Write an essay on Homeostasis.
Homeostasis is human body refers to the ability of body to physiologically regulate to its inside environment to ensure its ability to fluctuations to the external environment and the atmosphere conditions. The major organs of body that does homeostasis are liver, kidneys and the brain. Liver performs homeostasis by metabolizing toxic substance and regulating the carbohydrate metabolism. Kidney brings up homeostasis by regulating blood water level, re-absorbing of substances in to the blood, maintaining the salt and iron level in the blood, regulating pH, and excreting urea and other waste products. The body’s inability to maintain homeostasis may cause death or a disease it is known as homeostatic imbalance.
The regulation and working of homeostasis takes place in three parts. First is the receptor, it receives information from the environment that something is changing. Second is the control centre which takes and integrates the data from the receptor. Third one is the effector works by responding to the control centre by opposing or enhancing the stimulus. Homeostasis continuously takes place in the body. One example is to regulate the temperature of the body is done by the temperature receptors present in the skin area by giving information to the brain i.e. the control centre; the effector are the blood vessels and sweat glands. Homeostasis works on synthetic equilibrium as the inside and outside environment of body continuously changes and the body adjust to the set point via the homeostasis process only. Homeostasis maintains the internal environment by lessening the changes so, it may involve negative feedback loops.
Homeostasis works on the positive and negative feedback loop. When a change occurs, the body’s system works by two types of feedback. One is negative and other is positive feedback.
Negative feedback: it is a reaction in the system which responds in a way to reverse the way the change is occurring. It keeps the things constant and maintains homeostasis. Example is if the percentage of carbon dioxide in the body increments than the lungs are signaled to increment the body activity by expelling more carbon dioxide. Another example is thermoregulation. If the temperature of the body rises than the receptor in the skin and hypothalamus changes that, triggers a command to the brain. This command effects by decreasing the temperature of the body.
Positive feedback: It is a response to increase the change in the variable. It a destabilizing effect. Positive feedback is less common. Example is nerves the threshold action potential triggers is lactation that is milk production. When baby suckles, nerves messages from the mammary glands releases hormone prolactin by the pituitary gland. The more the baby will suckle, the more prolactin will be secreted by the body, stimulating more milk production. Very less amount of positive mechanisms occurs in the body. Positive feedback mainly speeds the direction of the change so as to increase the concentration of the hormones.
The main source of fuel for the cells present in the body is glucose. Due to its size, it is to be transported in to the cells. A hormone is produced by the pancreas to carry out the transport of glucose in to the cells. The hormone is called Insulin. To facilitate the transport of glucose in to the cells from the blood stream, insulin do it by lowering the blood glucose level in the body. The glucose production by the amino acid, fatty acid, and glycogen is also inhibited (Marino, Xu, & Hill, 2011). Glycogen, is a carbohydrate that has many subunits of glucose. All these together, bring up the lowering of glucose level in the blood. Another hormone named, Glucagon is released by the pancreas to raise the blood glucose level in the blood. It stimulates the increase by breaking down the glycogen in to glucose and by facilitating the production of glucose from the amino acids and fatty acids. Additionally, it also stimulates the release of glucose from the liver. Bothe the hormones, insulin and glucagon has opposite effects. In general, the glucose level in the blood are in a range of 70 to 110 mg/dl. When glucose level goes out of the range, than the insulin and glucagon released by the pancreas adjust the change and brings the glucose back to the normal range. When the body system is carrying out the proper functioning, body is producing some amount of insulin and glucagon so to balance the glucose release and glucose intake in the body.
Homeostasis control: Controlling the blood glucose
The control in blood glucose level is an example of negative feedback of homeostasis. The homeostasis role in controlling blood glucose level is explained in below lines.
Before taking a meal, the glucagon level in the body is high as no glucose is absorbed by the small intestine. In such case, glucose must be released by the liver and stimulation of glucose synthesis must be carried out by the glucagon hormone. However, after taking a high carbohydrate food the blood glucose level in the body becomes higher and same time the level of insulin also becomes high. The insulin level becomes high due to high glucose level in the body. This mechanism takes place so quickly that the two spikes occur simultaneously. In fact, the insulin level rise whenever the glucose level rises and falls whenever glucose levels. After some time, when the glucose level reaches the highest end that is the normal range of 70-110 mg/dl, than glucagon level starts to decrease. The glucagon level falls until the glucose returns to the normal range. At this point, the glucagon concentration levels off and then slowly start to increments again as glucose levels drift back down to where they were before the meal was consumed. Thus it is a clear example of negative feedback. In this example of homeostasis the stimulus is the rise blood glucose level, the receptors is the Insulin secreted by pancreas. After the meal the increase in the blood glucose causes insulin to be released. The response is the take up of glucose by the body cells and removing glucose from the blood. To adapt to the change, the homeostasis is achieved by bringing the blood glucose level back to the normal range by release of insulin.
During the absorption stage, when there is an increase in the blood glucose level. The increase is detected by the beta cells of pancreas leading to the release of insulin in the bloodstream. The release of Insulin brings up the stimulation in the adipose and muscle cell to carry out the glucose from the bloodstream. Glucose requires trans-membrane transporters to enter the cells. The trans-membrane transporters belong to the family of GLUT (Glucose Transporter). In high amount, GLUT4 is found in the muscle and fat cells (Mayer & Emeran, 2011). After the insulin binds up to the Insulin receptor on the cell membrane. It is the cells that brings about the increase in the number of the glucose transporters. The increment in glucose transporters brings about the increment in the transport of glucose to the cells with a simultaneous drop in blood glucose level. The exact mechanism when insulin binds to the receptors to bring up the translocation is yet not known fully. All tissues of the body does not require Insulin to take up the glucose like the cells of brain and liver use up the GLUT transporters that do not depend on Insulin for the transport. The other ways by which Insulin brought up the increase in glucose level are as follows:
• Promoting glycolysis, the process which breaks down the glucose for providing cellular energy.
• Promotion glycogenesis, the process which changes glucose into the glycogen.
• Inhibiting lipolysis, the process which breaks down the lipids so as to release the energy.
When there is decrease in the blood glucose level, the insulin level in the body also falls. When the body is in the post-absorptive state that is the blood glucose level is low and the insulin level is low, than the alpha cells of pancreas cause the release of glucagon in the blood stream. The glucagon release increases the level of blood glucose in the blood stream (Levin, 2011). Glucagon binds to the receptors of glucagon that belongs to G-Protein Coupled Receptor Family. It stimulates a series of enzyme reaction, causing the activation of glycogen phosphorylase. The glucagon release is inhibited by somatostatin and insulin. The glucagon works by converting glycogen in to glucose and releasing in to the blood and also by promoting gluconeogenesis, a process by which new glucose is produced by the lactic acid and various metabolites.
Levin, B.E. (2011). Glucosensing neurons do more than just sense glucose. International Journal of Obesity.2011;25 Suppl. 5:S68–S72
Marino, J.S., Xu, Y., & Hill, J.W. (2011) Central insulin and leptin-mediated autonomic control of glucose homeostasis. Trends EndocrinolMetab 22: 275-285.
Mayer & Emeran, A. (2011). "Gut feelings: the emerging biology of gut-brain communication". Nature Reviews Neuroscience 12 (8): 453–466.
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