1) Homeostatic feedback system in response to decreased temperatures
Homeostasis is the tendency of human body for gaining equilibrium with external changes in the surroundings. Dynamic equilibrium is maintained by the body internally but when state of homeostasis is left, a response or feedback system is initiated. In case of elevated or decreased temperatures in the external environment, the body reacts in the form of sweating or shivering respectively. The main components of the feedback system are receptors, control centre and effectors. The stimulus that is sensed by the body is identified by receptors while control centre or the central nervous system interprets this stimuli. According to the stimulus, effectors provide a response to the body which is visible in the form of action and reactions.
The feedback system that is activated in case of homeostasis can be of two types i.e. negative and positive depending on the type of stimuli. Decreased temperatures is a stimuli which means that there is a difference in the external surroundings as compared to the internal body temperature. The feedback system in this kind of stimulus is negative. The receptor in decreased temperatures is skin. When the body detects that external environment has lower temperatures, then a message signal is activated from skin and transferred to the control centre. In case of homeostatic feedback of decreased temperatures, the control centre is hypothalamus.
Thermoreceptors transfer the signal of decreased temperature in external surroundings to the hypothalamus. Here, the deflection from equilibrium is measured and identified accordingly. Effectors are skeletal muscles and blood vessels that receive the information of shivering and vasoconstrict. The effectors make the body shiver and try bringing the balance in equilibrium that was lost due to difference in temperature of external and internal surroundings. Skeletal muscles rapidly contract and try generating heat which makes body warm (Johnson, Minson & Kellogg, 2014). On the other hand, blood vessels undergo vasoconstrict. In this process, the diameter of blood vessel is decreased and the blood flow beneath the surface of skin is reduced. This causes the skin to turn pale. Heath generated by muscle contraction is trapped and not lost to the surface. As a result, the body starts shivering in the stimulus of decreased temperatures.
The negative feedback system that is activated in this case helps in reaching equilibrium state by making the body shiver and become warm internally by contraction of muscles and blood vessels.
2) Homeostatic feedback system for elevated blood glucose level
The body requires oxygen for maintaining different functions. Cells being the basic unit of human body require glucose for respiration. It is important to control the level of blood sugar that is produced in the blood. Different kinds of hormones are involved in regulation of blood glucose. Insulin and glucagon are the hormones that are responsible for controlling the levels of blood sugar. Homeostatic feedback is generated in tow conditions i.e. when blood glucose level is low or high. The increase in concentration of blood glucose after eating, is an action which is considered as a stimulus for generating insulin (Stanford & et. al. 2013).
The control centre in this feedback system is pancreas and specifically insulin hormone. Elevated blood glucose is a stimulus that is activated immediately after eating food. Carbohydrates, proteins, vitamins and minerals are the constituents of this food that begin to breakdown during digestion. When carbohydrates are being digested in the body, blood glucose increases. This activates the homeostatic feedback system which has islets of Langerhans or pancreas is the control centre. Receptors in this system are proteins which are present in the cell membranes of liver (Vogt & Brüning, 2013). Cells absorb desired quantities of glucose and this enhances the process of conversion of glucose to glycogen.
Since, it has been realised that blood glucose is essential for maintaining the flow of internal body functions; it is important to understand the effect elevated blood sugar levels can have on the body (Holick & et. al. 2012). When too high, pancreas being the control centre of feedback system will release insulin. Beta cells that are present in the pancreas release insulin in such conditions. Fat cells become the effectors for maintaining the balance of glucose in normal blood. The response is provided in the form of consumption of glucose from fat cells. Hence, excessive fat gets accumulated in different parts of the body (Wei & et. al. 2014). Imbalance in diet and inappropriate consumption of food can lead to high blood glucose which means increase in fat cells.
Once, excess glucose from the body is absorbed by fat cells with help of insulin, the blood flow is normalised. This type of feedback system is considered as negative feedback because the equilibrium is disturbed negatively (Reid, Bolland & Grey, 2014). The maintenance of this blood glucose level in the body is possible with help of rigorous exercises and proper physical activity of the body.
3) Consequence on bone health
Bones help in providing support and strength to the human body. Calcium and vitamin D are some important components which enhance the growth and maintenance of bone health. The main sources of calcium are milk and its products. Skimmed milk, plain or fruit yogurt, all sorts of cheese, calcium fortified cereals and juices help in inducing calcium ions. On the other hand, vitamin D is essential because it helps in absorbing calcium by bones. Sun is the greatest source of vitamin D in the body. Egg yolks and fatty fish are also genuine supporters for enhancing vitamin D.
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Inappropriate diet can lead to deficiency of this vitamin and calcium in the body. Severe deficiency can lead to various consequences on the bone health and may invite diseases. Cognitive impairment and high risk towards cardiovascular problems are some severe outcomes which can be experienced by the person who is deficient in vitamin D and calcium ions. In more extreme cases, the person can also have cancer and severe asthma (Vitamin D Deficiency, 2017). Hence, it is important to maintain bone health by timely consumption of calcium and vitamin D rick foods. This will also help in reducing weaknesses for muscles.
- Johnson, J. M., Minson, C. T., & Kellogg, D. L. (2014). Cutaneous vasodilator and vasoconstrictor mechanisms in temperature regulation. Comprehensive physiology.
- Modell, H. & et. al. (2015). A physiologist's view of homeostasis. Advances in physiology education. 39(4). pp. 259-266.
- Stanford, K. I. & et. al. (2013). Brown adipose tissue regulates glucose homeostasis and insulin sensitivity. The Journal of clinical investigation. 123(1). pp.215-223.
- Vogt, M. C. & Brüning, J. C. (2013). CNS insulin signaling in the control of energy homeostasis and glucose metabolism–from embryo to old age. Trends in Endocrinology & Metabolism. 24(2) pp.76-84.
- Wei, J. & et. al. (2014). Bone-specific insulin resistance disrupts whole-body glucose homeostasis via decreased osteocalcin activation. The Journal of clinical investigation. 124(4). pp. 1781-1793.
- Holick, M. F. & et. al. (2012). Guidelines for preventing and treating vitamin D deficiency and insufficiency revisited. The Journal of Clinical Endocrinology & Metabolism. 97(4). 1153-1158.
- Reid, I. R., Bolland, M. J., & Grey, A. (2014). Effects of vitamin D supplements on bone mineral density: a systematic review and meta-analysis. The Lancet. 383(9912). pp. 146-155.
- Norman, J. (2017). Normal Regulation of Blood Glucose. Retrieved from: https://www.endocrineweb.com/conditions/diabetes/normal-regulation-blood-glucose. [Accessed on 23rd March, 2017].
- Vitamin D Deficiency. (2017). Retrieved from: http://www.webmd.com/diet/guide/vitamin-d-deficiency#1. [Accessed on 23rd March, 2017].