Positive Feedback System in the Human Body - Essay Example

Platelets contract to release essential substances which make them adhere to the damaged wall and in particular to the collagen in the walls of the damaged vessels.  They also tend to release ADP. This substance further assists the platelets in their function and tends to stimulate the platelets which lie close to the damaged vessel by making them active. These platelets tend to cluster together and come and join the initial platelets that adhered to the vessel wall that was damaged. This results in the formation of a platelet plug which closes the damaged vessel. At the same time, there is the further release of clotting factors. This mechanism indicates the positive feedback system of the human body where the activation of one platelet further stimulates the cascade and results in more stimulation and the formation of a platelet plug (Lauralee 2006 p322).

How do the isotopes of a single element differ from each other? Give an example of a radioactive isotope that can be used as an important medical diagnostic tool.

            An element comprises atoms. An atom further comprises a nucleus that is placed centrally and electrons that revolve around the central nucleus. The nucleus is made up of protons as well as neutrons. An isotope is basically a different form of the same element which consists of the same number of electrons and protons but the only difference lies in the number of neutrons. The neutrons of the isotopes of a single element vary in number. Because of this variation in the number of protons, the mass of the isotopes of the same element also differs. This is because the mass of elements is determined by the addition of neutrons and protons. An example of an isotope is that of carbon which has three isotopes which include carbon-12, carbon-13, and carbon-14.  As the number of electrons for all the isotopes is the same, therefore there is no variation in the chemical properties of the isotopes of the same element. But owing to the different masses of these isotopes, the rates of the reactions of the isotopes of the same element differ from each other. The bonds that the isotopes of the same element form with other elements are also different from each other due to the different masses. Also, some isotopes of the same element are radioactive whereas other isotopes exist in stable forms. This is true of carbon as carbon-14 is radioactive and undergoes the process of decay whereas carbon-12 and carbon-13 are not radioactive and are hence stable (Lasen 2010 p446, Brown et al 2011 p80). Radioactive iodine-123 is an example of a radioactive isotope that is an important medical diagnostic tool. This isotope is basically taken up by the thyroid gland and helps in assessing the function of the thyroid gland by measuring the amount of iodine that is taken up by the gland (Pilling 1999 p132).