Endocrine System Essay

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1. Much of the activities of the cells in our body are regulated by circulating or local hormones of the endocrine system . Growth, development and rerpoduction are some of the useful effects of the various hormones in the body. Using your knowledge of hormones and their functions, answer the following questions: (25 marks in total) a) Most endocrine hormones are circulating hormones, but some act locally. Give an example of a circulating hormone, and an example of a local hormone. How are your chosen hormones regulated?. (5marks) A Circulating Hormone are hormones that travel in blood and act on distant target cells. An example of a circulating hormone is Insulin. Insulin is released by the beta cells in our pancreas into our blood stream when our blood glucose level is high. This is done to try and decrease our blood glucose levels. If our blood glucose levels are low, our pancrease then secretes the hormone glucagon which is then used by the liver to release glucose into our blood stream. A Local Hormone are hormones which act locally without first entering the blood stream. An example of a local hormone is Gastrin which is a polypeptide hormone secreted by the mucous lining in our stomach. Its purpose is to promote gastric juice secretion. Gastrin is released by G cells and is regulated/stimulated by the amino acids and peptides found in the food we are consuming entering our stomachs. b) There are two different chemical classes of hormones that interact differently with the target-cell. Outline the two classes of hormones, how they are transported in the blood and how they exert their general mechanism of actions at the target cell. (8 marks) The two difference chemical classes of hormones are those that are soluble in lipids and those that are soluble in water. Lipid soluble hormones include steirod, thyroid hormones and nitric oxide.

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