The processes of communication between distinct tissues and organsAmong the various types of organ systems, the nervous system is one of the most important in the human body. It is responsible for producing, controlling, and guiding our thoughts and responses to the world around us according to James W. Pennebaker (2012). During embryonic development, the cells that form the nervous system are incredibly specialized and work in a more complex way than the cells that form the skin or other parts of the body. Neurosecretory cells are one of the examples of specialized cells in the nervous system that produce neurosecretions. Neurosecretions are hormones that carry information from sensor cells to target cells and can be released directly into the bloodstream according to Rene Fester Kratz, Donna Rae Siegfried (2010). The nervous system is made up of two main parts: central nervous system (CNS) and peripheral nervous system (PNS), where the CNS is made up of the brain and spinal cord while the CNS is made up of ganglia and nerves that connect the CNS to different parts of the body. The main function of the nervous system is to coordinate the voluntary and involuntary actions of the human body and transmit signals between different parts of the body. The components of the central nervous system are protected by three layers of connective tissue called meninges which are: the external dura mater, the arachnoid membrane and the internal pia mater. Inside the central nervous system there is a system of cavities called ventricles, filled with cerebrospinal fluid. This acts like a cushion and protects the components of the central nervous system and also helps in the circulation of nutrients to the brain. Source: http://smallcollation.blogspot.co.uk/2013/05/brian.html The peripheral nervous system is divided into . ..... middle of paper ......nna Rae Siegfried . (2010). What is the basic structure of nerves?. Available: http://www.dummies.com/how-to/content/whats-the-basic-structure-of-nerves.html. Last accessed 15 December 2013.4. Antranik. (2012). Neurons in the nervous system. Available: http://antranik.org/neurons-in-the-nervous-system/. Last accessed 15 December 2013.5. The human nervous system. Available: http://www.biologymad.com/nervoussystem/nervoussystemintro.htm. Last accessed 15 December 2013.6. Ellen Bowness et. al (2009). The review guide. Cambridge: Macmillan. p76-80.7. Chen Y, Stevens B, Chang J, Milbrandt J, Barres BA, Hell JW. NS21: Redefined and modified B27 supplement for neuronal cultures. J Neurosci Methods, 171 (2) 239-0247, 2008.8. J Neurosurgery. (2003). Effect of Neuregen nutrient medium on the survival of cortical neurons after aspiration injury in rats. JNS. 98 (6), p1291-8.