce the Anti-diuretic hormone, which fuels the re-absorption of water into the blood by the kidneys (Blinn, Rohde and Templin, 2005). This leads to a rise in blood volume and eventually increase in blood pressure. This is a significant example of how the nervous system works together with the endocrine system. Another system that the nervous system works in conjunction with is the cardiovascular system that is essential to the control of blood pressure. The urinary system is also useful in controlling blood pressure as in the case of the re-absorption of water into the blood by the kidneys regulating blood volume and ly pressure. 4. Aspirin and Thermoregulation One crucial concept of homeostasis is thermoregulation. Thermoregulation ensures that the internal body temperature remains within the appropriate range (“Hyperthermia”, 2012). Abnormalities within thermoregulation can result in two conditions: hypothermia and hyperthermia. Aspirin is used to treat hyperthermia, more correctly, fever. Normal body temperature varies over an extremely narrow range of 37oC and 37.8oC (“Hyperthermia”, 2012). Hyperthermia is an unusually high body temperature that is caused by defects in the heat-regulating mechanisms of the body to deal with the excess heat. The body temperatures can get up to 42oC causing severe brain damage (“Hyperthermia”, 2012). Some common forms of hyperthermia include fever, exercise hyperthermia, and heat stroke. Lifestyle factors that tend to result in hyperthermia include dehydration, fever, lack of proper air conditioning, exercise, and extreme hot and humid conditions (“Hyperthermia”, 2012). Aspirin acts on the body by targeting all nerves in the body (Crawford, 2015). Increases in body temperature occur when the concentrations of prostaglandin (PGE2) increase within certain sections of the brain (Aronoff & Neilson, 2001). These increases result in the alteration of the firing rate of neurons controlling thermoregulation in the hypothalamus. Aspirin relieves the resultant fever by inhibiting the enzyme cyclooxygenase-2 (COX-2) and lowering PGE2 levels within the hypothalamus (Aronoff & Neilson, 2001). Pharmacokinetics of Asprin Aspirin is absorbed very fast from the gastrointestinal tract when administered as a solution and slower when administered in the form of tablets. It is converted into salicylate in the stomach, internal mucosa, blood and primarily in the liver (Crawford, 2015). Salicylate is the active metabolite with the role of reducing the analgesic effects of a fever. Gastrointestinal intolerance is observed which is controlled through the development of formulations with enteric coating (Crawford, 2015). Salicylate distributes swiftly into the body fluid compartments binding to the albumin in the plasma (Crawford, 2015). The plasma concentration of the salicylate must be retained within a somewhat narrow range to minimize the systemic unfavorable effects. Salicylate may be transferred across the placenta and also through breast milk (Crawford, 2015). Due to aspirin’s rapid transformation into salicylate, its half-life is very short. The half-life of salicylate is dependent on the metabolic pathway used at a given concentration that is either to be the conjugation with glycin or glucuronic acid, in the liver (Crawford, 2015). The urinary excretion of unchanged salicylate is about 10% of the total salicylate eliminated (Crawford, 2015). Urinary excretion of salicylate is dependent upon the pH of urine. The percentage of free ionised salicylate of the total dose present in urine increases with the increasing pH of urine. Dosage is tailored to suit each patient dependent upon plasma concentration and clinical response. Pharmacodynamics of Aspirin Regardless of aspirin alleviating the effects of fever, it also has adverse side effects that are usually dose related. For that reason, it is prudent to use the least effective dose to keep side effects to a minimum. The most common side effects include: stomach ulceration and bleeding (Crawford, 2015), black tarry stools, dizziness and weakness due to the internal bleeding, rash, kidney impairment, vertigo, and light-headedness (Crawford, 2015). Other side effects include ulcerations, abdominal burning, pain, cramping, nausea, gastritis, gastrointestinal bleeding and liver toxicity (Crawford, 2015). Word count (1970) Bibliography Aronoff, D. M., & Neilson, E. G., 2001. 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